顔写真

オオノ ヒデオ
大野 英男
Hideo Ohno
所属
役員
職名
総長
学位
  • 工学博士(東京大学)

プロフィール

1982年東京大学大学院工学系研究科博士課程修了。

1982年北海道大学工学部講師、1983年北海道大学工学部助教授、この間に1988年~1990年 アメリカ合衆国IBM T. J. Watson Research Center客員研究員。1994年東北大学工学部教授、1995年東北大学電気通信研究所教授(2013年~2018年 所長)。あわせて2010年東北大学省エネルギー・スピントロニクス集積化システムセンター長、2010年東北大学原子分子材料科学高等研究機構主任研究者、2012年東北大学国際集積エレクトロニクス研究開発センター教授、2016年東北大学スピントロニクス学術連携研究教育センター長を務め、2018年第22代東北大学総長。

2010年~2014年 内閣府 最先端研究開発支援プログラム「省エネルギー・スピントロニクス論理集積回路の研究開発」中心研究者。

専門分野:スピントロニクス、半導体物理・半導体工学

委員歴 24

  • Institute of Electrical and Electronics Engineers (IEEE) フェロー

    2018年1月 ~ 継続中

  • American Physical Society (APS) フェロー

    2013年3月 ~ 継続中

  • Journal of SPIN Editional Board (Consulting Editor)

    2010年4月 ~ 継続中

  • Journal of Magnetics, Korean Magnetics Society Overseas Editor

    2009年4月 ~ 継続中

  • NPG Asia Materials Advisory Board

    2009年4月 ~ 継続中

  • 応用物理学会 フェロー

    2007年8月 ~ 継続中

  • Institute of Physics (IOP) フェロー

    2004年9月 ~ 継続中

  • 日本学術会議 会員(第三部部長)

    2014年10月 ~ 2020年9月

  • 日本学術会議 日本学術会議連携会員

    2020年10月 ~ 継続中

  • 科学技術振興機構 外部評価委員

    2011年8月 ~ 2012年3月

  • 新機能素子研究開発協会 不揮発性技術を用いたIT機器の低消費電力化技術調査委員会 委員

    2011年7月 ~ 2012年3月

  • 新世代研究所「スピントロニクス研究会」 委員

    2009年4月 ~ 2012年3月

  • 新エネルギー・産業技術総合開発機構(NEDO) 技術委員

    2009年8月 ~ 2011年3月

  • 国際高等研究所「ナノ物質量子相の科学」 研究開発専門委員

    2009年4月 ~ 2011年3月

  • 文部科学省「科学技術・学術審議会」 専門委員

    2007年2月 ~ 2010年1月

  • 電子情報技術産業協会「スピントロニクス技術分科会」 委員長

    2008年4月 ~ 2009年3月

  • 電子情報技術産業協会「電子材料・デバイス技術専門委員会」 委員

    2008年4月 ~ 2009年3月

  • 文部科学省、経済産業省「ナノエレクトロニクス戦略合同委員会」 委員

    2007年2月 ~ 2009年3月

  • 新エネルギー産業技術総合開発機構研究評価委員会 評価委員

    2006年4月 ~ 2009年3月

  • Solid State Communications Editor

    2005年11月 ~ 2009年2月

  • 日本学術会議 連携委員

    2006年4月 ~ 2008年9月

  • 新機能素子研究開発協会「スピントロニクス不揮発性技術調査委員会」 委員

    2006年9月 ~ 2008年3月

  • Japanese Journal of Applied Physics Editor

    1993年1月 ~ 1998年12月

  • 日本結晶成長学会 評議員(1995,1996)

    1995年4月 ~ 1997年3月

︎全件表示 ︎最初の5件までを表示

所属学協会 6

  • 電子情報通信学会

  • 日本物理学会

  • アメリカ電気電子学会

  • アメリカ物理学会

  • 日本結晶成長学会

  • 応用物理学会

︎全件表示 ︎最初の5件までを表示

研究分野 4

  • ナノテク・材料 / 結晶工学 / 半導体結晶成長

  • ナノテク・材料 / 応用物性 / 半導体結晶成長

  • ものづくり技術(機械・電気電子・化学工学) / 電子デバイス、電子機器 / 半導体デバイス

  • ものづくり技術(機械・電気電子・化学工学) / 電気電子材料工学 / 半導体スピントロニクス

受賞 23

  1. ISCS Heinrich Welker Award

    2019年5月 Seminal contributions to the materials science, physics of ferromagnetic III-V semiconductors and spintronics

  2. Institute of Electrical and Electronics Engineers (IEEE)フェロー

    2018年1月

  3. 2016年度C&C賞

    2016年11月30日 NEC C&C財団 スピントロニクス技術に関する先駆的先導的研究への貢献

  4. 第13回江崎玲於奈賞

    2016年11月22日 茨城県科学技術振興財団 強磁性物質におけるスピンの電気的制御と素子応用に関する先駆的研究

  5. 応用物理学会化合物半導体エレクトロニクス業績賞(赤﨑勇賞)

    2015年3月11日 応用物理学会 強磁性化合物半導体の創成とスピントロニクスの先導的研究

  6. American Physical Society (APS)フェロー

    2013年3月

  7. IEEE David Sarnoff Award

    2012年5月9日 Institute of Electrical and Electronic Engineers (IEEE) For seminal contributions and leadership in bridging semiconductor electronics with magnetism and spintronics

  8. 第12回応用物理学会業績賞(研究業績)

    2012年3月15日 応用物理学会 半導体スピントロニクスにおける先駆的研究

  9. Thomson Reuters Citation Laureates

    2011年9月21日 Thomson Reuters

  10. IEEE Magnetics Society Distinguished Lecturer for 2009

    2008年10月13日 IEEE Magnetics Society

  11. 応用物理学会フェロー

    2007年8月 半導体を中心としたスピントロニクスに関する研究

  12. 中国科学院半導体研究所 Honorary Professor

    2006年10月12日 Institute of Semiconductors, Chinese Academy of Sciences

  13. The 2005 Agilent Technologies Europhysics Prize

    2005年7月12日 European Physical Society

  14. 東北大学総長特別賞

    2005年6月29日 東北大学

  15. 日本学士院賞

    2005年6月13日 日本学士院 半導体ナノ構造による電子の量子制御と強磁性の研究

  16. Fellow (IOP)

    2004年9月1日 The Institute of Physics (IOP)

  17. 国際純粋応用物理学連合磁気学賞

    2003年7月27日 International Union of Pure and Applied Physics 新しい強磁性半導体の開発

  18. 日本IBM科学賞

    1998年11月 日本IBM株式会社

  19. 第41回(2019年度)応用物理学会優秀論文賞

    2019年9月 応用物理学会 Analogue spin-orbit torque device for artificial-neural-network-based associative memory operation

  20. 平成29年度科学技術分野の文部科学大臣表彰

    2017年4月19日 文部科学省 STT-RAM大容量化回路技術に関する先駆的研究開発

  21. DPS Paper Award

    2016年11月21日 International Symposium on Dry Process Plasma process induced physical damages on multilayered magnetic films for magnetic domain wall motion

  22. 東北大学ディスティングイッシュトプロフェッサー

    2011年10月1日 東北大学

  23. 東北大学ディスティングイッシュトプロフェッサー

    2008年4月1日 東北大学

︎全件表示 ︎最初の5件までを表示

論文 577

  1. Double-Free-Layer Stochastic Magnetic Tunnel Junctions with Synthetic Antiferromagnets

    Kemal Selcuk, Shun Kanai, Rikuto Ota, Hideo Ohno, Shunsuke Fukami, Kerem Y. Camsari

    arXiv 2311.06642 2023年11月11日

    DOI: 10.48550/arXiv.2311.06642  

  2. Handedness anomaly in a non-collinear antiferromagnet under spin–orbit torque

    Ju-Young Yoon, Pengxiang Zhang, Chung-Tao Chou, Yutaro Takeuchi, Tomohiro Uchimura, Justin T. Hou, Jiahao Han, Shun Kanai, Hideo Ohno, Shunsuke Fukami, Luqiao Liu

    Nature Materials 22 (9) 1106-1113 2023年8月3日

    出版者・発行元:Springer Science and Business Media LLC

    DOI: 10.1038/s41563-023-01620-2  

    ISSN:1476-1122

    eISSN:1476-4660

  3. Nonlinear conductance in nanoscale CoFeB/MgO magnetic tunnel junctions with perpendicular easy axis 査読有り

    Motoya Shinozaki, Junta Igarashi, Shuichi Iwakiri, Takahito Kitada, Keisuke Hayakawa, Butsurin Jinnai, Tomohiro Otsuka, Shunsuke Fukami, Kensuke Kobayashi, Hideo Ohno

    Physical Review B 107 (9) 2023年3月30日

    DOI: 10.1103/PhysRevB.107.094436  

    ISSN:2469-9950

    eISSN:2469-9969

    詳細を見る 詳細を閉じる

    Magnetic tunnel junctions (MTJ) exhibit spin-dependent conductance that governs their performance in various applications. While the transport characteristics are known to show nonlinearity, their behavior and underlying mechanism have not yet understood well. Here we investigate nonlinear conductance at a low bias regime in nanoscale MTJs with a perpendicular magnetic easy axis and various junction sizes, by measuring current-voltage (IV) characteristics and ferromagnetic resonance. We evaluate IV properties as I=G1V+G2V2+G3V3 under various external magnetic fields and examine the correlations among G1, G2, and G3. We find that G2 increases with decrease in the junction size, G3 has a negative correlation with G1, and δG3/δG1(=k) has a positive correlation with G2. These results can be explained by considering the spin flip during the tunneling and a modulation of material properties at the device edge caused by the nanofabrication process. Ferromagnetic resonance measurements support the physical picture suggested by the transport measurements. Our findings shed light on the mechanism of electron transport in nanoscale MTJs and facilitate the establishment of a rigorous model describing their nonlinear conductance.

  4. Thermal stability of non-collinear antiferromagnetic Mn<inf>3</inf>Sn nanodot

    Yuma Sato, Yutaro Takeuchi, Yuta Yamane, Ju Young Yoon, Shun Kanai, Jun'Ichi Ieda, Hideo Ohno, Shunsuke Fukami

    Applied Physics Letters 122 (12) 2023年3月20日

    DOI: 10.1063/5.0135709  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    D019-Mn3Sn, an antiferromagnet having a non-collinear spin structure in a kagome lattice, has attracted great attention owing to various intriguing properties such as large anomalous Hall effect. Stability of a magnetic state against thermal fluctuation, characterized in general by the thermal stability factor Δ, has been well studied in ferromagnetic systems but not for antiferromagnets. Here, we study Δ of the antiferromagnetic Mn3Sn nanodots as a function of their diameter D. To quantify Δ, we measure the switching probability as a function of the pulse-field amplitude and analyze the results based on a model taking account of two and sixfold magnetic anisotropies in the kagome plane. We observe no significant change in Δ down to D = 300 nm below which it decreases with D. The obtained D dependence is well explained by a single-domain and nucleation-mediated reversal models. These findings provide a basis to understand the thermal fluctuation and reversal mechanism of antiferromagnets for device applications.

  5. A full-stack view of probabilistic computing with p-bits: devices, architectures and algorithms

    Shuvro Chowdhury, Andrea Grimaldi, Navid Anjum Aadit, Shaila Niazi, Masoud Mohseni, Shun Kanai, Hideo Ohno, Shunsuke Fukami, Luke Theogarajan, Giovanni Finocchio, Supriyo Datta, Kerem Y. Camsari

    IEEE Journal on Exploratory Solid-State Computational Devices and Circuits 2023年

    DOI: 10.1109/JXCDC.2023.3256981  

    eISSN:2329-9231

    詳細を見る 詳細を閉じる

    The transistor celebrated its 75th birthday in 2022. The continued scaling of the transistor defined by Moore&#x2019;s Law continues, albeit at a slower pace. Meanwhile, computing demands and energy consumption required by modern artificial intelligence (AI) algorithms have skyrocketed. As an alternative to scaling transistors for general-purpose computing, the integration of transistors with unconventional technologies has emerged as a promising path for domain-specific computing. In this article, we provide a full-stack review of probabilistic computing with p-bits as a representative example of the energy-efficient and domain-specific computing movement. We argue that p-bits could be used to build energy-efficient probabilistic systems, tailored for probabilistic algorithms and applications. From hardware, architecture, and algorithmic perspectives, we outline the main applications of probabilistic computers ranging from probabilistic machine learning and AI to combinatorial optimization and quantum simulation. Combining emerging nanodevices with the existing CMOS ecosystem will lead to probabilistic computers with orders of magnitude improvements in energy efficiency and probabilistic sampling, potentially unlocking previously unexplored regimes for powerful probabilistic algorithms.

  6. Local bifurcation with spin-transfer torque in superparamagnetic tunnel junctions

    Takuya Funatsu, Shun Kanai, Jun’ichi Ieda, Shunsuke Fukami, Hideo Ohno

    Nature Communications 13 (1) 2022年12月

    DOI: 10.1038/s41467-022-31788-1  

    eISSN:2041-1723

    詳細を見る 詳細を閉じる

    Modulation of the energy landscape by external perturbations governs various thermally-activated phenomena, described by the Arrhenius law. Thermal fluctuation of nanoscale magnetic tunnel junctions with spin-transfer torque (STT) shows promise for unconventional computing, whereas its rigorous representation, based on the Néel-Arrhenius law, has been controversial. In particular, the exponents for thermally-activated switching rate therein, have been inaccessible with conventional thermally-stable nanomagnets with decade-long retention time. Here we approach the Néel-Arrhenius law with STT utilising superparamagnetic tunnel junctions that have high sensitivity to external perturbations and determine the exponents through several independent measurements including homodyne-detected ferromagnetic resonance, nanosecond STT switching, and random telegraph noise. Furthermore, we show that the results are comprehensively described by a concept of local bifurcation observed in various physical systems. The findings demonstrate the capability of superparamagnetic tunnel junction as a useful tester for statistical physics as well as sophisticated engineering of probabilistic computing hardware with a rigorous mathematical foundation.

  7. External-Field-Robust Stochastic Magnetic Tunnel Junctions Using a Free Layer with Synthetic Antiferromagnetic Coupling

    Keito Kobayashi, Keisuke Hayakawa, Junta Igarashi, William A. Borders, Shun Kanai, Hideo Ohno, Shunsuke Fukami

    Physical Review Applied 18 (5) 2022年11月29日

    出版者・発行元:American Physical Society (APS)

    DOI: 10.1103/physrevapplied.18.054085  

    eISSN:2331-7019

  8. Generalized scaling of spin qubit coherence in over 12,000 host materials

    Shun Kanai, F. Joseph Heremans, Hosung Seo, Gary Wolfowicz, Christopher P. Anderson, Sean E. Sullivan, Mykyta Onizhuk, Giulia Galli, David D. Awschalom, Hideo Ohno

    Proceedings of the National Academy of Sciences 119 (15) 2022年4月12日

    出版者・発行元:Proceedings of the National Academy of Sciences

    DOI: 10.1073/pnas.2121808119  

    ISSN:0027-8424

    eISSN:1091-6490

    詳細を見る 詳細を閉じる

    Significance Atomic defects in solid-state materials are promising candidates as quantum bits, or qubits. New materials are actively being investigated as hosts for new defect qubits; however, there are no unifying guidelines that can quantitatively predict qubit performance in a new material. One of the most critical property of qubits is their quantum coherence. While cluster correlation expansion (CCE) techniques are useful to simulate the coherence of electron spins in defects, they are computationally expensive to investigate broad classes of stable materials. Using CCE simulations, we reveal a general scaling relation between the electron spin coherence time and the properties of qubit host materials that enables rapid and quantitative exploration of new materials hosting spin defects.

  9. Observation of domain structure in non-collinear antiferromagnetic Mn3Sn thin films by magneto-optical Kerr effect

    Tomohiro Uchimura, Ju-Young Yoon, Yuma Sato, Yutaro Takeuchi, Shun Kanai, Ryota Takechi, Keisuke Kishi, Yuta Yamane, Samik DuttaGupta, Jun'ichi Ieda, Hideo Ohno, Shunsuke Fukami

    APPLIED PHYSICS LETTERS 120 (17) 2022年4月

    出版者・発行元:AIP Publishing

    DOI: 10.1063/5.0089355  

    ISSN:0003-6951

    eISSN:1077-3118

    詳細を見る 詳細を閉じる

    We perform hysteresis-loop measurement and domain imaging for ( 1 (1) over bar 00 )-oriented D0(19)-Mn3+xSn1-x (-0.11 <= x <= 0.14) thin films using the magneto-optical Kerr effect (MOKE) and compare it with the anomalous Hall effect (AHE) measurement. We obtain a large Kerr rotation angle of 10 mdeg, comparable with bulk single-crystal Mn3Sn. The composition x dependence of AHE and MOKE shows a similar trend, suggesting the same origin, i.e., the non-vanishing Berry curvature in the momentum space. Magnetic domain observation at the saturated state shows that x dependence of AHE and MOKE is explained by the amount of the reversible area that crucially depends on the crystalline structure of the film. Furthermore, in-depth observation of the reversal process reveals that the reversal starts with nucleation of sub-micrometer-scale domains dispersed in the film, followed by domain expansion, where the domain wall preferentially propagates along the [ 11(2) over bar 0 ] direction. Our study provides a basic understanding of the spatial evolution of the reversal of the chiral-spin structure in non-collinear antiferromagnetic thin films.& nbsp;Published under an exclusive license by AIP Publishing.

  10. Nanometer-thin L10-MnAl film with B2-CoAl underlayer for high-speed and high-density STT-MRAM: Structure and magnetic properties

    Yutaro Takeuchi, Ryotaro Okuda, Junta Igarashi, Butsurin Jinnai, Takaharu Saino, Shoji Ikeda, Shunsuke Fukami, Hideo Ohno

    Applied Physics Letters 120 (5) 2022年1月31日

    出版者・発行元:AIP Publishing

    DOI: 10.1063/5.0077874  

    ISSN:0003-6951

    eISSN:1077-3118

    詳細を見る 詳細を閉じる

    The material development of magnetic tunnel junction with a perpendicular easy axis is in great demand to advance spin-transfer torque magnetoresistive random access memory (STT-MRAM) technologies. To realize high-speed and high-density STT-MRAM, a thin-film magnetic material with large perpendicular anisotropy and small spontaneous magnetization has great potential. Here, we develop a thin-film deposition technique for a-few-nanometer-thin L10-MnAl by sputtering and investigate its structure and magnetic properties. Utilization of the B2-CoAl buffer layer allows us to grow L10-MnAl with a large crystalline anisotropy of 8.5 × 105 J/m3, the small spontaneous magnetization of 0.62 T, and the tolerance for 400 °C annealing even at the MnAl thickness of 2 nm. We calculate the device properties based on the obtained material parameters and find that high retention properties, high-speed switching, and low write-error rate can be obtained at the single-digit-nm region, which are not readily achieved by conventional material systems. The results show the potential of L10-MnAl for high-density and high-speed STT-MRAM.

  11. Experimental evaluation of simulated quantum annealing with MTJ-augmented p-bits

    Andrea Grimaldi, Kemal Selcuk, Navid Anjum Aadit, Keito Kobayashi, Qixuan Cao, Shuvro Chowdhury, Giovanni Finocchio, Shun Kanai, Hideo Ohno, Shunsuke Fukami, Kerem Y. Camsari

    Technical Digest - International Electron Devices Meeting, IEDM 2022-December 2241-2244 2022年

    DOI: 10.1109/IEDM45625.2022.10019530  

    ISSN:0163-1918

    詳細を見る 詳細を閉じる

    The slowing down of Moore's Law has created an exciting new era of electronics, leading to the emergence of various types of CMOS+X devices and architectures. Here, we present the first experimental demonstration of a probabilistic computer where a stochastic magnetic tunnel junction (sMTJ) drives a powerful CMOS-based field programmable gate array (FPGA) in a heterogeneous compute fabric. We use our machine to experimentally evaluate the simulated quantum annealing (SQA) algorithm, known to closely mimic the behavior of D-Wave's quantum annealers which implement the transverse field Ising model (TFIM). Our machine matches the exact solution of the TFIM where p-bits in the FPGA are asynchronously driven by the stochastic dynamics of a magnetic tunnel junction. To compare the performance of SQA against classical annealing (CA) in hard combinatorial optimization at large scale, we also design a fully digital emulator of our asynchronous architecture in the FPGA. Our digital system uses 7,085 p-bits to factor up to 26-bit integers and is about 10X faster than optimized Tensor (TPU) and Graphics Processing Units (GPU) at lower power. Surprisingly, we find that the additional replica networks necessary for SQA do not lead to appreciably better performance over an optimized CA that is using the same computational resources. The systematic evaluation of the SQA algorithm we present will be relevant for other types of accelerators, such as photonic or electronic Ising machines and the integrated scaling of our CMOS + sMTJ architecture could lead to orders of magnitude further improvements over TPU and GPUs, according to experimentally-validated projections.

  12. Hardware-Aware In Situ Learning Based on Stochastic Magnetic Tunnel Junctions

    Jan Kaiser, William A. Borders, Kerem Y. Camsari, Shunsuke Fukami, Hideo Ohno, Supriyo Datta

    Physical Review Applied 17 (1) 2022年1月

    出版者・発行元:AMER PHYSICAL SOC

    DOI: 10.1103/PhysRevApplied.17.014016  

    ISSN:2331-7019

    eISSN:2331-7019

    詳細を見る 詳細を閉じる

    One of the big challenges of current electronics is the design and implementation of hardware neural networks that perform fast and energy-efficient machine learning. Spintronics is a promising catalyst for this field with the capabilities of nanosecond operation and compatibility with existing microelectronics. Considering large-scale, viable neuromorphic systems however, variability of device properties is a serious concern. In this paper, we show an autonomously operating circuit that performs hardware-aware machine learning utilizing probabilistic neurons built with stochastic magnetic tunnel junctions. We show that in situ learning of weights and biases in a Boltzmann machine can counter device-to-device variations and learn the probability distribution of meaningful operations such as a full adder. This scalable autonomously operating learning circuit using spintronics-based neurons could be especially of interest for standalone artificial-intelligence devices capable of fast and efficient learning at the edge.

  13. Memristive control of mutual spin Hall nano-oscillator synchronization for neuromorphic computing

    Mohammad Zahedinejad, Himanshu Fulara, Roman Khymyn, Afshin Houshang, Mykola Dvornik, Shunsuke Fukami, Shun Kanai, Hideo Ohno, Johan Åkerman

    Nature Materials 21 (1) 81-87 2022年1月

    出版者・発行元:NATURE PORTFOLIO

    DOI: 10.1038/s41563-021-01153-6  

    ISSN:1476-1122

    eISSN:1476-4660

    詳細を見る 詳細を閉じる

    Synchronization of large spin Hall nano-oscillator (SHNO) arrays is an appealing approach toward ultrafast non-conventional computing. However, interfacing to the array, tuning its individual oscillators and providing built-in memory units remain substantial challenges. Here, we address these challenges using memristive gating of W/CoFeB/MgO/AlOx-based SHNOs. In its high resistance state, the memristor modulates the perpendicular magnetic anisotropy at the CoFeB/MgO interface by the applied electric field. In its low resistance state the memristor adds or subtracts current to the SHNO drive. Both electric field and current control affect the SHNO auto-oscillation mode and frequency, allowing us to reversibly turn on/off mutual synchronization in chains of four SHNOs. We also demonstrate that two individually controlled memristors can be used to tune a four-SHNO chain into differently synchronized states. Memristor gating is therefore an efficient approach to input, tune and store the state of SHNO arrays for non-conventional computing models.

  14. Temperature dependence of intrinsic critical current in perpendicular easy axis CoFeB/MgO magnetic tunnel junctions

    Yutaro Takeuchi, Eli Christopher I. Enobio, Butsurin Jinnai, Hideo Sato, Shunsuke Fukami, Hideo Ohno

    Applied Physics Letters 119 (24) 2021年12月13日

    出版者・発行元:AIP Publishing

    DOI: 10.1063/5.0072957  

    ISSN:0003-6951

    eISSN:1077-3118

    詳細を見る 詳細を閉じる

    Current induced magnetization switching in CoFeB/MgO-based magnetic tunnel junctions (MTJs) with a perpendicular easy axis is studied above room temperature. The intrinsic critical current IC0 of the MTJs decreases with increasing temperature. From a vector-network-analyzer ferromagnetic resonance measurement with a heating system, temperature dependence of magnetic anisotropy and damping constant is evaluated. We find that the reduction of IC0 at elevated temperature is mainly due to a decrease in magnetic anisotropy. A slight increase in the damping constant with temperature rise is also observed, consistent with the mechanism considering electron scattering through the inter-band transition.

  15. Sigmoidal curves of stochastic magnetic tunnel junctions with perpendicular easy axis

    Keito Kobayashi, William A. Borders, Shun Kanai, Keisuke Hayakawa, Hideo Ohno, Shunsuke Fukami

    Applied Physics Letters 119 (13) 2021年9月27日

    出版者・発行元:AIP Publishing

    DOI: 10.1063/5.0065919  

    ISSN:0003-6951

    eISSN:1077-3118

    詳細を見る 詳細を閉じる

    We investigate the physical mechanism governing the sigmoid-like time-averaged response of stochastic magnetic tunnel junctions (s-MTJ), which is a promising building block for probabilistic computers. We measure the time-averaged resistance of perpendicular easy-axis s-MTJs with various free-layer thicknesses and diameters as functions of an external magnetic field and current. The time-averaged response shows no significant dependence on the free-layer thickness, whereas significantly varies with the diameter. Based on the Néel-Arrhenius law, we derive an analytical expression of the time-averaged response against both the magnetic field and current and discuss the underlying mechanism accounting for the obtained results. We show that the experimental results are well explained by considering magnetically active and electrically active volumes of the superparamagnetic free layer in s-MTJs. The obtained finding provides an important design guideline of s-MTJs for probabilistic computers.

  16. Unconventional Hall effect and its variation with Co-doping in van der Waals Fe3GeTe2 査読有り

    Rajeswari Roy Chowdhury, Samik DuttaGupta, Chandan Patra, Oleg A. Tretiakov, Sudarshan Sharma, Shunsuke Fukami, Hideo Ohno, Ravi Prakash Singh

    Scientific Reports 11 (1) 2021年7月

    出版者・発行元:Springer Science and Business Media LLC

    DOI: 10.1038/s41598-021-93402-6  

    eISSN:2045-2322

    詳細を見る 詳細を閉じる

    <title>Abstract</title>Two-dimensional (2D) van der Waals (vdW) magnetic materials have attracted a lot of attention owing to the stabilization of long range magnetic order down to atomic dimensions, and the prospect of novel spintronic devices with unique functionalities. The clarification of the magnetoresistive properties and its correlation to the underlying magnetic configurations is essential for 2D vdW-based spintronic devices. Here, the effect of Co-doping on the magnetic and magnetotransport properties of Fe<sub>3</sub>GeTe<sub>2</sub> have been investigated. Magnetotransport measurements reveal an unusual Hall effect behavior whose strength was considerably modified by Co-doping and attributed to arise from the underlying complicated spin textures. The present results provide a clue to tailoring of the underlying interactions necessary for the realization of a variety of unconventional spin textures for 2D vdW FM-based spintronics.

  17. Influence of domain wall anisotropy on the current-induced hysteresis loop shift for quantification of the Dzyaloshinskii-Moriya interaction 査読有り

    Takaaki Dohi, Shunsuke Fukami, Hideo Ohno

    Physical Review B 103 (21) 2021年6月19日

    出版者・発行元:American Physical Society (APS)

    DOI: 10.1103/physrevb.103.214450  

    ISSN:2469-9950

    eISSN:2469-9969

    詳細を見る 詳細を閉じる

    Using several material systems with various magnitudes of the interfacial Dzyaloshinskii-Moriya interaction (DMI), we elucidate a critical influence of domain wall (DW) anisotropy on the current-induced hysteresis loop shift scheme widely employed to determine the magnitude of the Dzyaloshinskii-Moriya effective field (HDMI). Taking into account the DW anisotropy in the analysis of the hysteresis loop shift, which has not been included in the original model [Phys. Rev. B 93, 144409 (2016)10.1103/PhysRevB.93.144409], we show that it provides quantitative agreement of HDMI with that determined from an asymmetric bubble expansion technique for small DMI material systems. For large DMI systems, the DW anisotropy gives rise to nonlinearity in the response of spin-orbit torque efficiency to the in-plane magnetic field, from which HDMI can be determined. The consequence of the directions of DW motion in the Hall device on the current-induced shift of the hysteresis loop is also discussed. The present findings deliver important insights for reliable evaluation of DMI, which are of significance in spintronics with chiral objects.

  18. Correlation of anomalous Hall effect with structural parameters and magnetic ordering in Mn3+xSn1−x thin films 査読有り

    Ju-Young Yoon, Yutaro Takeuchi, Samik DuttaGupta, Yuta Yamane, Shun Kanai, Jun’ichi Ieda, Hideo Ohno, Shunsuke Fukami

    AIP Advances 11 (6) 065318-065318 2021年6月14日

    出版者・発行元:AIP Publishing

    DOI: 10.1063/5.0043192  

    eISSN:2158-3226

    詳細を見る 詳細を閉じる

    We investigate the relationship between structural parameters, magnetic ordering, and the anomalous Hall effect (AHE) of Mn3+xSn1-x (-0.42 ≤ x ≤ +0.23) thin films annealed at various temperatures Ta. The crystal structure changes with x and Ta, and at Ta ≥ 500 °C near the stoichiometric composition (-0.08 ≤ x ≤ +0.04), epitaxial single-phase D019-Mn3+xSn1-x(101̄0) is obtained. At room temperature, a larger AHE is obtained when the single-phase epitaxial Mn3Sn with the lattice constant closer to that of bulk is formed. The temperature dependence of the AHE shows different behaviors depending on Ta and can be explained by considering the variation of magnetic ordering. A close inspection into the temperature and composition dependence suggests a variation of magnetic phase transition temperature with composition and/or a possible correlation between the AHE and Fermi level position with respect to the Weyl points. Our comprehensive study on (101̄0)-oriented epitaxial Mn3Sn thin films would provide the basis for utilizing the unique functionalities of non-collinear antiferromagnetic materials.

  19. Chiral-spin rotation of non-collinear antiferromagnet by spin–orbit torque 査読有り

    Yutaro Takeuchi, Yuta Yamane, Ju-Young Yoon, Ryuichi Itoh, Butsurin Jinnai, Shun Kanai, Jun’ichi Ieda, Shunsuke Fukami, Hideo Ohno

    Nature Materials 20 (10) 1364-+ 2021年5月13日

    出版者・発行元:Springer Science and Business Media LLC

    DOI: 10.1038/s41563-021-01005-3  

    ISSN:1476-1122

    eISSN:1476-4660

    詳細を見る 詳細を閉じる

    Electrical manipulation of magnetic materials by current-induced spin torque constitutes the basis of spintronics. Here, we show an unconventional response to spin-orbit torque of a non-collinear antiferromagnet Mn3Sn, which has attracted attention owing to its large anomalous Hall effect despite a vanishingly small net magnetization. In epitaxial heavy-metal/Mn3Sn heterostructures, we observe a characteristic fluctuation of the Hall resistance under the application of electric current. This observation is explained by a rotation of the chiral-spin structure of Mn3Sn driven by spin-orbit torque. We find that the variation of the magnitude of anomalous Hall effect fluctuation with sample size correlates with the number of magnetic domains in the Mn3Sn layer. In addition, the dependence of the critical current on Mn3Sn layer thickness reveals that spin-orbit torque generated by small current densities, below 20 MA cm(-2), effectively acts on the chiral-spin structure even in Mn3Sn layers that are thicker than 20 nm. The results provide additional pathways for electrical manipulation of magnetic materials.Current-induced rotation in epitaxial films of the non-collinear antiferromagnet Mn3Sn is investigated.

  20. Electrically connected spin-torque oscillators array for 2.4 GHz WiFi band transmission and energy harvesting 査読有り

    Raghav Sharma, Rahul Mishra, Tung Ngo, Yong-Xin Guo, Shunsuke Fukami, Hideo Sato, Hideo Ohno, Hyunsoo Yang

    Nature Communications 12 (1) 2021年5月

    出版者・発行元:Springer Science and Business Media LLC

    DOI: 10.1038/s41467-021-23181-1  

    ISSN:2041-1723

    eISSN:2041-1723

    詳細を見る 詳細を閉じる

    <title>Abstract</title>The mutual synchronization of spin-torque oscillators (STOs) is critical for communication, energy harvesting and neuromorphic applications. Short range magnetic coupling-based synchronization has spatial restrictions (few µm), whereas the long-range electrical synchronization using vortex STOs has limited frequency responses in hundreds MHz (&lt;500 MHz), restricting them for on-chip GHz-range applications. Here, we demonstrate electrical synchronization of four non-vortex uniformly-magnetized STOs using a single common current source in both parallel and series configurations at 2.4 GHz band, resolving the frequency-area quandary for designing STO based on-chip communication systems. Under injection locking, synchronized STOs demonstrate an excellent time-domain stability and substantially improved phase noise performance. By integrating the electrically connected eight STOs, we demonstrate the battery-free energy-harvesting system by utilizing the wireless radio-frequency energy to power electronic devices such as LEDs. Our results highlight the significance of electrical topology (series vs. parallel) while designing an on-chip STOs system.

  21. Double-Free-Layer Magnetic Tunnel Junctions for Probabilistic Bits 査読有り

    Kerem Y. Camsari, Mustafa Mert Torunbalci, William A. Borders, Hideo Ohno, Shunsuke Fukami

    Physical Review Applied 15 (4) 2021年4月29日

    出版者・発行元:American Physical Society (APS)

    DOI: 10.1103/physrevapplied.15.044049  

    ISSN:2331-7019

    eISSN:2331-7019

    詳細を見る 詳細を閉じる

    Naturally random devices that exploit ambient thermal noise have recently attracted attention as hardware primitives for accelerating probabilistic computing applications. One such approach is to use a low barrier nanomagnet as the free layer of a magnetic tunnel junction (MTJ), the magnetic fluctuations of which are converted to resistance fluctuations in the presence of a stable fixed layer. Here, we propose and theoretically analyze a MTJ with no fixed layers but two free layers that are circularly shaped disk magnets. We use an experimentally benchmarked model that accounts for finite-temperature magnetization dynamics, bias-dependent charge, and spin-polarized currents as well as the dipolar coupling between the free layers. We obtain analytical results for statistical averages of fluctuations that are in good agreement with the numerical model. We find that the free layers with low diameters fluctuate to randomize the resistance of the MTJ in an approximately bias-independent manner. We show how such MTJs can be used to build a binary stochastic neuron (or ap-bit) in hardware. Unlike earlier stochastic MTJs that need to operate at a specific bias point to produce random fluctuations, the proposed design can be random for a wide range of bias values, independent of spin-transfer-torque pinning. Moreover, in the absence of a carefully optimized stabled fixed layer, the symmetric double-free-layer stack can be manufactured using present-day magnetoresistive random-access memory (MRAM) technology by minimal changes to the fabrication process. Such devices can be used as hardware accelerators in energy-efficient computing schemes that require a large throughput of tunably random bits.

  22. Dual-Port SOT-MRAM Achieving 90-MHz Read and 60-MHz Write Operations under Field-Assistance-Free Condition

    Masanori Natsui, Akira Tamakoshi, Hiroaki Honjo, Toshinari Watanabe, Takashi Nasuno, Chaoliang Zhang, Takaho Tanigawa, Hirofumi Inoue, Masaaki Niwa, Toru Yoshiduka, Yasuo Noguchi, Mitsuo Yasuhira, Yitao Ma, Hui Shen, Shunsuke Fukami, Hideo Sato, Shoji Ikeda, Hideo Ohno, Tetsuo Endoh, Takahiro Hanyu

    IEEE Journal of Solid-State Circuits 56 (4) 1116-1128 2021年4月

    DOI: 10.1109/JSSC.2020.3039800  

    ISSN:0018-9200

    eISSN:1558-173X

    詳細を見る 詳細を閉じる

    The development of new functional memories using emerging nonvolatile devices has been widely investigated. Spin-transfer torque magnetoresistive random access memory (STT-MRAM) has become new technology platform to overcome the issue in power consumption of logic for the application from IoT to AI; however, STT-MRAM has a tradeoff relationship between endurance, retention, and access time. This is because the MTJ device used in STT-MRAM is a two-terminal device, and excessive read current for high-speed readout can cause unexpected data writing, or so-called read disturbance. In order to meet the demand for the realization of high-speed nonvolatile memory, the development of new memories based on innovative circuit, device, and integration process is required. In this article, we demonstrate an SOT-MRAM, a nonvolatile memory using MTJ devices with spin-orbit-torque (SOT) switching that have a read-disturbance-free characteristic. The SOT-MRAM fabricated using a 55-nm CMOS process is implemented in a dual-port configuration utilizing a three-terminal structure of the device for realizing a wide bandwidth applicable to high-speed applications. In addition, a read-energy reduction technique called a self-termination scheme is also implemented. Through the measurement results of the fabricated prototype chip, we will demonstrate the proposed SOT-MRAM achieves 60-MHz write and 90-MHz read operations with 1.2-V supply voltage under a magnetic-field-free condition.

  23. Erratum: Coherent magnetization reversal of a cylindrical nanomagnet in shape-anisotropy magnetic tunnel junctions (Appl. Phys. Lett. (2021) 118 (082404) DOI: 10.1063/5.0043058)

    Butsurin Jinnai, Junta Igarashi, Kyota Watanabe, Eli Christopher I. Enobio, Shunsuke Fukami, Hideo Ohno

    Applied Physics Letters 118 (13) 2021年3月29日

    DOI: 10.1063/5.0050431  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    In the original article,1 “sin” and “cos” were mistakenly swapped in Eq. (2). The correct formof Eq. (2) should be (Formula Presented).The conversion from Fig. 4(c) to Fig. 4(d) in the original article was based on the correct form of Eq. (2), and thus, the conclusions of the paper are not affected by this erratum.

  24. Nanosecond Random Telegraph Noise in In-Plane Magnetic Tunnel Junctions 査読有り

    K. Hayakawa, S. Kanai, T. Funatsu, J. Igarashi, B. Jinnai, W. A. Borders, H. Ohno, S. Fukami

    Physical Review Letters 126 (11) 2021年3月17日

    出版者・発行元:American Physical Society (APS)

    DOI: 10.1103/physrevlett.126.117202  

    ISSN:0031-9007

    eISSN:1079-7114

    詳細を見る 詳細を閉じる

    We study the timescale of random telegraph noise (RTN) of nanomagnets in stochastic magnetic tunnel junctions (MTJs). From analytical and numerical calculations based on the Landau-Lifshitz-Gilbert and the Fokker-Planck equations, we reveal mechanisms governing the relaxation time of perpendicular easy-axis MTJs (p-MTJs) and in-plane easy-axis MTJs (i-MTJs), showing that i-MTJs can be made to have faster RTN. Superparamagnetic i-MTJs with small in-plane anisotropy and sizable perpendicular effective anisotropy show relaxation times down to 8 ns at negligible bias current, which is more than 5 orders of magnitude shorter than that of typical stochastic p-MTJs and about 100 times faster than the shortest time of i-MTJs reported so far. The findings give a new insight and foundation in developing stochastic MTJs for high-performance probabilistic computers.

  25. Theory of relaxation time of stochastic nanomagnets 査読有り

    Shun Kanai, Keisuke Hayakawa, Hideo Ohno, Shunsuke Fukami

    Physical Review B 103 (9) 2021年3月17日

    出版者・発行元:American Physical Society (APS)

    DOI: 10.1103/physrevb.103.094423  

    ISSN:2469-9950

    eISSN:2469-9969

    詳細を見る 詳細を閉じる

    We theoretically investigate the switching dynamics of stochastic nanomagnets and highlight the mechanism describing their relaxation time. We reveal the distinct switching mechanisms in perpendicular and in-plane easy-axis nanomagnets, and report that the relaxation time in in-plane nanomagnets varies by a few orders of magnitude only by changing the effective perpendicular anisotropy field, even though it does not contribute to the thermal stability factor. We introduce the entropy of nanomagnets into Brown's theory [Phys. Rev. 130, 1677 (1963)10.1103/PhysRev.130.1677], and reveal that the system with faster precession as well as larger damping and smaller magnetic moment shows shorter relaxation time, and explains the different time scale of relaxation times in perpendicular- and in-plane easy-axis nanomagnets. We also show that the attempt frequency changes in both perpendicular and in-plane nanomagnets depending on the magnitude of anisotropy and show that there is a lower limit of relaxation time in perpendicular systems. This work gives physical insights of thermally activated dynamics of nanomagnets as well as its material/device design guidelines for achieving shorter relaxation times.

  26. Field-free and sub-ns magnetization switching of magnetic tunnel junctions by combining spin-transfer torque and spin–orbit torque 査読有り

    Chaoliang Zhang, Yutaro Takeuchi, Shunsuke Fukami, Hideo Ohno

    Applied Physics Letters 118 (9) 092406-092406 2021年3月1日

    出版者・発行元:AIP Publishing

    DOI: 10.1063/5.0039061  

    ISSN:0003-6951

    eISSN:1077-3118

    詳細を見る 詳細を閉じる

    We investigate the magnetization switching via a combination of spin-transfer torque (STT) and spin-orbit torque (SOT). STT and SOT are simultaneously induced by a pulsed current flowing through an in-plane easy-axis magnetic tunnel junction and an underneath Ta/W channel. SOT allows the magnetization to be switched with the sub-ns pulse down to 200 ps and STT eliminates the necessity of an external field. The switching current is much smaller than the case driven solely by STT in the short pulse regime. We also compare the threshold current between two structures having orthogonal (Type Y) and collinear (Type X) magnetic easy axes to the longitudinal direction of the channel and find that the Type X achieves smaller switching current by a factor of 1/4 at 200 ps.

  27. Coherent magnetization reversal of a cylindrical nanomagnet in shape-anisotropy magnetic tunnel junctions 査読有り

    Butsurin Jinnai, Junta Igarashi, Kyota Watanabe, Eli Christopher I. Enobio, Shunsuke Fukami, Hideo Ohno

    Applied Physics Letters 118 (8) 082404-082404 2021年2月22日

    出版者・発行元:AIP Publishing

    DOI: 10.1063/5.0043058  

    ISSN:0003-6951

    eISSN:1077-3118

    詳細を見る 詳細を閉じる

    A shape-anisotropy magnetic tunnel junction (MTJ) holds promise for its scaling into single-digit nanometers while possessing high data-retention capability. Understanding magnetization reversal mode is crucial to quantify the thermal stability factor Delta for data retention with high accuracy. Here, we study magnetization reversal mode in the shape-anisotropy MTJ with a 15-nm-thick CoFeB layer by evaluating Delta from two different methods: switching probability and retention time measurements. We find that magnetization reversal coherently proceeds in the 15-nm-thick and X/1X-nm-diameter cylindrical nanomagnet in the shape-anisotropy MTJs, in contrast to the conventional interfacial-anisotropy MTJs with a smaller thickness and larger diameter. The coherent magnetization reversal of the shape-anisotropy MTJ is also confirmed by astroid curve measurements. This study provides insight into the development of ultrasmall and high-reliability MTJ devices.

  28. Temperature dependence of the energy barrier in X/1X nm shape-anisotropy magnetic tunnel junctions 査読有り

    Junta Igarashi, Butsurin Jinnai, Valentin Desbuis, Stéphane Mangin, Shunsuke Fukami, Hideo Ohno

    Applied Physics Letters 118 (1) 012409-012409 2021年1月4日

    出版者・発行元:AIP Publishing

    DOI: 10.1063/5.0029031  

    ISSN:0003-6951

    eISSN:1077-3118

    詳細を見る 詳細を閉じる

    Shape-anisotropy magnetic tunnel junctions (MTJs) are attracting much attention as a high-performance nonvolatile spintronic device in the X/1X nm regime. In this study, we investigate an energy barrier relevant to the retention property in CoFeB/MgO-based shape-anisotropy MTJs with various diameters at high temperatures and compare it with that in conventional interfacial-anisotropy MTJs. We find that the scaling relationship between the energy barrier and the spontaneous magnetization in shape-anisotropy MTJs is well described by a model assuming the dominant contribution of shape anisotropy to the energy barrier. Also, the scaling exponent is much smaller than that for the interfacial-anisotropy MTJs, indicating that the properties of shape-anisotropy MTJs are less sensitive to the temperature. Using the experimentally determined scaling relationship, we discuss the design window of the MTJ dimensions to achieve data retention of 10years at various temperatures. This study demonstrates that the shape-anisotropy MTJ holds promise of scaling beyond 20nm for high-temperature applications.

  29. Fast Switching Down to 3.5 ns in Sub-5-nm Magnetic Tunnel Junctions Achieved by Engineering Relaxation Time

    B. Jinnai, J. Igarashi, T. Shinoda, K. Watanabe, S. Fukami, H. Ohno

    Technical Digest - International Electron Devices Meeting, IEDM 2021-December 1-4 2021年

    DOI: 10.1109/IEDM19574.2021.9720509  

    ISSN:0163-1918

    詳細を見る 詳細を閉じる

    We show fast switching down to 3.5 ns while maintaining high data retention in sub-5-nm ultra-small magnetic tunnel junctions (MTJs) using multilayered ferromagnets (FMs). We engineer characteristic relaxation time, a critical factor for fast magnetization switching, by varying the number of CoFeB/MgO interfaces in multilayered FMs. We also find that switching efficiency improves with increasing the number of CoFeB/MgO interfaces. Harnessing the advantages of both the MTJ using multilayered FMs and shape-Anisotropy MTJ, the MTJ technology can cover a wide variety of applications even at the ultra-small scale needed for advanced-node integrated technology.

  30. Magnetization processes and magnetic domain structures in Ta/CoFeB/MgO stacks 査読有り

    A.K. Dhiman, T. Dohi, W. Dobrogowski, Z. Kurant, I. Sveklo, S. Fukami, H. Ohno, A. Maziewski

    Journal of Magnetism and Magnetic Materials 529 167699-167699 2021年1月

    出版者・発行元:Elsevier BV

    DOI: 10.1016/j.jmmm.2020.167699  

    ISSN:0304-8853

    詳細を見る 詳細を閉じる

    Magnetization processes and magnetic domain structures in Ta/CoFeB/MgO stacks were studied in a series of samples with various CoFeB thicknesses d ranging from 1.24 to 1.60 nm with a step of 0.04 nm, using polar magneto-optical Kerr effect (PMOKE) magnetometry and microscopy. Thickness dependence of the magnetic anisotropy was evaluated and the first and second order anisotropy constants were quantified for each thickness. Accordingly, this dependence was deduced to result in magnetization reorientation from out-of-plane to in-plane through an easy-cone magnetization region (1.39 nm ≤ d ≤ 1.41 nm) as d was increased. PMOKE imaging of the magnetization reversal processes for stacks with out-of-plane easy axis indicated both a significant increase of the density of nucleation centers and a change in domain morphology with increasing d up to the magnetization reorientation thickness. Magnetization reversal dynamics was described by a thermal activation model consistent with a Barkhausen length of about 120 nm. The thinnest films with d = 1.24 and 1.28 nm exhibited straightened narrow stripe domains resulting from magnetic dipolar repulsion. A thorough study of narrow stripe domains was performed via direct and indirect magnetization reversal processes. The application of such structures as spin wave nano-channels could be promising.

  31. High-performance shape-anisotropy magnetic tunnel junctions down to 2.3 nm

    B. Jinnai, J. Igarashi, K. Watanabe, T. Funatsu, H. Sato, S. Fukami, H. Ohno

    Technical Digest - International Electron Devices Meeting, IEDM 2020-December 24.6.1-24.6.4 2020年12月12日

    DOI: 10.1109/IEDM13553.2020.9371972  

    ISSN:0163-1918

    詳細を見る 詳細を閉じる

    We show scalability down to 2.3 nm and high performance at single-digit nanometers of shape-anisotropy magnetic tunnel junctions (MTJs) employing a multilayered ferromagnetic structure. We reveal that a free layer with two ferromagnets separated by a MgO layer behaves as a single magnet at small device dimensions owing to magnetostatic coupling in addition to exchange coupling. This nature, in turn, leads to a notable performance increase of the MTJs in the single-digit-nm regime: thermal stability factor Δ of higher than 100 at room temperature; stable switching at temperatures of 150°C or higher; and spin-transfer torque (STT) switching with a dc voltage (intrinsic critical current IC0 of 8.5 μA) and with a 10-ns pulse below 1.0 V. Also, we find that switching efficiency (Δ/IC0) increases by a factor of three or more as the size decreases. The results show that the shape-anisotropy MTJ provides a route to high-density and high-performance STT-MRAMs in the era of the ultimate scaling.

  32. Engineering Single-Shot All-Optical Switching of Ferromagnetic Materials 国際誌 査読有り

    Junta Igarashi, Quentin Remy, Satoshi Iihama, Grégory Malinowski, Michel Hehn, Jon Gorchon, Julius Hohlfeld, Shunsuke Fukami, Hideo Ohno, Stéphane Mangin

    Nano Letters 20 (12) 8654-8660 2020年11月23日

    出版者・発行元:American Chemical Society (ACS)

    DOI: 10.1021/acs.nanolett.0c03373  

    ISSN:1530-6984

    eISSN:1530-6992

    詳細を見る 詳細を閉じる

    Since it was recently demonstrated in a spin-valve structure, magnetization reversal of a ferromagnetic layer using a single ultrashort optical pulse has attracted attention for future ultrafast and energy-efficient magnetic storage or memory devices. However, the mechanism and the role of the magnetic properties of the ferromagnet as well as the time scale of the magnetization switching are not understood. Here, we investigate single-shot all-optical magnetization switching in a GdFeCo/Cu/[Co x Ni1-x/Pt] spin-valve structure. We demonstrate that the threshold fluence for switching both the GdFeCo and the ferromagnetic layer depends on the laser pulse duration and the thickness and the Curie temperature of the ferromagnetic layer. We are able to explain most of the experimental results using a phenomenological model. This work provides a way to engineer ferromagnetic materials for energy efficient single-shot all-optical magnetization switching.

  33. Probing edge condition of nanoscale CoFeB/MgO magnetic tunnel junctions by spin-wave resonance 査読有り

    M. Shinozaki, T. Dohi, J. Igarashi, J. Llandro, S. Fukami, H. Sato, H. Ohno

    Applied Physics Letters 117 (20) 202404-202404 2020年11月16日

    出版者・発行元:AIP Publishing

    DOI: 10.1063/5.0020591  

    ISSN:0003-6951

    eISSN:1077-3118

    詳細を見る 詳細を閉じる

    We investigate spin-wave resonance in nanoscale CoFeB/MgO magnetic tunnel junctions (MTJs) with a perpendicular easy axis and various free-layer sizes. Two types of MTJs are fabricated by different process conditions, and the spin-wave resonance is measured with homodyne-detected ferromagnetic resonance. We focus on the distance between resonance frequencies of the uniform and spin-wave modes as a function of the free-layer size in order to examine the effect of the edge state of MTJs. A marked difference is observed between the two types of MTJs, and the result is consistently reproduced by a model assuming free-or fixed-edge boundary conditions with or without reduced magnetic properties near the pattern edge for each MTJ. The obtained results indicate that the edge state of nanoscale MTJs is crucially affected by the process condition, and spin-wave resonance can serve as a sensitive probe for the edge condition.

  34. Spin-orbit torque switching of an antiferromagnetic metallic heterostructure 査読有り

    Samik DuttaGupta, A. Kurenkov, Oleg A. Tretiakov, G. Krishnaswamy, G. Sala, V. Krizakova, F. Maccherozzi, S. S. Dhesi, P. Gambardella, S. Fukami, H. Ohno

    Nature Communications 11 (1) 2020年11月

    出版者・発行元:Springer Science and Business Media LLC

    DOI: 10.1038/s41467-020-19511-4  

    eISSN:2041-1723

    詳細を見る 詳細を閉じる

    <title>Abstract</title>The ability to represent information using an antiferromagnetic material is attractive for future antiferromagnetic spintronic devices. Previous studies have focussed on the utilization of antiferromagnetic materials with biaxial magnetic anisotropy for electrical manipulation. A practical realization of these antiferromagnetic devices is limited by the requirement of material-specific constraints. Here, we demonstrate current-induced switching in a polycrystalline PtMn/Pt metallic heterostructure. A comparison of electrical transport measurements in PtMn with and without the Pt layer, corroborated by x-ray imaging, reveals reversible switching of the thermally-stable antiferromagnetic Néel vector by spin-orbit torques. The presented results demonstrate the potential of polycrystalline metals for antiferromagnetic spintronics.

  35. Multidomain Memristive Switching of Pt38Mn62/[Co/Ni]n Multilayers 査読有り

    G. Krishnaswamy, A. Kurenkov, G. Sala, M. Baumgartner, V. Krizakova, C. Nistor, F. Maccherozzi, S. S. Dhesi, S. Fukami, H. Ohno, P. Gambardella

    Physical Review Applied 14 (4) 2020年10月20日

    出版者・発行元:American Physical Society (APS)

    DOI: 10.1103/physrevapplied.14.044036  

    eISSN:2331-7019

    詳細を見る 詳細を閉じる

    We investigate the mechanism of analoglike switching of Pt38Mn62/[Co/Ni] multilayers induced by spin-orbit torques. X-ray photoemission microscopy performed during magnetization reversal driven by current pulses shows that sequential switching of reproducible domain patterns can be achieved. Switching proceeds by domain-wall displacement starting from the edges of blocked ferromagnetic domains, which do not switch for either direction of the current and represent up to 24% of the total ferromagnetic area. The antiferromagnetic Pt38Mn62 layer has a granular texture, with the majority of the domains being smaller than 100 nm, whereas the ferromagnetic domains in Co/Ni are typically larger than 200 nm. The blocked domains and the granular distribution of exchange bias constrain the origin as well as the displacement of the domain walls, thus leading to highly reproducible switching patterns as a function of the applied current pulses. These measurements clarify the origin of the memristive behavior in antiferromagnet-ferromagnet structures and provide clues for further optimization of spin-orbit torque switching and memristivity in these systems.

  36. Energy Efficient Control of Ultrafast Spin Current to Induce Single Femtosecond Pulse Switching of a Ferromagnet 国際誌 査読有り

    Quentin Remy, Junta Igarashi, Satoshi Iihama, Grégory Malinowski, Michel Hehn, Jon Gorchon, Julius Hohlfeld, Shunsuke Fukami, Hideo Ohno, Stéphane Mangin

    Advanced Science 7 (23) 2001996-2001996 2020年10月

    出版者・発行元:Wiley

    DOI: 10.1002/advs.202001996  

    ISSN:2198-3844

    eISSN:2198-3844

    詳細を見る 詳細を閉じる

    New methods to induce magnetization switching in a thin ferromagnetic material using femtosecond laser pulses without the assistance of an applied external magnetic field have recently attracted a lot of interest. It has been shown that by optically triggering the reversal of the magnetization in a GdFeCo layer, the magnetization of a nearby ferromagnetic thin film can also be reversed via spin currents originating in the GdFeCo layer. Here, using a similar structure, it is shown that the magnetization reversal of the GdFeCo is not required in order to reverse the magnetization of the ferromagnetic thin film. This switching is attributed to the ultrafast spin current and can be generated by the GdFeCo demagnetization. A larger energy efficiency of the ferromagnetic layer single pulse switching is obtained for a GdFeCo with a larger Gd concentration. Those ultrafast and energy efficient switchings observed in such spintronic devices open a new path toward ultrafast and energy efficient magnetic memories.

  37. Giant voltage-controlled modulation of spin Hall nano-oscillator damping 国際誌 査読有り

    Himanshu Fulara, Mohammad Zahedinejad, Roman Khymyn, Mykola Dvornik, Shunsuke Fukami, Shun Kanai, Hideo Ohno, Johan Åkerman

    Nature Communications 11 (1) 4006-4006 2020年8月

    出版者・発行元:Springer Science and Business Media LLC

    DOI: 10.1038/s41467-020-17833-x  

    eISSN:2041-1723

    詳細を見る 詳細を閉じる

    Spin Hall nano-oscillators (SHNOs) are emerging spintronic devices for microwave signal generation and oscillator-based neuromorphic computing combining nano-scale footprint, fast and ultra-wide microwave frequency tunability, CMOS compatibility, and strong non-linear properties providing robust large-scale mutual synchronization in chains and two-dimensional arrays. While SHNOs can be tuned via magnetic fields and the drive current, neither approach is conducive to individual SHNO control in large arrays. Here, we demonstrate electrically gated W/CoFeB/MgO nano-constrictions in which the voltage-dependent perpendicular magnetic anisotropy tunes the frequency and, thanks to nano-constriction geometry, drastically modifies the spin-wave localization in the constriction region resulting in a giant 42% variation of the effective damping over four volts. As a consequence, the SHNO threshold current can be strongly tuned. Our demonstration adds key functionality to nano-constriction SHNOs and paves the way for energy-efficient control of individual oscillators in SHNO chains and arrays for neuromorphic computing.

  38. Composition dependence of spin−orbit torque in Pt1−xMnx/CoFeB heterostructures 査読有り

    K. Vihanga De Zoysa, Samik DuttaGupta, Ryuichi Itoh, Yutaro Takeuchi, Hideo Ohno, Shunsuke Fukami

    Applied Physics Letters 117 (1) 012402-012402 2020年7月9日

    出版者・発行元:AIP Publishing

    DOI: 10.1063/5.0011448  

    ISSN:0003-6951

    eISSN:1077-3118

    詳細を見る 詳細を閉じる

    We investigate spin-orbit torques (SOTs) in heterostructures with Pt1-xMnx alloy and CoFeB as a function of Mn composition (x) by using an extended harmonic Hall measurement. Slonczewski-like and field-like SOT efficiencies (xiSL andxiFL) show non-monotonic variation and a different trend with respect to x, and considerably largexiSL up to 0.21 is obtained at x=0.20. Compared to the x dependence of longitudinal resistivity, the Slonczewski-like SOT in the low x region is mainly attributed to an intrinsic spin-Hall mechanism, whereas a non-monotonic variation in the higher x region suggests the presence of additional factors. The present findings deliver useful clues to understand the physics behind SOT generation in antiferromagnetic heterostructures and offer a route to realize efficient devices.

  39. Neuromorphic computing with antiferromagnetic spintronics 査読有り

    Aleksandr Kurenkov, Shunsuke Fukami, Hideo Ohno

    Journal of Applied Physics 128 (1) 010902-010902 2020年7月7日

    出版者・発行元:AIP Publishing

    DOI: 10.1063/5.0009482  

    ISSN:0021-8979

    eISSN:1089-7550

    詳細を見る 詳細を閉じる

    While artificial intelligence, capable of readily addressing cognitive tasks, has transformed technologies and daily lives, there remains a huge gap with biological systems in terms of performance per energy unit. Neuromorphic computing, in which hardware with alternative architectures, circuits, devices, and/or materials is explored, is expected to reduce the gap. Antiferromagnetic spintronics could offer a promising platform for this scheme. Active functionalities of antiferromagnetic systems have been demonstrated recently and several works indicated their potential for biologically inspired computing. In this perspective, we look through the prism of these works and discuss prospects and challenges of antiferromagnetic spintronics for neuromorphic computing. Overview and discussion are given on non-spiking artificial neural networks, spiking neural networks, and reservoir computing.

  40. Current distribution in metallic multilayers from resistance measurements 査読有り

    Ondřej Stejskal, André Thiaville, Jaroslav Hamrle, Shunsuke Fukami, Hideo Ohno

    Physical Review B 101 (23) 2020年6月24日

    出版者・発行元:American Physical Society (APS)

    DOI: 10.1103/physrevb.101.235437  

    ISSN:2469-9950

    eISSN:2469-9969

    詳細を見る 詳細を閉じる

    The in-plane current profile within multilayers of the generic structure Ta/Pt/(CoNi)/Pt/Ta is investigated. A large set of samples where the thickness of each layer was systematically varied was grown, followed by the measurement of the sheet resistance of each sample. The data are analyzed by a series of increasingly elaborate models, from a macroscopic engineering approach to mesoscopic transport theory. Non-negligible variations of the estimated repartition of current between the layers are found. The importance of having additional structural data is highlighted.

  41. Probabilistic computing based on spintronics technology 査読有り

    Shunsuke Fukami, William A. Borders, Ahmed Z. Pervaiz, Kerem Y. Camsari, Supriyo Datta, Hideo Ohno

    2020 IEEE Silicon Nanoelectronics Workshop (SNW) 2020年6月

    出版者・発行元:IEEE

    DOI: 10.1109/snw50361.2020.9131622  

  42. Visualizing magnetic structure in 3d nanoscale ni-fe gyroid networks 査読有り

    Justin Llandro, David M. Love, András Kovács, Jan Caron, Kunal N. Vyas, Attila Kákay, Ruslan Salikhov, Kilian Lenz, Jürgen Fassbender, Maik R.J. Scherer, Christian Cimorra, Ullrich Steiner, Crispin H.W. Barnes, Rafal E. Dunin-Borkowski, Shunsuke Fukami, Hideo Ohno

    Nano Letters 20 (5) 3642-3650 2020年5月13日

    DOI: 10.1021/acs.nanolett.0c00578  

    ISSN:1530-6984

    eISSN:1530-6992

    詳細を見る 詳細を閉じる

    © 2020 American Chemical Society. Arrays of interacting 2D nanomagnets display unprecedented electromagnetic properties via collective effects, demonstrated in artificial spin ices and magnonic crystals. Progress toward 3D magnetic metamaterials is hampered by two challenges: fabricating 3D structures near intrinsic magnetic length scales (sub-100 nm) and visualizing their magnetic configurations. Here, we fabricate and measure nanoscale magnetic gyroids, periodic chiral networks comprising nanowire-like struts forming three-connected vertices. Via block copolymer templating, we produce Ni75Fe25 single-gyroid and double-gyroid (an inversion pair of single-gyroids) nanostructures with a 42 nm unit cell and 11 nm diameter struts, comparable to the exchange length in Ni-Fe. We visualize their magnetization distributions via off-axis electron holography with nanometer spatial resolution and interpret the patterns using finite-element micromagnetic simulations. Our results suggest an intricate, frustrated remanent state which is ferromagnetic but without a unique equilibrium configuration, opening new possibilities for collective phenomena in magnetism, including 3D magnonic crystals and unconventional computing.

  43. Scaling magnetic tunnel junction down to single-digit nanometers—Challenges and prospects 査読有り

    Butsurin Jinnai, Kyota Watanabe, Shunsuke Fukami, Hideo Ohno

    Applied Physics Letters 116 (16) 160501-160501 2020年4月20日

    出版者・発行元:AIP Publishing

    DOI: 10.1063/5.0004434  

    ISSN:0003-6951

    eISSN:1077-3118

  44. Zero-field spin precession dynamics of high-mobility two-dimensional electron gas in persistent spin helix regime 査読有り

    Jun Ishihara, Go Kitazawa, Yuya Furusho, Yuzo Ohno, Hideo Ohno, Kensuke Miyajima

    Physical Review B 101 (9) 2020年3月31日

    出版者・発行元:American Physical Society ({APS})

    DOI: 10.1103/PhysRevB.101.094438  

  45. Stack structure and temperature dependence of spin-orbit torques in heterostructures with antiferromagnetic PtMn 査読有り

    Ryuichi Itoh, Yutaro Takeuchi, Samik DuttaGupta, Shunsuke Fukami, Hideo Ohno

    Applied Physics Letters 115 (24) 242404-242404 2019年12月11日

    出版者・発行元:AIP Publishing

    DOI: 10.1063/1.5129829  

    ISSN:0003-6951

    eISSN:1077-3118

    詳細を見る 詳細を閉じる

    We evaluate the stack structure and temperature dependence of the spin-orbit torques (SOTs) in metallic antiferromagnet (AFM)/ferromagnet (FM) PtMn/CoFeB heterostructures using an extended harmonic Hall measurement. We show that PtMn/CoFeB exhibits sizable Slonczewski-like and fieldlike SOTs whose magnitude is comparable to that of heterostructures with nonmagnetic heavy metals like Pt or Ta. We also find that the SOTs in our PtMn/CoFeB structures are virtually constant with temperature. The findings will offer clues to understand the generation mechanism of SOTs in AFM/FM systems and pave the way for nonvolatile memory and neuromorphic computing applications.

  46. Crystal orientation and anomalous Hall effect of sputter-deposited non-collinear antiferromagnetic Mn3Sn thin films 査読有り

    Juyoung Yoon, Yutaro Takeuchi, Ryuichi Itoh, Shun Kanai, Shunsuke Fukami, Hideo Ohno

    Applied Physics Express 13 (1) 013001-013001 2019年12月4日

    出版者・発行元:IOP Publishing

    DOI: 10.7567/1882-0786/ab5874  

    ISSN:1882-0778

    eISSN:1882-0786

    詳細を見る 詳細を閉じる

    We study a growth technique of non-collinear antiferromagnetic Mn3Sn thin films deposited by sputtering with various substrates and underlayers. The relation between their crystal structure and magnetic/transport properties is also investigated. We achieve the formation of epitaxial films with both C-plane and M-plane orientations, whose Kagome lattices are parallel and perpendicular to the plane, respectively. Transverse resistivity originating from the anomalous Hall effect shows different trends reflecting the Kagome lattice orientation of each stack. The established technique and findings offer a platform to study functional devices utilizing the unconventional physical properties of non-collinear antiferromagnets with controlled Kagome lattice orientation. (c) 2019 The Japan Society of Applied Physics

  47. Spin-orbit torque neuron and synapse devices for brainmorphic computing 査読有り

    堀尾喜彦, Aleksandr Kurenkov, 深見俊輔, 大野英男

    Proceedings of International Symposium on Nonlinear Theory and Its Applications 78-78 2019年12月

  48. Write-error rate of nanoscale magnetic tunnel junctions in the precessional regime 査読有り

    Takaharu Saino, Shun Kanai, Motoya Shinozaki, Butsurin Jinnai, Hideo Sato, Shunsuke Fukami, Hideo Ohno

    Applied Physics Letters 115 (14) 142406-142406 2019年9月30日

    出版者・発行元:AIP Publishing

    DOI: 10.1063/1.5121157  

    ISSN:0003-6951

    eISSN:1077-3118

  49. Integer factorization using stochastic magnetic tunnel junctions 国際誌 査読有り

    Borders William A, Pervaiz Ahmed Z, Fukami Shunsuke, Camsari Kerem Y, Ohno Hideo, Datta Supriyo

    NATURE 573 (7774) 390-+ 2019年9月19日

    出版者・発行元:None

    DOI: 10.1038/s41586-019-1557-9  

    ISSN:0028-0836

    eISSN:1476-4687

  50. Spin-Pumping-Free Determination of Spin-Orbit Torque Efficiency from Spin-Torque Ferromagnetic Resonance 査読有り

    Atsushi Okada, Yutaro Takeuchi, Kaito Furuya, Chaoliang Zhang, Hideo Sato, Shunsuke Fukami, Hideo Ohno

    Physical Review Applied 12 (1) 2019年7月23日

    出版者・発行元:American Physical Society (APS)

    DOI: 10.1103/physrevapplied.12.014040  

    eISSN:2331-7019

    詳細を見る 詳細を閉じる

    Spin-torque ferromagnetic resonance (ST-FMR) provides a useful tool to investigate various magnetic properties in spintronic systems, where one excites FMR by applying a rf current and detects the dc voltage generated through rectification effects. While this scheme has been used to characterize spin-orbit torques (SOTs) that have attracted much attention recently, it is known that dc voltages can also be generated by spin pumping that overlaps with the signal from the rectification effects. Here, we show a method to determine the SOT generation efficiency by ST-FMR free from spin pumping using two representative material systems, W/Co-Fe-B/MgO and Pt/Co/MgO. In addition, using the values determined by the method, which are confirmed to agree well with the results of a separately performed extended harmonic Hall measurement, we also quantify the amount of overestimation if the results obtained by a conventional ST-FMR setup are analyzed without considering the spin pumping. The present finding offers a useful insight to obtain a reliable value of SOT efficiency using ST-FMR, in particular for systems that exhibit large SOT, which accompanies large spin pumping.

  51. Evidence for Ferromagnetic Clusters in the Colossal-Magnetoresistance Material EuB6 査読有り

    Merlin Pohlit, Sahana Rößler, Yuzo Ohno, Hideo Ohno, Stephan Von Molnár, Zachary Fisk, Jens Müller, Steffen Wirth

    Physical Review Letters 120 (25) 2018年6月19日

    出版者・発行元:American Physical Society

    DOI: 10.1103/PhysRevLett.120.257201  

    ISSN:1079-7114 0031-9007

    詳細を見る 詳細を閉じる

    We combined scanning tunneling microscopy and locally resolved magnetic stray field measurements on the ferromagnetic semimetal EuB6, which exhibits a complex ferromagnetic order and a colossal magnetoresistance effect. In a zero magnetic field, scanning tunneling spectroscopy visualizes the existence of local inhomogeneities in the electronic density of states, which we interpret as the localization of charge carriers due to the formation of magnetic polarons. Micro-Hall magnetometry measurements of the total stray field emanating from the end of a rectangular-shaped platelike sample reveals evidence for magnetic clusters also in finite magnetic fields. In contrast, the signal detected below the faces of the magnetized sample measures a local stray field indicating the formation of pronounced magnetic inhomogeneities consistent with large clusters of percolated magnetic polarons.

  52. MTJ-based nonvolatile logic LSI for ultra low-power and highly dependable computing 査読有り

    Masanori Natsui, Tetsuo Endoh, Hideo Ohno, Takahiro Hanyu

    China Semiconductor Technology International Conference 2018, CSTIC 2018 1-4 2018年5月29日

    出版者・発行元:Institute of Electrical and Electronics Engineers Inc.

    DOI: 10.1109/CSTIC.2018.8369189  

    詳細を見る 詳細を閉じる

    A novel logic-LSI architecture, 'nonvolatile logic-in-memory (NV-LIM) architecture,' where nonvolatile storage elements are distributed over a logic-circuit plane, is proposed as a promising candidate to overcome performance, power and reliability wall on the present CMOS-only-based logic LSIs. Some concrete design examples based on the NV-LIM architecture using MTJ device are demonstrated and their usefulness is discussed in comparison with the corresponding CMOS-only-based realization.

  53. Impact of sputtering condition for tungsten on magnetic and transport properties of magnetic tunneling junction with CoFeB/W/CoFeB free layer

    H. Honjo, H. Sato, S. Ikeda, T. Watanabe, S. Miura, T. Nasuno, Y. Noguchi, M. Yasuhira, T. Tanigawa, H. Koike, M. Muraguchi, M. Niwa, K. Ito, H. Ohno, T. Endoh

    2017 IEEE International Magnetics Conference, INTERMAG 2017 2017年8月10日

    DOI: 10.1109/INTMAG.2017.8008047  

    詳細を見る 詳細を閉じる

    © 2017 IEEE. Spin-transfer-torque magnetoresistive random access memories using CoFeB-MgO based magnetic tunnel junctions with perpendicular easy axis (p-MTJs) are attracting much attention owing to their high potential in offering electronics with both low-power-consumption and high-performance [1-3].

  54. An artificial neural network with an analogue spin-orbit torque device 査読有り

    W.A. Borders, H. Akima, S. Fukami, S. Moriya, S. Kurihara, A. Kurenkov, Yoshihiko Horio, S. Sato, H. Ohno

    Proceedings of the IEEE International Magnetics Conference 2017年4月24日

    DOI: 10.1109/INTMAG.2017.8007937  

  55. Magnetization dynamics and its scattering mechanism in thin CoFeB films with interfacial anisotropy 査読有り

    Atsushi Okada, Shikun He, Bo Gu, Shun Kanai, Anjan Soumyanarayanan, Sze Ter Lim, Michael Tran, Michiyasu Mori, Sadamichi Maekawa, Fumihiro Matsukura, Hideo Ohno, Christos Panagopoulos

    PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 114 (15) 3815-3820 2017年4月

    出版者・発行元:NATL ACAD SCIENCES

    DOI: 10.1073/pnas.1613864114  

    ISSN:0027-8424

    詳細を見る 詳細を閉じる

    Studies of magnetization dynamics have incessantly facilitated the discovery of fundamentally novel physical phenomena, making steady headway in the development of magnetic and spintronics devices. The dynamics can be induced and detected electrically, offering new functionalities in advanced electronics at the nanoscale. However, its scattering mechanism is still disputed. Understanding the mechanism in thin films is especially important, because most spintronics devices are made from stacks of multilayers with nanometer thickness. The stacks are known to possess interfacial magnetic anisotropy, a central property for applications, whose influence on the dynamics remains unknown. Here, we investigate the impact of interfacial anisotropy by adopting CoFeB/MgO as a model system. Through systematic and complementary measurements of ferromagnetic resonance (FMR) on a series of thin films, we identify narrower FMR linewidths at higher temperatures. We explicitly rule out the temperature dependence of intrinsic damping as a possible cause, and it is also not expected from existing extrinsic scattering mechanisms for ferromagnets. We ascribe this observation to motional narrowing, an old concept so far neglected in the analyses of FMR spectra. The effect is confirmed to originate from interfacial anisotropy, impacting the practical technology of spin-based nanodevices up to room temperature.

  56. Design of a variation-resilient single-ended non-volatile six-input lookup table circuit with a redundant-magnetic tunnel junction-based active load for smart Internet-of-things applications 査読有り

    D. Suzuki, M. Natsui, S. Ikeda, T. Endoh, H. Ohno, T. Hanyu

    ELECTRONICS LETTERS 53 (7) 456-458 2017年3月

    出版者・発行元:INST ENGINEERING TECHNOLOGY-IET

    DOI: 10.1049/el.2016.4233  

    ISSN:0013-5194

    eISSN:1350-911X

    詳細を見る 詳細を閉じる

    A variation-resilient single-ended six-input lookup table circuit, which makes it possible to implement any arbitrary six-input logic gates, is proposed. Since operating point is optimally tuned by the redundant magnetic tunnel junction devices after chip fabrication, adequate p-channel metal-oxide semiconductor (PMOS) feedback can be performed, which results in variation-resilient, energy-efficient operation. In fact, the energy consumption of the proposed circuit is 66% smaller than that of the conventional single-ended circuit.

  57. Current-induced magnetization switching in a nano-scale CoFeB-MgO magnetic tunnel junction under in-plane magnetic field 査読有り

    N. Ohshima, H. Sato, S. Kanai, J. Llandro, S. Fukami, H. Ohno

    AIP Advances 7 055927(1)-055927(5) 2017年2月22日

  58. Fabrication of a magnetic-tunnel-junction-based nonvolatile logic-in-memory LSI with content-aware write error masking scheme achieving 92% storage capacity and 79% power reduction

    Natsui Masanori, Tamakoshi Akira, Endoh Tetsuo, Ohno Hideo, Hanyu Takahiro

    Jpn. J. Appl. Phys. 56 (4) 04CN01 2017年2月16日

    出版者・発行元:Institute of Physics

    DOI: 10.7567/JJAP.56.04CN01  

    ISSN:0021-4922

    詳細を見る 詳細を閉じる

    A magnetic-tunnel-junction (MTJ)-based video coding hardware with an MTJ-write-error-rate relaxation scheme as well as a nonvolatile storage capacity reduction technique is designed and fabricated in a 90 nm MOS and 75 nm perpendicular MTJ process. The proposed MTJ-oriented dynamic error masking scheme suppresses the effect of write operation errors on the operation result of LSI, which results in the increase in an acceptable MTJ write error rate up to 7.8 times with less than 6% area overhead, while achieving 79% power reduction compared with that of the static-random-access-memory-based one.

  59. Damping constant in a free layer in nanoscale CoFeB/MgO magnetic tunnel junctions investigated by homodyne-detected ferromagnetic resonance 査読有り

    M. Shinozaki, E. Hirayama, S. Kanai, H. Sato, F. Matsukura, H. Ohno

    Applied Physics Express 10 013001(1)-013001(3) 2017年2月

  60. Device-size dependence of field-free spin-orbit torque induced magnetization switching in antiferromagnet/ferromagnet structures 査読有り

    A. Kurenkov, C. Zhang, S. DuttaGupta, S. Fukami, H. Ohno

    APPLIED PHYSICS LETTERS 110 (9) 092410(1)-092410(5) 2017年2月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.4977838  

    ISSN:0003-6951

    eISSN:1077-3118

    詳細を見る 詳細を閉じる

    We study spin-orbit torque induced magnetization switching in devices consisting of an antiferromagnetic PtMn and ferromagnetic Co/Ni multilayer with sizes ranging from 5 mu m to 50 nm. As the size decreases, switching behavior changes from analogue-like to stepwise with several intermediate levels. The number of intermediate levels decreases with the decreasing size and finally evolves into a binary mode below a certain threshold. The results are found to be explained by a unique reversal process of this system, where ferromagnetic domains comprising a number of polycrystalline grains reverse individually and among the domains both out-of-plane and in-plane components of exchange bias vary. Published by AIP Publishing.

  61. Ferromagnetic resonance spectra of Py deposited on (Bi1-xSbx)2Te3 査読有り

    S. Gupta, S. Kanai, F. Matsukura, H. Ohno

    AIP Advances 7 055919(1)-055919(4) 2017年1月23日

  62. Magnetic domain-wall creep driven by field and current in Ta/CoFeB/MgO 査読有り

    S. DuttaGupta, S. Fukami, B. Kuebanjiang, H. Sato, F. Matsukura, V. K. Lazarov, H. Ohno

    AIP Advances 7 055918(1)-055918(7) 2017年1月20日

  63. Use of Analog Spintronics Device in Performing Neuro-Morphic Computing Functions

    Shunsuke Fukami, William A. Borders, Aleksandr Kurenkov, Chaoliang Zhang, Samik DuttaGupta, Hideo Ohno

    2017 FIFTH BERKELEY SYMPOSIUM ON ENERGY EFFICIENT ELECTRONIC SYSTEMS & STEEP TRANSISTORS WORKSHOP (E3S) 2017年

    出版者・発行元:IEEE

  64. Analogue spin-orbit torque device for artificial-neural-network-based associative memory operation 査読有り

    W. A. Borders, H. Akima, S. Fukami, S. Moriya, S. Kurihara, Y. Horio, S. Sato, H. Ohno

    Applied Physics Express 10 013007(1)-013007(4) 2017年1月

  65. Beyond MRAM: Nonvolatile Logic-in-Memory VLSI 査読有り

    Takahiro Hanyu, Tetsuo Endoh, Shoji Ikeda, Tadahiko Sugibayashi, Naoki Kasai, Daisuke Suzuki, Masanori Natsui, Hiroki Koike, Hideo Ohno

    Introduction to Magnetic Random-Access Memory 199-229 2016年11月26日

    出版者・発行元:wiley

    DOI: 10.1002/9781119079415.ch7  

    詳細を見る 詳細を閉じる

    The combination of spintronic devices with semiconductor integrated circuits will enable the replacement of conventional dynamic random-access memory (DRAM) with spin-transfer torque magnetic random-access memory (STT-MRAM) and facilitate high-performance, low-power, large-scale-integrated (LSI) logic circuits. Logic-in-memory architectures can take advantage of complementary metal-oxide-semiconductor/magnetic tunnel junction hybrid technology. The principles and benefits expected from these innovative architectures are explained and illustrated by several types of circuits that have been successfully designed, built, and tested. The benefits of low-power, high-performance, nonvolatile, spintronics-based logic LSIs discussed in this chapter could trigger a revolutionary change in our information- and communication-based society.

  66. Critical role of W deposition condition on spin-orbit torque induced magnetization switching in nanoscale W/CoFeB/MgO 査読有り

    C. Zhang, S. Fukami, K. Watanabe, A. Ohkawara, S. DuttaGupta, H. Sato, F. Matsukura, H. Ohno

    APPLIED PHYSICS LETTERS 109 (19) 192405(1)-192405(4) 2016年11月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.4967475  

    ISSN:0003-6951

    eISSN:1077-3118

    詳細を見る 詳細を閉じる

    We study the spin-orbit torque induced magnetization switching in W/CoFeB/MgO heterostructures with W deposited under different sputtering conditions. We show that the crystal structure and resistivity of W depend on the employed sputtering conditions. Switching current of nanoscale devices is smaller while effective anisotropy field is larger for the devices with more resistive W channel deposited at lower sputtering power and higher Ar gas pressure. The effective spin Hall angle evaluated from the switching probability varies by a factor of 2-3 depending on the W resistivity controlled by the sputtering conditions. Published by AIP Publishing.

  67. Standby-Power-Free Integrated Circuits Using MTJ-Based VLSI Computing 査読有り

    Takahiro Hanyu, Tetsuo Endoh, Daisuke Suzuki, Hiroki Koike, Yitao Ma, Naoya Onizawa, Masanori Natsui, Shoji Ikeda, Hideo Ohno

    PROCEEDINGS OF THE IEEE 104 (10) 1844-1863 2016年10月

    出版者・発行元:IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

    DOI: 10.1109/JPROC.2016.2574939  

    ISSN:0018-9219

    eISSN:1558-2256

    詳細を見る 詳細を閉じる

    Nonvolatile spintronic devices have potential advantages, such as fast read/write and high endurance together with back-end-of-the-line compatibility, which offers the possibility of constructing not only stand-alone RAMs and embedded RAMs that can be used in conventional VLSI circuits and systems but also standby-power-free high-performance nonvolatile CMOS logic employing logic-in-memory architecture. The advantages of employing spintronic devices, especially magnetic tunnel junction (MTJ) devices with CMOS circuits, are discussed, and the current status of the MTJ-based VLSI computing paradigm is presented along with its prospects and remaining challenges.

  68. Spintronics 査読有り

    H. Ohno, M. D. Stiles, B. Dieny

    Proc. Institute of Electrical and Electronics Engineers 104 1782-1786 2016年10月

    DOI: 10.1109/JPROC.2016.2601163  

  69. Free- and reference-layer magnetization modes versus in-plane magnetic field in a magnetic tunnel junction with perpendicular magnetic easy axis 査読有り

    Hamid Mazraati, Tuan Q. Le, Ahmad A. Awad, Sunjae Chung, Eriko Hirayama, Shoji Ikeda, Fumihiro Matsukura, Hideo Ohno, Johan Akerman

    PHYSICAL REVIEW B 94 (10) 104428(1)-104428(6) 2016年9月

    出版者・発行元:AMER PHYSICAL SOC

    DOI: 10.1103/PhysRevB.94.104428  

    ISSN:2469-9950

    eISSN:2469-9969

    詳細を見る 詳細を閉じる

    We study the magnetodynamic modes of a magnetic tunnel junction with perpendicular magnetic easy axis (p-MTJ) in in-plane magnetic fields using device-level ferromagnetic resonance spectroscopy. We compare our experimental results to those of micromagnetic simulations of the entire p-MTJ. Using an iterative approach to determine the material parameters that best fit our experiment, we find excellent agreement between experiments and simulations in both the static magnetoresistance and magnetodynamics in the free and reference layers. From the micromagnetic simulations, we determine the spatial mode profiles, the localization of the modes and, as a consequence, their distribution in the frequency domain due to the inhomogeneous internal field distribution inside the p-MTJ under different applied field regimes. We also conclude that the excitation mechanism is a combination of the microwave voltage modulated perpendicular magnetic anisotropy, the microwave Oersted field, and the spin-transfer torque generated by the microwave current.

  70. Peculiar temperature dependence of electric-field effect on magnetic anisotropy in Co/Pd/MgO system 査読有り

    Y. Hibino, T. Koyama, A. Obinata, T. Hirai, S. Ota, K. Miwa, S. Ono, F. Matsukura, H. Ohno, D. Chiba

    APPLIED PHYSICS LETTERS 109 (8) 082403(1)-082403(4) 2016年8月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.4961621  

    ISSN:0003-6951

    eISSN:1077-3118

    詳細を見る 詳細を閉じる

    We report on the temperature dependence of the magnetic anisotropy in Co/Pd/MgO system, in which magnetic moment in Pd is induced by the magnetic proximity effect. We demonstrate that the magnetic anisotropy is modulated by applying an electric field to the Pd surface. At temperatures below 100K, we find the nonlinear electric-field dependence of the anisotropy with the sign reversal. We obtain a huge anisotropy modulation efficiency of similar to 1600 fJ/V m at 10K. Published by AIP Publishing.

  71. Magnetic Properties of CoFeB-MgO Stacks With Different Buffer-Layer Materials (Ta or Mo) 査読有り

    Kyota Watanabe, Shunsuke Fukami, Hideo Sato, Fumihiro Matsukura, Hideo Ohno

    IEEE TRANSACTIONS ON MAGNETICS 52 (7) 3400904(1)-3400904(4) 2016年7月

    出版者・発行元:IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

    DOI: 10.1109/TMAG.2016.2514525  

    ISSN:0018-9464

    eISSN:1941-0069

    詳細を見る 詳細を閉じる

    We investigate the effect of the buffer-layer materials and their crystallographic structures on the magnetic properties of the CoFeB-MgO stacks. Amorphous Ta, amorphous Mo, and crystalline Mo are used as the buffer layer of CoFeB-MgO. The CoFeB-MgO stacks on both the Mo buffer layers show higher perpendicular anisotropy than that on Ta after 400-degrees C annealing. Difference is also seen between the samples with amorphous and crystalline Mo in the intermixing property between Mo and CoFeB; intermixing is much more unlikely for the crystalline sample. Magnetic damping constant is also evaluated from ferromagnetic resonance measurements. Samples with crystalline Mo buffer layer show smaller damping constant than those with Ta buffer layer after 400-degrees C annealing. This paper clarifies that the magnetic properties of CoFeB-MgO depend on the buffer-layer materials and their crystallinities.

  72. Current-Induced Magnetization Switching of CoFeB/Ta/[Co/Pd (Pt)]-Multilayers in Magnetic Tunnel Junctions With Perpendicular Anisotropy 査読有り

    Shinya Ishikawa, Eli C. I. Enobio, Hideo Sato, Shunsuke Fukami, Fumihiro Matsukura, Hideo Ohno

    IEEE TRANSACTIONS ON MAGNETICS 52 (7) 3400704(1)-3400704(4) 2016年7月

    出版者・発行元:IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

    DOI: 10.1109/TMAG.2016.2517098  

    ISSN:0018-9464

    eISSN:1941-0069

    詳細を見る 詳細を閉じる

    We investigate magnetic properties of CoFeB/Ta/[Co/Pd (Pt)] multilayers and properties of magnetic tunnel junctions (MTJs) with the structures as a recording layer. CoFeB/Ta/[Co/Pd] multilayer shows a lower damping constant a than that of CoFeB/Ta/[Co/Pt] multilayer. We evaluate current-induced magnetization switching (CIMS) properties of the MTJs with CoFeB/Ta/[Co/Pd (Pt)] multilayers with the junction diameter of 15 (13) nm that show similar thermal stability factor. CIMS is observed for the MTJ with a CoFeB/Ta/[Co/Pd] multilayer at zero magnetic field, whereas it is observed for the MTJ with the CoFeB/Ta/[Co/Pt] multilayer only in the presence of an external field.

  73. Improvement of Thermal Tolerance of CoFeB-MgO Perpendicular-Anisotropy Magnetic Tunnel Junctions by Controlling Boron Composition 査読有り

    H. Honjo, S. Ikeda, H. Sato, S. Sato, T. Watanabe, S. Miura, T. Nasuno, Y. Noguchi, M. Yasuhira, T. Tanigawa, H. Koike, M. Muraguchi, M. Niwa, K. Ito, H. Ohno, T. Endoh

    IEEE TRANSACTIONS ON MAGNETICS 52 (7) 3401104(1)-3401104(4) 2016年7月

    出版者・発行元:IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

    DOI: 10.1109/TMAG.2016.2518203  

    ISSN:0018-9464

    eISSN:1941-0069

    詳細を見る 詳細を閉じる

    We investigated annealing temperature T-a dependence of tunnel magnetoresistance (TMR) ratio and magnetic properties for perpendicular-anisotropy (CoFe)(100-X)B-X/MgO magnetic tunnel junctions (MTJs) with single (CoFe)(100-X)B-X/MgO interface (s-MTJ) and double CoFeB-MgO interface (d-MTJ) structures with various boron compositions X. High TMR ratio over 100% was observed in the s-MTJ with X = 35 at.% after annealing at 360 degrees C-400 degrees C, whereas the s-MTJ with X = 30 at.% showed the degradation of TMR ratio with the increase of T-a above 360 degrees C, resulting from the decrease of perpendicular anisotropy. The d-MTJ with X = 25 at.% maintained high TMR ratio up to T-a = 400 degrees C owing to its higher perpendicular anisotropy compared with the s-MTJ. The difference of perpendicular anisotropy between the s-MTJ and the d-MTJ can be attributed to higher interfacial anisotropy together with lower saturation magnetization of the d-MTJs. The lower saturation magnetization is attributable to two MgO layers that suppress boron diffusion from CoFeB layers, which was verified by cross-sectional line analysis using electron energy-loss spectroscopy.

  74. Effect of electric-field modulation of magnetic parameters on domain structure in MgO/CoFeB 査読有り

    T. Dohi, S. Kanai, A. Okada, F. Matsukura, H. Ohno

    AIP ADVANCES 6 (7) 075017(1)-075017(4) 2016年7月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.4959905  

    ISSN:2158-3226

    詳細を見る 詳細を閉じる

    We observe magnetic domain structures of MgO/CoFeB with a perpendicular magnetic easy axis under an electric field. The domain structure shows a maze pattern with electric-field dependent isotropic period. The analysis of the period indicates a major role of the electric-field modulation of interfacial magnetic anisotropy for the observation and possible contribution from electric-field modulation of the exchange stiffness constant. (C) 2016 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

  75. Fermi level position, Coulomb gap, and Dresselhaus splitting in (Ga,Mn)As 査読有り

    S. Souma, L. Chen, R. Oszwaldowski, T. Sato, F. Matsukura, T. Dietl, H. Ohno, T. Takahashi

    SCIENTIFIC REPORTS 6 27266 (1)-27266 (10) 2016年6月

    出版者・発行元:NATURE PUBLISHING GROUP

    DOI: 10.1038/srep27266  

    ISSN:2045-2322

    詳細を見る 詳細を閉じる

    Carrier-induced nature of ferromagnetism in a ferromagnetic semiconductor, (Ga, Mn) As, offers a great opportunity to observe novel spin-related phenomena as well as to demonstrate new functionalities of spintronic devices. Here, we report on low-temperature angle-resolved photoemission studies of the valence band in this model compound. By a direct determination of the distance of the split-off band to the Fermi energy E-F we conclude that E-F is located within the heavy/light hole band. However, the bands are strongly perturbed by disorder and disorder-induced carrier correlations that lead to the Coulomb gap at E-F, which we resolve experimentally in a series of samples, and show that its depth and width enlarge when the Curie temperature decreases. Furthermore, we have detected surprising linear magnetic dichroism in photoemission spectra of the split-off band. By a quantitative theoretical analysis we demonstrate that it arises from the Dresselhaus-type spin-orbit term in zinc-blende crystals. The spectroscopic access to the magnitude of such asymmetric part of spin-orbit coupling is worthwhile, as they account for spin-orbit torque in spintronic devices of ferromagnets without inversion symmetry.

  76. Magnetization switching by spin-orbit torque in an antiferromagnet-ferromagnet bilayer system 査読有り

    Shunsuke Fukami, Chaoliang Zhang, Samik DuttaGupta, Aleksandr Kurenkov, Hideo Ohno

    NATURE MATERIALS 15 (5) 535-+ 2016年5月

    出版者・発行元:NATURE PUBLISHING GROUP

    DOI: 10.1038/NMAT4566  

    ISSN:1476-1122

    eISSN:1476-4660

    詳細を見る 詳細を閉じる

    Spin-orbit torque (SOT)-induced magnetization switching shows promise for realizing ultrafast and reliable spintronics devices. Bipolar switching of the perpendicular magnetization by the SOT is achieved under an in-plane magnetic field collinear with an applied current. Typical structures studied so far comprise a nonmagnet/ferromagnet (NM/FM) bilayer, where the spin Hall effect in the NM is responsible for the switching. Here we show that an antiferromagnet/ferromagnet (AFM/FM) bilayer system also exhibits a SOT large enough to switch the magnetization of the FM. In this material system, thanks to the exchange bias of the AFM, we observe the switching in the absence of an applied field by using an antiferromagnetic PtMn and ferromagnetic Co/Ni multilayer with a perpendicular easy axis. Furthermore, tailoring the stack achieves a memristor-like behaviour where a portion of the reversed magnetization can be controlled in an analogue manner. The AFM/FM system is thus a promising building block for SOT devices as well as providing an attractive pathway towards neuromorphic computing.

  77. Electric-field-induced magnetization switching in CoFeB/MgO magnetic tunnel junctions with high junction resistance 査読有り

    S. Kanai, F. Matsukura, H. Ohno

    APPLIED PHYSICS LETTERS 108 (19) 192406 (1)-192406 (3) 2016年5月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.4948763  

    ISSN:0003-6951

    eISSN:1077-3118

    詳細を見る 詳細を閉じる

    We show the electric-field induced magnetization switching for CoFeB/MgO magnetic tunnel junctions with thick MgO barrier layer of 2.8 nm, whose resistance-area product is 176 k Omega mu m(2), and achieve the small switching energy of 6.3 fJ/bit. The increase of the junction resistance is expected to suppress the energy consumption due to the Joule heating during the switching; however, the energy is still dominated by the Joule energy rather than the charging energy. This is because the junction resistance decreases more rapidly for junctions with thicker MgO as bias voltage increases. Published by AIP Publishing.

  78. Current-induced domain wall motion in magnetic nanowires with various widths down to less than 20 nm 査読有り

    Shunsuke Fukami, Toru Iwabuchi, Hideo Sato, Hideo Ohno

    JAPANESE JOURNAL OF APPLIED PHYSICS 55 (4) 04EN01(1)-04EN01(4) 2016年4月

    出版者・発行元:IOP PUBLISHING LTD

    DOI: 10.7567/JJAP.55.04EN01  

    ISSN:0021-4922

    eISSN:1347-4065

    詳細を見る 詳細を閉じる

    We experimentally and theoretically study the current-induced domain wall motion in magnetic nanowires with various widths, and discuss the issues concerning the domain wall motion in wires with reduced widths down to less than 20 nm. For Co/Ni nanowires, the threshold current density significantly increases as the width decreases below 30nm and the domain wall motion is not observed within the studied current density range for a number of devices with the wire width of around 20 nm. The relationship between the threshold current density and wire width is reasonably reproduced by a theoretical calculation based on the adiabatic spin-transfer torque model. The micromagnetic simulation suggests that high-anisotropy materials are promising for domain-wall-motion devices with wire widths beyond 20 nm. (C) 2016 The Japan Society of Applied Physics

  79. Study on initial current leakage spots in CoFeB-capped MgO tunnel barrier by conductive atomic force microscopy 査読有り

    Soshi Sato, Hiroaki Honjo, Shoji Ikeda, Hideo Ohno, Tetsuo Endoh, Masaaki Niwa

    Japanese Journal of Applied Physics 55 (4) 04EE05(1)-04EE05(7) 2016年4月1日

    出版者・発行元:Japan Society of Applied Physics

    DOI: 10.7567/JJAP.55.04EE05  

    ISSN:1347-4065 0021-4922

    詳細を見る 詳細を閉じる

    Although a microscopic study on a MgO tunnel barrier by atomic force microscopy has been required to study the reliability of magnetic tunnel junctions, the deterioration of bare MgO due to the adsorption of H2O and CO2 has been a problem. For an accurate evaluation of the initial current leakage spots distributed in a MgO tunnel barrier, a CoFeB-capped MgO tunnel barrier structure is proposed for evaluation by means of conductive atomic force microscopy. The CoFeB capping layer thickness was optimized to be 2.0nm to prevent H2O and CO2 adsorption on the MgO and to minimize the series resistance due to the capping layer. The initial current leakage spot density of the MgO tunnel barrier with the optimized CoFeB capping layer exponentially increased as the thickness of the MgO tunnel barrier decreased from 1.6 to 0.8nm, and was 157 spots/μm2 at the MgO thickness of 1.2nm and the bias voltage of 0.5V.

  80. Electric field control of Skyrmions in magnetic nanodisks 査読有り

    Y. Nakatani, M. Hayashi, S. Kanai, S. Fukami, H. Ohno

    APPLIED PHYSICS LETTERS 108 (15) 152403(1)-152403(5) 2016年4月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.4945738  

    ISSN:0003-6951

    eISSN:1077-3118

    詳細を見る 詳細を閉じる

    The control of magnetic Skyrmions confined in a nanometer scale disk using electric field pulses is studied by micromagnetic simulation. A stable Skyrmion can be created and annihilated by an electric field pulse depending on the polarity of the electric field. Moreover, the core direction of the Skyrmion can be switched using the same electric field pulses. Such creation and annihilation of Skyrmions, and its core switching do not require any magnetic field and precise control of the pulse length. This unconventional manipulation of magnetic texture using electric field pulses allows a robust way of controlling magnetic Skyrmions in nanodiscs, a path toward building ultralow power memory devices. (C) 2016 AIP Publishing LLC.

  81. A spin-orbit torque switching scheme with collinear magnetic easy axis and current configuration 査読有り

    S. Fukami, T. Anekawa, C. Zhang, H. Ohno

    Nature Nanotechnology 1-6 2016年3月21日

    DOI: 10.1038/nnano.2016.29  

  82. Atomic-Scale Structure and Local Chemistry of CoFeB-MgO Magnetic Tunnel Junctions 査読有り

    Zhongchang Wang, Mitsuhiro Saito, Keith P. McKenna, Shunsuke Fukami, Hideo Sato, Shoji Ikeda, Hideo Ohno, Yuichi Ikuhara

    NANO LETTERS 16 (3) 1530-1536 2016年3月

    出版者・発行元:AMER CHEMICAL SOC

    DOI: 10.1021/acs.nanolett.5b03627  

    ISSN:1530-6984

    eISSN:1530-6992

    詳細を見る 詳細を閉じる

    Magnetic tunnel junctions (MTJs) constitute a promising building block for future nonvolatile memories and logic circuits. Despite their pivotal role, spatially resolving and chemically identifying each individual stacking layer remains challenging due to spatially localized features that complicate characterizations limiting understanding of the physics of MTJs. Here, we combine advanced electron microscopy, spectroscopy, and first-principles calculations to obtain a direct structural and chemical imaging of the atomically confined layers in a CoFeB-MgO MTJ, and clarify atom diffusion and interface structures in the MTJ following annealing. The combined techniques demonstrate that B diffuses out of CoFeB electrodes into Ta interstitial sites rather than MgO after annealing, and CoFe bonds atomically to MgO grains with an epitaxial orientation relationship by forming Fe(Co)-O bonds, yet without incorporation of CoFe in MgO. These findings afford a comprehensive perspective on structure and chemistry of MTJs, helping to develop high-performance spintronic devices by atomistic design.

  83. Temperature dependence of in-plane magnetic anisotropy and anisotropic magnetoresistance in (Ga,Mn)As codoped with Li 査読有り

    Shohei Miyakozawa, Lin Chen, Fumihiro Matsukura, Hideo Ohno

    APPLIED PHYSICS LETTERS 108 (11) 112404 (1)-112404 (3) 2016年3月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.4944328  

    ISSN:0003-6951

    eISSN:1077-3118

    詳細を見る 詳細を閉じる

    We evaluate the temperature dependence of in-plane magnetic anisotropy and anisotropic magnetoresistance (AMR) in (Ga,Mn)As codoped with Li by magnetotransport measurements. We find that the signs of in-plane uniaxial anisotropy and AMR change at the same temperature of similar to 75 K, and that the sign of planar Hall effect does not depend on temperature. (C) 2016 AIP Publishing LLC.

  84. Magnetic stray-field studies of a single Cobalt nanoelement as a component of the building blocks of artificial square spin ice 査読有り

    Merlin Pohlit, Fabrizio Porrati, Michael Huth, Yuzo Ohno, Hideo Ohno, Jens Mueller

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 400 206-212 2016年2月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/j.jmmm.2015.08.072  

    ISSN:0304-8853

    eISSN:1873-4766

    詳細を見る 詳細を閉じる

    We use Focused Electron Beam Deposition (FEBID) to directly write Cobalt magnetic nanoelements onto a micro-Hall magnetometer, which allows for high-sensitivity measurements of the magnetic stray field emanating from the samples. In a previous study [M. Pohlit et al., J. Appl. Phys. 117 (2015) 17C7461 [21] we investigated thermal dynamics of an individual building block (nanocluster) of artificial square spin ice. In this work, we compare the results of this structure with interacting elements to the switching of a single nanoisland. By analyzing the survival function of the repeatedly prepared state in a given temperature range, we find thermally activated switching dynamics. A detailed analysis of the hysteresis loop reveals a metastable microstate preceding the overall magnetization reversal of the single nanoelement, also found in micromagnetic simulations. Such internal degrees of freedom may need to be considered, when analyzing the thermal dynamics of larger spin ice configurations on different lattice types. (C) 2015 Elsevier B.V. All rights reserved.

  85. (Ga,Mn)Asのin-situ高分解能ARPES

    相馬 清吾, Chen L, Oszwałdowski R, 佐藤 宇史, 松倉 文礼, Ditel T, 大野 英男, 高橋 隆

    日本物理学会講演概要集 71 848-848 2016年

    出版者・発行元:一般社団法人 日本物理学会

    DOI: 10.11316/jpsgaiyo.71.2.0_848  

    詳細を見る 詳細を閉じる

    <p>強磁性半導体(Ga,Mn)Asは、多くのスピントロニクス新現象の実証に貢献してきたモデル物質であるが、強磁性機構の土台となるフェルミ準位近傍の電子構造が未だに決着していない。今回我々はTc~100Kの高ドープ試料についてin-situ高分解能ARPESを行い、フェルミ準位がAsホールバンド内にあることを見出した。この結果は、ホールキャリアが磁性を媒介するp-d Zenerモデルを強力に支持している。</p>

  86. Magnetization Reversal by Field and Current Pulses in Elliptic CoFeB/MgO Tunnel Junctions With Perpendicular Easy Axis 査読有り

    Eriko Hirayama, Hideo Sato, Shun Kanai, Fumihiro Matsukura, Hideo Ohno

    IEEE MAGNETICS LETTERS 7 3104004(1)-3104004(4) 2016年

    出版者・発行元:IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

    DOI: 10.1109/LMAG.2016.2568163  

    ISSN:1949-307X

    詳細を見る 詳細を閉じる

    We fabricate elliptic CoFeB/MgO magnetic tunnel junctions (MTJs) with perpendicular magnetic easy axis with different in-plane aspect ratios (ARs) from 1 to 4 with the same area as that of a 100 nm diameter circular MTJ. We evaluate their thermal stability factors from magnetization switching probability measurements by using either applied magnetic field pulses or current pulses. The thermal stability factors determined from field-pulse measurement appear to decrease with increasing AR, whereas those from current-pulse measurement depend much less on AR. These results imply that the different drives induce switching through different magnetization reversal modes.

  87. Adiabatic spin-transfer-torque-induced domain wall creep in a magnetic metal 査読有り

    S. DuttaGupta, S. Fukami, C. Zhang, H. Sato, M. Yamanouchi, F. Matsukura, H. Ohno

    Nature Physics 3593 1-5 2015年12月14日

  88. Temperature dependence of energy barrier in CoFeB-MgO magnetic tunnel junctions with perpendicular easy axis 査読有り

    Y. Takeuchi, H. Sato, S. Fukami, F. Matsukura, H. Ohno

    APPLIED PHYSICS LETTERS 107 (15) 152405(1)-152405(3) 2015年10月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.4933256  

    ISSN:0003-6951

    eISSN:1077-3118

    詳細を見る 詳細を閉じる

    We investigate an energy barrier E that determines the thermal stability factor of nanoscale CoFeB-MgO magnetic tunnel junctions (MTJs) with a perpendicular easy axis as a function of temperature between 298 and 393 K. For the MTJs with a junction diameter above 43 nm, E is much smaller and less sensitive to the temperature than the magnetic anisotropy energy of the total recording volume. For the MTJ with a diameter of 33 nm, E and the anisotropy energy take about the same value and show similar temperature dependence. The results can be explained by considering a crossover of magnetization reversal mode from nucleation type to single-domain like type, as the device dimensions reduce. (C) 2015 AIP Publishing LLC.

  89. Ferromagnetic resonance of Py deposited on ZnO grown by molecular beam epitaxy 査読有り

    Sophie D'Ambrosio, Lin Chen, Hiroyasu Nakayama, Fumihiro Matsukura, Tomasz Dietl, Hideo Ohno

    JAPANESE JOURNAL OF APPLIED PHYSICS 54 (9) 093001(1)-093001(4) 2015年9月

    出版者・発行元:IOP PUBLISHING LTD

    DOI: 10.7567/JJAP.54.093001  

    ISSN:0021-4922

    eISSN:1347-4065

    詳細を見る 詳細を閉じる

    We report on the growth of a high-quality single crystal ZnO film on an a-plane sapphire substrate by plasma-assisted molecular beam epitaxy and the properties of a sputtered permalloy (Py) film on the ZnO investigated by ferromagnetic resonance. The results show that one can obtain the Py with a reasonable quality on ZnO, which is expected to provide a testbed system for the investigation of the spin current-related phenomena in materials with a weak spin-orbit interaction. (C) 2015 The Japan Society of Applied Physics

  90. Temperature dependence of lattice parameter of (Ga,Mn)As on GaAs substrate 査読有り

    Fumihiro Matsukura, Hideo Ohno

    JAPANESE JOURNAL OF APPLIED PHYSICS 54 (9) 098003(1)-098003(2) 2015年9月

    出版者・発行元:IOP PUBLISHING LTD

    DOI: 10.7567/JJAP.54.098003  

    ISSN:0021-4922

    eISSN:1347-4065

    詳細を見る 詳細を閉じる

    We measure the temperature dependence of the lattice parameter of (Ga,Mn)As by X-ray diffraction. The result shows that the lattice parameter of (Ga,Mn)As shows similar temperature dependence to that of GaAs, and no obvious change is observed in the vicinity of its Curie temperature. (C) 2015 The Japan Society of Applied Physics

  91. Vertical electric field induced suppression of fine structure splitting of excited state excitons in a single GaAs/AlGaAs island quantum dots 査読有り

    Mohsen Ghali, Yuzo Ohno, Hideo Ohno

    APPLIED PHYSICS LETTERS 107 (12) 123102(1)-123102(5) 2015年9月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.4931360  

    ISSN:0003-6951

    eISSN:1077-3118

    詳細を見る 詳細を閉じる

    We report experimentally on fine structure splitting (FSS) of various excitonic transitions in single GaAs island quantum dots, formed by a monolayer thickness fluctuation in the narrow GaAs/AlGaAs quantum well, and embedded in an n-i-Schottky diode device. By applying a forward vertical electric field (F) between the top metallic contact and the sample substrate, we observed an in-plane polarization rotation of both the ground and the excited state excitons with increasing the electric field. The polarization rotations were accompanied with a strong decrease in the FSS of the ground as well as the excited state excitons with the field, until the FSS vanished as F approached 30 kV/cm. (C) 2015 AIP Publishing LLC.

  92. Electric-field induced nonlinear ferromagnetic resonance in a CoFeB/MgO magnetic tunnel junction 査読有り

    E. Hirayama, S. Kanai, J. Ohe, H. Sato, F. Matsukura, H. Ohno

    APPLIED PHYSICS LETTERS 107 (13) 132404(1)-132404(4) 2015年9月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.4932092  

    ISSN:0003-6951

    eISSN:1077-3118

    詳細を見る 詳細を閉じる

    We investigate the rf power dependence of homodyne-detected ferromagnetic resonance (FMR) spectra of a nanoscale CoFeB/MgO magnetic tunnel junction, in which the FMR is induced by the electric-field modulation of the magnetic anisotropy. The increase of the rf power changes the spectral lineshape and decreases characteristic frequency, at which drastic change in spectrum is observed. The behavior is consistent with nonlinear magnetization precession with a large precessional angle at high powers. From the rf power dependence of FMR spectra, we determine electric-field modulation ratio of magnetic anisotropy energy density to be 78 fJ/Vm, which is in agreement with the reported values. (C) 2015 AIP Publishing LLC.

  93. Spin-orbit torque induced magnetization switching in nano-scale Ta/CoFeB/MgO 査読有り

    C. Zhang, S. Fukami, H. Sato, F. Matsukura, H. Ohno

    APPLIED PHYSICS LETTERS 107 (1) 012401(1)-012401(4) 2015年7月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.4926371  

    ISSN:0003-6951

    eISSN:1077-3118

    詳細を見る 詳細を閉じる

    We study the device size dependence of spin-orbit torque induced magnetization switching in a Ta/CoFeB/MgO structure with perpendicular easy axis. The miniaturization of the device from micrometer-sized wire to 80-nm dot results in the increase of the threshold current density Jth by one order, whereas Jth increases only slightly with further reducing the device size down to 30 nm. No significant increase in Jth is seen, as the current pulse width decreases from 100 ms down to 3 ns. We reveal that the switching in devices at reduced size is reasonably well explained by the macrospin model, in which the effects of both the Slonczewski-like torque and field-like torque are included. (C) 2015 AIP Publishing LLC.

  94. Electric-Field Modulation of Damping Constant in a Ferromagnetic Semiconductor (Ga,Mn) As 査読有り

    Lin Chen, Fumihiro Matsukura, Hideo Ohno

    PHYSICAL REVIEW LETTERS 115 (5) 057204(1)-057204(5) 2015年7月

    出版者・発行元:AMER PHYSICAL SOC

    DOI: 10.1103/PhysRevLett.115.057204  

    ISSN:0031-9007

    eISSN:1079-7114

    詳細を見る 詳細を閉じる

    The modulation of the Gilbert damping constant alpha in (Ga,Mn) As by the application of an electric field is detected by ferromagnetic resonance measurements, where alpha increases with decreasing hole concentration. The smaller modulation of other magnetic parameters, such as magnetic anisotropy fields and Lande g factor, suggests that the modulation of alpha is governed by other effects rather than the spin-orbit coupling. Comparison of the conductivity dependence of alpha with that of the magnetization indicates that the magnetic disorder induced by carrier localization plays a major role in determining the magnitude of alpha in (Ga,Mn) As.

  95. Erratum: “Evidence of a reduction reaction of oxidized iron/cobalt by boron atoms diffused toward naturally oxidized surface of CoFeB layer during annealing” [Appl. Phys. Lett. 106, 142407 (2015)] 査読有り

    Soshi Sato, Hiroaki Honjo, Shoji Ikeda, Hideo Ohno, Tetsuo Endoh, Masaaki Niwa

    Applied Physics Letters 106 (24) 249901 2015年6月

    出版者・発行元:{AIP} Publishing

    DOI: 10.1063/1.4922749  

    ISSN:0003-6951

    eISSN:1077-3118

  96. Fabrication of a 3000-6-Input-LUTs Embedded and Block-Level Power-Gated Nonvolatile FPGA Chip Using p-MTJ-Based Logic-in-Memory Structure 査読有り

    D. Suzuki, M. Natsui, A. Mochizuki, S. Miura, H. Honjo, H. Sato, S. Fukami, S. Ikeda, T. Endoh, H. Ohno, T. Hanyu

    2015 Diguest of Technical Papers, Symp. VLSI Circuit 172-173 2015年6月

  97. Inverse spin Hall effect in Pt/(Ga,Mn)As 査読有り

    H. Nakayama, L. Chen, H. W. Chang, H. Ohno, F. Matsukura

    APPLIED PHYSICS LETTERS 106 (22) 222405(1)-222405(4) 2015年6月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.4922197  

    ISSN:0003-6951

    eISSN:1077-3118

    詳細を見る 詳細を閉じる

    We investigate dc voltages under ferromagnetic resonance in a Pt/(Ga,Mn)As bilayer structure. A part of the observed dc voltage is shown to originate from the inverse spin Hall effect. The sign of the inverse spin Hall voltage is the same as that in Py/Pt bilayer structure, even though the stacking order of ferromagnetic and nonmagnetic layers is opposite to each other. The spin mixing conductance at the Pt/(Ga,Mn)As interface is determined to be of the order of 10(19) m(-2), which is about ten times greater than that of (Ga,Mn)As/p-GaAs. (C) 2015 AIP Publishing LLC.

  98. Thermal stability of a magnetic domain wall in nanowires 査読有り

    S. Fukami, J. Ieda, H. Ohno

    PHYSICAL REVIEW B 91 (23) 235401(1)-235401(7) 2015年6月

    出版者・発行元:AMER PHYSICAL SOC

    DOI: 10.1103/PhysRevB.91.235401  

    ISSN:1098-0121

    eISSN:1550-235X

    詳細を見る 詳細を閉じる

    We study the thermal stability of a magnetic domain wall pinned in nanowires with various widths and thicknesses made of Co/Ni multilayers and analyze the effective volume that governs the thermal stability. We find that, above a critical wire width, the domain wall depinning is initiated by a subvolume excitation and that the critical width is dependent on the wire thickness. The obtained findings are supported by the distribution of critical current density for domain wall depinning and are qualitatively described by an analytical model in which the balance between the Zeeman energy and domain wall elastic energy is considered. We also show a different behavior between the device size dependence of the thermal stability and that of critical current, leading to an enhancement of domain wall motion efficiency with decreasing the device size.

  99. Driving Force in Diffusion and Redistribution of Reducing Agents during Redox Reaction on the Surface of CoFeB Film 査読有り

    S. Sato, H. Honjo, S. Ikeda, H. Ohno, M. Niwa, T. Endoh

    IEEE. Transactions on Magnetics PP (99) 1 2015年5月19日

    DOI: 10.1109/TMAG.2015.2434840  

  100. 1T1MTJ STT-MRAM Cell Array Design with an Adaptive Reference Voltage Generator for Improving Device Variation Tolerance 査読有り

    H. Koike, S. Miura, H. Honjo, T. Watanabe, H. Sato, S. Sato, T. Nasuno, Y. Noguchi, M. Yasuhira, T. Tanigawa, M. Muraguchi, M. Niwa, K. Ito, S. Ikeda, H. Ohno, T. Endoh

    2015 IEEE International Memory Workshop 1-4 2015年5月17日

    DOI: 10.1109/IMW.2015.7150264  

  101. Diffusion Behaviors Observed on the Surface of CoFeB Film after the Natural Oxidation and the Annealing 査読有り

    S. Sato, H. Honjo, S. Ikeda, H. Ohno, T. Endoh, M. Niwa

    2015 IEEE Magnetic Conference (INTERMAG2015) GP-01 2015年5月15日

    DOI: 10.1109/INTMAG.2015.7157496  

  102. Ferromagnetic resonance in nanoscale CoFeB/MgO magnetic tunnel junctions 査読有り

    E. Hirayama, S. Kanai, H. Sato, F. Matsukura, H. Ohno

    JOURNAL OF APPLIED PHYSICS 117 (17) 17B708(1)-17B708(4) 2015年5月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.4908149  

    ISSN:0021-8979

    eISSN:1089-7550

    詳細を見る 詳細を閉じる

    We investigate the junction size dependence of magnetic properties of a CoFeB free layer in CoFeB/MgO magnetic tunnel junctions (MTJs) by homodyne-detected ferromagnetic resonance, where the diameter of the circular MTJs is varied from 35 nm to 100 nm. We observe the increase of the effective perpendicular magnetic anisotropy field and the apparent damping constant in the free layers with decreasing diameter. (c) 2015 AIP Publishing LLC.

  103. Nanocluster building blocks of artificial square spin ice: Stray-field studies of thermal dynamics 査読有り

    Merlin Pohlit, Fabrizio Porrati, Michael Huth, Yuzo Ohno, Hideo Ohno, Jens Mueller

    JOURNAL OF APPLIED PHYSICS 117 (17) 17C746(1)-17C746(4) 2015年5月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.4917497  

    ISSN:0021-8979

    eISSN:1089-7550

    詳細を見る 詳細を閉じる

    We present measurements of the thermal dynamics of a Co-based single building block of an artificial square spin ice fabricated by focused electron-beam-induced deposition. We employ micro-Hall magnetometry, an ultra-sensitive tool to study the stray field emanating from magnetic nanostructures, as a new technique to access the dynamical properties during the magnetization reversal of the spin-ice nanocluster. The obtained hysteresis loop exhibits distinct steps, displaying a reduction of their "coercive field" with increasing temperature. Therefore, thermally unstable states could be repetitively prepared by relatively simple temperature and field protocols allowing one to investigate the statistics of their switching behavior within experimentally accessible timescales. For a selected switching event, we find a strong reduction of the so-prepared states' "survival time" with increasing temperature and magnetic field. Besides the possibility to control the lifetime of selected switching events at will, we find evidence for a more complex behavior caused by the special spin ice arrangement of the macrospins, i.e., that the magnetic reversal statistically follows distinct "paths" most likely driven by thermal perturbation. (C) 2015 AIP Publishing LLC.

  104. Evidence of a reduction reaction of oxidized iron/cobalt by boron atoms diffused toward naturally oxidized surface of CoFeB layer during annealing 査読有り

    Soshi Sato, Hiroaki Honjo, Shoji Ikeda, Hideo Ohno, Tetsuo Endoh, Masaaki Niwa

    Applied Physics Letters 106 (14) 142407(1)-142407(5) 2015年4月6日

    出版者・発行元:American Institute of Physics Inc.

    DOI: 10.1063/1.4917277  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    We have investigated the redox reaction on the surface of Ta/CoFeB/MgO/CoFeB magnetic tunnel junction stack samples after annealing at 300, 350, and 400 °C for 1 h using angle-resolved X-ray photoelectron spectroscopy for precise analysis of the chemical bonding states. At a capping tantalum layer thickness of 1 nm, both the capping tantalum layer and the surface of the underneath CoFeB layer in the as-deposited stack sample were naturally oxidized. By comparison of the Co 2p and Fe 2p spectra among the as-deposited and annealed samples, reduction of the naturally oxidized cobalt and iron atoms occurred on the surface of the CoFeB layer. The reduction reaction was more significant at higher annealing temperature. Oxidized cobalt and iron were reduced by boron atoms that diffused toward the surface of the top CoFeB layer. A single CoFeB layer was prepared on SiO2, and a confirmatory evidence of the redox reaction with boron diffusion was obtained by angle-resolved X-ray photoelectron spectroscopy analysis of the naturally oxidized surface of the CoFeB single layer after annealing. The redox reaction is theoretically reasonable based on the Ellingham diagram.

  105. In-plane anisotropy of a nano-scaled magnetic tunnel junction with perpendicular magnetic easy axis 査読有り

    Eriko Hirayama, Shun Kanai, Koji Sato, Michihiko Yamanouchi, Hideo Sato, Shoji Ikeda, Fumihiro Matsukura, Hideo Ohno

    JAPANESE JOURNAL OF APPLIED PHYSICS 54 (4) 04DM03(1)-04DM03(3) 2015年4月

    出版者・発行元:IOP PUBLISHING LTD

    DOI: 10.7567/JJAP.54.04DM03  

    ISSN:0021-4922

    eISSN:1347-4065

    詳細を見る 詳細を閉じる

    We investigate magnetic properties of a 100-nm-diameter CoFeB/MgO magnetic tunnel junction (MTJ) with perpendicular magnetic easy axis by homodyne-detected ferromagnetic resonance (FMR) and junction resistance measurements. The resonant frequency depends clearly on the direction of the in-plane magnetic field, which is also the case for the angle dependence of the junction resistance. A good correspondence between the two independent measurements indicates the presence of unintentionally introduced in-plane magnetic anisotropy in the present MTJ. (C) 2015 The Japan Society of Applied Physics

  106. Dependence of magnetic properties of MgO/CoFeB/Ta stacks on CoFeB and Ta thicknesses 査読有り

    Kyota Watanabe, Shinya Ishikawa, Hideo Sato, Shoji Ikeda, Michihiko Yamanouchi, Shunsuke Fukami, Fumihiro Matsukura, Hideo Ohno

    JAPANESE JOURNAL OF APPLIED PHYSICS 54 (4) 04DM04(1)-04DM04(3) 2015年4月

    出版者・発行元:IOP PUBLISHING LTD

    DOI: 10.7567/JJAP.54.04DM04  

    ISSN:0021-4922

    eISSN:1347-4065

    詳細を見る 詳細を閉じる

    We investigate the dependence of magnetic properties of MgO/CoFeB/Ta stacks on thicknesses of CoFeB ranging from 2 to 30 nm and Ta from 1 to 10nm before and after annealing at 300-400 degrees C for 1-3 h. The annealing increases the saturation magnetic moment per unit area and reduces the magnitude of the damping constant in CoFeB. The annealing effect becomes smaller with increasing CoFeB thickness and with decreasing Ta thickness, indicating that the effect is related to B diffusion from CoFeB to Ta. We show that the amount of diffused B can be controlled by Ta layer thickness and annealing duration. (C) 2015 The Japan Society of Applied Physics

  107. Properties of perpendicular-anisotropy magnetic tunnel junctions fabricated over the bottom electrode contact 査読有り

    Sadahiko Miura, Hiroaki Honjo, Keizo Kinoshita, Keiichi Tokutome, Hiroaki Koike, Shoji Ikeda, Tetsuo Endoh, Hideo Ohno

    JAPANESE JOURNAL OF APPLIED PHYSICS 54 (4) 04DM06(1)-04DM06(4) 2015年4月

    出版者・発行元:IOP PUBLISHING LTD

    DOI: 10.7567/JJAP.54.04DM06  

    ISSN:0021-4922

    eISSN:1347-4065

    詳細を見る 詳細を閉じる

    Perpendicular-anisotropy magnetic tunnel junctions (MTJs) were prepared on four substrate geometries, i.e., directly on the axis of the bottom electrode contact, directly off the axis of the bottom electrode contact, on the axis of the bottom electrode contact with a polished bottom electrode, and off the axis of the bottom electrode contact with a polished bottom electrode. Electrical shorts were observed for direct on-axis geometry at a certain extent, whereas there were no electrical shorts for the other three geometries. The MR ratio/sigma R, J(C0), and thermal stability factor of the devices for polish on-axis geometry were almost the same as those for polish off-axis geometry. From TEM observations of the polish on-axis device, the interface between the bottom contact and the base electrode was determined to be rough, whereas the MgO barrier layer was determined to be smooth, indicating that the polish process was effective for smooth magnetic tunnel junction fabrication over the bottom contact. MTJs for polish on-axis geometry eliminated the base electrode resistance and increased the magnetoresistance ratio. This technology contributes to the higher density of spin transfer torque magnetic random access memory. (C) 2015 The Japan Society of Applied Physics

  108. Power-gated 32 bit microprocessor with a power controller circuit activated by deep-sleep-mode instruction achieving ultra-low power operation 査読有り

    Hiroki Koike, Takashi Ohsawa, Sadahiko Miura, Hiroaki Honjo, Shoji Ikeda, Takahiro Hanyu, Hideo Ohno, Tetsuo Endoh

    JAPANESE JOURNAL OF APPLIED PHYSICS 54 (4) 04DE08(1)-04DE08(5) 2015年4月

    出版者・発行元:IOP PUBLISHING LTD

    DOI: 10.7567/JJAP.54.04DE08  

    ISSN:0021-4922

    eISSN:1347-4065

    詳細を見る 詳細を閉じる

    A spintronic-based power-gated micro-processing unit (MPU) is proposed. It includes a power control circuit activated by the newly supported power-off instruction for the deep-sleep mode. These means enable the power-off procedure for the MPU to be executed appropriately. A test chip was designed and fabricated using 90nm CMOS and an additional 100nm MTJ process; it was successfully operated. The guideline of the energy reduction effects for this MPU was presented, using the estimation based on the measurement results of the test chip. The result shows that a large operation energy reduction of 1/28 can be achieved when the operation duty is 10%, under the condition of a sufficient number of idle clock cycles. (C) 2015 The Japan Society of Applied Physics

  109. Nature Nanotechnology 査読有り

    F. Matsuura, Y. Tokura, H. Ohno

    Nature Nanotechnology 10 209-220 2015年3月5日

  110. Control of magnetism by electric fields 査読有り

    Fumihiro Matsukura, Yoshinori Tokura, Hideo Ohno

    NATURE NANOTECHNOLOGY 10 (3) 209-220 2015年3月

    出版者・発行元:NATURE PUBLISHING GROUP

    DOI: 10.1038/NNANO.2015.22  

    ISSN:1748-3387

    eISSN:1748-3395

    詳細を見る 詳細を閉じる

    The electrical manipulation of magnetism and magnetic properties has been achieved across a number of different material systems. For example, applying an electric field to a ferromagnetic material through an insulator alters its charge-carrier population. In the case of thin films of ferromagnetic semiconductors, this change in carrier density in turn affects the magnetic exchange interaction and magnetic anisotropy; in ferromagnetic metals, it instead changes the Fermi level position at the interface that governs the magnetic anisotropy of the metal. In multiferroics, an applied electric field couples with the magnetization through electrical polarization. This Review summarizes the experimental progress made in the electrical manipulation of magnetization in such materials, discusses our current understanding of the mechanisms, and finally presents the future prospects of the field.

  111. Localized precessional mode of domain wall controlled by magnetic field and dc current 査読有り

    Ryo Hiramatsu, Kab-Jin Kim, Takuya Taniguchi, Takayuki Tono, Takahiro Moriyama, Shunsuke Fukami, Michihiko Yamanouchi, Hideo Ohno, Yoshinobu Nakatani, Teruo Ono

    APPLIED PHYSICS EXPRESS 8 (2) 023003(1)-023003(4) 2015年2月

    出版者・発行元:IOP PUBLISHING LTD

    DOI: 10.7567/APEX.8.023003  

    ISSN:1882-0778

    eISSN:1882-0786

    詳細を見る 詳細を閉じる

    We present evidence of a localized magnetic domain-wall (DW) oscillator in Co/Ni nanowires. It is found that a DW is localized by the simultaneous application of a high magnetic field larger than the depinning field and a dc current smaller than the threshold current. A one-dimensional model and micromagnetic simulation reveal that the localized DW is in a precessional mode. Our results suggest that a localized magnetic DW oscillator can be realized by appropriately adjusting the magnetic field and dc current. (C) 2015 The Japan Society of Applied Physics

  112. Nonvolatile Logic-in-Memory LSI Using Cycle-Based Power Gating and its Application to Motion-Vector Prediction 査読有り

    Masanori Natsui, Daisuke Suzuki, Noboru Sakimura, Ryusuke Nebashi, Yukihide Tsuji, Ayuka Morioka, Tadahiko Sugibayashi, Sadahiko Miura, Hiroaki Honjo, Keizo Kinoshita, Shoji Ikeda, Tetsuo Endoh, Hideo Ohno, Takahiro Hanyu

    IEEE JOURNAL OF SOLID-STATE CIRCUITS 50 (2) 476-489 2015年2月

    出版者・発行元:IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

    DOI: 10.1109/JSSC.2014.2362853  

    ISSN:0018-9200

    eISSN:1558-173X

    詳細を見る 詳細を閉じる

    A magnetic tunnel junction (MTJ)-based logic-in-memory hardware accelerator LSI with cycle-based power gating is fabricated using a 90 nm MTJ/MOS process on a 300 mm wafer fabrication line for practical-scale, fully parallel motion-vector prediction, without wasted power dissipation. The proposed nonvolatile LSI is designed by establishing an automated design environment with MTJ-based logic-circuit IPs and peripheral assistant tools, as well as a precise MTJ device model produced by the fabricated test chips. Through the measurement results of the fabricated LSI, this study shows both the impact of the power-gating technique in a fine temporal granularity utilizing the non-volatility of the MTJ device and the effectiveness of the established automated design environment for designing random logic LSI using nonvolatile logic-in-memory.

  113. Spintronics: from basic research to VLSI application 査読有り

    S. Kanai, F. Matsukura, H. Sato, S. Fukami

    Association of Aisa Pacific Physical Societies, AAPPS 25 4-11 2015年2月

  114. 17pCB-8 磁気異方性の電界制御とその応用

    金井 駿, 松倉 文礼, 大野 英男

    日本物理学会講演概要集 70 2288-2288 2015年

    出版者・発行元:一般社団法人日本物理学会

    DOI: 10.11316/jpsgaiyo.70.2.0_2288  

    ISSN:2189-079X

  115. 23pAD-1 磁場および電流によって制御された磁壁発振器

    平松 亮, Kim Kab-Jin, 谷口 卓也, 東野 隆之, 森山 貴広, 深見 俊輔, 山ノ内 路彦, 大野 英男, 仲谷 栄伸, 小野 輝男

    日本物理学会講演概要集 70 1196-1196 2015年

    出版者・発行元:一般社団法人日本物理学会

    DOI: 10.11316/jpsgaiyo.70.1.0_1196  

    ISSN:2189-079X

  116. CoFeB Thickness Dependence of Damping Constants for Single and Double CoFeB-MgO Interface Structures 査読有り

    Eli Christopher I. Enobio, Hideo Sato, Shunsuke Fukami, Fumihiro Matsukura, Hideo Ohno

    IEEE MAGNETICS LETTERS 6 5700303(1)-5700303(3) 2015年

    出版者・発行元:IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

    DOI: 10.1109/LMAG.2015.2475718  

    ISSN:1949-307X

    詳細を見る 詳細を閉じる

    We investigate the CoFeB thickness dependence of the damping constant a of single and double CoFeB-MgO interface structures by vector-network-analyzer ferromagnetic resonance (VNA-FMR). The damping constant increases with decreasing the CoFeB thickness for the single interface structure, and the damping constant for the double-interface structure takes a similar value to that for the single-interface structures with the same CoFeB thickness.

  117. Magnetic anisotropy in Ta/CoFeB/MgO investigated by x-ray magnetic circular dichroism and first-principles calculation 査読有り

    Shun Kanai, Masahito Tsujikawa, Yoshio Miura, Masafumi Shirai, Fumihiro Matsukura, Hideo Ohno

    APPLIED PHYSICS LETTERS 105 (22) 222409(1)-222409(4) 2014年12月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.4903296  

    ISSN:0003-6951

    eISSN:1077-3118

    詳細を見る 詳細を閉じる

    We study the spin and orbital magnetic moments in Ta/Co0.4Fe0.4B0.2/MgO by x-ray magnetic circular dichroism measurements as well as first-principles calculations, in order to clarify the origin of the perpendicular magnetic anisotropy. Both experimental and theoretical results show that orbital magnetic moment of Fe is more anisotropic than that of Co with respect to the magnetization direction. The anisotropy is larger for thinner CoFeB, indicating that Fe atoms at the interface with MgO contribute more than Co to the observed perpendicular magnetic anisotropy. (C) 2014 AIP Publishing LLC.

  118. A Nonvolatile Associative Memory-Based Context-Driven Search Engine Using 90 nm CMOS/MTJ-Hybrid Logic-in-Memory Architecture 査読有り

    Hooman Jarollahi, Naoya Onizawa, Vincent Gripon, Noboru Sakimura, Tadahiko Sugibayashi, Tetsuo Endoh, Hideo Ohno, Takahiro Hanyu, Warren J. Gross

    IEEE JOURNAL ON EMERGING AND SELECTED TOPICS IN CIRCUITS AND SYSTEMS 4 (4) 460-474 2014年12月

    出版者・発行元:IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

    DOI: 10.1109/JETCAS.2014.2361061  

    ISSN:2156-3357

    詳細を見る 詳細を閉じる

    This paper presents algorithm, architecture, and fabrication results of a nonvolatile context-driven search engine that reduces energy consumption as well as computational delay compared to classical hardware and software-based approaches. The proposed architecture stores only associations between items from multiple search fields in the form of binary links, and merges repeated field items to reduce the memory requirements and accesses. The fabricated chip achieves memory reduction and 89% energy saving compared to a classical field-based approach in hardware, based on content-addressable memory (CAM). Furthermore, it achieves reduced number of clock cycles in performing search operations compared to the CAM, and five orders of magnitude reduced number of clock cycles compared to a fabricated and measured ultra low-power CPU-based counterpart running a classical search algorithm in software. The energy consumption of the proposed architecture is on average three orders of magnitude smaller than that of a software-based approach. A magnetic tunnel junction (MTJ)-based logic-in-memory architecture is presented that allows simple routing and eliminates leakage current in standby using 90 nm CMOS/MTJ-hybrid technologies.

  119. Electric field-induced ferromagnetic resonance in a CoFeB/MgO magnetic tunnel junction under dc bias voltages 査読有り

    Shun Kanai, Martin Gajek, D. C. Worledge, Fumihiro Matsukura, Hideo Ohno

    APPLIED PHYSICS LETTERS 105 (24) 242409(1)-242409(4) 2014年12月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.4904956  

    ISSN:0003-6951

    eISSN:1077-3118

    詳細を見る 詳細を閉じる

    We measure homodyne-detected ferromagnetic resonance (FMR) induced by the electric-field effect in a CoFeB/MgO/CoFeB magnetic tunnel junction (MTJ) with perpendicular magnetic easy axis under dc bias voltages up to 0.1 V. From the bias dependence of the resonant frequency, we find that the first order perpendicular magnetic anisotropy is modulated by the applied electric field, whereas the second order component is virtually independent of the electric field. The lineshapes of the FMR spectra are bias dependent, which are explained by the combination of electric-field effect and reflection of the bias voltage from the MTJ. (C) 2014 AIP Publishing LLC.

  120. Material stack design with high tolerance to process induced damage in domain wall motion device 査読有り

    H. Honjo, S. Fukami, K. Ishihara, K. Kinoshita, Y. Tsuji, A. Morioka, R. Nebashi, K. Tokutome, N. Sakimura, M. Murahata, S. Miura, T. Sugibayashi, N. Kasai, H. Ohno

    IEEE Transaction on Magnetics 50 (11) 1401904-1401904 2014年11月18日

    DOI: 10.1109/TMAG.2014.2325019  

    ISSN:0018-9464

  121. Domain Wall Motion Device for Nonvolatile Memory and Logic - Size Dependence of Device Properties 査読有り

    Shunsuke Fukami, Michihiko Yamanouchi, Shoji Ikeda, Hideo Ohno

    IEEE TRANSACTIONS ON MAGNETICS 50 (11) 3401006(1)-3401006(6) 2014年11月

    出版者・発行元:IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

    DOI: 10.1109/TMAG.2014.2321396  

    ISSN:0018-9464

    eISSN:1941-0069

    詳細を見る 詳細を閉じる

    Current-induced magnetic domain wall (DW)-motion device with a three-or four-terminal structure has considerable potential to trigger a profound transformation in memory and logic technologies. In this paper, we give an overview of DW-motion devices and describe their structure, operation method, and characteristics. Previous studies on the DW motion in nanowires with a Co/Ni multilayer are also reviewed. We also report on the experimental results regarding device properties, such as critical current, the time and energy required to displace the DW in the device, and retention properties with various device sizes down to 20 nm. The results reveal that writing properties are enhanced while sufficient retention properties are maintained as the device size is reduced, indicating that the DW-motion device has high scalability and compatibility with conventional semiconductor-based cells as well as ultralow power capability.

  122. Process-induced damage and its recovery for a CoFeB-MgO magnetic tunnel junction with perpendicular magnetic easy axis 査読有り

    Keizo Kinoshita, Hiroaki Honjo, Shunsuke Fukami, Hideo Sato, Kotaro Mizunuma, Keiichi Tokutome, Michio Murahata, Shoji Ikeda, Sadahiko Miura, Naoki Kasai, Hideo Ohno

    JAPANESE JOURNAL OF APPLIED PHYSICS 53 (10) 103001(1)-103001(6) 2014年10月

    出版者・発行元:IOP PUBLISHING LTD

    DOI: 10.7567/JJAP.53.103001  

    ISSN:0021-4922

    eISSN:1347-4065

    詳細を見る 詳細を閉じる

    We investigate the effect of process-induced damage (PID) caused by reactive ion etching using methanol (Me-OH) gas on the magnetic properties of the CoFeB free layer in a magnetic tunnel junction with a perpendicular easy axis (p-MTJ), and on the tunnel magnetoresistance (TMR) ratio of CoFeB-MgO p-MTJs. The dot pattern of the MTJ stack with size varied from 65 to 430 nm etched by the Me-OH plasma showed a smaller coercivity (H-c) than that fabricated by Ar ion milling. The increase in H-c was observed in the dot pattern of large size (430 nm) upon increasing He/H-2 plasma treatment temperature after the Me-OH etching. A possible origin of the increase in H-c is the increase in nucleation field after He/H-2 treatment. This suggests that H-c of the large dot pattern has the potential to be an index for detecting PID during the MTJ fabrication process. The TMR ratio of CoFeB-MgO p-MTJ deteriorated after the Me-OH plasma etching. This PID was considered to be due to oxidation from the pattern edge of the CoFeB free layer of the MTJ. The recovery process by the He/H-2 plasma treatment was examined just after the Me-OH etching to reduce the oxidized part. The median TMR ratio of 102%, which is 5% higher than that of the sample without the He/H-2 treatment, was observed after applying this reductive treatment at 180 degrees C. In addition, the recovery process had scalability with MTJ size, as the effect was observed more clearly in the MTJ smaller than 97 nm. (C) 2014 The Japan Society of Applied Physics

  123. Influence of Heavy Ion Irradiation on Perpendicular-Anisotropy CoFeB-MgO Magnetic Tunnel Junctions 査読有り

    Daisuke Kobayashi, Yuya Kakehashi, Kazuyuki Hirose, Shinobu Onoda, Takahiro Makino, Takeshi Ohshima, Shoji Ikeda, Michihiko Yamanouchi, Hideo Sato, Eli Christopher Enobio, Tetsuo Endoh, Hideo Ohno

    IEEE TRANSACTIONS ON NUCLEAR SCIENCE 61 (4) 1710-1716 2014年8月

    出版者・発行元:IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

    DOI: 10.1109/TNS.2014.2304738  

    ISSN:0018-9499

    eISSN:1558-1578

    詳細を見る 詳細を閉じる

    A non-volatile memory element called a perpendicular-anisotropy magnetic tunnel junction was fabricated using CoFeB/MgO/CoFeB film stack technology. It exhibits two stable resistance values, high or low, depending on the relative directions of the magnetizations of the two ferromagnetic CoFeB layers. After being programmed into the high resistance state with a current injection scheme based on the spin transfer torque theory, the tunnel junction was exposed to 15-MeV Si ions under different voltage stress conditions. The tested structure remained in the programmed high resistance state after being bombarded with 10-100 Si ions, even under the stressed situations. A time-domain analysis proved that this result is due to the perfect immunity of the tested magnetic tunnel junction to single event upsets. Some degradation in resistance due to the heavy-ion irradiation was detected through a precise parameter analysis based on a tunneling theory but it was negligibly small (1%). There were no statistically significant changes in the thermal stability factor before and after irradiation, and this means the long-term retention properties remained unchanged.

  124. Electric-field effects on magnetic anisotropy and damping constant in Ta/CoFeB/MgO investigated by ferromagnetic resonance 査読有り

    A. Okada, S. Kanai, M. Yamanouchi, S. Ikeda, F. Matsukura, H. Ohno

    APPLIED PHYSICS LETTERS 105 (5) 052415-(1)-052415-(4) 2014年8月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.4892824  

    ISSN:0003-6951

    eISSN:1077-3118

    詳細を見る 詳細を閉じる

    We investigate electric-field effects on the effective magnetic anisotropy energy density K-eff and the Gilbert damping constant alpha in Ta/CoFeB/MgO structures with CoFeB thickness t ranging from 1.4 to 1.8 nm by ferromagnetic resonance. The electric field-induced modulation ratio of the areal energy density K(eff)t does not depend on the CoFeB thickness, indicating that the electric-field effect on the magnetic anisotropy originates from the modulation of CoFeB/MgO-interfacial magnetic anisotropy. A clear electric-field modulation of alpha is observed for the structure with t = 1.4 nm, and almost no modulation for the structures with t &gt;= 1.5 nm. (C) 2014 AIP Publishing LLC.

  125. Properties of magnetic tunnel junctions with a MgO/CoFeB/Ta/CoFeB/MgO recording structure down to junction diameter of 11 nm 査読有り

    H. Sato, E. C. I. Enobio, M. Yamanouchi, S. Ikeda, S. Fukami, S. Kanai, F. Matsukura, H. Ohno

    APPLIED PHYSICS LETTERS 105 (6) 062403(1)-062403(4) 2014年8月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.4892924  

    ISSN:0003-6951

    eISSN:1077-3118

    詳細を見る 詳細を閉じる

    We investigate properties of perpendicular anisotropy magnetic tunnel junctions (MTJs) with a recording structure of MgO/CoFeB/Ta/CoFeB/MgO down to junction diameter (D) of 11 nm from 56 nm. Thermal stability factor (Delta) of MTJ with the structure starts to decrease at D = 30 nm. D dependence of Delta agrees well with that expected from magnetic properties of blanket film taking into account the change in demagnetizing factors of MTJs. Intrinsic critical current (I-C0) reduces with decrease of D in the entire investigated D range. A ratio of D to IC0 shows continuous increase with decrease of D down to 11 nm. (C) 2014 AIP Publishing LLC.

  126. Interface control of the magnetic chirality in CoFeB/MgO heterostructures with heavy-metal underlayers 査読有り

    Jacob Torrejon, Junyeon Kim, Jaivardhan Sinha, Seiji Mitani, Masamitsu Hayashi, Michihiko Yamanouchi, Hideo Ohno

    NATURE COMMUNICATIONS 5 (4693) 5693-(1)-5693-(8) 2014年8月

    出版者・発行元:NATURE PUBLISHING GROUP

    DOI: 10.1038/ncomms5655  

    ISSN:2041-1723

    詳細を見る 詳細を閉じる

    Recent advances in the understanding of spin orbital effects in ultrathin magnetic hetero-structures have opened new paradigms to control magnetic moments electrically. The Dzyaloshinskii-Moriya interaction (DMI) is said to play a key role in forming a Neel-type domain wall that can be driven by the spin Hall torque. Here we show that the strength and sign of the DMI can be changed by modifying the adjacent heavy-metal underlayer (X) in perpendicularly magnetized X/CoFeB/MgO heterostructures. The sense of rotation of a domain wall spiral is reversed when the underlayer is changed from Hf, Ta to W and the strength of DMI varies as the filling of 5d orbitals, or the electronegativity, of the heavy-metal layer changes. The DMI can even be tuned by adding nitrogen to the underlayer, thus allowing interface engineering of the magnetic texture in ultrathin magnetic heterostructures.

  127. Properties of (Ga,Mn)As codoped with Li 査読有り

    Shohei Miyakozawa, Lin Chen, Fumihiro Matsukura, Hideo Ohno

    APPLIED PHYSICS LETTERS 104 (22) 222408-(1)-222408-(4) 2014年6月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.4881636  

    ISSN:0003-6951

    eISSN:1077-3118

    詳細を見る 詳細を閉じる

    We grow Li codoped (Ga,Mn)As layers with nominal Mn composition up to 0.15 by molecular beam epitaxy. The layers before and after annealing are characterized by x-ray diffraction, transport, magnetization, and ferromagnetic resonance measurements. The codoping with Li reduces the lattice constant and electrical resistivity of (Ga,Mn)As after annealing. We find that (Ga,Mn)As: Li takes similar Curie temperature to that of (Ga,Mn)As, but with pronounced magnetic moments and in-plane magnetic anisotropy, indicating that the Li codoping has nontrivial effects on the magnetic properties of (Ga,Mn)As. (C) 2014 AIP Publishing LLC.

  128. Co/Pt multilayer-based magnetic tunnel junctions with a CoFeB/Ta insertion layer 査読有り

    S. Ishikawa, H. Sato, M. Yamanouchi, S. Ikeda, S. Fukami, F. Matsukura, H. Ohno

    JOURNAL OF APPLIED PHYSICS 115 (17) 17C719(1)-17C719(3) 2014年5月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.4862724  

    ISSN:0021-8979

    eISSN:1089-7550

    詳細を見る 詳細を閉じる

    We investigate properties of magnetic tunnel junctions (MTJs) having a Co/Pt multilayer as a recording layer. A CoFeB layer is inserted between MgO barrier and the recording layer in order to enhance the tunnel magnetoresistance ratio. We show that an additional layer of Ta inserted between CoFeB and Co/Pt multilayer is effective in improving the MTJ properties after annealing. A high effective magnetic anisotropy energy per unit area over 1.2mJ/m(2) is obtained after annealing at 300 degrees C. Using a 1.6 nm-thick CoFeB insertion layer, both high thermal stability factor of 92 and high tunnel magnetoresistance ratio of 91% are achieved in a MTJ with 17 nm in diameter. (C) 2014 AIP Publishing LLC.

  129. Distribution of critical current density for magnetic domain wall motion 査読有り

    S. Fukami, M. Yamanouchi, Y. Nakatani, K. -J. Kim, T. Koyama, D. Chiba, S. Ikeda, N. Kasai, T. Ono, H. Ohno

    JOURNAL OF APPLIED PHYSICS 115 (17) 17D508(1)-17D508(3) 2014年5月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.4866394  

    ISSN:0021-8979

    eISSN:1089-7550

    詳細を見る 詳細を閉じる

    The bit-to-bit distribution of a critical current density for magnetic domain wall (DW) motion is studied using Co/Ni wires with various wire widths (ws). The distribution inherently decreases with the w, and the ratio of standard deviation to average is 9.8% for wires with w = 40 nm. It is found that a self-distribution within one device, which is evaluated through repeated measurement, is a dominant factor in the bit-to-bit distribution. Micromagnetic simulation reveals that the distribution originates from DW configuration, which varies with device size. (C) 2014 AIP Publishing LLC.

  130. Anomalous temperature dependence of current-induced torques in CoFeB/MgO heterostructures with Ta-based underlayers 査読有り

    Junyeon Kim, Jaivardhan Sinha, Seiji Mitani, Masamitsu Hayashi, Saburo Takahashi, Sadamichi Maekawa, Michihiko Yamanouchi, Hideo Ohno

    PHYSICAL REVIEW B 89 (17) 174424-(1)-174424-(8) 2014年5月

    出版者・発行元:AMER PHYSICAL SOC

    DOI: 10.1103/PhysRevB.89.174424  

    ISSN:1098-0121

    eISSN:1550-235X

    詳細を見る 詳細を閉じる

    We have studied the underlayer thickness and temperature dependencies of the current-induced effective field in CoFeB/MgO heterostructures with Ta-based underlayers. The underlayer thickness at which the effective field saturates is found to be different between the two orthogonal components of the effective field; i.e., the dampinglike term tends to saturate at a smaller underlayer thickness than the fieldlike term. For large underlayer thickness films in which the effective field saturates, we find that the measurement temperature significantly influences the size of the effective field. A striking difference is found in the temperature dependence of the two components: the dampinglike term decreases whereas the fieldlike term increases with increasing temperature. Using a simple spin diffusion-spin transfer model, we find that all of these results can be accounted for provided the real and imaginary parts of an effective spin mixing conductance are negative. These results imply that either spin transport in this system is different from conventional metallic interfaces or effects other than spin diffusion into the magnetic layer need to be taken into account in order to model the system accurately.

  131. Magnetization switching in a CoFeB/MgO magnetic tunnel junction by combining spin-transfer torque and electric field-effect 査読有り

    S. Kanai, Y. Nakatani, M. Yamanouchi, S. Ikeda, H. Sato, F. Matsukura, H. Ohno

    APPLIED PHYSICS LETTERS 104 (21) 212406(1)-212406(3) 2014年5月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.4880720  

    ISSN:0003-6951

    eISSN:1077-3118

    詳細を見る 詳細を閉じる

    We propose and demonstrate a scheme for magnetization switching in magnetic tunnel junctions, in which two successive voltage pulses are applied to utilize both spin-transfer torque and electric field effect. Under this switching scheme, a CoFeB/MgO magnetic tunnel junction with perpendicular magnetic easy axis is shown to switch faster than by spin-transfer torque alone and more reliably than that by electric fields alone. (C) 2014 AIP Publishing LLC.

  132. Co/Pt multilayer based reference layers in magnetic tunnel junctions for nonvolatile spintronics VLSIs 査読有り

    Hideo Sato, Shoji Ikeda, Shunsuke Fukami, Hiroaki Honjo, Shinya Ishikawa, Michihiko Yamanouchi, Kotaro Mizunuma, Fumihiro Matsukura, Hideo Ohno

    JAPANESE JOURNAL OF APPLIED PHYSICS 53 (4) 04EM02(1)-04EM02(3) 2014年4月

    出版者・発行元:IOP PUBLISHING LTD

    DOI: 10.7567/JJAP.53.04EM02  

    ISSN:0021-4922

    eISSN:1347-4065

    詳細を見る 詳細を閉じる

    We investigated properties of Co/Pt multilayer for reference layer in CoFeB-MgO magnetic tunnel junctions with perpendicular easy axis. The sufficient thermal stability factor of 284 was obtained under zero applied field in 40-nm-diameter Co/Pt multilayer based reference layer annealed at 350 degrees C. By applying a synthetic ferrimagnetic (SyF) structure to the Co/Pt multilayer based reference layer, the shift of the center of minor resistance-magnetic field curves was suppressed, leading to higher thermal stability of antiparallel magnetization configuration than that without a SyF structure. (C) 2014 The Japan Society of Applied Physics

  133. Direct mapping of photoexcited local spins in a modulation-doped GaAs/AlGaAs wires 査読有り

    Jun Ishihara, Yuzo Ohno, Hideo Ohno

    JAPANESE JOURNAL OF APPLIED PHYSICS 53 (4) 04EM04(1)-04EM04(3) 2014年4月

    出版者・発行元:IOP PUBLISHING LTD

    DOI: 10.7567/JJAP.53.04EM04  

    ISSN:0021-4922

    eISSN:1347-4065

    詳細を見る 詳細を閉じる

    We directly measured the spatiotemporal evolution of photoexcited local spins in wires made from a modulation-doped GaAs/AlGaAs quantum well by using a time- and spatially resolved Kerr microscopy. We observed the spatial pattern of spin-up and -down near the case of persistent spin helix (PSH) in [110] wires and the retention of the initial spin state in [110] wires which were designed such that the Dresselhaus and Rashba spinorbit interaction are nearly equal to each other in magnitude. (C) 2014 The Japan Society of Applied Physics

  134. Quantitative characterization of the spin-orbit torque using harmonic Hall voltage measurements 査読有り

    Masamitsu Hayashi, Junyeon Kim, Michihiko Yamanouchi, Hideo Ohno

    PHYSICAL REVIEW B 89 (14) 144425-(1)-144425-(15) 2014年4月

    出版者・発行元:AMER PHYSICAL SOC

    DOI: 10.1103/PhysRevB.89.144425  

    ISSN:1098-0121

    eISSN:1550-235X

    詳細を見る 詳細を閉じる

    Solid understanding of current induced torques is a key to the development of current and voltage controlled magnetization dynamics in ultrathin magnetic heterostructures. To evaluate the size and direction of such torques, or effective fields, a number of methods have been employed. Here, we examine the adiabatic (low-frequency) harmonic Hall voltage measurement that has been used to study the effective field. We derive an analytical formula for the harmonic Hall voltages to evaluate the effective field for both out of plane and in-plane magnetized systems. The formula agrees with numerical calculations based on a macrospin model. Two different in-plane magnetized films, Pt|CoFeB|MgO and CuIr|CoFeB|MgO are studied using the formula developed. The effective field obtained for the latter system shows relatively good agreement with that estimated using spin torque switching phase diagram measurements reported previously. Our results illustrate the versatile applicability of harmonic Hall voltage measurement for studying current induced torques in magnetic heterostructures.

  135. MgO/CoFeB/Ta/CoFeB/MgO recording structure with low intrinsic critical current and high thermal stability 査読有り

    H. Sato, M. Yamanouchi, S. Ikeda, S. Fukami, F. Matsukura, H. Ohno

    Journal of the Magnetics Society of Japan 38 (No. 2-2) 56-60 2014年3月20日

    DOI: 10.3379/msjmag.1403R002  

  136. Strain and origin of inhomogeneous broadening probed by optically detected nuclear magnetic resonance in a (110) GaAs quantum well 査読有り

    M. Ono, J. Ishihara, G. Sato, S. Matsuzaka, Y. Ohno, H. Ohno

    PHYSICAL REVIEW B 89 (11) 115308(1)-115308(4) 2014年3月

    出版者・発行元:AMER PHYSICAL SOC

    DOI: 10.1103/PhysRevB.89.115308  

    ISSN:1098-0121

    eISSN:1550-235X

    詳細を見る 詳細を閉じる

    We obtained strain and electric field gradient (EFG) in an n-GaAs/Al0.3Ga0.7As (110) quantum well (QW) by optically detected nuclear magnetic resonance (NMR). The dependence of the quadrupolar splitting on an angle between the QW plane and a static magnetic field provided the crystalline-orientation-dependent EFG and strain in the GaAs QW. We also explored the dependence of the NMR line widths on the direction of the external magnetic field with respect to the QWplane. It is likely that the nonuniform EFG as well as the hyperfine interaction governs the inhomogeneous broadening of NMR spectra.

  137. Dilute ferromagnetic semiconductors: Physics and spintronic structures 査読有り

    Tomasz Dietl, Hideo Ohno

    REVIEWS OF MODERN PHYSICS 86 (1) 187-251 2014年3月

    出版者・発行元:AMER PHYSICAL SOC

    DOI: 10.1103/RevModPhys.86.187  

    ISSN:0034-6861

    eISSN:1539-0756

    詳細を見る 詳細を閉じる

    This review compiles results of experimental and theoretical studies on thin films and quantum structures of semiconductors with randomly distributed Mn ions, which exhibit spintronic functionalities associated with collective ferromagnetic spin ordering. Properties of p-type Mn-containing III-V as well as II-VI, IV-VI, V-2 -VI3, I-II-V, and elemental group IV semiconductors are described, paying particular attention to the most thoroughly investigated system (Ga, Mn)As that supports the hole-mediated ferromagnetic order up to 190 K for the net concentration of Mn spins below 10%. Multilayer structures showing efficient spin injection and spin-related magnetotransport properties as well as enabling magnetization manipulation by strain, light, electric fields, and spin currents are presented together with their impact on metal spintronics. The challenging interplay between magnetic and electronic properties in topologically trivial and nontrivial systems is described, emphasizing the entangled roles of disorder and correlation at the carrier localization boundary. Finally, the case of dilute magnetic insulators is considered, such as (Ga, Mn)N, where low-temperature spin ordering is driven by short-ranged superexchange that is ferromagnetic for certain charge states of magnetic impurities.

  138. Journal of Applied Physics 査読有り

    C. Zhang, M. Yamanouchi, H .Sato, S. Fukami, S. Ikeda, F. Matsukura, H. Ohno

    Magnetization reversal induced by in-plane current in Ta/CoFeB/MgO structures with perpendicular magnetic easy axis 115 17C714(1)-17C714(3) 2014年1月29日

  139. Plasma process induced physical damages on ultra-thin multilayered films for magnetic domain wall motion devices 査読有り

    K. Kinoshita, H. Honjo, S. Fukami, R. Nebashi, S. Miura, N. Kasai, S. Ikeda, H. Ohno

    Japanese Journal of Applied Physics 53 (3 SPEC. ISSUE 2) 2014年

    DOI: 10.7567/JJAP.53.03DF03  

    ISSN:0021-4922

    eISSN:1347-4065

  140. Three-terminal magnetic tunneling junction device with perpendicular anisotropy CoFeB sensing layer 査読有り

    H. Honjo, S. Fukami, K. Ishihara, R. Nebashi, K. Kinoshita, K. Tokutome, M. Murahata, S. Miura, N. Sakimura, T. Sugibayashi, N. Kasai, H. Ohno

    Journal of Applied Physics 115 (17) 17B750 2014年

    DOI: 10.1063/1.4868623  

    ISSN:0021-8979

    eISSN:1089-7550

  141. IEEE Transactions on Magnetics 査読有り

    S. Kanai, M. Yamanouchi, S. Ikeda, Y. Nakatani, F. Matsukura, H. Ohno

    Electric field-induced magnetization switching in CoFeB-MgO-static magnetic field angle dependence 50 (1) 4200103(1)-4200103(3) 2014年1月

  142. Applied Physics Express 査読有り

    J. Ishihara, Y. Ohno, H. Ohno

    Direct imaging of gate-controlled persistent spin helix state in a modulation-doped GaAs/AlGaAs quantum well 7 013001(1)-013001(4) 2014年1月

  143. Applied Physics Express 査読有り

    L. Chen, S. Ikeda, F. Matsukura, H. Ohno

    DC voltages in Py and Py/Pt under ferromagnetic resonance 7 013002(1)-013002(4) 2014年1月

  144. Applied Physics Letters 査読有り

    C. Zhang, M. Yamanouchi, H. Sato, S. Fukami, S. Ikeda, F. Matsukura, H. Ohno

    Magnetotransport measurements of current induced effective fields in Ta/CoFeB/MgO 103 262407(1)-262407(3) 2013年12月31日

  145. Applied Physics Letters 査読有り

    E. C. I. Enobio, K. Ohtani, Y. Ohno, H. Ohno

    Detection and measurement of electroreflectance on quantum cascade laser device using Fourier transform infrared microscope 103 231106(1)-231106(4) 2013年12月4日

  146. Fabrication of a Perpendicular-MTJ-Based Compact Nonvolatile Programmable Switch Using Shared-Write-Control-Transistor Structure 査読有り

    D. Suzuki, M. Natsui, A. Mochizuki, S. Miura, H. Honjo, K. Kinoshita, H. Sato, S. Fukami, S. Ikeda, T. Endoh, H. Ohno, T. Hanyu

    Abst. 58th Annual Conference on Magnetism and Magnetic Materials 233 2013年11月

  147. MTJ resistance distribution and its bit error rate of 1-kbit 1T-1MTJ STT-MRAM cell arrays fabricated on a 300-mm wafer 査読有り

    H. Koike, T. Ohsawa, S. Miura, H. Honjo, S. Ikeda, T. Hanyu, H. Ohno

    58th Annual Conference on Magnetism & Magnetic Materials Abstract 2013年11月

  148. Applied Physics Express 査読有り

    M. Kawaguchi, K. Shimamura, S. Fukami, F. Matsukura, H. Ohno, T. Moriyama, D. Chiba, T. Ono

    Current-induced effectivve fields detected by magnetotransport measurements 6 113002(1)-113002(4) 2013年10月18日

  149. Applied Physics Letters 査読有り

    D. Chiba, T. Ono, F. Matsukura, H. Ohno

    Electric field control of thermal stability and magnetization switching in (Ga,Mn)As 103 142418(1)-142418(4) 2013年10月4日

  150. Applied Physics Letters 査読有り

    H. W. Chang, S. Akita, F. Matsukura, H. Ohno

    Hole concentration dependence of the Curie temperature of (Ga,Mn)Sb in a field-effect structure 103 142402(1)-142402(4) 2013年9月30日

  151. Applied Physics Letters 査読有り

    S. Kanai, Y. Nakatani, M. Yamanouchi, S. Ikeda, F. Matsukura, H. Ohno

    In-plane magnetic field dependence of electric field-induced magnetization switching 103 072408(1)-072408(4) 2013年8月16日

  152. Nature Communications 査読有り

    S. Fukami, M. Yamanouchi, S. Ikeda, H. Ohno

    Depinning probability of a magnetic domain wall in nanowires by spin-polarized currents 4 1-7 2013年8月15日

  153. Applied Physics Express 査読有り

    S. Fukami, H. Sato, M. Yamanouchi, S. Ikeda, H. Ohno

    CoNi films with perpendicular magnetic anisotropy prepared by alternate monoatomic layer deposition 6 073010(1)-073010(3) 2013年7月9日

  154. IEEE Transactions on Magnetics 査読有り

    H. Sato, M. Yamanouchi, S. Ikeda, S. Fukami, F. Matsukura, H. Ohno

    MgO/CoFeB/Ta/CoFeB/MgO recording structure in magnetic tunnel junctions with perpendicular easy axis 49 (7) 4437-4440 2013年7月7日

  155. IEEE Journal of Solid-State Circuits 査読有り

    T. Ohsawa, H. Koike, S. Miura, H. Honjo, K. Kinoshita, S. Ikeda, T. Hanyu, H. Ohno, T. Endoh

    A 1 Mb nonvolatile embedded memory using 4T2MTJ cell with 32 b fine-grained power gating scheme 48 (6) 1511-1520 2013年6月22日

  156. Nature Communications 査読有り

    L. Chen, F. Matsukura, H. Ohno

    Direct-current voltages in (Ga,Mn)As structures induced by ferromagnetic resonance 4 1-6 2013年6月20日

  157. Applied Physics Letters 査読有り

    J. Sinha, M. Hayashi, A. J. Kellock, S. Fukami, M. Yamanouchi, H. Sato, S. Ikeda, S. Mitani, S. H. Yang, S. S. P. Parkin, H. Ohno

    Enhanced interface perpendicular magnetic anisotropy in Ta|CoFeB|MgO using nitrogen doped Ta underlayers 102 l 242405(1)-l 242405(4) 2013年6月18日

  158. Nature Communications 査読有り

    K. J. Kim, R. Hiramatsu, T. Koyama, K. Ueda, Y. Yoshimura, D. Chiba, K. Kobayashi, Y. Nakatani, S. Fukami, M. Yamanouchi, H. Ohno, H. Kohno, G. Tatara, T. Ono

    Two-barrier stability that allows low-power operation in current-induced domain-wall motion 4 1-6 2013年6月17日

  159. Applied Physics Letters 査読有り

    S. Fukami, M. Yamanouchi, H. Honjo, K. Kinoshita, K. Tokutome, S. Miura, S. Ikeda, N. Kasai, H. Ohno

    Electrical endurance of Co/Ni wire for magnetic domain wall motion device 102 222410(1)-222410(4) 2013年6月6日

  160. Fabrication of a 99%-Energy-Less Nonvolatile Multi-Functional CAM Chip Using Hierarchical Power Gating for a Massively-Parallel Full-Text-Search Engine 査読有り

    S. Matsunaga, N. Sakimura, R. Nebashi, Y. Tsuji, A. Morioka, T. Sugibayashi, S. Miura, H. Honjo, K. Kinoshita, H. Sato, S. Fukami, M. Natsui, A. Mochizuki, S. Ikeda, T. Endoh, H. Ohno, T. Hanyu

    2013 Symposium on VLSI Circuits Digest of Technical Papers 106-107 2013年6月

  161. Applied Physics Letters 査読有り

    M. Yamanouchi, L. Chen, J. Kim, M. Hayashi, S. Sato, S. Fukami, S. Ikeda, F. Matsukura, H. Ohno

    Three terminal magnetic tunnel junction utilizing the spin Hall effect of iridium-doped copper 102 212408(1)-212408(4) 2013年5月30日

  162. Applied Physics Letters 査読有り

    J. Ishihara, M. Ono, Y. Ohno, H. Ohno

    A strong anisotropy of spin dephasing time of quasi-one dimensional electron gas in modulation-doped GaAs/AlGaAs wires 102 212402(1)-212402(4) 2013年5月28日

  163. Applied Physics Express 査読有り

    K. Mizunuma, M. Yamanouchi, H. Sato, S. Ikeda, S. Kanai, F. Matsukura, H. Ohno

    Size dependence of magnetic properties of nanoscale CoFeB-MgO magnetic tunnel junctions with perpendicular magnetic easy axis observed by ferromagnetic resonance 6 063002(1)-063002(3) 2013年5月22日

  164. Journal of Applied Physics 査読有り

    S. Ishikawa, H. Sato, M. Yamanouchi, S. Ikeda, S. Fukami, F. Matsukura, H. Ohno

    Magnetic properties of MgO-[Co/Pt] multilayers with a CoFeB insertion layer 113 17C721(1)-17C721(3) 2013年4月3日

  165. Bridging semiconductor and magnetism 査読有り

    H. Ohno

    JOURNAL OF APPLIED PHYSICS 113 (13) 136509(1)-136509(5) 2013年4月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.4795537  

    ISSN:0021-8979

    詳細を見る 詳細を閉じる

    Carrier-induced ferromagnetism and its manipulation in Mn-doped III-V semiconductors, such as (In, Mn) As and (Ga, Mn) As, offer a wide variety of phenomena that originate from the interplay between magnetism and semiconducting properties, forming a bridge between semiconductor and magnetism. A review is given on the electrical manipulation of magnetism, its understanding, and potential applications both from the physics point of view and from the technological point of view. The electric-field study on magnetism is now being extended to magnetic metals, leading to an energy efficient way of magnetization reversal important for future semiconductor integrated circuit technology, yet another route to bridge semiconductor and magnetism in a fruitful way. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4795537]

  166. Journal of Applied Physics 招待有り

    H. Ohno

    Bridging semiconductor and magnetism 113 136509(1)-136509(5) 2013年3月29日

  167. Coherent Manipulation of Nuclear Spins in Semiconductors with an Electric Field 査読有り

    Masaaki Ono, Jun Ishihara, Genki Sato, Yuzo Ohno, Hideo Ohno

    APPLIED PHYSICS EXPRESS 6 (3) 033002(1)-033002(3) 2013年3月

    出版者・発行元:JAPAN SOC APPLIED PHYSICS

    DOI: 10.7567/APEX.6.033002  

    ISSN:1882-0778

    詳細を見る 詳細を閉じる

    Electrical coherent manipulation of a quadrupolar-split nuclear spin ensemble in a GaAs quantum well (QW) with an rf electric field is demonstrated by the optical time-resolved Kerr rotation technique. Rabi oscillations and phase control between two spin-3/2 states are demonstrated by nuclear electric resonance in a gated GaAs QW device. This enables us to achieve coherent control of geometrically specified nuclear spins. (C) 2013 The Japan Society of Applied Physics

  168. Nature Materials 査読有り

    J. Kim, J. Sinha, M. Hayashi, M. Yamanouchi, S. Fukami, T. Suzuki, S. Mitani, H. Ohno

    Layer thickness dependence of the current-induced effective field vector in Ta/CoFeB/MgO 12 240-245 2013年3月

  169. Applied Physics Express 査読有り

    M. Ono, J. Ishihara, G. Sato, Y. Ohno, H. Ohno

    Coherent manipulation of nuclear spins in semiconductors with an electric field 6 033002(1)-033002(3) 2013年2月28日

  170. Physical Review B 査読有り

    L. R. Fleet, K. Yoshida, H. Kobayaashi, Y. Kaneko, S. Matsuzaka, Y. Ohno, H. Ohno, S. Honda, J. Inoue, A. Hirohata

    Correlating the interface structure to spin injection in abrupt Fe/GaAs(001)films 87 024401(1)-024401(5) 2013年1月2日

  171. Low-current domain wall motion MRAM with perpendicularly magnetized CoFeB/MgO magnetic tunnel junction and underlying hard magnets

    T. Suzuki, H. Tanigawa, Y. Kobayashi, K. Mori, Y. Ito, Y. Ozaki, K. Suemitsu, T. Kitamura, K. Nagahara, E. Kariyada, N. Ohshima, S. Fukami, M. Yamanouchi, S. Ikeda, M. Hayashi, M. Sakao, H. Ohno

    Digest of Technical Papers - Symposium on VLSI Technology 2013年

    ISSN:0743-1562

    詳細を見る 詳細を閉じる

    We have developed magnetic domain wall (DW) motion cells with a perpendicularly magnetized CoFeB free layer and underlying hard magnets. Low current writing operation of 0.16 mA and a high MR ratio of 80% were attained for the 130-nm-wide free layer. Write/read operation for a 16kb array and high endurance features were also confirmed. © 2013 JSAP.

  172. Fabrication of a Magnetic Tunnel Junction-Based 240-Tile Nonvolatile Field-Programmable Gate Array Chip Skipping Wasted Write Operations for Greedy Power-Reduced Logic Applications 査読有り

    D. Suzuki, M. Natsui, A. Mochizuki, S. Miura, H. Honjo, K. Kinoshita, H. Sato, S. Ikeda, T. Endoh, H. Ohno, T. Hanyu

    IEICE Electronics Express 10 (23) 20130772 2013年

    DOI: 10.1587/elex.10.20130772  

    ISSN:1349-2543

  173. Correlating the interface structure to spin injection in abrupt Fe/GaAs(001) films 査読有り

    L. R. Fleet, K. Yoshida, H. Kobayashi, Y. Kaneko, S. Matsuzaka, Y. Ohno, H. Ohno, S. Honda, J. Inoue, A. Hirohata

    PHYSICAL REVIEW B 87 (2) 024401(1)-024401(5) 2013年1月

    出版者・発行元:AMER PHYSICAL SOC

    DOI: 10.1103/PhysRevB.87.024401  

    ISSN:2469-9950

    eISSN:2469-9969

    詳細を見る 詳細を閉じる

    Understanding the effect of the interface on electrical spin injection is of great importance for the development of semiconductor spintronics. Fe/GaAs(001) is one of the leading systems for exploring these effects due to the small lattice mismatch. We report on the correlation between the experimentally observed Fe/GaAs(001) interface with the spin-transport properties. Using high-angle annular dark-field scanning transmission electron microscopy, we observe a predominantly abrupt interface with some regions of partial mixing also observed in the same film. We report that reproducible behavior with no bias-dependent polarization inversion was achieved for three-terminal devices. Using ab initio calculations of the experimentally observed interfaces, we show that the contribution to the transport from minority carriers is strongly dependent on the interface structure. DOI: 10.1103/PhysRevB.87.024401

  174. Layer thickness dependence of the current-induced effective field vector in Ta/CoFeB/MgO 査読有り

    J. Kim, J. Sinha, M. Hayashi, M. Yamanouchi, S. Fukami, T. Suzuki, S. Mitani, H. Ohno

    Nature Materials 12 1-6 2012年12月23日

    DOI: 10.1038/nmat3522  

  175. Spin 査読有り

    S. Ikeda, H. Sato, M. Yamanouchi, H. Gan, K. Miura, K. Mizunuma, S. Kanai, S. Fukami, F. Matsukura, N. Kasai, H. Ohno

    Recent progress of perpendicular anisotropy magnetic tunnel junctions for nonvolatile VLSI 2 (3) 1240003(1)-1240003(12) 2012年12月4日

    DOI: 10.4018/ijfsa.2012070101  

  176. Applied Physics Letters 査読有り

    A. A. Greer, A. X. Gray, S. Kanai, A. M. Kaiser, S. Ueda, Y. Yamashita, C. Bordel, G. Palsson, N. Maejima, S. H. Yang, G. Conti, K. Kobayashi, S. Ikeda, F. Matsukura, H. Ohno, C. M. Schneider, J. B. Kortright, F. Hellman, C. S. Fadley

    Observation of boron diffusion in an annealed Ta/CoFeB/MgO magnetic tunnel junction with standing-wave hard x-ray photoemission 101 202402(1)-202402(4) 2012年11月12日

  177. Boron Composition Dependence of Magnetic Anisotropy and Tunnel Magnetoresistance in MgO/CoFe(B) Based Stack Structures 査読有り

    Shoji Ikeda, Ryohei Koizumi, Hideo Sato, Michihiko Yamanouchi, Katsuya Miura, Kotaro Mizunuma, Huadong Gan, Fumihiro Matsukura, Hideo Ohno

    IEEE TRANSACTIONS ON MAGNETICS 48 (11) 3829-3832 2012年11月

    出版者・発行元:IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

    DOI: 10.1109/TMAG.2012.2203588  

    ISSN:0018-9464

    詳細を見る 詳細を閉じる

    We investigated magnetic anisotropy and tunnelmagnetoresistance (TMR) properties in MgO/(Co0.25Fe0.75)(100-x)B-x stack structures with, x = 0, 15, 20, and 25 (in at.%). After annealing at 350 degrees C, the easy axis of magnetization switches from in-plane to perpendicular direction in 1.5-nm-thick CoFeB with the B composition near x = 15. The effective magnetic anisotropy energy density (K-eff) shows a maximum of 1.9 x 10(5) J/m(2) in the 1.5 nm-thick CoFeB film with x = 20 annealed at 350 degrees C. K-eff is determined by the competition between contributions of interface anisotropy energy per effective CoFeB thickness (K-i/t*, where t* is the effective CoFeB layer thickness) and demagnetization energy (-M-s(2)/2 mu(0)). Bulk magnetic anisotropy energy (K-b) is negligibly small with comparison to those two terms. To obtain MgO/ferromagnetic stack structure with a high K-eff, materials and structures that reduce demagnetization energy while maintaining a high K-i and a thin t* have to be explored. In MTJs with the higher B compositions, high TMR ratio is obtained at higher annealing temperature. High TMR ratio of 136% is observed in a MTJ with x = 25 annealed at 350 degrees C.

  178. IEEE Transactions on Magnetics 査読有り

    S. Ikeda, R. Koizumi, H. Sato, M. Yamanouchi, K. Miura, K. Mizunuma, H. Gan, F. Matsukura, H. Ohno

    Boron composition dependence of magnetic anisotropy and tunnel magnetoresistance in MgO/CoFe(B) based stack structures 48 (11) 3829-3832 2012年11月

  179. Observation of boron diffusion in an annealed Ta/CoFeB/MgO magnetic tunnel junction with standing-wave hard x-ray photoemission 査読有り

    A. A. Greer, A. X. Gray, S. Kanai, A. M. Kaiser, S. Ueda, Y. Yamashita, C. Bordel, G. Palsson, N. Maejima, S. -H. Yang, G. Conti, K. Kobayashi, S. Ikeda, F. Matsukura, H. Ohno, C. M. Schneider, J. B. Kortright, F. Hellman, C. S. Fadley

    APPLIED PHYSICS LETTERS 101 (20) 202402(1)-202402(4) 2012年11月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.4766351  

    ISSN:0003-6951

    eISSN:1077-3118

    詳細を見る 詳細を閉じる

    The CoFeB/MgO system shows promise as a magnetic tunnel junction with perpendicular magnetization and low critical current densities for spin-torque driven magnetization switching. The distribution of B after annealing is believed to be critical to performance. We have studied the distribution of B in a Ta/Co0.2Fe0.6B0.2/MgO sample annealed at 300 degrees C for 1 h with standing-wave hard x-ray photoemission spectroscopy (SW-HXPS). Comparing experimental rocking curve data to x-ray optical calculations indicates diffusion of 19.5% of the B uniformly into the MgO and of 23.5% into a thin TaB interface layer. SW-HXPS is effective for probing depth distributions in such spintronic structures. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4766351]

  180. Current-induced magnetic domain wall motion below intrinsic threshold triggered by Walker breakdown 査読有り

    T. Koyama, K. Ueda, K. -J. Kim, Y. Yoshimura, D. Chiba, K. Yamada, J. -P. Jamet, A. Mougin, A. Thiaville, S. Mizukami, S. Fukami, N. Ishiwata, Y. Nakatani, H. Kohno, K. Kobayashi, T. Ono

    NATURE NANOTECHNOLOGY 7 (10) 635-639 2012年10月

    出版者・発行元:NATURE PUBLISHING GROUP

    DOI: 10.1038/nnano.2012.151  

    ISSN:1748-3387

    eISSN:1748-3395

    詳細を見る 詳細を閉じる

    Controlling the position of a magnetic domain wall with electric current(1-11) may allow for new types of non-volatile memory and logic devices(10,12-14). To be practical, however, the threshold current density necessary for domain wall motion must be reduced below present values. Intrinsic pinning due to magnetic anisotropy(2), as recently observed in perpendicularly magnetized Co/Ni nanowires(15), has been shown to give rise to an intrinsic current threshold J(th)(0). Here, we show that domain wall motion can be induced at current densities 40% below J(th)(0) when an external magnetic field of the order of the domain wall pinning field is applied. We observe that the velocity of the domain wall motion is the vector sum of current- and field-induced velocities, and that the domain wall can be driven against the direction of a magnetic field as large as 2,000 Oe, even at currents below J(th)(0). We show that this counterintuitive phenomenon is triggered by Walker breakdown(16), and that the additive velocities provide a unique way of simultaneously determining the spin polarization of current and the Gilbert damping constant.

  181. On the influence of nanometer-thin antiferromagnetic surface layer on ferromagnetic CrO2 査読有り

    P. Das, A. Bajpai, Y. Ohno, H. Ohno, J. Mueller

    JOURNAL OF APPLIED PHYSICS 112 (5) 053921(1)-053921(4) 2012年9月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.4751350  

    ISSN:0021-8979

    詳細を見る 詳細を閉じる

    We investigate the influence of naturally grown 2-5 nm thin surface layer of antiferromagnetic (AFM) Cr2O3 on the half metallic ferromagnet CrO2 by measuring the magnetic behavior of a single micro-crystal. The temperature variation of the magnetic stray fields of the micro-crystal measured by micro-Hall magnetometry shows an anomalous increase below similar to 60 K. We find clear evidence that this behavior is due to the influence of the AFM surface layer. The average amplitude of the Barkahausen jumps exhibits a similar temperature dependence indicating that the AFM surface layer plays a role in defining the potential landscape seen by the domain configuration in the ferromagnetic grain. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4751350]

  182. Material parameters and thermal stability of synthetic ferrimagnet free layers in magnetic tunnel junction nanopillars 査読有り

    D. Marko, T. Devolder, K. Miura, K. Ito, Joo-Von Kim, C. Chappert, S. Ikeda, H. Ohno

    JOURNAL OF APPLIED PHYSICS 112 (5) 053922(1)-053922(4) 2012年9月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.4751025  

    ISSN:0021-8979

    詳細を見る 詳細を閉じる

    We have determined the material parameters of optimized synthetic ferrimagnet (SyF) free layers in magnetic tunnel junctions by means of magneto-resistance loops as well as microwave noise spectroscopy under constant voltage, and the field dependence thereof. By comparing the experimental data with calculated loops and spin wave modes from a 2-macrospin model, we have deduced the saturation magnetization, anisotropy, damping, and interlayer exchange coupling. From waiting time experiments of field-induced switching, the energy barrier relevant for the thermally activated switching of the free SyF has been experimentally evaluated and compared to an existing model in order to assess its consistency. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4751025]

  183. Electric field-induced magnetization reversal in a perpendicular-anisotropy CoFeB-MgO magnetic tunnel junction 招待有り 査読有り

    S. Kanai, M. Yamanouchi, S. Ikeda, Y. Nakatani, F. Matsukura, H. Ohno

    APPLIED PHYSICS LETTERS 101 (12) 122403(1)-122403(3) 2012年9月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.4753816  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    The electric field-induced similar to 180 degrees magnetization reversal is realized for a sputtered CoFeB/MgO-based magnetic tunnel junction with perpendicular magnetic easy axis in a static external magnetic field. Application of bias voltage with nanoseconds duration results in a temporal change of magnetic easy axis in the free layer CoFeB to in-plane, which induces precessional motion of magnetization in the free layer. The magnetization reversal takes place when the bias voltage pulse duration is adjusted to a half period of the precession. We show that the back and forth magnetization reversal can be observed by using successive application of half-period voltage pulses. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4753816]

  184. Damage Recovery by Reductive Chemistry after Methanol-Based Plasma Etch to Fabricate Magnetic Tunnel Junctions 査読有り

    Keizo Kinoshita, Tadashi Yamamoto, Hiroaki Honjo, Naoki Kasai, Shoji Ikeda, Hideo Ohno

    JAPANESE JOURNAL OF APPLIED PHYSICS 51 (8) 08HA01(1)-08HA01(6) 2012年8月

    出版者・発行元:JAPAN SOC APPLIED PHYSICS

    DOI: 10.1143/JJAP.51.08HA01  

    ISSN:0021-4922

    eISSN:1347-4065

    詳細を見る 詳細を閉じる

    The damage recovery process for magnetic tunnel junctions (MTJs) after methanol- (Me-OH) based plasma etch has been demonstrated. Me-OH and O-2 plasma, which contain oxygen in the molecule, caused unavoidable modification of magnetic materials in the MTJ stack. For example, the magnetization saturation and MR ratio decreased. H-2 base reductive plasma treatment was effective in recovering from this deterioration. No harmful side effects were observed in other aspects of MTJ performance such as MTJ resistance, hysteresis loop offset, and switching field. Heavier initial damage required a longer treatment time for recovery. Other types of reductive chemistry such as NH3 plasma deteriorated the MTJ when the treatment lasted more than 15 s, probably due to nitridation. The use of a highly selective Ar/Me-OH etch process along with He/H-2 plasma recovery treatment is very promising for the MTJs' etch process to fabricate high-density magnetic random access memory (MRAM) and non-volatile logic devices. (C) 2012 The Japan Society of Applied Physics

  185. Scalability Prospect of Three-Terminal Magnetic Domain-Wall Motion Device 査読有り

    Shunsuke Fukami, Nobuyuki Ishiwata, Naoki Kasai, Michihiko Yamanouchi, Hideo Sato, Shoji Ikeda, Hideo Ohno

    IEEE TRANSACTIONS ON MAGNETICS 48 (7) 2152-2157 2012年7月

    出版者・発行元:IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

    DOI: 10.1109/TMAG.2012.2187792  

    ISSN:0018-9464

    eISSN:1941-0069

    詳細を見る 詳細を閉じる

    We studied a scaling property of a three-terminal domain wall (DW)-motion device, which is one of the promising candidates for future low-power nonvolatile memory and logic-in-memory architecture. Using several assumptions, we derived the scaling factor of the switching current, switching time, resistance of the write-current path, and data storage stability. We also quantitatively evaluated the variation of these parameters with the device size. It was found that the switching current and time decrease almost linearly with the device size, while the variation of the resistance of the write-current path is negligible. The switching current and time for 32-nm-wide device are less than 100 mu A and 2 ns, respectively. A required critical field which assures a sufficient thermal stability of stored data was calculated for each generation. Furthermore, future issues and intrinsic limiter for the size reduction were discussed.

  186. Perpendicular-anisotropy CoFeB-MgO magnetic tunnel junctions with a MgO/CoFeB/Ta/CoFeB/MgO recording structure 査読有り

    H. Sato, M. Yamanouchi, S. Ikeda, S. Fukami, F. Matsukura, H. Ohno

    APPLIED PHYSICS LETTERS 101 (2) 022414(1)-022414(4) 2012年7月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.4736727  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    We investigated perpendicular CoFeB-MgO magnetic tunnel junctions (MTJs) with a recording structure consisting of two CoFeB-MgO interfaces, MgO/CoFeB (1.6 nm)/Ta (0.4 nm)/CoFeB (1.0 nm)/MgO. Thermal stability factor of MTJ with the structure having junction size of 70 nm phi was increased by a factor of 1.9 from the highest value of perpendicular MTJs with single CoFeB-MgO interface having the same device structure. On the other hand, intrinsic critical current for spin transfer torque switching of the double-and single-interface MTJs was comparable. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4736727]

  187. Current-Induced Domain Wall Motion in Perpendicularly Magnetized Co/Ni Nanowire under In-Plane Magnetic Fields 査読有り

    Yoko Yoshimura, Tomohiro Koyama, Daichi Chiba, Yoshinobu Nakatani, Shunsuke Fukami, Michihiko Yamanouchi, Hideo Ohno, Teruo Ono

    APPLIED PHYSICS EXPRESS 5 (6) 063001(1)-063001(3) 2012年6月

    出版者・発行元:JAPAN SOC APPLIED PHYSICS

    DOI: 10.1143/APEX.5.063001  

    ISSN:1882-0778

    詳細を見る 詳細を閉じる

    We have investigated current-induced domain wall (DW) motion in a perpendicularly magnetized Co/Ni nanowire under in-plane (hard-axis) and perpendicular (easy-axis) external magnetic fields. The DW velocity was found to be almost independent of them in the range of +/- 50 Oe. The result shows that reliable device operation against an external magnetic field disturbance can be achieved using the present system. (C) 2012 The Japan Society of Applied Physics

  188. Electric Field Effect on Magnetization of an Fe Ultrathin Film 査読有り

    Masashi Kawaguchi, Kazutoshi Shimamura, Shimpei Ono, Shunsuke Fukami, Fumihiro Matsukura, Hideo Ohno, Daichi Chiba, Teruo Ono

    APPLIED PHYSICS EXPRESS 5 (6) 063007(1)-063007(3) 2012年6月

    出版者・発行元:JAPAN SOC APPLIED PHYSICS

    DOI: 10.1143/APEX.5.063007  

    ISSN:1882-0778

    詳細を見る 詳細を閉じる

    We show the effect of an applied electric field on the magnetization of an Fe ultrathin film. An electric double layer was formed at the interface between an ionic liquid and the Fe layer by the accumulation of ions caused by applying a gate voltage, and a large electric field was exerted on the Fe film surface. The saturation magnetization increased when the electron density at the Fe surface increased. A change in the saturation magnetization of similar to 50% was observed by applying a gate voltage of +/- 2 V. (C) 2012 The Japan Society of Applied Physics

  189. Vertical-Electrical-Field-Induced Control of the Exciton Fine Structure Splitting in GaAs Island Quantum Dots for the Generation of Polarization-Entangled Photons 査読有り

    Mohsen Ghali, Keita Ohtani, Yuzo Ohno, Hideo Ohno

    JAPANESE JOURNAL OF APPLIED PHYSICS 51 (6) 06FE14(1)-06FE14(3) 2012年6月

    出版者・発行元:IOP PUBLISHING LTD

    DOI: 10.1143/JJAP.51.06FE14  

    ISSN:0021-4922

    eISSN:1347-4065

    詳細を見る 詳細を閉じる

    We report on the polarization-resolved photoluminescence spectroscopy of a single GaAs island quantum dot (QD) formed by the monolayer thickness fluctuation of a GaAs/Al0.3Ga0.7As quantum well and embedded in a Schottky device. By applying a forward vertical electric field between the top metallic contact and the sample substrate we suppress the QD excitonic fine structure splitting to approximate to 1.5 mu eV. These results open the door toward the possible generation of visible entangled photon pairs using GaAs island QDs. (C) 2012 The Japan Society of Applied Physics

  190. Photocurrent Measurements on a Quantum Cascade Laser Device by Fourier Transform Infrared Microscope 査読有り

    Eli Christopher I. Enobio, Hiroki Sato, Keita Ohtani, Yuzo Ohno, Hideo Ohno

    JAPANESE JOURNAL OF APPLIED PHYSICS 51 (6) 06FE15(1)-06FE15(3) 2012年6月

    出版者・発行元:IOP PUBLISHING LTD

    DOI: 10.1143/JJAP.51.06FE15  

    ISSN:0021-4922

    eISSN:1347-4065

    詳細を見る 詳細を閉じる

    Intersubband photocurrent in the InAs/AlSb mid-infrared quantum cascade laser (QCL) device is measured. To characterize subband energies in a fabricated and functioning QCL laser device, Fourier-transform infrared (FTIR) microscope is used to focus the probe light on the cleaved mirror of QCL. Photocurrent associated with intersubband transitions in the active layer are observed up to room temperature and the origin of peaks is identified by numerical simulation, which demonstrates the potential as a characterization tool for QCL devices. (C) 2012 The Japan Society of Applied Physics

  191. Spin-motive force due to a gyrating magnetic vortex 査読有り

    K. Tanabe, D. Chiba, J. Ohe, S. Kasai, H. Kohno, S. E. Barnes, S. Maekawa, K. Kobayashi, T. Ono

    NATURE COMMUNICATIONS 3 2012年5月

    出版者・発行元:NATURE PUBLISHING GROUP

    DOI: 10.1038/ncomms1824  

    ISSN:2041-1723

    詳細を見る 詳細を閉じる

    A change of magnetic flux through a circuit induces an electromotive force. By analogy, a recently predicted force that results from the motion of non-uniform spin structures has been termed the spin-motive force. Although recent experiments seem to confirm its presence, a direct signature of the spin-motive force has remained elusive. Here we report the observation of a real-time spin-motive force produced by the gyration of a magnetic vortex core. We find a good agreement between the experimental results, theory and micromagnetic simulations, which taken as a whole provide strong evidence in favour of a spin-motive force.

  192. Dependence of Magnetic Anisotropy in Co20Fe60B20 Free Layers on Capping Layers in MgO-Based Magnetic Tunnel Junctions with In-Plane Easy Axis 査読有り

    Hiroyuki Yamamoto, Jun Hayakawa, Katsuya Miura, Kenchi Ito, Hideyuki Matsuoka, Shoji Ikeda, Hideo Ohno

    APPLIED PHYSICS EXPRESS 5 (5) 053002(1)-053002(3 2012年5月

    出版者・発行元:JAPAN SOC APPLIED PHYSICS

    DOI: 10.1143/APEX.5.053002  

    ISSN:1882-0778

    詳細を見る 詳細を閉じる

    Perpendicular magnetic anisotropy (PMA) in Co20Fe60B20 films depending on the adjacent layers of Ta, Ru, and MgO was studied for reduction of switching current density J(c0) in in-plane magnetic tunnel junctions (MTJs). A MgO layer reduces the out-of-plane saturation field (H-s) of in-plane easy axis Co20Fe60B20 films by inducing a strong PMA at the Co20Fe60B20/MgO interface. The PMA is not affected much by the crystallinity in Co20Fe60B20 films with different capping layers. MTJ with a MgO capping layer shows a lower J(c0) than that with a Ru capping layer, in accordance with the reduction of H-s. (c) 2012 The Japan Society of Applied Physics

  193. Current-induced torques in magnetic materials 査読有り

    Arne Brataas, Andrew D. Kent, Hideo Ohno

    NATURE MATERIALS 11 (5) 372-381 2012年5月

    出版者・発行元:NATURE PUBLISHING GROUP

    DOI: 10.1038/NMAT3311  

    ISSN:1476-1122

    eISSN:1476-4660

    詳細を見る 詳細を閉じる

    The magnetization of a magnetic material can be reversed by using electric currents that transport spin angular momentum. In the reciprocal process a changing magnetization orientation produces currents that transport spin angular momentum. Understanding how these processes occur reveals the intricate connection between magnetization and spin transport, and can transform technologies that generate, store or process information via the magnetization direction. Here we explain how currents can generate torques that affect the magnetic orientation and the reciprocal effect in a wide variety of magnetic materials and structures. We also discuss recent state-of-the-art demonstrations of current-induced torque devices that show great promise for enhancing the functionality of semiconductor devices.

  194. Spatial control of magnetic anisotropy for current induced domain wall injection in perpendicularly magnetized CoFeB vertical bar MgO nanostructures 査読有り

    Masamitsu Hayashi, Michihiko Yamanouchi, Shunsuke Fukami, Jaivardhan Sinha, Seiji Mitani, Hideo Ohno

    APPLIED PHYSICS LETTERS 100 (19) 192411(1)-192411(4) 2012年5月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.4711016  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    Magnetic anisotropy of perpendicularly magnetized CoFeB vertical bar MgO films is spatially tailored using depth controlled Ar ion etching with patterned etching masks. Nanowires with patterned etching have significantly reduced coercivity compared to those without the etching. We show that the sign of the anisotropy can be locally changed by partially etching the MgO layer, and as a consequence, 90 degrees domain walls can be created at the boundary of etched/non-etched region. Direct current application to the nanowire can result in moving such 90 degrees domain walls, which can prove as an efficient mean to inject domain walls into perpendicularly magnetized nanowires. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4711016]

  195. Magnetism of Co-doped ZnO epitaxially grown on a ZnO substrate 査読有り

    Li Li, Y. Guo, X. Y. Cui, Rongkun Zheng, K. Ohtani, C. Kong, A. V. Ceguerra, M. P. Moody, J. D. Ye, H. H. Tan, C. Jagadish, Hui Liu, C. Stampfl, H. Ohno, S. P. Ringer, F. Matsukura

    PHYSICAL REVIEW B 85 (17) 174430(1)-174430(8) 2012年5月

    出版者・発行元:AMER PHYSICAL SOC

    DOI: 10.1103/PhysRevB.85.174430  

    ISSN:1098-0121

    詳細を見る 詳細を閉じる

    In order to unravel the magnetism of Co-doped ZnO films, we have performed rigorous experiments on Co-doped ZnO grown onO-polar ZnO (000(1) over bar) substrates by molecular beam epitaxy. We find that the ZnO:Co with Co composition less than 20% is paramagnetic even at low temperatures, whereas that with Co composition of 20% shows ferromagnetism at room temperature. Although an additional n-type doping with Ga increases the magnitude of magnetization, the origin of the observed ferromagnetism is not carrier induced, as confirmed by electric-field effect measurements. Three-dimensional atom probe tomography shows that Co ions are randomly distributed, indicating that Co clustering or spinodal decomposition is not the origin of the ferromagnetism either. One possible mechanism for the ferromagnetism is hydrogen-facilitated interaction, which is supported experimentally by magnetic measurements on hydrogen-treated ZnO: Co as well as theoretically by first-principles calculation.

  196. Spin-transfer torque RAM technology: Review and prospect 査読有り

    T. Kawahara, K. Ito, R. Takemura, H. Ohno

    MICROELECTRONICS RELIABILITY 52 (4) 613-627 2012年4月

    出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD

    DOI: 10.1016/j.microrel.2011.09.028  

    ISSN:0026-2714

    詳細を見る 詳細を閉じる

    Non-volatile RAM (NV-RAM) enables instant-on/off computing, which drastically reduces power consumption. One of the most promising candidates for NV-RAM technology is the spin-transfer torque RAM (SPRAM) based on magnetic tunnel junction (MTJ) device technology. This paper reviews the development of MTJ device technology and formulates considerations regarding its memory application, including SPRAM memory cell structure and operation, write voltage limitation, and thermal stability. At the circuit level, a disruptive read operation for future large integration scale is described. A 4F(2) memory cell and a multi-bit cell approach are also presented. Finally, the potential value of instant-on/off computing through NV-RAM and its impact are explored. (C) 2011 Elsevier Ltd. All rights reserved.

  197. Domain-wall-motion cell with perpendicular anisotropy wire and in-plane magnetic tunneling junctions 査読有り

    H. Honjo, S. Fukami, T. Suzuki, R. Nebashi, N. Ishiwata, S. Miura, N. Sakimura, T. Sugibayashi, N. Kasai, H. Ohno

    JOURNAL OF APPLIED PHYSICS 111 (7) C7C903(1)-C7C903(3) 2012年4月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.3671437  

    ISSN:0021-8979

    eISSN:1089-7550

    詳細を見る 詳細を閉じる

    A wire with perpendicular magnetic anisotropy (PA) is suitable for domain-wall-motion (DWM) cells because its critical current is small. However, it is not easy to design a cell consisting of a high magnetoresistance (MR) ratio magnetic tunneling junction (MTJ) and a DWM using PA material alone. We propose a combination of a PA-DWM element and in-plane (IP) MTJ for detection. The structure can be designed in a way that reduces the write current by the use of a perpendicular layer, yet maintains a high MR ratio by the independent use of in-plane material stacks. We fabricated a cell and ran tests to determine its read and write properties. A critical write current of 700 mu A and a MR ratio of 50% were achieved. These properties are almost the same as when a DWM wire and in-plane MTJ are fabricated separately, which means it is possible to design the two elements independently. (C) 2012 American Institute of Physics. [doi:10.1063/1.3671437]

  198. Six-input lookup table circuit with 62 fewer transistors using nonvolatile logic-in-memory architecture with series/parallel-connected magnetic tunnel junctions 査読有り

    D. Suzuki, M. Natsui, T. Endoh, H. Ohno, T. Hanyu

    Journal of Applied Physics 111 (7) 07E318(1)-07E318(3) 2012年4月1日

    DOI: 10.1063/1.3672411  

    ISSN:0021-8979

    詳細を見る 詳細を閉じる

    A compact 6-input lookup table (LUT) circuit using nonvolatile logic-in-memory (LIM) architecture with series/parallel-connected magnetic tunnel junction (MTJ) devices is proposed for a standby-power-free field-programmable gate array. Series/parallel connections of MTJ devices make it possible not only to reduce the effect of resistance variation, but also to enhance the programmability of resistance values, which achieves a sufficient sensing margin even when process variation is serious in the recent nanometer-scaled VLSI. Moreover, the additional MTJ devices do not increase the effective chip area because the configuration circuit using MTJ devices is simplified and these devices are stacked over the CMOS plane. As a result, the transistor counts of the proposed circuit are reduced by 62 in comparison with those of a conventional nonvolatile LUT circuit where CMOS-only-based volatile static random access memory cell circuits are replaced by MTJ-based nonvolatile ones. © 2012 American Institute of Physics.

  199. Magnetic tunneling junction with Fe/NiFeB free layer for magnetic logic circuits 査読有り

    H. Honjo, S. Fukami, R. Nebashi, N. Ishiwata, S. Miura, N. Sakimura, T. Sugibayashi, N. Kasai, H. Ohno

    JOURNAL OF APPLIED PHYSICS 111 (7) 07C709(1)-07C709(3) 2012年4月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.3675268  

    ISSN:0021-8979

    eISSN:1089-7550

    詳細を見る 詳細を閉じる

    We have developed a shape varying magnetic tunneling junction (SVM) with a Fe/NiFeB free layer for use in magnetic logic circuits. Inserting the thin Fe film between an NiFeB free layer and MgO tunneling barrier improved the magnetoresistance (MR) ratio: it increased up to 130%, as the thickness of the Fe film increased. In addition, the switching current distribution of the SVM was reduced to 8%. By using NiFeB as a free layer, the roughness under the MgO was reduced and the crystallization of the MgO was enhanced. This led to both the high MR ratio and the low switching current distribution. Our developed Fe (0.4 nm)/NiFeB free layer satisfies the requirement of the MTJ's characteristics that the magnetic logic circuits operate with a high bit yield. VC 2012 American Institute of Physics. [doi: 10.1063/1.3675268]

  200. Design of a 270ps-access 7-transistor/2-magnetic-tunnel-junction cell circuit for a high-speed-search nonvolatile ternary content-addressable memory 査読有り

    Shoun Matsunaga, Akira Katsumata, Masanori Natsui, Tetsuo Endoh, Hideo Ohno, Takahiro Hanyu

    JOURNAL OF APPLIED PHYSICS 111 (7) 07E336(1)-07E336(3) 2012年4月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.3677875  

    ISSN:0021-8979

    eISSN:1089-7550

    詳細を見る 詳細を閉じる

    A novel 7-transistor/2-magnetic-tunnel-junction (7T-2MTJ) cell circuit is proposed for a high-speed and compact nonvolatile ternary content-addressable memory (TCAM). Since critical path for switching in the TCAM cell circuit, which determines the performance of the TCAM, is only a single MOS transistor, switching delay of the TCAM word circuit is minimized. As a result, 270 ps of switching delay in 144-bit TCAM word circuit is achieved under a 90 nm CMOS/MTJ technology with magneto-resistance ratio of 100%, which is about two times faster than a conventional CMOS-based TCAM. (C) 2012 American Institute of Physics. [doi:10.1063/1.3677875]

  201. Spin-transfer torque RAM technology: Review and prospect 査読有り

    T. Kawahara, K. Ito, R. Takemura, H. Ohno

    MICROELECTRONICS RELIABILITY 52 (4) 613-627 2012年4月

    出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD

    DOI: 10.1016/j.microrel.2011.09.028  

    ISSN:0026-2714

    詳細を見る 詳細を閉じる

    Non-volatile RAM (NV-RAM) enables instant-on/off computing, which drastically reduces power consumption. One of the most promising candidates for NV-RAM technology is the spin-transfer torque RAM (SPRAM) based on magnetic tunnel junction (MTJ) device technology. This paper reviews the development of MTJ device technology and formulates considerations regarding its memory application, including SPRAM memory cell structure and operation, write voltage limitation, and thermal stability. At the circuit level, a disruptive read operation for future large integration scale is described. A 4F(2) memory cell and a multi-bit cell approach are also presented. Finally, the potential value of instant-on/off computing through NV-RAM and its impact are explored. (C) 2011 Elsevier Ltd. All rights reserved.

  202. Design of a Compact Nonvolatile Four-Input Logic Element Using a Magnetic Tunnel Junction and Metal-Oxide-Semiconductor Hybrid Structure 査読有り

    Daisuke Suzuki, Masanori Natsui, Tetsuo Endoh, Hideo Ohno, Takahiro Hanyu

    JAPANESE JOURNAL OF APPLIED PHYSICS 51 (4) 04DM02(1)-04DM02(5) 2012年4月

    出版者・発行元:IOP PUBLISHING LTD

    DOI: 10.1143/JJAP.51.04DM02  

    ISSN:0021-4922

    eISSN:1347-4065

    詳細を見る 詳細を閉じる

    A nonvolatile logic element (NV-LE) using a magnetic tunnel junction (MTJ) and metal-oxide-semiconductor (MOS)-hybrid structure is proposed for a high-density field-programmable gate array with an instant-on capability. Since the output current level of a multiplexer tree including MTJ devices is directly evaluated and amplified by a single differential amplifier on the final stage of the LUT circuit, the number of wasted sense amplifiers is greatly reduced and a compact 4-input NV-LE can be implemented. Moreover, the use of dynamic current-mode logic based circuitry makes it possible a high-speed operation with low-active power dissipation due to the elimination of steady current-path. In fact, the proposed 4-input NV-LE reduces transistor counts to 63% with no performance degradation compared to those of a conventional complementary-MOS-based implementation. (C) 2012 The Japan Society of Applied Physics

  203. Transmission electron microscopy study on the effect of various capping layers on CoFeB/MgO/CoFeB pseudo spin valves annealed at different temperatures 査読有り

    S. V. Karthik, Y. K. Takahashi, T. Ohkubo, K. Hono, H. D. Gan, S. Ikeda, H. Ohno

    JOURNAL OF APPLIED PHYSICS 111 (8) 083922(1)-083922(8) 2012年4月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.4707964  

    ISSN:0021-8979

    eISSN:1089-7550

    詳細を見る 詳細を閉じる

    The microstructure of pseudo spin-valve magnetic tunnel junctions (MTJs) comprising a stacking structure of Ta/Ru/Ta/CoFeB/MgO/CoFeB/ with and without X = Pd, Ti, Ta fabricated on thermally oxidized Si wafer with different annealing temperatures, T-a = 250 degrees C, 300 degrees C, 400 degrees C, and 500 degrees C, has been investigated. The as-deposited MTJs exhibit an amorphous CoFeB structure that crystallizes into bcc Fe-Co (001) from the MgO (001) interface upon annealing at T-a &gt;= 250 degrees C. A bcc Fe-Co (110) crystallizes from the fcc Pd (111) interface. The Fe-Co layer is alloyed with Pd layer at T-a = 500 degrees C to form an (Fe, Co)-Pd alloy layer, which causes a drastic reduction in the tunneling magnetoresistance (TMR) from 171% to -2.7%. In the Ti capped MTJs, bcc Fe-Co (001) crystallizes from the hcp (001) Ti interface at T-a = 300 degrees C. Upon further annealing to T-a &gt;= 400 degrees C, the Ti oxidizes to form amorphous Ti-O-x. The rejected B diffuses back to the CoFe layer at T-a = 500 degrees C that degrades the TMR. On the other hand, the Ta capped MTJs annealed at 300 &lt;= T-a &lt;= 500 degrees C show a perfect grain-to-grain epitaxy with an orientation relationship of (001)[110](MgO)//(001)[100](CoFe) without interdiffusion or oxidation, resulting in the highest TMR value among all the MTJs with various capping layers. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4707964]

  204. A Content Adddressable Memory Using Three-Terminal Magnetic Domain Wall Motion Cells 招待有り 査読有り

    R. Nebashi, N. Sakimura, Y Tsuji, S. Fukami, H. Honjo, S. Saito, S.Miura, N.Ishiwata, K. kinoshita, T. Hanyu, T. Endoh, N. Kasai, H. Ohno, T. Sugibayashi

    The 2nd CSIS International Symposium on Spintronics-based VLSIs F7 24-24 2012年2月2日

  205. Generation and control of polarization-entangled photons from GaAs island quantum dots by an electric field 査読有り

    Mohsen Ghali, Keita Ohtani, Yuzo Ohno, Hideo Ohno

    NATURE COMMUNICATIONS 3 2012年2月

    出版者・発行元:NATURE PUBLISHING GROUP

    DOI: 10.1038/ncomms1657  

    ISSN:2041-1723

    詳細を見る 詳細を閉じる

    Semiconductor quantum dots are potential sources for generating polarization-entangled photons efficiently. The main prerequisite for such generation based on biexciton-exciton cascaded emission is to control the exciton fine-structure splitting. Among various techniques investigated for this purpose, an electric field is a promising means to facilitate the integration into optoelectronic devices. Here we demonstrate the generation of polarization-entangled photons from single GaAs quantum dots by an electric field. In contrast to previous studies, which were limited to In(Ga)As quantum dots, GaAs island quantum dots formed by a thickness fluctuation were used because they exhibit a larger oscillator strength and emit light with a shorter wavelength. A forward voltage was applied to a Schottky diode to control the fine-structure splitting. We observed a decrease and suppression in the fine-structure splitting of the studied single quantum dot with the field, which enabled us to generate polarization-entangled photons with a high fidelity of 0.72 +/- 0.05.

  206. High-Density and Low-Power Nonvolatile Static Random Access Memory Using Spin-Transfer-Torque Magnetic Tunnel Junction 査読有り

    Takashi Ohsawa, Fumitaka Iga, Shoji Ikeda, Takahiro Hanyu, Hideo Ohno, Tetsuo Endoh

    JAPANESE JOURNAL OF APPLIED PHYSICS 51 (2) 02BD01(1)-02BD01(6) 2012年2月

    出版者・発行元:JAPAN SOC APPLIED PHYSICS

    DOI: 10.1143/JJAP.51.02BD01  

    ISSN:0021-4922

    詳細を見る 詳細を閉じる

    A novel nonvolatile static random access memory cell is proposed that consists of four transistors and two spin-transfer-torque magnetic tunnel junctions (STT-MTJs). In the case of the NFET driver cell, the free layers of the magnetic tunnel junctions are connected to the transistors' sources and drains to make the cell read-disturb free. The static power is totally eliminated as the power line is shut down during data hold. The static noise margin of the cell is calculated based on the experimental data on MTJ switching that is enhanced from the resistive load SRAM cell due to the MTJ's switching operation. The cell size is estimated to become smaller than the 6-transistor SRAM cell when it is designed at 45nm node and beyond owing to the MTJ's area shrink as well as the thinning of its tunnel dielectrics (MgO). (C) 2012 The Japan Society of Applied Physics

  207. Time-Resolved Switching Characteristic in Magnetic Tunnel Junction with Spin Transfer Torque Write Scheme 査読有り

    Fumitaka Iga, Yasuhiro Yoshida, Shoji Ikeda, Takahiro Hanyu, Hideo Ohno, Tetsuo Endoh

    JAPANESE JOURNAL OF APPLIED PHYSICS 51 (2) 02BM02(1)-02BM02(5) 2012年2月

    出版者・発行元:JAPAN SOC APPLIED PHYSICS

    DOI: 10.1143/JJAP.51.02BM02  

    ISSN:0021-4922

    詳細を見る 詳細を閉じる

    The time-resolved switching characteristics of 100 x 200nm(2) size CoFeB/MgO/CoFeB-based magnetic tunnel junction (MTJ) are investigated by using the 20 GHz sampling measurement technique. We focused on the physical quantities of the time-resolved characteristics such as incubation time t(A), transit time t(B), and the standard deviations sigma V's of the period of the switching waveform. Furthermore, the dependencies of t(A) and t(B) on the applied pulse waveforms are analyzed. We found t(A) exponentially decreases as the applied voltage to MTJ increases, while t(B) remains less than two nano seconds regardless of the applied voltage. Furthermore, it is observed that the standard deviations of the waveform during t(A) is larger than that of the other periods. Finally, we discuss the switching characteristics with proposed toy model based on spin transfer torque (STT) phenomena. (C) 2012 The Japan Society of Applied Physics

  208. Design of a Nine-Transistor/Two-Magnetic-Tunnel-Junction-Cell-Based Low-Energy Nonvolatile Ternary Content-Addressable Memory 査読有り

    Shoun Matsunaga, Akira Katsumata, Masanori Natsui, Tetsuo Endoh, Hideo Ohno, Takahiro Hanyu

    JAPANESE JOURNAL OF APPLIED PHYSICS 51 (2) 02BM06(1)-02BM06(5) 2012年2月

    出版者・発行元:JAPAN SOC APPLIED PHYSICS

    DOI: 10.1143/JJAP.51.02BM06  

    ISSN:0021-4922

    詳細を見る 詳細を閉じる

    Towards a low search-energy nonvolatile ternary content-addressable memory (TCAM), we propose a novel nine-transistor/two-magnetic-tunnel-junction (9T-2MTJ) nonvolatile TCAM cell circuit with a high-speed accessibility. Since critical path for switching in the TCAM cell circuit is only a single metal-oxide-semiconductor (MOS) transistor, switching delay of the TCAM word circuit is minimized. As a result, the worst-case switching delay of 0.22 ns is achieved in a 144-bit word circuit under a 90 nm complementary MOS (CMOS)/MTJ technology, which is about 2.6 times faster than that of a conventional CMOS-based TCAM. In order to minimize the active power dissipation in the proposed TCAM, a multi-level segmented match-line scheme that maximally brings inessential cells to standby state is also applied to the 9T-2MTJ-cell-based word circuit. Finally, low search-energy of 0.73 fJ/bit/search is achieved in a 144-bit x 256-word nonvolatile TCAM together with eliminating standby power using nonvolatility. (C) 2012 The Japan Society of Applied Physics

  209. Effects of boron composition on tunneling magnetoresistance ratio and microstructure of CoFeB/MgO/CoFeB pseudo-spin-valve magnetic tunnel junctions 査読有り

    M. Kodzuka, T. Ohkubo, K. Hono, S. Ikeda, H. D. Gan, H. Ohno

    JOURNAL OF APPLIED PHYSICS 111 (4) 043913(1)-043913(3) 2012年2月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.3688039  

    ISSN:0021-8979

    eISSN:1089-7550

    詳細を見る 詳細を閉じる

    The effect of B concentration on the tunneling magnetoresistance (TMR) of (Co25Fe75)(100-x) B-x/MgO/(Co25Fe75)(100-x)B-x (x = 22 and 33) pseudo-spin-valve (P-SV) magnetic tunnel junctions (MTJs) was investigated. The TMR ratios for optimally annealed MTJs with x = 22 and 33 were 340% and 170%, respectively, at room temperature. High resolution transmission electron microscopy (HRTEM) observation showed a weaker (001) texture in the MgO barrier in the MTJ with x = 33. The bottom electrode was not fully crystallized even with a considerable amount of B in the (Co25Fe75)(67)B-33, while good epitaxy was observed between (001) textured MgO and (Co25Fe75)(78)B-22 electrodes. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3688039]

  210. Domain wall dynamics driven by spin transfer torque and the spin-orbit field 査読有り

    Masamitsu Hayashi, Yoshinobu Nakatani, Shunsuke Fukami, Michihiko Yamanouchi, Seiji Mitani, Hideo Ohno

    JOURNAL OF PHYSICS-CONDENSED MATTER 24 (2) 024221(1)-024221(8) 2012年1月

    出版者・発行元:IOP PUBLISHING LTD

    DOI: 10.1088/0953-8984/24/2/024221  

    ISSN:0953-8984

    詳細を見る 詳細を閉じる

    We have studied current-driven dynamics of domain walls when an in-plane magnetic field is present in perpendicularly magnetized nanowires using an analytical model and micromagnetic simulations. We model an experimentally studied system, ultrathin magnetic nanowires with perpendicular anisotropy, where an effective in-plane magnetic field is developed when current is passed along the nanowire due to the Rashba-like spin-orbit coupling. Using a one-dimensional model of a domain wall together with micromagnetic simulations, we show that the existence of such in-plane magnetic fields can either lower or raise the threshold current needed to cause domain wall motion. In the presence of the in-plane field, the threshold current differs for positive and negative currents for a given wall chirality, and the wall motion becomes sensitive to out-of-plane magnetic fields. We show that large non-adiabatic spin torque can counteract the effect of the in-plane field.

  211. CoFeB Thickness Dependence of Thermal Stability Factor in CoFeB/MgO Perpendicular Magnetic Tunnel Junctions 査読有り

    H. Sato, M. Yamanouchi, K. Miura, S. Ikeda, R. Koizumi, F. Matsukura, H. Ohno

    IEEE MAGNETICS LETTERS 3 3000204(1)-3000204(4) 2012年

    出版者・発行元:IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

    DOI: 10.1109/LMAG.2012.2190722  

    ISSN:1949-307X

    詳細を見る 詳細を閉じる

    Thermal stability factor Delta of the recording layer was studied in perpendicular anisotropy CoFeB/MgO magnetic tunnel junctions (p-MTJs) with various CoFeB recording layer thicknesses and junction sizes. In all series of p-MTJs with different thicknesses, Delta is virtually independent of the junction sizes of 48-81 nm in diameter. The values of Delta increase linearly as the recording layer thickness increases. The slope of the linear fit is explained well by a model based on nucleation-type magnetization reversal.

  212. Origin of the collapse of tunnel magnetoresistance at high annealing temperature in CoFeB/MgO perpendicular magnetic tunnel junctions 査読有り

    H. D. Gan, H. Sato, M. Yamanouchi, S. Ikeda, K. Miura, R. Koizumi, F. Matsukura, H. Ohno

    APPLIED PHYSICS LETTERS 99 (25) 252507(1)-252507(3) 2011年12月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.3671669  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    We have investigated a tunnel magnetoresistance (TMR) ratio of CoFeB/MgO perpendicular magnetic tunnel junctions (p-MTJs) with a 40 nm diameter as a function of an annealing temperature T(a). The TMR ratio at room temperature (RT) increases with increasing T(a) and reaches 149% at T(a) = 350 degrees C, and further increase of T(a) results in a strong reduction of the TMR ratio, i.e., 2% at T(a) = 400 degrees C. The temperature dependence of the junction resistance versus magnetic field loops reveals that the reduced TMR ratio at RT is due to the disappearance of a stable antiparallel magnetization configuration. We find that reduction of dipole coupling restores the TMR ratio. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3671669]

  213. Reduction of intrinsic critical current density under a magnetic field along the hard axis of a free layer in a magnetic tunnel junction 査読有り

    Katsuya Miura, Ryoko Sugano, Masahiko Ichimura, Jun Hayakawa, Shoji Ikeda, Hideo Ohno, Sadamichi Maekawa

    PHYSICAL REVIEW B 84 (17) 174434(1)-174434(7) 2011年11月

    出版者・発行元:AMER PHYSICAL SOC

    DOI: 10.1103/PhysRevB.84.174434  

    ISSN:1098-0121

    詳細を見る 詳細を閉じる

    We investigated the effect of a magnetic field along a hard in-plane axis H(hard) on a current-induced magnetization switching (CIMS) in magnetic tunnel junctions (MTJs). Since H(hard) causes the effective field to tilt away from the easy axis, we evaluated the H(hard) dependence of two contributing factors in CIMS [the intrinsic critical current density (J(c0)) and the thermal stability factor (E/k(B)T)] as functions of the tilting angle (theta(H)). Both measurements and numerical simulations showed that the presence of H(hard) can reduce J(c0) by more than the amount estimated by Slonczewski's polarization function g(theta) by an order of magnitude and that E/k(B)T is independent of theta(H). These findings suggest that the effect of H(hard) mainly appears in the dynamic properties due to the nonconservative force of the spin-transfer torque based on the Slonczewski's model. A simple stability analysis demonstrated that the tilt of the magnetization direction away from the easy axis caused by the presence of H(hard) induces an imbalance between the spin-transfer and damping torques and that applying a current achieves the further tilted stable state. Achievement of this stable state can be interpreted as the suppression of the effect of the effective demagnetization field (H(d)*). Therefore the major reduction in J(c0) is due to the suppression of H(d)* caused by the presence of H(hard).

  214. Junction size effect on switching current and thermal stability in CoFeB/MgO perpendicular magnetic tunnel junctions 査読有り

    H. Sato, M. Yamanouchi, K. Miura, S. Ikeda, H. D. Gan, K. Mizunuma, R. Koizumi, F. Matsukura, H. Ohno

    APPLIED PHYSICS LETTERS 99 (4) 042501(1)-042501(3) 2011年7月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.3617429  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    Junction size dependence of critical current (I(C0)) for spin transfer torque switching and thermal stability factor (E/k(B)T) was examined in CoFeB/MgO perpendicular magnetic tunnel junctions (p-MTJs). The I(C0) increased with increasing recording layer area (S(rec)). On the other hand, the E/k(B)T showed almost constant values even though the S(rec) was increased from similar to 1500 nm(2) (44 nm phi) to similar to 5000 nm(2) (76 nm phi). Both I(C0) and E/k(B)T behavior can be explained with assuming that the nucleation type magnetization reversal takes place in CoFeB/MgO p-MTJs. (C) 2011 American Institute of Physics. [doi:10.1063/1.3617429]

  215. Tunnel Magnetoresistance Properties of Double MgO-Barrier Magnetic Tunnel Junctions With Different Free-Layer Alloy Compositions and Structures 査読有り

    Huadong Gan, Shoji Ikeda, Michihiko Yamanouchi, Katsuya Miura, Kotaro Mizunuma, Jun Hayakawa, Fumihiro Matsukura, Hideo Ohno

    IEEE TRANSACTIONS ON MAGNETICS 47 (6) 1567-1570 2011年6月

    出版者・発行元:IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

    DOI: 10.1109/TMAG.2010.2104137  

    ISSN:0018-9464

    eISSN:1941-0069

    詳細を見る 詳細を閉じる

    We investigated tunnel magnetoresistance (TMR) properties in double MgO-barrier magnetic tunnel junctions (DMTJs) with (Co25Fe75)(100-x)B-x free-layers with x = 15, 20, and 25 (in at.%) sputtered at different power. The TMR ratio of DMTJs increased with sputtering power, which is ascribed to the B composition reduction in the CoFeB free-layer with increasing sputtering power. The x-ray diffraction measurement showed that crystallization into (001)-oriented texture of CoFeB film sandwiched between the two MgO-layers as well as an improvement of (001) orientation of top MgO-barrier are realized. The TMR ratio over 200% was obtained in DMTJs with a (Co25Fe75)(85)B-15 free-layer sputtered at 0.88 and 1.77 W/cm(2)

  216. Design and Fabrication of a One-Transistor/One-Resistor Nonvolatile Binary Content-Addressable Memory Using Perpendicular Magnetic Tunnel Junction Devices with a Fine-Grained Power-Gating Scheme 査読有り

    Shoun Matsunaga, Masanori Natsui, Shoji Ikeda, Katsuya Miura, Tetsuo Endoh, Hideo Ohno, Takahiro Hanyu

    JAPANESE JOURNAL OF APPLIED PHYSICS 50 (6) 063004-(1)-063004-(7) 2011年6月

    出版者・発行元:JAPAN SOC APPLIED PHYSICS

    DOI: 10.1143/JJAP.50.063004  

    ISSN:0021-4922

    詳細を見る 詳細を閉じる

    A perpendicular magnetic tunnel junction (P-MTJ)-based one-transistor/one-resistor (1T-1R) binary content-addressable memory (CAM) is proposed for a high-density nonvolatile CAM. The proposed CAM cell performs an equality-search operation between an input bit and the corresponding stored bit by detecting the difference of a "cell resistance'', where the cell resistance is determined by the series connection of one metal-oxide-semiconductor (MOS) transistor and one P-MTJ device. This circuit structure makes it possible to implement a compact nonvolatile CAM cell circuit with 1.25 mu m(2) of a cell size in a 0.14 mu m complementary MOS (CMOS)/P-MTJ process. Moreover, the equality-search operation in a bit-serial fashion is used for great reduction of the activity rate in the proposed CAM cell array, since most of the mismatched words in the CAM are detected by just several higher bits of comparison results in the word circuits. By applying a bit-level fine-grained power gating scheme, a fabricated 64-bit x 128-word nonvolatile CAM achieves high density with maintaining low search energy under 3.1% of activity rate in the cell array. (C) 2011 The Japan Society of Applied Physics

  217. Tunnel magnetoresistance properties and annealing stability in perpendicular anisotropy MgO-based magnetic tunnel junctions with different stack structures 査読有り

    K. Mizunuma, S. Ikeda, H. Sato, M. Yamanouchi, H. D. Gan, K. Miura, H. Yamamoto, J. Hayakawa, F. Matsukura, H. Ohno

    JOURNAL OF APPLIED PHYSICS 109 (7) 07C711-(1)-07C711-(3) 2011年4月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.3554092  

    ISSN:0021-8979

    eISSN:1089-7550

    詳細を見る 詳細を閉じる

    We have investigated the effect of stack structures on tunnel magnetoresistance (TMR) properties in perpendicular anisotropy MgO-based magnetic tunnel junctions (p-MTJs) with CoFe/Pd multilayer and CoFeB insertion. By adopting Ta and Ru cap-layers, the TMR ratios of 113 and 106% are obtained at annealing temperature (T-a) of 325 degrees C, respectively. Particularly, the Ru cap-layer is effective in realizing a TMR ratio of 100% at T-a = 350 degrees C. By replacing (Co25Fe75)(80)B-20 with (Co25Fe75)(85)B-15, the TMR ratio increased quickly at low Ta, reaching a maximum of 120% at T-a = 300 degrees C. (C) 2011 American Institute of Physics. [doi:10.1063/1.3554092]

  218. Dependence of magnetic anisotropy on MgO thickness and buffer layer in Co20Fe60B20-MgO structure 査読有り

    M. Yamanouchi, R. Koizumi, S. Ikeda, H. Sato, K. Mizunuma, K. Miura, H. D. Gan, F. Matsukura, H. Ohno

    JOURNAL OF APPLIED PHYSICS 109 (7) 07C712-(1)-07C712-(3) 2011年4月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.3554204  

    ISSN:0021-8979

    詳細を見る 詳細を閉じる

    We investigated the dependence of perpendicular magnetic anisotropy in CoFeB-MgO on the MgO layer thickness. Magnetization curves show that a clear perpendicular magnetic easy axis is obtainable in a 1.5-nm thick CoFeB layer by depositing MgO of more than three monolayers. We investigated anisotropy in CoFeB-MgO deposited on four different buffer layers. Results show that a counter interface of CoFeB-nonmagnetic metal affects the perpendicular anisotropy of CoFeB/MgO. (C) 2011 American Institute of Physics. [doi:10.1063/1.3554204]

  219. Current-induced effective field in perpendicularly magnetized Ta/CoFeB/MgO wire 査読有り

    T. Suzuki, S. Fukami, N. Ishiwata, M. Yamanouchi, S. Ikeda, N. Kasai, H. Ohno

    APPLIED PHYSICS LETTERS 98 (14) 142505-(1)-142505-(3) 2011年4月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.3579155  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    The current-induced effective field in perpendicularly magnetized Ta/CoFeB/MgO wire was investigated. A threshold field decrease of 6.4 kOe/mA was observed by measuring the threshold field of Hall resistance versus the magnetic field curve with various bias currents. The decrease was probably caused by the in-plane effective field, mainly due to the Rashba effect. The effective field of the Ta/CoFeB/MgO wire was smaller and opposite in direction compared to that of Pt/Co/AlO(x) previously reported. (C) 2011 American Institute of Physics. [doi:10.1063/1.3579155]

  220. Spin-torque switching window, thermal stability, and material parameters of MgO tunnel junctions 査読有り

    T. Devolder, L. Bianchini, K. Miura, K. Ito, Joo-Von Kim, P. Crozat, V. Morin, A. Helmer, C. Chappert, S. Ikeda, H. Ohno

    APPLIED PHYSICS LETTERS 98 (16) 162502-(1)-162502-(3) 2011年4月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.3576937  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    We study the use of in-plane magnetized free layers with artificially lowered effective magnetization, in the context of spin-torque random access memories with magnetic tunnel junctions. We determine the field-voltage window for direct overwrite switching and thermal stability. We relate them to the magnetic constants extracted from the telegraph noise and high frequency noise exhibited by the junctions under specific conditions. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3576937]

  221. Magnetic Field Dependence of Quadrupolar Splitting and Nuclear Spin Coherence Time in a Strained (110) GaAs Quantum Well 査読有り

    Jun Ishihara, Masaaki Ono, Genki Sato, Shunichiro Matsuzaka, Yuzo Ohno, Hideo Ohno

    JAPANESE JOURNAL OF APPLIED PHYSICS 50 (4) 04DM03-(1)-04DM03-(3) 2011年4月

    出版者・発行元:JAPAN SOC APPLIED PHYSICS

    DOI: 10.1143/JJAP.50.04DM03  

    ISSN:0021-4922

    詳細を見る 詳細を閉じる

    We investigated the magnetic field dependence of quadrupolar splitting and phase relaxation time of nuclear spins in an n-GaAs/AlGaAs (110) quantum well (QW) by optically detected nuclear magnetic resonance (NMR). The NMR spectra show large quadrupolar splitting induced by an internal field gradient in the QW epilayer. At lower magnetic fields, the quadrupolar splitting become much enhanced, resulting in the appearance of the second order magnetic field dependence of the quadrupole interaction in the NMR spectra. It is also shown that the intrinsic coherence time and the effective coherence time for resonant transitions become shorter as a result that the energy splitting between the two levels becomes small and incoherent transition is occurred by irradiation of an rf magnetic field. (C) 2011 The Japan Society of Applied Physics

  222. Highly-scalable disruptive reading and restoring scheme for Gb-scale SPRAM and beyond 査読有り

    R. Takemura, T. Kawahara, K. Ono, K. Miura, H. Matsuoka, H. Ohno

    SOLID-STATE ELECTRONICS 58 (1) 28-33 2011年4月

    出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD

    DOI: 10.1016/j.sse.2010.11.032  

    ISSN:0038-1101

    eISSN:1879-2405

    詳細を見る 詳細を閉じる

    We propose a disruptive reading and restoration scheme for a high density spin-transfer-torque random access memory (SPRAM). The proposed scheme uses the feature that - with a desired error rate and a tunnel magneto resistance (TMR) device, which is the memory device of the SPRAM - does not switch its magnetization of free layer in a specific period of large current pulse. The restoration operation is performed to secure the storing data. As a result, by keeping good scalability of spin-transfer-torque writing toward Gb-scale and beyond, high-speed reading with read-disturbance-free operation can be achieved. This operation also enables the SPRAM to accept the DDRx-SDRAM compatible operation. In addition, we also proposed a 4-F-2 cell structure with a vertical transistor and prospected the reliability of a tunnel barrier of the TMR devices for a Gb-scale SPRAM. (C) 2010 Elsevier Ltd. All rights reserved.

  223. Pd Layer Thickness Dependence of Tunnel Magnetoresistance Properties in CoFeB/MgO-Based Magnetic Tunnel Junctions with Perpendicular Anisotropy CoFe/Pd Multilayers 査読有り

    Kotaro Mizunuma, Michihiko Yamanouchi, Shoji Ikeda, Hideo Sato, Hiroyuki Yamamoto, Hua-Dong Gan, Katsuya Miura, Jun Hayakawa, Fumihiro Matsukura, Hideo Ohno

    APPLIED PHYSICS EXPRESS 4 (2) 023002-(1)-023002-(3) 2011年2月

    出版者・発行元:JAPAN SOC APPLIED PHYSICS

    DOI: 10.1143/APEX.4.023002  

    ISSN:1882-0778

    詳細を見る 詳細を閉じる

    The authors investigated tunnel magnetoresistance (TMR) properties in [CoFe/Pd]-multilayer/CoFeB/MgO/CoFeB/[Pd/CoFe]-multilayer magnetic tunnel junctions (MTJs) having two different Pd layer thicknesses. By reducing the Pd layer thickness from 1.2 to 0.2 nm, the TMR ratio was enhanced from 7 to 101% at the annealing temperature (T(a)) of 300 degrees C. The thin Pd layers resulted in high residual B concentration in the CoFeB layer after high-T(a) annealing and in the suppression of crystallization of the CoFeB layer from the fcc(111)-Pd layer side. (C) 2011 The Japan Society of Applied Physics

  224. Current-induced domain wall motion in perpendicularly magnetized CoFeB nanowire 査読有り

    S. Fukami, T. Suzuki, Y. Nakatani, N. Ishiwata, M. Yamanouchi, S. Ikeda, N. Kasai, H. Ohno

    APPLIED PHYSICS LETTERS 98 (8) 082504-(1)-082504-(3) 2011年2月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.3558917  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    Current-induced domain wall motion in perpendicularly magnetized CoFeB nanowires with a stack structure of Ta(1.0 nm)/CoFeB(1.2 nm)/MgO(2.0 nm)/Ta(1.0 nm) was investigated. Domain wall motion driven by adiabatic spin-transfer torque was observed at a current of about 74 mu A, corresponding to a current density of 6.2 x 10(7) A/cm(2). The obtained results were compared with those of a micromagnetic simulation and the spin polarization of the CoFeB was estimated to be 0.72. (C) 2011 American Institute of Physics. [doi:10.1063/1.3558917]

  225. Magnetic anisotropy modulation in Ta/CoFeB/MgO structure by electric fields 査読有り

    S. Kanai, M. Endo, S. Ikeda, F. Matsukura, H. Ohno

    Journal of Physics; Conference Series 266 012092(1)-012092(5) 2011年1月28日

  226. Electric-Field Effects on Magnetic Materials –From Ferromagnetic Semiconductors to CoFeB-

    H. Ohno

    Magnetics and Optics Research International Symposium for New Storage Technology(MORIS2011) 2011年

  227. Domain Structure in CoFeB Thin Films With Perpendicular Magnetic Anisotropy 査読有り

    Michihiko Yamanouchi, Albrecht Jander, Pallavi Dhagat, Shoji Ikeda, Fumihiro Matsukura, Hideo Ohno

    IEEE MAGNETICS LETTERS 2 3000304(1)-3000304(4) 2011年

    出版者・発行元:IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

    DOI: 10.1109/LMAG.2011.2159484  

    ISSN:1949-307X

    詳細を見る 詳細を閉じる

    Domain structures in CoFeB-MgO thin films with a perpendicular easy magnetization axis were observed by magneto-optic Kerr-effect microscopy at various temperatures. The domain-wall surface energy was obtained by analyzing the spatial period of the stripe domains and fitting established domain models to the period. In combination with superconducting quantum interference device measurements of magnetization and anisotropy energy, this leads to an estimate of the exchange stiffness and domain-wall width in these films. These parameters are essential for determining whether domain walls will form in patterned structures and devices made of such materials.

  228. Domain wall dynamics in a single CrO(2) grain 査読有り

    P. Das, F. Porrati, S. Wirth, A. Bajpai, Y. Ohno, H. Ohno, M. Huth, J. Mueller

    JOINT EUROPEAN MAGNETIC SYMPOSIA (JEMS) 303 012056-(1)-012056-(6) 2011年

    出版者・発行元:IOP PUBLISHING LTD

    DOI: 10.1088/1742-6596/303/1/012056  

    ISSN:1742-6588

    詳細を見る 詳細を閉じる

    Recently we have reported on the magnetization dynamics of a single CrO(2) grain studied by micro Hall magnetometry (P. Das et al., Appl. Phys. Lett. 9 7 042507, 2010). For the external magnetic field applied along the grain's easy magnetization direction, the magnetization reversal takes place through a series of Barkhausen jumps. Supported by micromagnetic simulations, the ground state of the grain was found to correspond to a flux closure con figuration with a single cross-tie domain wall. Here, we report an analysis of the Barkhausen jumps, which were observed in the hysteresis loops for the external field applied along both the easy and hard magnetization directions. We find that the magnetization reversal takes place through only a view con figuration paths in the free-energy landscape, pointing to a high purity of the sample. The distinctly different statistics of the Barkhausen jumps for the two field directions is discussed.

  229. A window on the future of spintronics 招待有り

    Hideo Ohno

    NATURE MATERIALS 9 (12) 952-954 2010年12月

    出版者・発行元:NATURE PUBLISHING GROUP

    DOI: 10.1038/nmat2913  

    ISSN:1476-1122

    eISSN:1476-4660

  230. Electrically Defined Ferromagnetic Nanodots 査読有り

    Daichi Chiba, Fumihiro Matsukura, Hideo Ohno

    NANO LETTERS 10 (11) 4505-4508 2010年11月

    出版者・発行元:AMER CHEMICAL SOC

    DOI: 10.1021/nl102379h  

    ISSN:1530-6984

    eISSN:1530-6992

    詳細を見る 詳細を閉じる

    While ferromagnetic nanodots are being widely studied from fundamental as well as application points of views, so far all the dots have been physically defined: once made, one cannot change their dimension or size. We show that ferromagnetic nanodots can be electrically defined. To realize this, we utilize an electric field to modulate the in-plane distribution of carriers in a ferromagnetic semiconductor (Ga,Mn)As film with a meshed gate structure having a large number of nanoscaled windows.

  231. Observation of the fractional quantum Hall effect in an oxide 査読有り

    A. Tsukazaki, S. Akasaka, K. Nakahara, Y. Ohno, H. Ohno, D. Maryenko, A. Ohtomo, M. Kawasaki

    NATURE MATERIALS 9 (11) 889-893 2010年11月

    出版者・発行元:NATURE PUBLISHING GROUP

    DOI: 10.1038/NMAT2874  

    ISSN:1476-1122

    詳細を見る 詳細を閉じる

    The quantum Hall effect arises from the cyclotron motion of charge carriers in two-dimensional systems. However, the ground states related to the integer and fractional quantum Hall effect, respectively, are of entirely different origin(1-5). The former can be explained within a single-particle picture; the latter arises from electron correlation effects governed by Coulomb interaction. The prerequisite for the observation of these effects is extremely smooth interfaces of the thin film layers to which the charge carriers are confined. So far, experimental observations of such quantum transport phenomena have been limited to a few material systems based on silicon, III-V compounds and graphene(1-9). In ionic materials, the correlation between electrons is expected to be more pronounced than in the conventional heterostructures, owing to a large effective mass of charge carriers. Here we report the observation of the fractional quantum Hall effect in MgZnO/ZnO heterostructures grown by molecular-beam epitaxy, in which the electron mobility exceeds 180,000 cm(2) V(-1) s(-1). Fractional states such as v = 4/3, 5/3 and 8/3 clearly emerge, and the appearance of the v = 2/5 state is indicated. The present study represents a technological advance in oxide electronics that provides opportunities to explore strongly correlated phenomena in quantum transport of dilute carriers.

  232. Current induced effective magnetic field and magnetization reversal in uniaxial anisotropy (Ga,Mn)As 査読有り

    M. Endo, F. Matsukura, H. Ohno

    APPLIED PHYSICS LETTERS 97 (22) 222501-1-222501-3 2010年11月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.3520514  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    The authors investigate the current density and temperature dependence of current induced effective magnetic field H(eff) through spin-orbit interaction in a ferromagnetic semiconductor Ga(0.92)Mn(0.08)As having uniaxial magnetic anisotropy. The change of the magnitude of apparent magnetic anisotropy induced by H(eff) that is dependent on the current direction and density is observed by transport measurements using the planar Hall effect. The authors show the 180 degrees magnetization switching through H(eff) by applying pulsed current. (C) 2010 American Institute of Physics. [doi:10.1063/1.3520514]

  233. A perpendicular-anisotropy CoFeB-MgO magnetic tunnel junction 査読有り

    S. Ikeda, K. Miura, H. Yamamoto, K. Mizunuma, H. D. Gan, M. Endo, S. Kanai, J. Hayakawa, F. Matsukura, H. Ohno

    NATURE MATERIALS 9 (9) 721-724 2010年9月

    出版者・発行元:NATURE PUBLISHING GROUP

    DOI: 10.1038/NMAT2804  

    ISSN:1476-1122

    詳細を見る 詳細を閉じる

    Magnetic tunnel junctions (MTJS) with ferromagnetic electrodes possessing a perpendicular magnetic easy axis are of great interest as they have a potential for realizing next-generation hight-density non-volatile memory and logic chips with high thermal stability and low critical current for current-induced magnetization switching(1-3). To attain perpendicular anisotropy, a number of material system have been explored as electrodes, which include rare-earth/transition-metal alloys(4,5), L1(0)-ordered (Co, Fe)-Pt alloys(3,6,7) and Co/(Pd, Pt) multilayers(1,8-10). However, none of them so far satisfy high thermal stability at reduced dimension, low-current current-induced magnetization switching and high tunnel magnetoresistance ratio all at the same time. Here, we use interfacial perpendicular anisotropy between the ferro-magnetic electrodes and the tunnel barrier of the MTJ by employing the material combination of CoFeB-MgO, a system widely adopted to produce a giant tunnel magnetoresistance ratio in MTJs with in-plane anisotropy(11-13). This approach requires no material other than those used in conventional in-plane-anisotropy MTJs. The perpendicular MTJs consisting of Ta/CoFeB/MgO/CoFeB/Ta show a high tunnel magnetoresistance ratio, over 120%, high thermal stability at dimension as low as 40 nm diameter and a low switching current of 49 mu A.

  234. Band-tail shape and transport near the metal-insulator transition in Si-doped Al0.3Ga0.7As 査読有り

    Jennifer Misuraca, Jelena Trbovic, Jun Lu, Jianhua Zhao, Yuzo Ohno, Hideo Ohno, Peng Xiong, Stephan von Molnar

    PHYSICAL REVIEW B 82 (12) 125202-1-125202-6 2010年9月

    出版者・発行元:AMER PHYSICAL SOC

    DOI: 10.1103/PhysRevB.82.125202  

    ISSN:1098-0121

    詳細を見る 詳細を閉じる

    In the present work, an infrared light-emitting diode is used to photodope molecular-beam-epitaxy-grown Si: Al0.3Ga0.7As, a well-known persistent photoconductor, to vary the effective electron concentration of samples in situ. Using this technique, we examine the transport properties of two samples containing different nominal doping concentrations of Si [1 x 10(19) cm(-3) for sample 1 (S1) and 9 x 10(17) cm(-3) for sample 2 (S2)] and vary the effective electron density between 10(14) and 10(18) cm(-3). The metal-insulator transition for S1 is found to occur at a critical carrier concentration of 5.7 x 10(16) cm(-3) at 350 mK. The mobilities in both samples are found to be limited by ionized impurity scattering in the temperature range probed, and are adequately described by the Brooks-Herring screening theory for higher carrier densities. The shape of the band tail of the density of states in Al0.3Ga0.7As is found electrically through transport measurements. It is determined to have a power-law dependence, with an exponent of -1.25 for S1 and -1.38 for S2.

  235. Width and temperature dependence of lithography-induced magnetic anisotropy in (Ga,Mn)As wires 査読有り

    M. Kohda, J. Ogawa, J. Shiogai, F. Matsukura, Y. Ohno, H. Ohno, J. Nitta

    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES 42 (10) 2685-2689 2010年9月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/j.physe.2009.12.019  

    ISSN:1386-9477

    eISSN:1873-1759

    詳細を見る 詳細を閉じる

    In-plane magnetic anisotropy of 40-mu m-long (Ga,Mn)As wires with different widths (0.4, 1.0, and 20 mu m) has been investigated between 5 and 75 K by measuring anisotropic magneto-resistance (AMR). The wires show in-plane &lt; 1 0 0 &gt; cubic and [-1 1 0] uniaxial anisotropies, and an additional lithography-induced anisotropy along the wire direction in narrow wires with width of 0.4 and 1.0 mu m. We derive the temperature dependence of the cubic, uniaxial, and lithography-induced anisotropy constants from the results of AMR, and find that a sizable anisotropy can be provided by lithographic means, which allows us to control and detect the magnetization reversal process by choosing the direction of the external magnetic fields. (C) 2009 Elsevier B.V. All rights reserved.

  236. Magnetic anisotropy in a ferromagnetic (Ga,Mn)Sb thin film 査読有り

    Y. Nishitani, M. Endo, F. Matsukura, H. Ohno

    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES 42 (10) 2681-2684 2010年9月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/j.physe.2009.12.054  

    ISSN:1386-9477

    eISSN:1873-1759

    詳細を見る 詳細を閉じる

    We have grown a 5-nm-thick (Ga,Mn)Sb with Mn composition of 0.032, and investigated its magnetic properties and their electric-field dependence. The sample shows ferromagnetism below about 25 K, whose magnetic easy axis is perpendicular to plane. By utilizing a field-effect transistor structure, we show that the Curie temperature and magnetic anisotropy field can be controlled by the application of electric field. (C) 2009 Elsevier B.V. All rights reserved.

  237. Domain wall creep in (Ga,Mn)As 査読有り

    A. Kanda, A. Suzuki, F. Matsukura, H. Ohno

    APPLIED PHYSICS LETTERS 97 (3) 032504-(1)-032504-(3) 2010年7月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.3467048  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    We have compared the scaling exponents in scaling formula for magnetic domain wall creep by measuring the magnetic-field induced domain wall velocity of (Ga,Mn)As layers grown on (In,Al)As semistep-graded buffer layer and (In,Ga)As buffer layer. The different critical exponents for the two (Ga,Mn)As layers indicate that the observed creep motions belong to different universality classes, which are found to be governed by the degree of surface roughness due to crosshatch dislocation introduced during epitaxial growth. Domain wall creep motion in (Ga,Mn)As layer grown on (In,Al)As with flatter surface belongs to random-field disorder, whereas that in (In,Ga)As to random-bond disorder. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3467048]

  238. Magnetization dynamics of a CrO2 grain studied by micro-Hall magnetometry 査読有り

    P. Das, F. Porrati, S. Wirth, A. Bajpai, M. Huth, Y. Ohno, H. Ohno, J. Mueller

    APPLIED PHYSICS LETTERS 97 (4) 042507-(1)-042507-(3) 2010年7月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.3467870  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    Micro-Hall magnetometry is employed to study the magnetization dynamics of a single, micron-size CrO2 grain. With this technique, we track the motion of a single domain wall, which allows us to probe the distribution of imperfections throughout the material. An external magnetic field along the grain&apos;s easy magnetization direction induces magnetization reversal, giving rise to a series of sharp jumps in magnetization. Supported by micromagnetic simulations, we identify the transition to a state with a single cross-tie domain wall, where pinning/depinning of the wall results in stochastic Barkhausen jumps. (C) 2010 American Institute of Physics. [doi:10.1063/1.3467870]

  239. Simulation of magnetization switching by electric-field manipulation of magnetic anisotropy 査読有り

    D. Chiba, Y. Nakatani, F. Matsukura, H. Ohno

    APPLIED PHYSICS LETTERS 96 (19) 192506-(1)-192506-(3) 2010年5月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.3428959  

    ISSN:0003-6951

    eISSN:1077-3118

    詳細を見る 詳細を閉じる

    Electrical anisotropy modulation was recently observed in ferromagnetic semiconductors and metals. The authors have investigated magnetization switching through magnetic anisotropy modulation induced by external electric field by means of simulation. Macrospin simulation using Landau-Lifshitz-Gilbert equation shows that switching is possible by controlling magnetic anisotropy for appropriate sets of parameters. The condition for quasistatic magnetization switching is also presented, in which magnetization direction is determined to minimize the magnetic free energy. (C) 2010 American Institute of Physics. [doi:10.1063/1.3428959]

  240. Tunnel magnetoresistance properties and film structures of double MgO barrier magnetic tunnel junctions 査読有り

    H. D. Gan, S. Ikeda, W. Shiga, J. Hayakawa, K. Miura, H. Yamamoto, H. Hasegawa, F. Matsukura, T. Ohkubo, K. Hono, H. Ohno

    APPLIED PHYSICS LETTERS 96 (19) 192507-(1)-192507-(3) 2010年5月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.3429594  

    ISSN:0003-6951

    eISSN:1077-3118

    詳細を見る 詳細を閉じる

    The authors fabricated double MgO barrier magnetic tunnel junctions (MTJs) with 3-nm-thick Co40Fe40B20 free layer. When annealed at 350 degrees C, tunnel magnetoresistance (TMR) ratio at room temperature was 130%, much lower than that (297%) of single MgO barrier MTJs processed and annealed under the same condition. The middle CoFeB free layer sandwiched between the two MgO barriers was found to be mostly amorphous. Replacement of the Co40Fe40B20 free layer by a highly oriented Co50Fe50 layer and a composite Co50Fe50/Co40Fe40B20 layer led to the enhanced TMR ratios up to 165% and 212% at annealing temperature of 350 degrees C, respectively. (C) 2010 American Institute of Physics. [doi:10.1063/1.3429594]

  241. Electric-field effects on thickness dependent magnetic anisotropy of sputtered MgO/Co40Fe40B20/Ta structures 査読有り

    M. Endo, S. Kanai, S. Ikeda, F. Matsukura, H. Ohno

    APPLIED PHYSICS LETTERS 96 (21) 212503-(1)-212503-(3) 2010年5月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.3429592  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    We have investigated the effect of applied electric field E-G on thickness dependent magnetic anisotropy of sputtered Co40Fe40B20 sandwiched with MgO and Ta. The range of CoFeB thickness explored is 2 nm and below. As the thickness is reduced, the easy axis of magnetization becomes perpendicular from in-plane. We show that perpendicular magnetic anisotropy of in-plane samples and coercivity of perpendicular samples can be modified by applying E-G at room temperature. Furthermore, superparamagnetic behavior is observed for CoFeB layers with further reduced thickness below approximate to 0.9 nm, where electric-field effect is also observed below their blocking temperature. (C) 2010 American Institute of Physics. [doi:10.1063/1.3429592]

  242. Spatially homogeneous ferromagnetism of (Ga, Mn)As 査読有り

    S. R. Dunsiger, J. P. Carlo, T. Goko, G. Nieuwenhuys, T. Prokscha, A. Suter, E. Morenzoni, D. Chiba, Y. Nishitani, T. Tanikawa, F. Matsukura, H. Ohno, J. Ohe, S. Maekawa, Y. J. Uemura

    NATURE MATERIALS 9 (4) 299-303 2010年4月

    出版者・発行元:NATURE PUBLISHING GROUP

    DOI: 10.1038/NMAT2715  

    ISSN:1476-1122

    詳細を見る 詳細を閉じる

    Mn-doped GaAs is a ferromagnetic semiconductor(1,2), widely studied because of its possible application for spin-sensitive &apos;spintronics&apos; devices(3,4). The material also attracts great interest in fundamental research regarding its evolution from a paramagnetic insulator to a ferromagnetic metal(5,6). The high sensitivity of its physical properties to preparation conditions and heat treatments(7,8) and the strong doping and temperature dependencies of the magnetic anisotropy(9,10) have generated a view in the research community that ferromagnetism in (Ga, Mn) Asmay be associated with unavoidable and intrinsic strong spatial inhomogeneity. Muon spin relaxation (mu SR) probes magnetism, yielding unique information about the volume fraction of regions having static magnetic order, as well as the size and distribution of the ordered moments(11-13). By combining low-energy mu SR, conductivity and a. c. and d. c. magnetization results obtained on high-quality thin-film specimens, we demonstrate here that (Ga, Mn) As shows a sharp onset of ferromagnetic order, developing homogeneously in the full volume fraction, in both insulating and metallic films. Smooth evolution of the ordered moment size across the insulator metal phase boundary indicates strong ferromagnetic coupling between Mn moments that exists before the emergence of fully itinerant hole carriers.

  243. A 32-Mb SPRAM with 2T1R memory cell, localized Bi-directional write driver and ‘1’/’0’ dual-array equalized reference scheme 査読有り

    R. Takemura, T. Kawahara, K. Miura, H. Yamamoto, J. Hayakawa, N. Matsuzaki, K. Ono, M. Yamanouchi, K. Ito, H. Takahashi, S. Ikeda, H. Hasegawa, H. Matsuoka, H. Ohno

    IEEE Journal of Solid-State Circuits 45 (4) 869-879 2010年4月

    出版者・発行元:None

    DOI: 10.1109/JSSC.2010.2040120  

    ISSN:0018-9200

  244. Vertical electric field tuning of the exciton fine structure splitting and photon correlation measurements of GaAs quantum dot 査読有り

    S. Marcet, K. Ohtani, H. Ohno

    Applied Physics Letters 99 101117-(1)-101117-(3) 2010年3月12日

    DOI: 10.1063/1.3360212  

  245. Anomalous Hall Effect in Field-Effect Structures of (Ga,Mn)As 査読有り

    D. Chiba, A. Werpachowska, M. Endo, Y. Nishitani, F. Matsukura, T. Dietl, H. Ohno

    PHYSICAL REVIEW LETTERS 104 (10) 106601-(1)-106601-(4) 2010年3月

    出版者・発行元:AMER PHYSICAL SOC

    DOI: 10.1103/PhysRevLett.104.106601  

    ISSN:0031-9007

    詳細を見る 詳細を閉じる

    The anomalous Hall effect in metal-insulator-semiconductor structures having thin (Ga,Mn)As layers as a channel has been studied in a wide range of Mn and hole densities changed by the gate electric field. Strong and unanticipated temperature dependence, including a change of sign, of the anomalous Hall conductance sigma(xy) has been found in samples with the highest Curie temperatures. For more disordered channels, the scaling relation between sigma(xy) and sigma(xx), similar to the one observed previously for thicker samples, is recovered.

  246. A nondestructive analysis of the B diffusion in Ta-CoFeB-MgO-CoFeB-Ta magnetic tunnel junctions by hard x-ray photoemission 査読有り

    Xeniya Kozina, Siham Ouardi, Benjamin Balke, Gregory Stryganyuk, Gerhard H. Fecher, Claudia Felser, Shoji Ikeda, Hideo Ohno, Eiji Ikenaga

    APPLIED PHYSICS LETTERS 96 (7) 072105-1-072105-3 2010年2月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.3309702  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    This work reports on hard x-ray photoelectron spectroscopy (HAXPES) of CoFeB based tunnel junctions. Aim is to explain the role of the boron diffusion for the observed improvement of the tunneling magnetoresistance ratio with increasing annealing temperature. The high bulk sensitivity of HAXPES was used as a nondestructive technique to analyze CoFeB-MgO-CoFeB magnetic tunnel junctions. The investigated samples were processed at different annealing temperatures from 523 to 923 K. Hard x-ray core level spectroscopy reveals an enforced diffusion of boron from the CoFeB into the adjacent Ta layer with increasing annealing temperature. The dependence of the tunneling magnetoresistance on the annealing temperature is explained by the combined effects of an improved crystalline structure together with a change in the spin polarization at the Fermi energy caused by the removal of boron from the CoFeB layer and Ta diffusion at high annealing temperature.

  247. Gate voltage dependence of nuclear spin relaxation in an impurity-doped semiconductor quantum well 査読有り

    M. Ono, H. Kobayashi, S. Matsuzaka, Y. Ohno, H. Ohno

    APPLIED PHYSICS LETTERS 96 (7) 071907-1-071907-3 2010年2月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.3309687  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    We investigated the gate voltage dependence of the nuclear spin relaxation in a Schottky-gated n-GaAs/AlGaAs (110) quantum well by the time-resolved Kerr rotation measurement combined with the nuclear magnetic resonance technique. The Fermi contact hyperfine interaction is enhanced by decreasing the background electron density, as the electrons become localized at impurity site. The energy relaxation time T(1) and the decay time of the Rabi oscillation T(2Rabi) can be controlled by more than a factor of 10 and a factor of similar to 2, respectively.

  248. Experimental probing of the interplay between ferromagnetism and localization in (Ga, Mn)As 査読有り

    Maciej Sawicki, Daichi Chiba, Anna Korbecka, Yu Nishitani, Jacek A. Majewski, Fumihiro Matsukura, Tomasz Dietl, Hideo Ohno

    NATURE PHYSICS 6 (1) 22-25 2010年1月

    出版者・発行元:NATURE PUBLISHING GROUP

    DOI: 10.1038/NPHYS1455  

    ISSN:1745-2473

    詳細を見る 詳細を閉じる

    The question of whether the Anderson-Mott localization enhances or reduces magnetic correlations is central to the physics of magnetic alloys(1). Particularly intriguing is the case of (Ga, Mn)As and related magnetic semiconductors, for which diverging theoretical scenarios have been proposed(2-9). Here, by direct magnetization measurements we demonstrate how magnetism evolves when the density of carriers mediating the spin-spin coupling is diminished by the gate electric field in metal-insulator-semiconductor structures of (Ga, Mn)As. Our findings show that the channel depletion results in a monotonic decrease of the Curie temperature, with no evidence for the maximum expected within the impurity-band models(3,5,8,9). We find that the transition from the ferromagnetic to the paramagnetic state proceeds by means of the emergence of a superparamagnetic-like spin arrangement. This implies that carrier localization leads to a phase separation into ferromagnetic and non-magnetic regions, which we attribute to critical fluctuations in the local density of states, specific to the Anderson-Mott quantum transition.

  249. Scanning Kerr Microscopy of the Spin Hall Effect in n-Doped GaAs with Various Doping Concentration 査読有り

    S. Matsuzaka, Y. Ohno, H. Ohno

    JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM 23 (1) 37-39 2010年1月

    出版者・発行元:SPRINGER

    DOI: 10.1007/s10948-009-0558-6  

    ISSN:1557-1939

    詳細を見る 詳細を閉じる

    We investigated the doping concentration (N (D)) dependence of the extrinsic spin Hall effect (SHE) in n-doped GaAs with N (D) raging from 3x10(16) cm(-3) to 5x10(17) cm(-3). By using scanning Kerr microscopy (SKM) measurements, we observed the Kerr rotation signal due to the spin accumulation near the channel edges in all the samples with different N (D). Moreover, the position and in-plane magnetic field dependence of the Kerr rotation signal are found to vary with N (D). We analyzed the N (D) dependence of the spin Hall conductivity by taking account of the N (D)-dependent spin lifetime based on the typical drift-diffusion model.

  250. Gate Voltage Control of Nuclear Spin Relaxation in GaAs Quantum Well 査読有り

    M. Ono, S. Matsuzaka, Y. Ohno, H. Ohno

    JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM 23 (1) 131-133 2010年1月

    出版者・発行元:SPRINGER

    DOI: 10.1007/s10948-009-0568-4  

    ISSN:1557-1939

    詳細を見る 詳細を閉じる

    Gate-voltage dependences of nuclear spin relaxation and decoherence times in a Schottky-gated n-GaAs/AlGaAs (110) quantum well (QW) are investigated by time-resolved Kerr-rotation measurements combined with pulsed-rf nuclear magnetic resonance (NMR). We show that the nuclear spin relaxation and decoherence times decrease with decreasing electron density, indicating that the hyperfine interaction is enhanced as the electronic states becomes localized in an impurity-doped QW.

  251. Electric double layer transistor with a (Ga,Mn)As channel 査読有り

    M. Endo, D. Chiba, H. Shimotani, F. Matsukura, Y. Iwasa, H. Ohno

    APPLIED PHYSICS LETTERS 96 (2) 022515-1-022515-3 2010年1月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.3277146  

    ISSN:0003-6951

    eISSN:1077-3118

    詳細を見る 詳細を閉じる

    The authors have fabricated electric double layer transistors with a (Ga,Mn)As channel to investigate the possibility of larger modulation of magnetism by the application of electric fields. The sheet conductance as well as the Curie temperature can be modulated up to a few tens of percents by application of gate voltage of a few volts, which is almost one-order of magnitude smaller than that required in conventional metal-insulator-semiconductor structures. The 14 K modulation of the Curie temperature by applying gate voltage ranging from -1 to 3 V is the highest modulation ratio reported so far in ferromagnetic semiconductors.

  252. Curie temperature versus hole concentration in field-effect structures of Ga1-xMnxAs 査読有り

    Y. Nishitani, D. Chiba, M. Endo, M. Sawicki, F. Matsukura, T. Dietl, H. Ohno

    PHYSICAL REVIEW B 81 (4) 045208-1-045208-8 2010年1月

    出版者・発行元:AMER PHYSICAL SOC

    DOI: 10.1103/PhysRevB.81.045208  

    ISSN:1098-0121

    詳細を見る 詳細を閉じる

    The Curie temperature T-C is investigated as a function of the hole concentration p in thin films of ferromagnetic semiconductor (Ga,Mn)As. The magnetic properties are probed by transport measurements and p is varied by the application of an external electric field in a field-effect transistor configuration. It is found that T-C similar to p(gamma), where the exponent gamma = 0.19 +/- 0.02 over a wide range of Mn compositions and channel thicknesses. The magnitude of gamma is reproduced by a p-d Zener model taking into account nonuniform hole distribution along the growth direction, determined by interface states and the applied gate electric fields.

  253. Spin-transfer Switching in Magnetic Tunnel Junctions with Synthetic Ferri-magnetic Free Layer 査読有り

    M. Nishimura, M. Oogane, H. Naganuma, N. Inami, S. Ikeda, H. Ohno, Y. Ando

    INTERNATIONAL CONFERENCE ON MAGNETISM (ICM 2009) 200 052018-1-052018-4 2010年

    出版者・発行元:IOP PUBLISHING LTD

    DOI: 10.1088/1742-6596/200/5/052018  

    ISSN:1742-6588

    詳細を見る 詳細を閉じる

    We have fabricated the SyF structure with both high annealing stability and strong interlayer exchange coupling and investigated tunnelling magnetoresistance (TMR) and spin-transfer switching properties of magnetic tunnel junctions (MTJs) with developed SyF free layer. The fabricated SyF with structure of Ta/Ru/CoFe/Ru/CoFeB possessed high annealing stability of 400 degrees C and strong interlayer exchange coupling. Consequently, a large TMR ratio of 122% has been observed after annealing at high temperature of 350 degrees C. In addition, we have successfully observed spin-transfer switching by the net current density of 14 MA/cm(2) and the large thermal stability factor of 62.

  254. CoFeB Inserted Perpendicular Magnetic Tunnel Junctions with CoFe/Pd Multilayers for High Tunnel Magnetoresistance Ratio 査読有り

    Kotaro Mizunuma, Shoji Ikeda, Hiroyuki Yamamoto, Hua Dong Gan, Katsuya Miura, Haruhiro Hasegawa, Jun Hayakawa, Kenchi Ito, Fumihiro Matsukura, Hideo Ohno

    JAPANESE JOURNAL OF APPLIED PHYSICS 49 (4) 04DM04-(1)-04DM04-(4) 2010年

    出版者・発行元:JAPAN SOC APPLIED PHYSICS

    DOI: 10.1143/JJAP.49.04DM04  

    ISSN:0021-4922

    詳細を見る 詳細を閉じる

    The effect of Co20Fe60B20 insertion on tunnel magnetoresistance (TMR) properties of MgO barrier magnetic tunnel junctions (MTJs) was studied with Co90Fe10/Pd multilayer electrodes showing perpendicular anisotropy. The TMR ratio, which depended on the sputtering power density of the CoFeB layer, reached 43% at 1.77W/cm(2) in MTJs with a 1.8-nm-thick CoFeB layer inserted on both sides of the MgO barrier. With increasing CoFeB layer thickness, the optimal annealing temperature (T-a) realizing the maximum TMR ratio increased along with the TMR ratio. The MTJs with 3.0-nm-thick CoFeB deposited at 1.77W/cm(2) showed a TMR ratio of 91% at T-a 250 degrees C, where the perpendicular magnetic anisotropy is maintained. (C) 2010 The Japan Society of Applied Physics

  255. Fine-Grained Power-Gating Scheme of a Metal-Oxide-Semiconductor and Magnetic-Tunnel-Junction-Hybrid Bit-Serial Ternary Content-Addressable Memory 査読有り

    Shoun Matsunaga, Masanori Natsui, Kimiyuki Hiyama, Tetsuo Endoh, Hideo Ohno, Takahiro Hanyu

    JAPANESE JOURNAL OF APPLIED PHYSICS 49 (4) 04DM-05-(1)-04DM-05-(5) 2010年

    出版者・発行元:JAPAN SOC APPLIED PHYSICS

    DOI: 10.1143/JJAP.49.04DM05  

    ISSN:0021-4922

    詳細を見る 詳細を閉じる

    A fine-grained power-gating scheme combining metal-oxide-semiconductor (MOS) transistors with magnetic-tunnel-junction (MTJ) devices, where storage data still remains even if the power supply is cut off, is proposed for an ultra low-power bit-serial ternary content-addressable memory (TCAM). Once a mismatched result is detected in a sequence of a bit-level equality-search operation, the power supply of all the cells in the word circuit is cut off, which greatly reduces the standby power dissipation in the word circuit. The standby power dissipation of the proposed TCAM in the standby mode is reduced to about 1.2% in comparison with that of a complementary MOS (CMOS)-only-based TCAM. Moreover, the power-delay product of the proposed TCAM is reduced to 15.5% in comparison with that of the corresponding CMOS-only-based TCAM. (C) 2010 The Japan Society of Applied Physics

  256. The Performance of Magnetic Tunnel Junction Integrated on the Back-End Metal Line of Complimentary Metal-Oxide-Semiconductor Circuits 査読有り

    Tetsuo Endoh, Fumitaka Iga, Shoji Ikeda, Katsuya Miura, Jun Hayakawa, Masashi Kamiyanagi, Haruhiro Hasegawa, Takahiro Hanyu, Hideo Ohno

    JAPANESE JOURNAL OF APPLIED PHYSICS 49 (4) 04DM06-(1)-04DM06-(5) 2010年

    出版者・発行元:JAPAN SOC APPLIED PHYSICS

    DOI: 10.1143/JJAP.49.04DM06  

    ISSN:0021-4922

    詳細を見る 詳細を閉じる

    In this paper, we have described the complementary metal-oxide-semiconductor (CMOS)/magnetic tunnel junction (MTJ) integrated process technology; MTJs were fabricated on via metal with surface roughness of 0.3nm with 0.14 mu m CMOS process and 60 x 180nm(2) MTJ process. It is shown that by this process technology, the fabricated MTJ on CMOS logic circuit plane achieves a large change in a resistance of 3.63 k Omega (anti-parallel) with the TMR ratio of 138% at room temperature, which is large enough for a sensing scheme of standard CMOS logic. Furthermore, we have successfully demonstrated the DC and AC operation of this MTJ with write transistors. As the results, our MTJ achieves high enough write/read performance with transistors for realizing MTJ-based logic circuits. (C) 2010 The Japan Society of Applied Physics

  257. Electron density dependence of the spin Hall effect in GaAs probed by scanning Kerr rotation microscopy 査読有り

    S. Matsuzaka, Y. Ohno, H. Ohno

    PHYSICAL REVIEW B 80 (24) 241305-1-241305-4 2009年12月

    出版者・発行元:AMER PHYSICAL SOC

    DOI: 10.1103/PhysRevB.80.241305  

    ISSN:1098-0121

    詳細を見る 詳細を閉じる

    We studied electron density (n) dependence of the extrinsic spin Hall effect in n-doped GaAs with n raging from 1.8x10(16) to 3.3x10(17) cm(-3). By scanning Kerr microscopy measurements, we observed spin accumulation near the channel edges in all the samples due to the extrinsic spin Hall effect. The spin Hall conductivity sigma(SH) is obtained for each sample by comparing the Kerr rotation induced by optically injected spins. sigma(SH) is found to increase with n, and it is shown that a theoretical model reported earlier agrees well with the experimental n dependence of sigma(SH).

  258. MgO barrier-perpendicular magnetic tunnel junctions with CoFe/Pd multilayers and ferromagnetic insertion layers 査読有り

    K. Mizunuma, S. Ikeda, J. H. Park, H. Yamamoto, H. Gan, K. Miura, H. Hasegawa, J. Hayakawa, F. Matsukura, H. Ohno

    APPLIED PHYSICS LETTERS 95 (23) 232516-1-232516-3 2009年12月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.3265740  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    The authors studied an effect of ferromagnetic (Co(20)Fe(60)B(20) or Fe) layer insertion on tunnel magnetoresistance (TMR) properties of MgO-barrier magnetic tunnel junctions (MTJs) with CoFe/Pd multilayer electrodes. TMR ratio in MTJs with CoFeB/MgO/Fe stack reached 67% at annealing temperature (T(a)) of 200 degrees C and then decreased rapidly at T(a) over 250 degrees C. The degradation of the TMR ratio may be related to crystallization of CoFe(B) into fcc(111) or bcc(011) texture resulting from diffusion of B into Pd layers. MTJs which were in situ annealed at 350 degrees C just after depositing bottom CoFe/Pd multilayer showed TMR ratio of 78% by postannealing at T(a)= 200 degrees C. (C) 2009 American Institute of Physics. [doi: 10.1063/1.3265740]

  259. Perpendicular Magnetic Tunnel Junctions with CoFe/Pd Multilayer Electrodes and an MgO Barrier 査読有り

    Ji-Ho Park, Shoji Ikeda, Hiroyuki Yamamoto, Huadong Gan, Kotaro Mizunuma, Katsuya Miura, Haruhiro Hasegawa, Jun Hayakawa, Kenchi Ito, Fumihiro Matsukura, Hideo Ohno

    IEEE TRANSACTIONS ON MAGNETICS 45 (10) 3476-3479 2009年10月

    出版者・発行元:IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

    DOI: 10.1109/TMAG.2009.2023237  

    ISSN:0018-9464

    詳細を見る 詳細を閉じる

    We studied the magnetic and magnetoresistance characteristics of pseudospin-valve magnetic tunnel junctions (MTJs) based on CoFe/Pd multilayer electrodes with perpendicular magnetic anisotropy and an MgO barrier. The MTJs at annealing temperature (T(a)) of 473 K showed a tunnel-magnetoresistance (TMR) ratio of 1.5%. An fcc (111)-oriented texture of the bottom and top Co(90)Fe(10)/Pd multilayer electrodes, together with an imperfectly crystallized MgO, were revealed by cross-sectional TEM images. The TMR properties of perpendicular MTJs with a Co(20)Fe(60)B(20) or Co(50)Fe(50) layer inserted between the CoFe/Pd multilayer electrodes and the MgO barrier were also studied. The TMR ratio with Co(20)Fe(60)B(20) insertion was 1.7% at T(a) = 473 K and monotonically decreased at T(a) over 523 K. The TMR ratio with Co(50)Fe(50) insertion increased up to 3% at T(a) = 573 K and then decreased to 0.4% at T(a) = 598 K. The influence of the Pd layer on CoFeB was studied by using the simplified structures of Pd/CoFeB/MgO/CoFeB/Pd and Ta/CoFeB/MgO/CoFeB/Ta with inplane anisotropy. A former structure with Pd resulted in reduced TMR ratio which decreases with increasing T(a), whereas MTJs with a Ta-based structure showed a monotonic increase of a TMR ratio. The low TMR ratio observed in Pd-containing structures appears to result from crystallization of CoFeB in an unfavorable crystal orientation.

  260. Transmission electron microscopy investigation of CoFeB/MgO/CoFeB pseudospin valves annealed at different temperatures 査読有り

    S. V. Karthik, Y. K. Takahashi, T. Ohkubo, K. Hono, S. Ikeda, H. Ohno

    JOURNAL OF APPLIED PHYSICS 106 (2) 023920-1-023920-6 2009年7月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.3182817  

    ISSN:0021-8979

    eISSN:1089-7550

    詳細を見る 詳細を閉じる

    We have investigated the microstructure and local chemistry of Ta/Ru/Ta/CoFeB/MgO/CoFeB/Ta/Ru magnetic tunnel junctions with different values of tunneling magnetoresistance (TMR) as a result of annealing at different temperatures. Annealing at 500 degrees C led to the templated crystallization of the amorphous CoFeB layer having coherent interfaces with MgO grains with an orientation relationship of &lt; 001 &gt;[011](MgO)parallel to &lt; 001 &gt;[001](CoFe), and the B rejected from crystallized CoFeB was found to be dissolved in upper amorphous Ta layers and segregated in the bottom crystalline Ta layer. Annealing at 600 degrees C led to the dissolution of 3-4 at. % Ta in the MgO barrier, and B was found to be segregated at the CoFeB/MgO and Ta/Ru interfaces as a result of the crystallization of the top amorphous Ta layer. Further degradation in TMR of the samples annealed at 650 degrees C results from the loss of bcc-CoFe (001) texture in the bottom CoFeB electrode due to the pronounced Ta diffusion into the CoFe/MgO/CoFe layers. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3182817]

  261. Direct measurement of current-induced fieldlike torque in magnetic tunnel junctions 査読有り

    T. Devolder, Joo-Von Kim, C. Chappert, J. Hayakawa, K. Ito, H. Takahashi, S. Ikeda, H. Ohno

    JOURNAL OF APPLIED PHYSICS 105 (11) 113924-1-113924-5 2009年6月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.3143033  

    ISSN:0021-8979

    詳細を見る 詳細を閉じる

    present a direct and quantitative method to measure the current-induced fieldlike torques in current perpendicular to plane magnetic multilayers. We illustrate this method on nanopillars patterned from MgO-based magnetic tunnel junctions. By measuring how the Stoner astroids are displaced, shrinked, and distorted under the influence of a bias current, we separate the contributions of the current-induced fieldlike torque, the current-induced heating, and the current-induced spin torque. In contrast to high frequency based measurement methods that are better suited to analyze the spin torque than the fieldlike term, our measurement is direct and quantitative for the current-induced fieldlike term and the heating induced reduction in shape anisotropy, while only qualitative for the spin torque. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3143033]

  262. ac susceptibility of (Ga,Mn)As probed by the anomalous Hall effect 招待有り 査読有り

    Y. Nishitani, D. Chiba, F. Matsukura, H. Ohno

    JOURNAL OF APPLIED PHYSICS 105 (7) 07C516-1-07C516-3 2009年4月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.3072078  

    ISSN:0021-8979

    詳細を見る 詳細を閉じる

    ac susceptibility of a ferromagnetic semiconductor (Ga,Mn)As was measured using microscaled Hall bar through the anomalous Hall effect. The synchronous component of the Hall resistance with applied ac magnetic field (similar to 1 mT) was detected using a lock-in technique. The temperature dependence of the ac Hall resistance shows a clear peak in the vicinity of the Curie temperature T(C), when an offset dc field, whose magnitude is comparable to that of the ac field, is superimposed. We applied this method to detect the change of TC as a function of hole concentration by applying electric fields. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3072078]

  263. 3DAP analysis of (Ga,Mn)As diluted magnetic semiconductor thin film 招待有り 査読有り

    M. Kodzuka, T. Ohkubo, K. Hono, F. Matsukura, H. Ohno

    ULTRAMICROSCOPY 109 (5) 644-648 2009年4月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/j.ultramic.2008.11.011  

    ISSN:0304-3991

    詳細を見る 詳細を閉じる

    The distribution of Mn in a Ga(0.963)Mn(0.037)As ferromagnetic semiconductor film has been characterized by the three-dimensional atom probe (3DAP) technique. Atom probe specimens were directly prepared from the (Ga,Mn)As film grown epitaxially on a p-type GaAs substrate by the lift-out technique using a scanning electron microscope/focused ion beam system. The atom probe elemental map revealed that the Mn atoms in the Ga(0.963)Mn(0.037)As are uniformly dissolved without forming any nanometer-sized clusters. (C) 2008 Elsevier B.V. All rights reserved.

  264. Intersubband exchange interaction induced by optically excited electron spins in GaAs/AlGaAs quantum wells 招待有り 査読有り

    K. Morita, H. Sanada, S. Matsuzaka, Y. Ohno, H. Ohno

    APPLIED PHYSICS LETTERS 94 (16) 162104-1-162104-3 2009年4月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.3118584  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    Spin-dependent intersubband excitonic interactions have been investigated in GaAs/AlGaAs quantum wells by two-color pump and probe spectroscopy. We generated spin-polarized electrons in the lowest subband by resonant excitation of the heavy-hole exciton (E(1)-HH(1)) and observed polarization-dependent broadening of the second-subband exciton resonance (E(2)-HH(2) and E(2)-LH(1)). The exchange interaction between the first and the second-subband excitons is found to play a crucial role in polarization-dependent spectral modulation as well as spin-independent Coulomb screening.

  265. Intersubband optical transitions in ZnO-based quantum wells grown by plasma-assisted molecular beam epitaxy 招待有り 査読有り

    K. Ohtani, M. Belmoubarik, H. Ohno

    JOURNAL OF CRYSTAL GROWTH 311 (7) 2176-2178 2009年3月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/j.jcrysgro.2008.09.134  

    ISSN:0022-0248

    詳細を見る 詳細を閉じる

    Intersubband optical transitions in ZnO-based quantum wells grown by plasma-assisted molecular beam epitaxy are investigated by a photocurrent spectroscopy. ZnO/MgZnO multiple quantum well (MQW) Structures containing different ZnO well thicknesses are prepared. Photocurrent peaks are observed when the polarization of incident light is TM mode, following the intersubband selection rule. On reducing the ZnO well thickness, photocurrent peaks shifted to higher energies. Calculation indicates that the photocurrent peaks are due to intersubband transitions from the first to the third subband in ZnO/MgZnO MQWs. Comparison between experiment and calculation allows LIS to estimate the band offset ratio. (c) 2008 Elsevier B.V. All rights reserved.

  266. Thermally activated longitudinal optical phonon scattering of a 3.8THz GaAs quantum cascade laser 査読有り

    Tsung-Tse Lin, Keita Ohtani, Hideo Ohno

    Applied Physics Express 2 (2) 022102-(1)-022102-(3) 2009年2月

    DOI: 10.1143/APEX.2.022102  

    ISSN:1882-0778 1882-0786

    詳細を見る 詳細を閉じる

    Thermally activated longitudinal optical (LO) phonon scattering time (τtherma LO) of excited subbands in a 3.8THz quantum cascade laser is studied. The active region used herein is based on a LO phonon depopulation scheme. A single plasmon waveguide was used for optical confinement. By calculating the temperature dependence of threshold current density (Jth) and comparing with the experiment, τ therma LO limiting the characteristic temperature of Jth is estimated: τtherma LO is 246 ns at 5 K, which rapidly decreases 15 ps when temperature rises up to 100 K. © 2009 The Japan Society of Applied Physics.

  267. Standby-Power-Free Compact Ternary Content-Addressable Memory Cell Chip Using Magnetic Tunnel Junction Devices 査読有り

    Shoun Matsunaga, Kimiyuki Hiyama, Atsushi Matsumoto, Shoji Ikeda, Haruhiro Hasegawa, Katsuya Miura, Jun Hayakawa, Tetsuo Endoh, Hideo Ohno, Takahiro Hanyu

    APPLIED PHYSICS EXPRESS 2 (2) 023004-(1)-023004-(3) 2009年2月

    出版者・発行元:JAPAN SOCIETY APPLIED PHYSICS

    DOI: 10.1143/APEX.2.023004  

    ISSN:1882-0778

    詳細を見る 詳細を閉じる

    A compact ternary content-addressable memory (TCAM) cell of 3.15 mu m(2) with a 0.14 mu m complementary metal oxide semiconductor process is realized by the use of nonvolatile magnetic tunnel junction (MTJ) devices with spin-injection write. This TCAM cell based on logic-in-memory architecture with nonvolatile MTJs needs no standby power, yet allows instant shut-down of the supply voltage without data backup to an external nonvolatile device. (C) 2009 The Japan Society of Applied Physics

  268. MTJ-Based Nonvolatile Logic-in-Memory Circuit, Future Prospects and Issues 査読有り

    Shoun Matsunaga, Jun Hayakawa, Shoji Ikeda, Katsuya Miura, Tetsuo Endoh, Hideo Ohno, Takahiro Hanyu

    DATE: 2009 DESIGN, AUTOMATION & TEST IN EUROPE CONFERENCE & EXHIBITION, VOLS 1-3 433-+ 2009年

    出版者・発行元:IEEE

    ISSN:1530-1591

    詳細を見る 詳細を閉じる

    Nonvolatile logic-in-memory architecture, where nonvolatile memory elements are distributed over a logic-circuit plane, is expected to realize both ultra-low-power and reduced interconnection delay. This paper presents novel nonvolatile logic circuits based on logic-in-memory architecture using magnetic tunnel junctions (MTJs) in combination with MOS transistors. Since the MTJ with a spin-injection write capability is only one device that has all the following superior features as large resistance ratio, virtually unlimited endurance, fast read/write accessibility, scalability, complementary MOS (CMOS)-process compatibility, and nonvolatility, it is very suited to implement the MOS/MTJ-hybrid logic circuit with logic-in-memory architecture. A concrete nonvolatile logic-in-memory circuit is designed and fabricated using a 0.18 mu m CMOS/MTJ process, and its future prospects and issues are discussed.

  269. A novel SPRAM (spin-transfer torque RAM)-based reconfigurable logic block for 2D-stacked reconfigurable spin processor 招待有り 査読有り

    M. Sekikawa, K. Kiyoyama, H. Hasegawa, K. Miura, T. Fukushima, S. Ikeda, T. Tanaka, H. Ohno, M. Koyanagi

    Digests of technical papers of 2008 IEEE International Electron Devices Meeting (IEDM 2008) 935-937 2008年12月

    DOI: 10.1109/IEDM.2008.4796645  

  270. A Novel SPRAM (SPin-transfer torque RAM)-based Reconfigurable Logic Block for 3D-Stacked reconfigurable Spin Processor 招待有り 査読有り

    M. Sekikawa, K. Kiyoyama, H. Hasegawa, K. Miura, T. Fukushima, S. Ikeda, T. Tanaka, H. Ohno, M. Koyanagi

    IEEE Electron Devices Meeting, Technical Papers 935-937 2008年12月

    DOI: 10.1109/IEDM.2008.4796645  

  271. Low-temperature field-effect and magnetotransport properties in a ZnO based heterostructure with atomic-layer-deposited gate dielectric 査読有り

    A. Tsukazaki, A. Ohtomo, D. Chiba, Y. Ohno, H. Ohno, M. Kawasaki

    APPLIED PHYSICS LETTERS 93 (24) 241905-(1)-241905-(3) 2008年12月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.3035844  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    A top-gate field-effect device with atomic-layer-deposited Al(2)O(3) dielectric was fabricated to investigate magnetotransport properties of two-dimensional electron gas (2DEG) at a semi-insulating ZnO-Mg(0.12)Zn(0.88)O double heterostructure grown by laser molecular-beam epitaxy. Hall mobility monotonically increased as the density of accumulated electrons increased. The highest mobility at 2 K was recorded to be 5000 cm(2) V(-1) s(-1) at a 2DEG density of 1.2x10(12) cm(-2), which is comparable to the previously reported value for a metallic ZnO/Mg(0.2)Zn(0.8)O heterostructure. Insulator-to-metal transition was observed at a critical density of 6x10(11) cm(-2). The metallic-state channel exhibited Shubnikov-de Haas oscillations, demonstrating an electric-field tunable quantum device based on transparent oxide semiconductor.

  272. Multipulse Operation and Optical Detection of Nuclear Spin Coherence in a GaAs/AlGaAs Quantum Well 査読有り

    Y. Kondo, M. Ono, S. Matsuzaka, K. Morita, H. Sanada, Y. Ohno, H. Ohno

    PHYSICAL REVIEW LETTERS 101 (20) 207601-(1)-207601-(4) 2008年11月

    出版者・発行元:AMER PHYSICAL SOC

    DOI: 10.1103/PhysRevLett.101.207601  

    ISSN:0031-9007

    詳細を見る 詳細を閉じる

    We demonstrate manipulation of nuclear spin coherence in a GaAs/AlGaAs quantum well by optically detected nuclear magnetic resonance (NMR). A phase shift of the Larmor precession of photoexcited electron spins is detected to read out the hyperfine-coupled nuclear spin polarization. Multipulse NMR sequences are generated to control the population and examine the phase coherence in quadrupolar-split spin-3/2 (75)As nuclei. The phase coherence among the multilevel nuclear spin states is addressed by application of pulse sequences that are used in quantum gate operations.

  273. Fabrication of a nonvolatile full adder based on logic-in-memory architecture using magnetic tunnel junctions 査読有り

    Shoun Matsunaga, Jun Hayakawa, Shoji Ikeda, Katsuya Miura, Haruhiro Hasegawa, Tetsuo Endoh, Hideo Ohno, Takahiro Hanyu

    APPLIED PHYSICS EXPRESS 1 (9) 091301-(1)-091301-(3) 2008年9月

    出版者・発行元:JAPAN SOC APPLIED PHYSICS

    DOI: 10.1143/APEX.1.091301  

    ISSN:1882-0778

    詳細を見る 詳細を閉じる

    Nonvolatile logic-in-memory architecture, where nonvolatile memory elements are distributed over a logic-circuit plane, is expected to realize both ultra-low-power and reduced interconnection delay. We have fabricated a nonvolatile full adder based on logic-in-memory architecture using magnetic tunnel junctions (MTJs) in combination with metal oxide semiconductor (MOS) transistors. Magnesium oxide (MgO) barrier MTJs are used to take advantage of their high tunnel magneto-resistance (TMR) ratio and spin-injection write capability. The MOS transistors are fabricated using a 0.18 mu m complementary metal oxide semiconductor (CMOS) process. The basic operation of the full adder is confirmed. (C) 2008 The Japan Society of Applied Physics.

  274. Mott relation for anomalous Hall and Nernst effects in Ga1-xMnxAs ferromagnetic semiconductors 査読有り

    Yong Pu, Daichi Chiba, Fumihiro Matsukura, Hideo Ohno, Jing Shi

    PHYSICAL REVIEW LETTERS 101 (11) 117208-(1)-117208-(4) 2008年9月

    出版者・発行元:AMER PHYSICAL SOC

    DOI: 10.1103/PhysRevLett.101.117208  

    ISSN:0031-9007

    eISSN:1079-7114

    詳細を見る 詳細を閉じる

    The Mott relation between the electrical and thermoelectric transport coefficients normally holds for phenomena involving scattering. However, the anomalous Hall effect (AHE) in ferromagnets may arise from intrinsic spin-orbit interaction. In this work, we have simultaneously measured AHE and the anomalous Nernst effect (ANE) in Ga1-xMnxAs ferromagnetic semiconductor films, and observed an exceptionally large ANE at zero magnetic field. We further show that AHE and ANE share a common origin and demonstrate the validity of the Mott relation for the anomalous transport phenomena.

  275. Magnetization vector manipulation by electric fields 査読有り

    D. Chiba, M. Sawicki, Y. Nishitani, Y. Nakatani, F. Matsukura, H. Ohno

    NATURE 455 (7212) 515-518 2008年9月

    出版者・発行元:NATURE PUBLISHING GROUP

    DOI: 10.1038/nature07318  

    ISSN:0028-0836

    eISSN:1476-4687

    詳細を見る 詳細を閉じる

    Conventional semiconductor devices use electric fields to control conductivity, a scalar quantity, for information processing. In magnetic materials, the direction of magnetization, a vector quantity, is of fundamental importance. In magnetic data storage, magnetization is manipulated with a current-generated magnetic field (Oersted-Ampere field), and spin current(1,2) is being studied for use in non- volatile magnetic memories(3,4). To make control of magnetization fully compatible with semiconductor devices, it is highly desirable to control magnetization using electric fields. Conventionally, this is achieved by means of magnetostriction produced by mechanically generated strain through the use of piezoelectricity(5-8). Multiferroics(9,10) have been widely studied in an alternative approach where ferroelectricity is combined with ferromagnetism. Magnetic- field control of electric polarization has been reported in these multiferroics using the magnetoelectric effect, but the inverse effect - direct electrical control of magnetization - has not so far been observed(11). Here we show that the manipulation of magnetization can be achieved solely by electric fields in a ferromagnetic semiconductor, (Ga,Mn)As. The magnetic anisotropy, which determines the magnetization direction, depends on the charge carrier (hole) concentration in (Ga,Mn) As. By applying an electric field using a metal - insulator - semiconductor structure(12-14), the hole concentration and, thereby, the magnetic anisotropy can be controlled, allowing manipulation of the magnetization direction.

  276. Tunnel magnetoresistance of 604% at 300 K by suppression of Ta diffusion in CoFeB/MgO/CoFeB pseudo-spin-valves annealed at high temperature 査読有り

    S. Ikeda, J. Hayakawa, Y. Ashizawa, Y. M. Lee, K. Miura, H. Hasegawa, M. Tsunoda, F. Matsukura, H. Ohno

    APPLIED PHYSICS LETTERS 93 (8) 082508-(1)-082508-(3) 2008年8月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.2976435  

    ISSN:0003-6951

    eISSN:1077-3118

    詳細を見る 詳細を閉じる

    The authors observed tunnel magnetoresistance (TMR) ratio of 604% at 300 K in Ta/Co20Fe60B20/MgO/Co20Fe60B20/Ta pseudo-spin-valve magnetic tunnel junction annealed at 525 degrees C. To obtain high TMR ratio, it was found critical to anneal the structure at high temperature above 500 degrees C, while suppressing the Ta diffusion into CoFeB electrodes and in particular to the CoFeB/MgO interface. X-ray diffraction measurement of MgO on SiO2 or Co20Fe60B20 shows that an improvement of MgO barrier quality, in terms of the degree of the (001) orientation and stress relaxation, takes place at annealing temperatures above 450 degrees C. The highest TMR ratio observed at 5 K was 1144%. (C) 2008 American Institute of Physics.

  277. Current-induced magnetization switching in MgO barrier magnetic tunnel junctions with CoFeB-based synthetic ferrimagnetic free layers 査読有り

    Jun Hayakawa, Shoji Ikeda, Katsuya Miura, Michihiko Yarnanouchi, Young Min Lee, Ryutaro Sasaki, Masahiko Ichimura, Kenchi Ito, Takayuki Kawahara, Riichiro Takemura, Toshiyasu Meguro, Fumihiro Matsukura, Hiromasa Takahashi, Hideyuki Matsuoka, Hideo Ohno

    IEEE TRANSACTIONS ON MAGNETICS 44 (7) 1962-1967 2008年7月

    出版者・発行元:IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

    DOI: 10.1109/TMAG.2008.924545  

    ISSN:0018-9464

    詳細を見る 詳細を閉じる

    We investigated the effect of using a synthetic ferrimagnetic (SyF) free layer in MgO-based magnetic tunnel junctions (MTJs) on current-induced magnetization switching (CIMS), particularly for application to spin-transfer torque random access memory (SPRAM). The employed SyF free layer had a Co40Fe40B20/Ru/Co40Fe40B20 and Co20Fe60B20/Ru/Co20Fe60B20 structures, and the MTJs (100 x (150-300) nm(2)) were annealed at 300 degrees C. The use of SyF free layer resulted in low intrinsic critical current density (J(c0)) without degrading the thermal-stability factor (E/k(B)T, where E, k(B), and Tare the energy potential, the Boltzmann constant, and temperature, respectively). When the two CoFeB layers of a strongly antiferromagnetically coupled SyF free layer had the same thickness, J(c0) was reduced to 2-4 X 10(6) A/cm(2). This low J(c0) may be due to the decreased effective volume under the large spin accumulation at the CoFeB/Ru. The E/k(B)T was over 60, resulting in a retention time of over ten years and suppression of the write current dispersion for SPRAM. The use of the SyF free layer also resulted in a bistable (parallel/antiparallel) magnetization configuration at zero field, enabling the realization of CIMS without the need to apply external fields to compensate for the offset field.

  278. Intersubband transitions in ZnO multiple quantum wells 査読有り

    M. Belmoubarik, K. Ohtani, H. Ohno

    APPLIED PHYSICS LETTERS 92 (19) 191906(1)-191906(3) 2008年5月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.2926673  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    Intersubband transitions in ZnO/MgZnO multiple quantum wells (MQWs) are investigated by a photocurrent spectroscopy. Photocurrent peaks are observed in the energy range from 300 to 400 meV and shifted to higher energy by reducing the ZnO well thickness. Polarization-resolved photocurrent spectra show that these peaks are observed when the polarization of incident lights is TM mode, following the intersubband selection rule. Calculation indicates that the photocurrent peaks are the intersubband transition from the first to the third subband in ZnO/MgZnO MQWs. (C) 2008 American Institute of Physics.

  279. An extensive comparison of anisotropies in MBE grown (Ga, Mn)As material 査読有り

    C. Gould, S. Mark, K. Pappert, R. G. Dengel, J. Wenisch, R. P. Campion, A. W. Rushforth, D. Chiba, Z. Li, X. Liu, W. Van Roy, H. Ohno, J. K. Furdyna, B. Gallagher, K. Brunner, G. Schmidt, L. W. Molenkamp

    NEW JOURNAL OF PHYSICS 10 055007-(1)-055007-(10) 2008年5月

    出版者・発行元:IOP PUBLISHING LTD

    DOI: 10.1088/1367-2630/10/5/055007  

    ISSN:1367-2630

    詳細を見る 詳細を閉じる

    This paper reports on a detailed magnetotransport investigation of the magnetic anisotropies of (Ga, Mn) As layers produced by various sources worldwide. Using anisotropy fingerprints to identify the contributions of the various higher-order anisotropy terms, we show that the presence of both a [100] and a [110] uniaxial anisotropy in addition to the primary ([100] + [010]) anisotropy is common to all medium doped (Ga, Mn) As layers typically used in transport measurement, with the amplitude of these uniaxial terms being characteristic of the individual layers.

  280. Spin-transfer physics and the model of ferromagnetism in (Ga, Mn)As 査読有り

    Hideo Ohno, Tomasz Dietl

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 320 (7) 1293-1299 2008年4月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/j.jmmm.2007.12.016  

    ISSN:0304-8853

    詳細を見る 詳細を閉じる

    We describe recent progress and open questions in the physics of current-induced domain-wall displacement and creep in (Ga, Mn) As. Furthermore, the reasons are recalled why, despite strong disorder and localization, the p-d Zener model is suitable for the description of this system. (c) 2007 Elsevier B. V. All rights reserved.

  281. Properties of Ga(1-x)Mn(x)As with high x (&gt; 0.1) 査読有り

    D. Chiba, K. M. Yu, W. Walukiewicz, Y. Nishitani, F. Matsukura, H. Ohno

    JOURNAL OF APPLIED PHYSICS 103 (7) 07D136-1-07D136-3 2008年4月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.2837469  

    ISSN:0021-8979

    詳細を見る 詳細を閉じる

    We have investigated the magnetic and the crystalline properties of a set of Ga(1-x)Mn(x)As layers with high nominal Mn compositions (x=0.101-0.198). Magnetization measurements and combined channeling Rutherford backscattering (c-RBS) and particle induced x-ray emission (c-PIXE) measurements have been performed to determine the effective Mn composition x(eff) and the fraction of Mn atoms at various lattice sites. Here, x(eff) determined from magnetization measurements, which increases with increasing x, is consistent with the results determined from c-RBS-PIXE measurements. (c) 2008 American Institute of Physics.

  282. Electrical Curie temperature modulation in (Ga,Mn)As field-effect transistors with Mn composition from 0.027 to 0.200 査読有り

    Y. Nishitani, D. Chiba, F. Matsukura, H. Ohno

    JOURNAL OF APPLIED PHYSICS 103 (7) 07D139-1-07D139-3 2008年4月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.2838159  

    ISSN:0021-8979

    詳細を見る 詳細を閉じる

    The authors have fabricated field-effect transistor structures with a ferromagnetic Ga(1-x)Mn(x)As channel having Mn composition of x=0.027-0.200. The samples with larger x have higher Curie temperature T(C) and hole concentration p, while the controllable range of T(C) by applying external electric field does not increase with x. x dependence of effective Mn composition is also described. (c) 2008 American Institute of Physics.

  283. Electrical time-domain observation of magnetization switching induced by spin transfer in magnetic nanostructures (invited) 招待有り 査読有り

    T. Devolder, J. Hayakawa, K. Ito, H. Takahashi, S. Ikeda, J. A. Katine, M. J. Carey, P. Crozat, J. V. Kim, C. Chappert, H. Ohno

    JOURNAL OF APPLIED PHYSICS 103 (7) 07A723(1)-07A723(6) 2008年4月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.2839341  

    ISSN:0021-8979

    詳細を見る 詳細を閉じる

    We have measured the distribution of switching times in spin-transfer switching induced by fast current pulses in two pillar-shaped systems: (i) spin valves and (ii) MgO-based magnetic tunnel junctions. (i) Spin valves can sustain high currents, such that the application of pulsed currents of amplitude a few times that of the static switching threshold is possible. This makes subnanosecond switching within reach. In that limit, the pulse durations leading to switching follow a multiply stepped distribution at 300 K and a regular distribution at 40 K. At 300 K, this reflects the precessional nature of the switching, which proceeds through a small number of precession cycles. The switching time distribution can be modeled from the thermal variance of the initial magnetization orientations. At 40 K, nonuniform magnetization switching occurs. (ii) In MgO-based tunnel junctions, we could follow individual time-resolved switching events with a 13 GHz bandwidth. The switching proceeds through a nanosecond-scale random incubation delay during which the resistance is quiet, followed by a sudden (400 ps duration) transition terminated by a pronounced ringing that is damped within 1.5 ns. While the incubation delay is probabilistic, the following time dependence of the resistance is reproducible.

  284. Spin-transfer physics and the model of ferromagnetism in (Ga, Mn)As 査読有り

    Hideo Ohno, Tomasz Dietl

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 320 (7) 1293-1299 2008年4月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/j.jmmm.2007.12.016  

    ISSN:0304-8853

    詳細を見る 詳細を閉じる

    We describe recent progress and open questions in the physics of current-induced domain-wall displacement and creep in (Ga, Mn) As. Furthermore, the reasons are recalled why, despite strong disorder and localization, the p-d Zener model is suitable for the description of this system. (c) 2007 Elsevier B. V. All rights reserved.

  285. Fabrication of a few-electron In0.56Ga0.44As vertical quantum dot with Al2Oe gate insulator 査読有り

    T. Kita, D. Chiba, Y. Ohno, H. Ohno

    Physica E 40 1930-1932 2008年4月

    DOI: 10.1016/j.physe.2007.08.140  

  286. Effect of vertical electric fields on exciton fine structure of GaAs natural quantum dots 査読有り

    S. Marcet, T. Kita, K. Ohtani, H. Ohno

    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES 40 (6) 2069-2071 2008年4月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/j.physe.2007.09.106  

    ISSN:1386-9477

    詳細を見る 詳細を閉じる

    The effect of vertical electric fields on the neutral exciton of GaAs "natural" quantum dots is investigated. A Stark effect with a quadratic field dependence up to 2meV was observed and reveals a displacement of the excitonic wave function. The luminescencequenching limits the applied electric field range. No significative change on the fine structure splitting of the neutral exciton has been observed, suggesting that the lateral potential induced by the vertical electric field is too weak to modify the in-plane anisotropy of the exciton wave function. (C) 2007 Elsevier B.V. All rights reserved.

  287. 0.7 anomaly and magnetotransport of disordered quantum wires 査読有り

    M. Czapkiewicz, P. Zagrajek, J. Wrobel, G. Grabecki, K. Fronc, T. Dietl, Y. Ohno, S. Matsuzaka, H. Ohno

    EPL 82 (2) 27003-(1)-27003-(6) 2008年4月

    出版者・発行元:EPL ASSOCIATION, EUROPEAN PHYSICAL SOCIETY

    DOI: 10.1209/0295-5075/82/27003  

    ISSN:0295-5075

    詳細を見る 詳細を閉じる

    The unexpected "0.7" plateau of conductance quantisation is usually observed for ballistic one-dimensional devices. In this work we study a quasi-ballistic quantum wire, for which the disorder-induced backscattering reduces the conductance quantisation steps. We find that the transmission probability resonances coexist with the anomalous plateau. The studies of these resonances as a function of the in-plane magnetic field and electron density point to the presence of spin polarisation at low carrier concentrations and constitute a method for the determination of the effective g-factor suitable for disordered quantum wires. Copyright (c) EPLA, 2008.

  288. Electrical control of spin coherence in ZnO 査読有り

    S. Ghosh, D. W. Steuerman, B. Maertz, K. Ohtani, Huaizhe Xu, H. Ohno, D. D. Awschalom

    APPLIED PHYSICS LETTERS 92 (16) 162109(1)-162109(3) 2008年4月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.2913049  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    Electric field enhanced electron spin coherence is characterized using time-resolved Faraday rotation spectroscopy in n-type ZnO epilayers grown by molecular beam epitaxy. An in-plane dc electric field E almost doubles the transverse spin lifetime at 20 K without affecting the effective g factor. This effect persists until high temperatures, but decreases with increasing carrier concentration. Comparisons of the variations in the spin lifetime, the carrier recombination lifetime, and photoluminescence lifetimes indicate that the applied E enhances the radiative recombination rate. All observed effects are independent of crystal directionality and are performed at low magnetic fields (B &lt; 0.2 T). (C) 2008 American Institute of Physics.

  289. Spintronics - A renaissance in magnetism 査読有り

    H. Ohno

    Journal of the Physical Society of Japan 77 2008年3月

  290. Fine structure in magnetospectrum of vertical quantum dot 査読有り

    Oleksiy B. Agafonov, Tomohiro Kita, Hideo Ohno, Rolf J. Haug

    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES 40 (5) 1630-1632 2008年3月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/j.physe.2007.10.006  

    ISSN:1386-9477

    詳細を見る 詳細を閉じる

    The electronic transport properties of a gated vertical quantum dot fabricated of an asymmetrical InGaAs/AlGaAs double-barrier resonant tunneling heterostructure are studied experimentally. At a temperature of 15 mK, a series of small current peaks are observed far below the voltage of a main resonance peak. The voltage position of these peaks appeared to be strongly dependent on the presence of magnetic field oriented perpendicular to the plane of the barriers. The occurrence of the peaks is attributed to tunneling mechanisms involving inter- Landau- level resonant tunneling, longitudinal-optical (LO)-phonon-assisted tunneling and to electrostatic effects such as Coulomb blockade (C) 2007 Elsevier B.V. All rights reserved.

  291. Fine structure in magnetospectrum of vertical quantum dot 査読有り

    Oleksiy B. Agafonov, Tomohiro Kita, Hideo Ohno, Rolf J. Haug

    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES 40 (5) 1630-1632 2008年3月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/j.physe.2007.10.006  

    ISSN:1386-9477

    詳細を見る 詳細を閉じる

    The electronic transport properties of a gated vertical quantum dot fabricated of an asymmetrical InGaAs/AlGaAs double-barrier resonant tunneling heterostructure are studied experimentally. At a temperature of 15 mK, a series of small current peaks are observed far below the voltage of a main resonance peak. The voltage position of these peaks appeared to be strongly dependent on the presence of magnetic field oriented perpendicular to the plane of the barriers. The occurrence of the peaks is attributed to tunneling mechanisms involving inter- Landau- level resonant tunneling, longitudinal-optical (LO)-phonon-assisted tunneling and to electrostatic effects such as Coulomb blockade (C) 2007 Elsevier B.V. All rights reserved.

  292. Single-shot time-resolved measurements of nanosecond-scale spin-transfer induced switching: Stochastic versus deterministic aspects 査読有り

    T. Devolder, J. Hayakawa, K. Ito, H. Takahashi, S. Ikeda, P. Crozat, N. Zerounian, Joo-Von Kim, C. Chappert, H. Ohno

    PHYSICAL REVIEW LETTERS 100 (5) 057206-1-057206-3 2008年2月

    出版者・発行元:AMER PHYSICAL SOC

    DOI: 10.1103/PhysRevLett.100.057206  

    ISSN:0031-9007

    eISSN:1079-7114

    詳細を見る 詳細を閉じる

    Using high bandwidth resistance measurements, we study the single-shot response of tunnel junctions subjected to spin torque pulses. After the pulse onset, the switching proceeds by a ns-scale incubation delay during which the resistance is quiet, followed by a 400 ps transition terminated by a large ringing that is damped progressively. While the incubation delay fluctuates significantly, the resistance traces are reproducible once this delay is passed. After switching, the time-resolved resistance traces indicate micromagnetic configurations that are rather spatially coherent.

  293. 2 Mb SPRAM (SPin-transfer torque RAM) with bit-by-bit bi-directional current write and parallelizing-direction current read 査読有り

    Takayuki Kawahara, Riichiro Takemura, Katsuya Miura, Jun Hayakawa, Shoji Ikeda, Young Min Lee, Ryutaro Sasaki, Yasushi Goto, Kenchi Ito, Toshiyasu Meguro, Fumihiro Matsukura, Hiromasa Takahashi, Hideyuki Matsuoka, Hideo Ohno

    IEEE JOURNAL OF SOLID-STATE CIRCUITS 43 (1) 109-120 2008年1月

    出版者・発行元:IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

    DOI: 10.1109/JSSC.2007.909751  

    ISSN:0018-9200

    詳細を見る 詳細を閉じる

    A 1.8 V 2 Mb SPin-transfer torque RAM (SPRAM) chip using a 0.2 mu m logic process with an MgO tunneling barrier cell demonstrates the circuit technologies for potential low-power nonvolatile RAM, or universal memory. This chip features an array scheme with bit-by-bit bi-directional current writing to achieve proper spin-transfer torque writing of 100 ns, and parallelizing-direction current reading with a low-voltage bit-line for preventing read disturbances that lead to 40 ns access time.

  294. Simultaneous lasing of interband and intersubband transitions in InAs/AlSb quantum cascade laser structures 査読有り

    K. Ohtani, H. Ohnishi, H. Ohno

    APPLIED PHYSICS LETTERS 92 (4) 041102-1-041102-3 2008年1月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.2838296  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    We show that both interband and intersubband transitions in n-InAs/AlSb quantum cascade laser structures can have sufficient gain to enable simultaneous lasing at the two transitions. High electric fields generate holes, which are necessary for interband lasing in InAs. The doping concentration in the injection parts is shown to be critical for controlling the electric fields in the device, enabling the selection of lasing at the intersubband transition alone (high doping), at the interband transition alone (low doping), and simultaneous lasing at both transitions (intermediate doping). 2008 American Institute of physics.

  295. A few-electron vertical In0.56Ga0.44As quantum dot with an insulating gate 査読有り

    T. Kita, D. Chiba, Y. Ohno, H. Ohno

    APPLIED PHYSICS LETTERS 91 (23) 232101-1-232101-3 2007年12月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.2818712  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    Using an Al2O3 gate insulator by atomic layer deposition and air-bridge drain electrode, we fabricated a quantum dot with few electrons based on an In0.56Ga0.44As resonant tunneling diode structure. Artificial atomic properties manifested themselves in magnetotransport, enabling the determination of effective electron g factors. Results show that the insulating gate structure used here is effective for realizing quantum dots made of narrow-gap semiconductors for studying spin-related phenomena. (c) 2007 American Institute of Physics.

  296. Universality classes for domain wall motion in the ferromagnetic semiconductor (Ga, Mn)As 査読有り

    M. Yamanouchi, J. Ieda, F. Matsukura, S. E. Barnes, S. Maekawa, H. Ohno

    SCIENCE 317 (5845) 1726-1729 2007年9月

    出版者・発行元:AMER ASSOC ADVANCEMENT SCIENCE

    DOI: 10.1126/science.1145516  

    ISSN:0036-8075

    詳細を見る 詳細を閉じる

    Magnetic domain wall motion induced by magnetic fields and spin-polarized electrical currents is experimentally well established. A full understanding of the underlying mechanisms, however, remains elusive. For the ferromagnetic semiconductor (Ga, Mn)As, we have measured and compared such motions in the thermally activated subthreshold, or "creep," regime, where the velocity obeys an Arrhenius scaling law. Within this law, the clearly different exponents of the current and field reflect different universality classes, showing that the drive mechanisms are fundamentally different.

  297. Character of states near the Fermi level in (Ga,Mn)As: Impurity to valence band crossover 査読有り

    T. Jungwirth, Jairo Sinova, A. H. MacDonald, B. L. Gallagher, V. Novak, K. W. Edmonds, A. W. Rushforth, R. P. Campion, C. T. Foxon, L. Eaves, E. Olejnik, J. Masek, S-R. Eric Yang, J. Wunderlich, C. Gould, L. W. Molenkamp, T. Dietl, H. Ohno

    PHYSICAL REVIEW B 76 (12) 125206-1-125206-9 2007年9月

    出版者・発行元:AMER PHYSICAL SOC

    DOI: 10.1103/PhysRevB.76.125206  

    ISSN:1098-0121

    詳細を見る 詳細を閉じる

    We discuss the character of states near the Fermi level in Mn-doped GaAs, as revealed by a survey of dc transport and optical studies over a wide range of Mn concentrations. A thermally activated valence-band contribution to dc transport, a midinfrared peak at energy h omega approximate to 200 meV in the ac conductivity, and the hot photoluminescence spectra indicate the presence of an impurity band in low-doped (&lt; 1% Mn) insulating GaAs:Mn materials. Consistent with the implications of this picture, both the impurity-band ionization energy inferred from the dc transport and the position of the midinfrared peak move to lower energies, and the peak broadens with increasing Mn concentration. In metallic materials with &gt;2% doping, no traces of Mn-related activated contribution can be identified in dc transport, suggesting that the impurity band has merged with the valence band. No discrepancies with this perception are found when analyzing optical measurements in the high-doped GaAs:Mn. A higher-energy (h omega approximate to 250 meV) midinfrared feature which appears in the metallic samples is associated with inter-valence-band transitions. Its redshift with increased doping can be interpreted as a consequence of increased screening, which narrows the localized-state valence-band tails and weakens higher-energy transition amplitudes. Our examination of the dc and ac transport characteristics of GaAs:Mn is accompanied by comparisons with its shallow acceptor counterparts, confirming the disordered valence-band picture of high-doped metallic GaAs:Mn material.

  298. Channel thickness dependence of the magnetic properties in (Ga,Mn)As FET structures 査読有り

    M. Endo, D. Chiba, Y. Nishitani, F. Matsukura, H. Ohno

    JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM 20 (6) 409-411 2007年8月

    出版者・発行元:SPRINGER

    DOI: 10.1007/s10948-007-0242-7  

    ISSN:1557-1939

    詳細を見る 詳細を閉じる

    We have fabricated a series of field-effect transistor structures with a thin (Ga,Mn)As channel with thickness t of 3.5, 4.0, 4.5, and 5.0 nm, and investigated the effect of electric-field E on their magnetic properties. The Curie temperature T (C) showed a clear dependence on the magnitude of E, and its controllable range became larger with decreasing t and reached 15 K for the device with t=3.5 nm, which corresponded to 32% of T (C) of the layer.

  299. Switching of tunnel magnetoresistance by domain wall motion in (Ga,Mn)As-based magnetic tunnel junctions 査読有り

    M. Fukuda, M. Yamanouchi, F. Matsukura, H. Ohno

    APPLIED PHYSICS LETTERS 91 (5) 052503-1-052503-3 2007年7月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.2767230  

    ISSN:0003-6951

    eISSN:1077-3118

    詳細を見る 詳細を閉じる

    Switching of tunnel magnetoresistance in magnetic tunnel junctions (MTJs) has been achieved by magnetic domain wall motion in one of the electrodes. The fabricated devices have two (Ga,Mn)As-based MTJs with a common bottom (Ga,Mn)As electrode, in which the domain wall motion takes place both by magnetic field and by current. This configuration allows not only the observation of switching but also time-resolved detection of the position of the domain wall by the tunnel magnetoresistance. (c) 2007 American Institute of Physics.

  300. Above room-temperature operation of InAs/AlGaSb superlattice quantum cascade lasers emitting at 12μm 査読有り

    K. Ohtani, Y. Moriyasu, H. Ohnishi, H. Ohno

    Applied Physics Letters 90 (26) 261112(1)-261112(3) 2007年6月

    出版者・発行元:None

    DOI: 10.1063/1.2752771  

    ISSN:0003-6951

  301. Ferromagnetic semiconductor heterostructures for spintronics 査読有り

    Tomasz Dietl, Hideo Ohno, Fumihiro Matsukura

    IEEE TRANSACTIONS ON ELECTRON DEVICES 54 (5) 945-954 2007年5月

    出版者・発行元:IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

    DOI: 10.1109/TED.2007.894622  

    ISSN:0018-9383

    eISSN:1557-9646

    詳細を見る 詳細を閉じる

    Ferromagnetism in transition-metal-doped III-V and H-VI compound semiconductors and their heterostructures allow exploration of unprecedented possibilities, in which spin degrees of freedom and more common charge degrees of freedom are combined. These include quantum heterostructures that incorporate ferromagnetism, electric field as well as light control of ferromagnetism, and magnetization reversal by electrical means. Possibilities of achieving high ferromagnetic-transition temperature are also discussed.

  302. Magnetic tunnel junctions for spintronic memories and beyond 査読有り

    Shoji Ikeda, Jun Hayakawa, Young Min Lee, Futnihifo Matsukura, Yuzo Ohno, Takahiro Hanyu, Hideo Ohno

    IEEE TRANSACTIONS ON ELECTRON DEVICES 54 (5) 991-1002 2007年5月

    出版者・発行元:IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

    DOI: 10.1109/TED.2007.894617  

    ISSN:0018-9383

    eISSN:1557-9646

    詳細を見る 詳細を閉じる

    In this paper, recent developments in magnetic tunnel junctions (MTJs) are reported with their potential impacts on integrated circuits. MTJs consist of two metal ferromagnets separated by a thin insulator and exhibit two resistances, low (R-P) or high (R-AP), depending on the relative direction of ferromagnet magnetizations, parallel (P) or antiparallel (AP), respectively. Tunnel magnetoresistance (TMR) ratios, defined as (R-AP - R-P) R-P as high as 361 %, have been obtained in MTJs with Co40Fe40B20 fixed and free layers made by sputtering with an industry-standard exchange-bias structure and postdeposition annealing at T-a = 400 degrees C. The corresponding output voltage swing Delta V is over 500 mV, which is five times greater than that of the conventional amorphous Al-O-barrier MTJs. The highest TMR ratio obtained so far is 500% in a pseudospin-valve MTJ annealed at T-a = 475 degrees C, showing a high potential of the current material system. In addition to this high-output voltage swing, current-induced magnetization switching (CIMS) takes place at the critical current densities (J(co).) on the order, of 10(6) A/cm(2) in these MgO-barrier MTJs. Furthermore, high antiferromagnetic coupling between the two CoFeB layers in a synthetic ferrimagnetic free layer has been shown to result in a high thermal-stability factor with a reduced J(co) compared to single free-layer MTJs. The high TMR ratio enabled by the MgO-barrier MTJs, together with the demonstration of CIMS at a low J(co), allows development of not only scalable magnetoresistive random-access memory with feature sizes below 90 urn but also new memory-in-logic CMOS circuits that can overcome a number of bottlenecks in the current integrated-circuit architecture.

  303. Effect of electrode composition on the tunnel magnetoresistance of pseudo-spin-valve magnetic tunnel junction with a MgO tunnel barrier 査読有り

    Y. M. Lee, J. Hayakawa, S. Ikeda, F. Matsukura, H. Ohno

    APPLIED PHYSICS LETTERS 90 (21) 212507-1-212507-3 2007年5月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.2742576  

    ISSN:0003-6951

    eISSN:1077-3118

    詳細を見る 詳細を閉じる

    The authors investigate the effect of electrode composition on the tunnel magnetoresistance (TMR) ratio of (CoxFe100-x)(80)B-20/MgO/(CoxFe100-x)(80)B-20 pseudo-spin-valve magnetic tunnel junctions (MTJs). TMR ratio is found to strongly depend on the composition and thicknesses of CoFeB. High resolution transmission electron microscopy shows that the crystallization process of CoFeB during annealing depends on the composition and the thicknesses of the CoFeB film, resulting in different TMR ratios. A TMR ratio of 500% at room temperature and of 1010% at 5 K are observed in a MTJ having 4.3 nm and 4-nm-thick (Co25Fe75)(80)B-20 electrodes with a 2.1-nm-thick MgO barrier annealed at 475 degrees C. (c) 2007 American Institute of Physics.

  304. Effect of substrate temperature on the properties of heavily Mn-doped GaAs 査読有り

    H-J Lee, D. Chiba, F. Matsukura, H. Ohno

    JOURNAL OF CRYSTAL GROWTH 301 264-267 2007年4月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/j.jcrysgro.2006.11.155  

    ISSN:0022-0248

    詳細を見る 詳細を閉じる

    We report on molecular-beam epitaxy (MBE) of Mn-doped GaAs films grown. at relatively high temperatures and their properties. The samples were grown at 400, 450, 530, and 560 degrees C and their growth fronts were monitored by in situ reflection high-energy electron diffraction (RHEED) during the entire growth. From the RHEED pattern, we found that the maximum doping composition of Mn is subpercent at these temperatures. The RHEED pattern and the surface morphology of the samples grown at 400 and 450 degrees C were influenced strongly by As overpressure and Mn doping. (c) 2006 Elsevier B.V. All rights reserved.

  305. Room-temperature InAs/AlSb quantum-cascade laser operating at 8.9 μm 査読有り

    K. Ohtani, K. Fujita, H. Ohno

    Electronics Letters 43 520-521 2007年4月

    DOI: 10.1049/el:20070251  

  306. Magnetization reversal in a ferromagnetic circular dot under current induced resonant excitation 査読有り

    S. Kasai, Y. Nakatani, K. Kobayashi, H. Kohno, T. Ono

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 310 (2) 2351-2352 2007年3月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1006/j.jmmm.2006.11.102  

    ISSN:0304-8853

    詳細を見る 詳細を閉じる

    A magnetic vortex core in a ferromagnetic circular dot can be resonantly excited by a spin- polarized AC current at the eigenfrequency determined by the con. ning potential. We studied the magnetic properties of the dot in its dynamical state with a vortex core on resonance as well as off resonance. Magnetoresistance measurements under the AC current revealed that the annihilation field of the vortex core is reduced in the resonance state compared to the off- resonance state. This may be due to the additional energy accompanying the resonant motion. (c) 2006 Elsevier B. V. All rights reserved.

  307. Dependence of tunnel magnetoresistance on ferromagnetic electrode materials in MgO-barrier magnetic tunnel junctions 査読有り

    Shoji Ikeda, Jun Hayakawa, Young Min Lee, Fumihiro Matsukura, Hideo Ohno

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 310 (2) 1937-1939 2007年3月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/j.jmmm.2006.10.770  

    ISSN:0304-8853

    eISSN:1873-4766

    詳細を見る 詳細を閉じる

    We investigated the relationship between the tunnel magnetoresistance ( TMR) ratio and the electrode structure in MgO- barrier magnetic tunnel junctions ( MTJs). The TMR ratio in an MTJ with Co40Fe40B20 reference and free layers reached 355% at the post-deposition annealing temperature of T-a = 400 degrees C. When Co50Fe50 or Co90Fe10 is used for the reference layer material, no high TMR ratio was observed. The key to have high TMR ratio is to have highly oriented ( 0 0 1) MgO barrier/ CoFeB crystalline electrodes. The highest TMR ratio obtained so far is 450% at T-a =450 degrees C in a pseudo- spin- valve MTJ. (c) 2006 Elsevier B. V. All rights reserved.

  308. Dependence of tunnel magnetoresistance on ferromagnetic electrode materials in MgO-barrier magnetic tunnel junctions 査読有り

    Shoji Ikeda, Jun Hayakawa, Young Min Lee, Fumihiro Matsukura, Hideo Ohno

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 310 (2) 1937-1939 2007年3月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/j.jmmm.2006.10.770  

    ISSN:0304-8853

    eISSN:1873-4766

    詳細を見る 詳細を閉じる

    We investigated the relationship between the tunnel magnetoresistance ( TMR) ratio and the electrode structure in MgO- barrier magnetic tunnel junctions ( MTJs). The TMR ratio in an MTJ with Co40Fe40B20 reference and free layers reached 355% at the post-deposition annealing temperature of T-a = 400 degrees C. When Co50Fe50 or Co90Fe10 is used for the reference layer material, no high TMR ratio was observed. The key to have high TMR ratio is to have highly oriented ( 0 0 1) MgO barrier/ CoFeB crystalline electrodes. The highest TMR ratio obtained so far is 450% at T-a =450 degrees C in a pseudo- spin- valve MTJ. (c) 2006 Elsevier B. V. All rights reserved.

  309. Domain wall resistance in perpendicularly magnetized (Ga,Mn) As 査読有り

    D. Chiba, M. Yamanouchi, F. Matsukura, T. Dietl, H. Ohno

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 310 (2) 2078-2083 2007年3月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/j.jmmm.2006.10.1119  

    ISSN:0304-8853

    詳細を見る 詳細を閉じる

    Domain wall (DW) resistance in perpendicularly magnetized (Ga, Mn) As has been investigated. The observed DW resistance is decomposed into extrinsic and intrinsic contributions. The former is explained quantitatively by the zig-zaging current due to an abrupt polarity change of the Hall electric field at DW. The latter is consistent with the disorder-induced mixing of spin channels due to small non-adiabacity of carrier spins subject to spatially varying local magnetic moment and is shown to be an order of magnitude greater than a contribution from anisotropic magnetoresistance. (c) 2006 Elsevier B.V. All rights reserved.

  310. Quantum Hall effect in polar oxide heterostructures 査読有り

    A. Tsukazaki, A. Ohtomo, T. Kita, Y. Ohno, H. Ohno, M. Kawasaki

    SCIENCE 315 (5817) 1388-1391 2007年3月

    出版者・発行元:AMER ASSOC ADVANCEMENT SCIENCE

    DOI: 10.1126/science.1137430  

    ISSN:0036-8075

    詳細を見る 詳細を閉じる

    We observed Shubnikov-de Haas oscillation and the quantum Hall effect in a high-mobility two-dimensional electron gas in polar ZnO/Mg(x)Zn(1-x)O heterostructures grown by laser molecular beam epitaxy. The electron density could be controlled in a range of 0.7 x 10(12) to 3.7 x 10(12) per square centimeter by tuning the magnesium content in the barriers and the growth polarity. From the temperature dependence of the oscillation amplitude, the effective mass of the two-dimensional electrons was derived as 0.32 +/- 0.03 times the free electron mass. Demonstration of the quantum Hall effect in an oxide heterostructure presents the possibility of combining quantum Hall physics with the versatile functionality of metal oxides in complex heterostructures.

  311. Properties of Ga1-xMnxAs with high Mn composition (x &gt; 0.1) 査読有り

    D. Chiba, Y. Nishitani, F. Matsukura, H. Ohno

    APPLIED PHYSICS LETTERS 90 (12) 122503-1-122503-3 2007年3月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.2715095  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    A series of Ga1-xMnxAs layers with high Mn compositions x (=0.075-0.200) has been grown and investigated. Magnetization, magnetotransport, and magneto-optical properties reveal that the layers have single ferromagnetic phase as in the case of typical (Ga,Mn)As. The authors also describe the variation of magnetic anisotropy with x and the effect of low temperature annealing on Curie temperature. (c) 2007 American Institute of Physics.

  312. 2Mb spin-transfer torque RAM(SRAM) with bit-by-bit bi-directional current write and parallelizing-direction current read 査読有り

    T. Kawahara, R. Takemura, K. Miura, J. Hayakawa, S. Ikeda, Y. Lee, R. Sasaki, Y. Goto, K. Ito, T. Meguro, F. Matsukura, H. Takahashi, H. Matsuoka, H. Ohno

    in digest technical paper of ISSCC2007 480-481 2007年2月

    DOI: 10.1109/ISSCC.2007.373503  

  313. (In,Ga)As gated-vertical quantum dot with an Al2O3 insulator 査読有り

    T. Kita, D. Chiba, Y. Ohno, H. Ohno

    APPLIED PHYSICS LETTERS 90 (6) 062102-1-062102-3 2007年2月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.2437060  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    The authors fabricated a gated-vertical (In,Ga)As quantum dot with an Al2O3 gate insulator deposited using atomic layer deposition and investigated its electrical transport properties at low temperatures. The gate voltage dependence of the dI/dV-V characteristics shows clear Coulomb diamonds at 1.1 K. The metal-insulator gate structure allowed the authors to control the number of electrons in the quantum dot from 0 to a large number estimated to be about 130. (c) 2007 American Institute of Physics.

  314. Spin injection with three terminal device based on (Ga, Mn)As/n<SUP>+</SUP>-GaAs tunnel junction 査読有り

    T. Kita, M. Kohda, Y. Ohno, F. Matsukura, H. Ohno

    Phys. Stat. Sol. (c) 3 (12) 4164-4167 2007年1月23日

    DOI: 10.1002/pssc.200672865  

    詳細を見る 詳細を閉じる

    通研インポート200703

  315. 2Mb SPRAM design: Bi-directional current write and parallelizing-direction current read schemes based on spin-transfer torque switching 査読有り

    R. Takemura, T. Kawahara, K. Miura, J. Hayakawa, S. Ikeda, Y. M. Lee, R. Sasaki, Y. Goto, K. Ito, T. Meguro, F. Matsukura, H. Takahashi, H. Matsuoka, H. Ohno

    2007 IEEE INTERNATIONAL CONFERENCE ON INTEGRATED CIRCUIT DESIGN AND TECHNOLOGY, PROCEEDINGS 238-+ 2007年

    出版者・発行元:IEEE

    詳細を見る 詳細を閉じる

    A 1.8V 2-Mb SPRAM (SPin-transfer torque RAM) chip using 0.2-mu m logic process with MgO tunneling barrier cell demonstrates the circuit technologies for potential low power non-volatile RAM, or universal memory This chip features: an array scheme with bit-by-bit bi-directional current write to achieve proper spin-transfer torque writing of 100-ns, and parallelizing-direction current reading with low voltage bit-line that leads to 40-ns access time.

  316. Effect of high annealing temperature on giant tunnel magnetoresistance ratio of CoFeB/MgO/CoFeB magnetic tunnel junctions 査読有り

    J. Hayakawaa, S. Ikeda, Y. M. Lee, F. Matsukura, H. Ohno

    APPLIED PHYSICS LETTERS 89 (23) 232510-1-232510-3 2006年12月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.2402904  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    The authors report tunnel magnetoresistance (TMR) ratios as high as 472% at room temperature and 804% at 5 K in pseudo-spin-valve (PSV) CoFeB/MgO/CoFeB magnetic tunnel junctions (MTJs) annealed at 450 degrees C, which is approaching the theoretically predicted value. By contrast, the TMR ratios for exchange-biased (EB) SV MTJs with a MnIr antiferromagnetic layer are found to drop when they are annealed at 450 degrees C. Energy dispersive x-ray analysis shows that annealing at 450 degrees C induces interdiffusion of Mn and Ru atoms into the MgO barrier and ferromagnetic layers in EB-SV MTJs. Mechanisms behind the different annealing behaviors are discussed. (c) 2006 American Institute of Physics.

  317. Engineering magnetism in semiconductors 査読有り

    Tomasz Dietl, Hideo Ohno

    Materials today 9 2007/1/18-18-9 2006年11月

    DOI: 10.1016/S1369-7021(06)71691-1  

    詳細を見る 詳細を閉じる

    通研インポート200703

  318. Current-induced magnetization switching in MgO barrier based tunnel junctions with CoFeB/Ru/CoFeB synthetic ferrimagnetic free layer 査読有り

    J. Hayakawa, S. Ikeda, Y. M. Lee, R. Sasaki, T. Meguro, F. Matsukura, H. Takahashi, H. Ohno

    Japanese Journal of Applied Physics 45 (40) L1057-L1060 2006年10月6日

    DOI: 10.1143/JJAP.45.L1057  

    詳細を見る 詳細を閉じる

    通研インポート200703

  319. Electric-field control of ferromagnetism in (Ga,Mn)As 査読有り

    D. Chiba, F. Matsukura, H. Ohno

    APPLIED PHYSICS LETTERS 89 (16) 162505-1-162505-3 2006年10月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.2362971  

    ISSN:0003-6951

    eISSN:1077-3118

    詳細を見る 詳細を閉じる

    The authors show modulation of Curie temperature T-C and coercivity mu H-0(c) by applying external electric fields E in a ferromagnetic semiconductor (Ga,Mn)As, where a field-effect transistor structure with an Al2O3 gate insulator is utilized. Application of E=+5 (-5) MV/cm decreases (increases) T-C of the channel layer. mu H-0(c) also decreases (increases) with increasing (decreasing) E below T-C. The mechanism of the modulation of mu H-0(c) by E is discussed.

  320. Photoemission spectroscopy and X-ray absorption spectroscopy studies of the superconducting pyrochlore oxide Cd2Re2O7 査読有り

    A. Irizawa, A. Higashiya, S. Kasai, T. Sasabayashi, A. Shigemoto, A. Sekiyama, S. Imada, S. Suga, H. Sakai, H. Ohno, M. Kato, K. Yoshimura, H. Harima

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 75 (9) 094701-1-4 2006年9月

    出版者・発行元:PHYSICAL SOC JAPAN

    DOI: 10.1143/JPSJ.75.094701  

    ISSN:0031-9015

    詳細を見る 詳細を閉じる

    Photoemission spectroscopy (PES) and 0 1s X-ray absorption spectroscopy (XAS) measurements have been performed for Cd2Re2O7 single crystals. Temperature variations of their spectra reveal that the phase transition at 120 K directly changes the band structure near the Fermi level compared with another transition near 200 K. The roles of the transitions are discussed in terms of the changes in the Re-O orbital hybridization.

  321. Single-electron switching in AlxGa1-xAs/GaAs Hall devices 査読有り

    Jens Muller, Yongqing Li, Stephan von Molnar, Yuzo Ohno, Hideo Ohno

    PHYSICAL REVIEW B 74 (12) 125310-1-125310-7 2006年9月

    出版者・発行元:AMERICAN PHYSICAL SOC

    DOI: 10.1103/PhysRevB.74.125310  

    ISSN:1098-0121

    詳細を見る 詳細を閉じる

    We report on measurements of low-frequency noise in submicron Hall devices based on AlxGa1-xAs/GaAs heterostructures. In addition to the 1/f-type noise caused by switching events in the n-AlGaAs layer we observe a random telegraph signal in the time domain at elevated temperatures which we attribute to trapping or detrapping of a single electron from a deep donor (DX-type) center located near the space charge region in the vicinity of the AlxGa1-xAs/GaAs interface. A simple two-level model accounts for the observed gate-voltage dependence of the electronic transition rates.

  322. Surface morphologies of homoepitaxial ZnO on Zn- and O-polar substrates by plasma assisted molecular beam epitaxy 査読有り

    Huaizhe Xu, K. Ohtani, M. Yamao, H. Ohno

    APPLIED PHYSICS LETTERS 89 (7) 071918-1-071918-3 2006年8月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.2337541  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    Homoepitaxial ZnO layers are grown on Zn-polar (0001) and O-polar (000 (1) over bar) surfaces of single crystal ZnO substrates by plasma assisted molecular beam epitaxy. It is found that the growth conditions to obtain smooth surfaces are significantly different for the two surface polarities. For growth on Zn-polar surface, moderate temperature (650 degrees C) and highly O-rich condition (low Zn/O-2) are required, while high temperature (1000-1050 degrees C) and Zn-rich condition (high Zn/O-2 ratio) are essential for growth on O-polar surfaces. (c) 2006 American Institute of Physics.

  323. Bias voltage dependence of the electron spin injection studied in a three-terminal device based on a (Ga,Mn)As/n(+)-GaAs Esaki diode 査読有り

    M. Kohda, T. Kita, Y. Ohno, F. Matsukura, H. Ohno

    APPLIED PHYSICS LETTERS 89 (1) 012103-1-012103-3 2006年7月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.2219141  

    ISSN:0003-6951

    eISSN:1077-3118

    詳細を見る 詳細を閉じる

    We investigated injection of spin polarized electrons in a (Ga,Mn)As/n(+)-GaAs Esaki diode (ED) by using a three-terminal device integrating a (Ga,Mn)As ED and a light emitting diode (LED). Electroluminescence polarization (P-EL) from the LED was measured under the Faraday configuration as a function of bias voltages applied independently to the Esaki diode and to the LED. The maximum P-EL of 32.4% was observed when the valence electrons near the Fermi energy of (Ga,Mn)As are ballistically injected into the LED. (c) 2006 American Institute of Physics.

  324. Giant tunnel magnetoresistance and high annealing stability in CoFeB/MgO/CoFeB magnetic tunnel junctions with synthetic pinned layer 査読有り

    Y. M. Lee, J. Hayakawa, S. Ikeda, F. Matsukura, H. Ohno

    APPLIED PHYSICS LETTERS 89 (4) 042506-1-042506-3 2006年7月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.2234720  

    ISSN:0003-6951

    eISSN:1077-3118

    詳細を見る 詳細を閉じる

    We investigated the relationship between tunnel magnetoresistance (TMR) ratio and the crystallization of CoFeB layers through annealing in magnetic tunnel junctions (MTJs) with MgO barriers that had CoFe/Ru/CoFeB synthetic ferrimagnet pinned layers with varying Ru spacer thickness (t(Ru)). The TMR ratio increased with increasing annealing temperature (T-a) and t(Ru), reaching 361% at T-a=425 degrees C, whereas the TMR ratio of the MTJs with pinned layers without Ru spacers decreased at T-a over 325 degrees C. Ruthenium spacers play an important role in forming a (001)-oriented bcc CoFeB pinned layer, resulting in a high TMR ratio through annealing at high temperatures.

  325. Electrical magnetization reversal in ferromagnetic III-V semiconductors 査読有り

    D. Chiba, F. Matsukura, H. Ohno

    Journal of Physics D: Applied Physics 39 R215-R225 2006年6月16日

    DOI: 10.1088/0022-3727/39/13/R01  

  326. Effect of n(+)-GaAs thickness and doping density on spin injection of GaMnAs/n(+)-GaAs Esaki tunnel junction 査読有り

    M. Kohda, Y. Ohno, F. Matsukura, H. Ohno

    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES 32 (1-2) 438-441 2006年5月

    出版者・発行元:ELSEVIER

    DOI: 10.1016/j.physe.2005.12.085  

    ISSN:1386-9477

    eISSN:1873-1759

    詳細を見る 詳細を閉じる

    We investigated the influence of n(+)-GaAs thickness and doping density of GaMnAs/n(+)-GaAs Esaki tunnel junction on the efficiency of the electrical electron spin injection. We prepared seven samples of GaMnAs/n(+)-GaAs tunnel junctions with different n(+)-GaAs thickness and doping density grown on identical p-AlGaAs/p-GaAs/n-AlGaAs light emitting diode (LED) structures. Electroluminescence (EL) polarization of the surface emission was measured under the Faraday configuration with external magnetic field. All samples have the bias dependence of the EL polarization, and higher EL polarization is obtained in samples in which n(+)-GaAs is completely depleted at zero bias. The EL polarization is found to besensitive to the bias condition for both the (Ga,Mn)As/n(+)-GaAs tunnel junction and the LED structure. (c) 2006 Elsevier B.V. All rights reserved.

  327. Decomposition of 1/f noise in AlxGa1-xAs/GaAs Hall devices 査読有り

    J Muller, S von Molnar, Y Ohno, H Ohno

    PHYSICAL REVIEW LETTERS 96 (18) 186601-1-186601-4 2006年5月

    出版者・発行元:AMERICAN PHYSICAL SOC

    DOI: 10.1103/PhysRevLett.96.186601  

    ISSN:0031-9007

    詳細を見る 詳細を閉じる

    We present a systematic study of the low-frequency noise in micron and submicron Hall devices made from AlxGa1-xAs/GaAs heterostructures. In a sample with feature size as small as 0.45 mu m we observe a nonmonotonic temperature dependence of the noise power spectral densities (PSD's) at temperatures where surface states and deep-level excitations are frozen out. Near the temperature where the noise peaks, the PSD's can be described by a thermally activated two-level random telegraph signal, i.e., the 1/f noise originating from switching events in the highly doped AlxGa1-xAs layer is resolved into a single Lorentzian spectrum.

  328. Current-assisted domain wall motion in ferromagnetic semiconductors 査読有り

    Michihiko Yamanouchi, Daichi Chiba, Fumihiro Matsukura, Hideo Ohno

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS 45 (5A) 3854-3859 2006年5月

    出版者・発行元:JAPAN SOC APPLIED PHYSICS

    DOI: 10.1143/JJAP.45.3854  

    ISSN:0021-4922

    詳細を見る 詳細を閉じる

    We investigated the effect of electrical currents on magnetization reversal in ferromagnetic semiconductors. We fabricated a Hall bar-shaped device with a stepped channel from (Ga,Mn)As and that with a partially gated channel from (In,Mn)As. These structures realize in-plane patterning of coercivity H-C and allow us to study the dynamics of domain walls under application of currents by monitoring the Hall resistance. In both devices, we show that there exists a region, where its H-C is strongly influenced by the direction of the applied current. In addition, we demonstrate the current induced domain wall movement under a fixed magnetic field. These phenomena can be observed at current density of 10(4) A/cm(2) lower. Possible mechanisms are discussed.

  329. Ferromagnetic semiconductors for spintronics 査読有り

    H Ohno

    PHYSICA B-CONDENSED MATTER 376 19-21 2006年4月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/j.physb.2005.12.007  

    ISSN:0921-4526

    詳細を見る 詳細を閉じる

    An overview is given for the current understanding of the ferromagnetism in manganese-doped III-V compounds together with the description on prototype device structures that allow us to explore a number of new possibilities in spintronics. (c) 2005 Elsevier B.V. All rights reserved.

  330. Pulse-width and magnetic-field dependences of current-induced magnetization switching in a (Ga,Mn)As magnetic tunnel junction 査読有り

    D Chiba, T Kita, F Matsukura, H Ohno

    JOURNAL OF APPLIED PHYSICS 99 (8) 08G514-1-08G514-3 2006年4月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.2170063  

    ISSN:0021-8979

    詳細を見る 詳細を閉じる

    We have investigated the pulse-width and magnetic-field dependences of current-induced magnetization switching in a (Ga,Mn)As/GaAs/(Ga,Mn)As magnetic tunnel junction. Critical current to induce magnetization switching shows a linear dependence on pulse width from 10 to 1000 mu s. The magnetic-field dependence appears to indicate that the observed current-induced magnetization switching proceeds through metastable magnetization structures. (C) 2006 American Institute of Physics.

  331. Fabrication and evaluation of magnetic tunnel junction with MgO tunneling barrier 査読有り

    Takeshi Sakaguchi Hoon Choi, Ahn Sung-Jin, Takeaki Sugimura, Mungi Park, Milcihiko Oogane, Hyuckjae Oh, Jun Hayakawa, Shoji Ikeda, Young Min Lee, Takafumi Fukushima, Terunobu Miyazaki, Hideo Ohno, Mitsumasa Koyanagi

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS 45 (4B) 3228-3232 2006年4月

    出版者・発行元:JAPAN SOC APPLIED PHYSICS

    DOI: 10.1143/JJAP.45.3228  

    ISSN:0021-4922

    詳細を見る 詳細を閉じる

    Magnetoresistive random access' memory (MRAM) has recently attracted considerable attention due to its non-volatility and high programming speed. A high Tunnel magnetoresistance (TMR) ratio is a key factor of MRAM. However, a conventional MRAM using aluminum oxide as insulator film shows a low TMR ratio of several tens of percents. MgO tunneling insulator is one of the candidates for achieving a high TMR ratio. In this study, we fabricated and evaluated Magnetic tunnel junctions (MTJs) with MgO tunneling barrier on a clad Cu word line.

  332. Tunnel magnetoresistance in MgO-barrier magnetic tunnel junctions with bcc-CoFe(B) and fcc-CoFe free layers 査読有り

    S. Ikeda, J. Hayakawa, Y. M. Lee, T. Tanikawa, F. Matsukura, H. Ohno

    JOURNAL OF APPLIED PHYSICS 99 (8) 08A901-1-08A901-3 2006年4月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.2176588  

    ISSN:0021-8979

    eISSN:1089-7550

    詳細を見る 詳細を閉じる

    We have investigated the spin tunneling transport in magnetic tunnel junctions (MTJs) with Co40Fe40B20, Co50Fe50, and Co90Fe10 free layers which were deposited on the lower electrode consisting of the same Co40Fe40B20 reference layer/MgO barrier. The tunnel magnetoresistance (TMR) ratio depends critically on the choice of the free layer; the TMR ratios up to 355% were obtained for the MTJs with Co40Fe40B20 free layers and up to 277% with Co50Fe50 free layers, both of which have highly (001)-oriented bcc structures. No high TMR ratio was observed for the MTJs with Co90Fe10 free layer having a polycrystalline fcc structure. (C) 2006 American Institute of Physics.

  333. Domain-wall resistance in ferromagnetic (Ga, Mn)As 査読有り

    D. Chiba, M. Yamanouchi, F. Matsukura, T. Dietl, H. Ohno

    Physical Review Letters 96 096602-1-096602-4 2006年3月10日

    詳細を見る 詳細を閉じる

    通研DBインポート

  334. Velocity of domain-wall motion induced by electrical current in the ferromagnetic semiconductor (Ga,Mn)As 査読有り

    M Yamanouchi, D Chiba, F Matsukura, T Dietl, H Ohno

    PHYSICAL REVIEW LETTERS 96 (9) 096601-1-096601-4 2006年3月

    出版者・発行元:AMERICAN PHYSICAL SOC

    DOI: 10.1103/PhysRevLett.96.096601  

    ISSN:0031-9007

    詳細を見る 詳細を閉じる

    Current-induced domain-wall motion with velocity spanning over 5 orders of magnitude up to 22 m/s has been observed by the magneto-optical Kerr effect in (Ga,Mn)As with perpendicular magnetic anisotropy. The data are employed to verify theories of spin transfer by the Slonczewski-like mechanism as well as by the torque resulting from spin-flip transitions in the domain-wall region. Evidence for domain-wall creep at low currents is found.

  335. Control of ZnO (0001)/Al2O3(1120) surface morphologies using plasma-assisted molecular beam epitaxy 査読有り

    HZ Xu, K Ohtani, M Yarnao, H Ohno

    PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS 243 (4) 773-777 2006年3月

    出版者・発行元:WILEY-V C H VERLAG GMBH

    DOI: 10.1002/pssb.200564657  

    ISSN:0370-1972

    詳細を見る 詳細を閉じる

    The surface morphologies of ZnO thin films grown on Al2O3 (1120) (a-plane sapphire) substrate by plasma-assisted molecular beam epitaxy (PAMBE) were systematically investigated by in situ reflection high energy electron diffraction (RHEED) and ex situ atomic force microscopy (AFM) as a function of Zn beam flux intensity and substrate temperature. The ZnO films are uniquely (000 (1) over bar) oriented with no trace of secondary orientation. A phase diagram for ZnO growth was established, which described the ZnO growth mode transition at fixed O-2 flow rate of 0.3 seem. For the growth at 750 degrees C with Zn beam flux of 3.6 x 10(-7) Torr, the RHEED showed a (3 x 3) pattern and a smooth surface represented by atomically flat terraces and half unit cell high steps (similar to 0.26 nm, a charge neutral unit of ZnO) was observed corresponding to a monolayer or bilayer thickness of Zn-O along the c-axis of (000 (1) over bar) ZnO. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  336. Optical pump-probe measurements of local nuclear spin coherence in semiconductor quantum wells 査読有り

    H Sanada, Y Kondo, S Matsuzaka, K Morita, CY Hu, Y Ohno, H Ohno

    PHYSICAL REVIEW LETTERS 96 (6) 067602-1-067602-4 2006年2月

    出版者・発行元:AMERICAN PHYSICAL SOC

    DOI: 10.1103/PhysRevLett.96.067602  

    ISSN:0031-9007

    詳細を見る 詳細を閉じる

    We demonstrate local manipulation and detection of nuclear spin coherence in semiconductor quantum wells by an optical pump-probe technique combined with pulse rf NMR. The Larmor precession of photoexcited electron spins is monitored by time-resolved Kerr rotation (TRKR) as a measure of nuclear magnetic field. Under the irradiation of resonant pulsed rf magnetic fields, Rabi oscillations of nuclear spins are traced by TRKR signals. The intrinsic coherence time evaluated by a spin-echo technique reveals the dependence on the orientation of the magnetic field with respect to the crystalline axis as expected by the nearest neighbor dipole-dipole interaction.

  337. High-throughput synthesis and characterization of Mg1-xCaxO films as a lattice and valence-matched gate dielectric for ZnO based field effect transistors 査読有り

    J Nishii, A Ohtomo, M Ikeda, Y Yamada, K Ohtani, H Ohno, M Kawasaki

    APPLIED SURFACE SCIENCE 252 (7) 2507-2511 2006年1月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/j.apsusc.2005.06.040  

    ISSN:0169-4332

    eISSN:1873-5584

    詳細を見る 詳細を閉じる

    Using composition-spread technique, we have grown metastable Mg1-xCaxO solid solution films on ZnO layers by pulsed laser deposition. All the films exhibited (1 1 1) oriented cubic phase. Despite a large miscibility gap, no phase separation took place at growth temperatures up to 700 degrees C, whereas an optimal growth temperature was found at 400 degrees C in terms of the crystallinity. The composition-spread films were characterized by X-ray diffraction mapping technique. Both lattice parameters and diffraction intensity increased with increasing the CaO composition. The present isovalent heterointerfaces realized the perfect lattice-matching by properly adjusting the CaO composition, leading to particular interest for ZnO based field effect transistors. (c) 2005 Elsevier B.V. All rights reserved.

  338. Magnetic anisotropy in (Ga,Mn)As probed by magnetotransport measurements 査読有り

    T. Yamada, D. Chiba, F. Matsukura, S. Yakata, H. Ohno

    Physica Status Solidi (C) Current Topics in Solid State Physics 3 (12) 4086-4089 2006年

    DOI: 10.1002/pssc.200672877  

    ISSN:1862-6351

    詳細を見る 詳細を閉じる

    In-plane magnetic anisotropy of a (Ga,Mn)As film has been investigated by measuring anisotropic magnetoresistance as a function of the direction of in-plane magnetic fields. Two Hall bars with channel direction [-110] or [100] were fabricated to detect the in-plane magnetization reversal process from both the longitudinal and the transverse components of anisotropic magnetoresistance. The results show the coexistence of cubic &lt 100&gt easy axes and uniaxial [100] hard axis. The data are fitted well by a coherent magnetization model. Temperature dependence of the in-plane anisotropic fields, determined both by the magnetotransport measurements and by ferromagnetic resonance, is presented. © 2006 WILEY-VCH Verlag GmbH &amp Co. KGaA.

  339. Physics and materials of spintronics in semiconductors 査読有り

    Hideo Ohno

    Physica Status Solidi (C) Current Topics in Solid State Physics 3 (12) 4057-4061 2006年

    DOI: 10.1002/pssc.200672893  

    ISSN:1862-6351

    詳細を見る 詳細を閉じる

    Ferromagnetic III-V semiconductors allow us to observe a wide variety of phenomena that either cannot be realized or are very difficult to observe in metal ferromagnets ranging from reversible electric-field control of ferromagnetic phase transition to obtaining current-induced domain wall velocity as a function of current-density in a wide range of velocity. Here, I present a few recent developments in these fronts focusing on (Ga,Mn)As. A brief discussion on the material front is also given. © 2006 WILEY-VCH Verlag GmbH &amp Co. KGaA.

  340. Mid-infrared InAs/AlGaSb superlattice quantum-cascade lasers 査読有り

    K Ohtani, K Fujita, H Ohno

    APPLIED PHYSICS LETTERS 87 (21) 211113-1-211113-3 2005年11月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.2136428  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    We report on the demonstration of mid-infrared InAs/AlGaSb superlattice quantum-cascade lasers operating at 10 mu m. The laser structures are grown on n-InAs (100) substrate by solid-source molecular-beam epitaxy. An InAs/AlGaSb chirped superlattice structure providing a large oscillator strength and fast carrier depopulation is employed as the active part. The observed minimum threshold current density at 80 K is 0.7 kA/cm(2), and the maximum operation temperature in pulse mode is 270 K. The waveguide loss of an InAs plasmon waveguide is estimated, and the factors that determine the operation temperature are discussed. (c) 2005 American Institute of Physics.

  341. Strong anisotropic spin dynamics in narrow n-InGaAs/AlGaAs (110) quantum wells 査読有り

    K Morita, H Sanada, S Matsuzaka, CY Hu, Y Ohno, H Ohno

    APPLIED PHYSICS LETTERS 87 (17) 171905-1-171905-2 2005年10月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.2112193  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    Anisotropic spin dynamics of two-dimensional electrons in strained n-InGaAs/AlGaAs (110) quantum wells (QWs) is investigated by a time-resolved Faraday rotation technique. Strong anisotropy of the relaxation time for the electron spins in parallel (tau(parallel to)) and perpendicular (tau(perpendicular to)) to the QWs is observed (tau(perpendicular to)/tau(parallel to)similar to 60) at 150 K as a result of the enhanced D'yakonov-Perel' (DP) spin relaxation mechanism. At 5 K, an anisotropic feature of the spin relaxation time is also observed in the presence of in-plane magnetic field, suggesting that the DP mechanism is effective for low-temperature spin relaxation. (C) 2005 American Institute of Physics.

  342. Detection of single magnetic bead for biological applications using an InAs quantum-well micro-Hall sensor 査読有り

    G. Mihajlovic, P. Xiong, S. von Molnar, K. Ohtani, H. Ohno, M. Field, G. J. Sullivan

    Applied Physics Letters 87 112502-1-112502-2 2005年9月7日

    DOI: 10.1063/1.2043238  

  343. Taking the Hall effect for a spin 査読有り

    J Inoue, H Ohno

    SCIENCE 309 (5743) 2004-2005 2005年9月

    出版者・発行元:AMER ASSOC ADVANCEMENT SCIENCE

    DOI: 10.1126/science.1113956  

    ISSN:0036-8075

    eISSN:1095-9203

  344. Spin precession of holes in wurtzite GaN studied using the time-resolved Kerr rotation technique 査読有り

    CY Hu, K Morita, H Sanada, S Matsuzaka, Y Ohno, H Ohno

    PHYSICAL REVIEW B 72 (12) 121203-1-121203-4 2005年9月

    出版者・発行元:AMER PHYSICAL SOC

    DOI: 10.1103/PhysRevB.72.121203  

    ISSN:2469-9950

    eISSN:2469-9969

    詳細を見る 詳細を閉じる

    The coherent spin dynamics of holes in Mg-doped (p-type) wurtzite GaN is studied by time-resolved Kerr rotation technique. We observe the spin precession of holes with the spin coherence time of 120 ps, which is distinguished from that of electrons by comparison with the results in Si-doped n-GaN. The g factor anisotropy of holes is determined to be g(perpendicular to)(h)=2.17 +/- 0.03 and g(parallel to)(h)=2.27 +/- 0.03. We identify that the involved holes are in the valence band B (upper Gamma(7)) of wurtzite GaN.

  345. Effect of GaAs intermediary layer thickness on the properties of (Ga,Mn)As tri-layer structures 査読有り

    Y. Sato, D. Chiba, F. Matsukura, H. Ohno

    Journal of Superconductivity; Incorporating Novel Magnetism 1-3 2005年7月8日

    DOI: 10.1007/sl0948-005-0008-z  

    詳細を見る 詳細を閉じる

    通研DBインポート

  346. Current-driven magnetization reversal in exchange-biased spin-valve nanopillars 査読有り

    J Hayakawa, H Takahashi, K Ito, M Fujimori, S Heike, T Hashizume, M Ichimura, S Ikeda, H Ohno

    JOURNAL OF APPLIED PHYSICS 97 (11) 114321-1-114321-3 2005年6月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.1927707  

    ISSN:0021-8979

    詳細を見る 詳細を閉じる

    We have investigated the current-driven magnetization reversal of exchange-biased spin-valve giant magnetoresistive nanopillars with a magnetically pinned ferromagnetic layer. Current-driven magnetization reversal of a ferromagnetic layer with a smaller MV (M: magnetization, V: volume) value is found to take place even when the layer is pinned by the exchange bias induced by an antiferromagnet. The critical current density J(c) of the spin-valve nanopillar with a MnIr layer adjacent to the current-driven free layer is of the same order as that of a Co/Cu/Co nanopillar (similar to 10(7) A/cm(2)). (C) 2005 American Institute of Physics.

  347. Magnetization reversal in elongated Fe nanoparticles - art. no. 21445 査読有り

    YQ Li, P Xiong, S von Molnar, Y Ohno, H Ohno

    PHYSICAL REVIEW B 71 (21) 214425-1-214425-6 2005年6月

    出版者・発行元:AMER PHYSICAL SOC

    DOI: 10.1103/PhysRevB.71.214425  

    ISSN:2469-9950

    eISSN:2469-9969

    詳細を見る 詳細を閉じる

    Magnetization reversal of individual, isolated high-aspect-ratio Fe nanoparticles with diameters comparable to the magnetic exchange length is studied by high-sensitivity submicron Hall magnetometry. For a Fe nanoparticle with diameter of 5 nm, the magnetization reversal is found to be an incoherent process with localized nucleation assisted by thermal activation, even though the particle has a single-domain static state. For a larger elongated Fe nanoparticle with a diameter greater than 10 nm, the inhomogeneous magnetic structure of the particle plays important role in the reversal process.

  348. InAs quantum cascade lasers based on coupled quantum well structures 査読有り

    K Ohtani, K Fujita, H Ohno

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS 44 (4B) 2572-2574 2005年4月

    出版者・発行元:JAPAN SOC APPLIED PHYSICS

    DOI: 10.1143/JJAP.44.2572  

    ISSN:0021-4922

    詳細を見る 詳細を閉じる

    We report the operation of mid-infrared InAs quantum cascade lasers based on coupled quantum well structures. The laser structures are grown on n-type InAs(100) substrate by solid-source molecular beam epitaxy. The resonant longitudinal optical phonon scattering is used for carrier extraction from ground state in active layers. The laser emitting around 9.1 mm in the pulse mode operates up to 160 K. The observed minimum threshold current density is 3.6 kA/cm2 at 80 K. We also measure the waveguide loss and compare with the design.

  349. Low-frequency noise in submicron GaAs/AlxGa1-xAs Hall devices 査読有り

    J Muller, YQ Li, S Molnar, Y Ohno, H Ohno

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 290 1161-1164 2005年4月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/j.jmmm.2004.11.502  

    ISSN:0304-8853

    詳細を見る 詳細を閉じる

    We present systematic studies of the excess low-frequency noise in GaAs/AlxGa1-xAs heterostructure 2DES Hall devices. We studied structures of various sizes made from different wafer materials. In larger samples a significant suppression of the l/f noise level by gating has been observed. In structures as small as (0.45 x 0.45) &mu; m(2) the overall noise level is significantly higher and non-Gaussian-type noise dominates at all temperatures. Random telegraph fluctuations finally limit the device miniaturization in these materials. &COPY; 2004 Elsevier B.V. All rights reserved.

  350. Gate control of dynamic nuclear polarization in GaAs quantum wells 査読有り

    H Sanada, S Matsuzaka, K Morita, CY Hu, Y Ohno, H Ohno

    PHYSICAL REVIEW LETTERS 94 (9) 097601-1-097601-4 2005年3月

    出版者・発行元:AMER PHYSICAL SOC

    DOI: 10.1103/PhysRevLett.94.097601  

    ISSN:0031-9007

    eISSN:1079-7114

    詳細を見る 詳細を閉じる

    Gate control of dynamic nuclear polarization under optical orientation is demonstrated in a Schottky-gated n-GaAs/AlGaAs (110) quantum well by time-resolved Kerr rotation measurements. Spin relaxation of electrons due to mechanisms other than the hyperfine interaction is effectively suppressed as the donor induced background electron density is reduced from metallic to insulating regimes. Subsequent accumulation of photoexcited electron spins dramatically enhances dynamic nuclear polarization at low magnetic field, allowing us to tune nuclear spin polarization by external gate voltages.

  351. Fabrication of ternary phase composition-spread thin film libraries and their high-throughput characterization: Ti1-x-yZrxHfyO2 for bandgap engineering 査読有り

    Y Yamada, T Fukumura, M Ikeda, M Ohtani, H Toyosaki, A Ohtomo, F Matsukura, H Ohno, M Kawasaki

    JOURNAL OF SUPERCONDUCTIVITY 18 (1) 109-113 2005年2月

    出版者・発行元:SPRINGER/PLENUM PUBLISHERS

    DOI: 10.1007/s10948-005-2160-x  

    ISSN:0896-1107

    詳細を見る 詳細を閉じる

    Ternary phase composition-spread thin film libraries, TiO2-ZrO2-HfO2, were synthesized by using a combinatorial pulsed laser deposition system. The composition, crystalline structure, and optical transmission properties were characterized in a high-throughput way. TiO2 doped with Zr and Hf was found to exhibit a wider bandgap than pure TiO2; hence, these compounds can be used as wide gap semiconductors for heteroepitaxial spintronics devices, based on a ferromagnetic semiconductor, Co-doped TiO2.

  352. Fabrication of ternary phase composition-spread thin film libraries and their high-throughput characterization: Ti1-x-yZrxHf yO2 for bandgap engineering 査読有り

    Y. Yamada, T. Fukumura, M. Ikeda, M. Ohtani, H. Toyosaki, A. Ohtomo, F. Matsukura, H. Ohno, M. Kawasaki

    Journal of Superconductivity and Novel Magnetism 18 (1) 109-113 2005年

    DOI: 10.1007/s10948-005-2160-x  

    ISSN:1557-1939 1557-1947

    詳細を見る 詳細を閉じる

    Ternary phase composition-spread thin film libraries, TiO 2-ZrO2-HfO2, were synthesized by using a combinatorial pulsed laser deposition system. The composition, crystalline structure, and optical transmission properties were characterized in a high-throughput way. TiO2 doped with Zr and Hf was found to exhibit a wider bandgap than pure TiO2 hence, these compounds can be used as wide gap semiconductors for heteroepitaxial spintronics devices, based on a ferromagnetic semiconductor, Co-doped TiO2. © 2005 Springer Science+Business Media, Inc.

  353. Repeated temperature modulation epitaxy for p-type doping and light-emitting diode based on ZnO 査読有り

    A Tsukazaki, A Ohtomo, T Onuma, M Ohtani, T Makino, M Sumiya, K Ohtani, SF Chichibu, S Fuke, Y Segawa, H Ohno, H Koinuma, M Kawasaki

    NATURE MATERIALS 4 (1) 42-46 2005年1月

    出版者・発行元:NATURE PUBLISHING GROUP

    DOI: 10.1038/nmat1284  

    ISSN:1476-1122

    eISSN:1476-4660

    詳細を見る 詳細を閉じる

    Since the successful demonstration of a blue light-emitting diode (LED)(1), potential materials for making short-wavelength LEDs and diode lasers have been attracting increasing interest as the demands for display, illumination and information storage grow(2-4). Zinc oxide has substantial advantages including large exciton binding energy, as demonstrated by efficient excitonic lasing on optical excitation(5,6). Several groups have postulated the use of p-type ZnO doped with nitrogen, arsenic or phosphorus(7-10), and even p-n junctions(11-13). However, the choice of dopant and growth technique remains controversial and the reliability of p-type ZnO is still under debate(14). If ZnO is ever to produce long-lasting and robust devices, the quality of epitaxial layers has to be improved as has been the protocol in other compound semiconductors(15). Here we report high-quality undoped films with electron mobility exceeding that in the bulk. We have used a new technique to fabricate p-type ZnO reproducibly. Violet electroluminescence from homostructural p-i-n junctions is demonstrated at room-temperature.

  354. Dependence of giant tunnel magnetoresistance of sputtered CoFeB/MgO/CoFeB magnetic tunnel junctions on MgO barrier thickness and annealing temperature 査読有り

    J Hayakawa, S Ikeda, F Matsukura, H Takahashi, H Ohno

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS & EXPRESS LETTERS 44 (16-19) L587-L589 2005年

    出版者・発行元:JAPAN SOC APPLIED PHYSICS

    DOI: 10.1143/JJAP.44.L587  

    ISSN:0021-4922

    詳細を見る 詳細を閉じる

    We investigated the dependence of giant tunnel magnetoresistance (TMR) on the thickness of an MgO barrier and on the annealing temperature of sputtered CoFeB/MgO/CoFeB magnetic tunnel junctions deposited on SiO2/Si wafers. The resistance-area product exponentially increases with MgO thickness, indicating that the quality of MO barriers is high in the investigated thickness range of 1.15-2.4 nm. High-resolution transmission electron microscope images show that annealing at 375 degrees C results in the formation of crystalline CoFeB/MgO/CoFeB structures, even though CoFeB electrodes are amorphous in the as-sputtered state. The TMR ratio increases with annealing temperature and is as high as 260 % at room temperature and 403 % at 5 K.

  355. Blue light-emitting diode based on ZnO 査読有り

    A Tsukazaki, M Kubota, A Ohtomo, T Onuma, K Ohtani, H Ohno, SF Chichibu, M Kawasaki

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS & EXPRESS LETTERS 44 (20-23) L643-L645 2005年

    出版者・発行元:INST PURE APPLIED PHYSICS

    DOI: 10.1143/JJAP.44.L643  

    ISSN:0021-4922

    詳細を見る 詳細を閉じる

    A near-band-edge bluish electroluminescence (EL) band centered at around 440 nm was observed from ZnO p-i-n homojunction diodes through a semi-transparent electrode deposited on the p-type ZnO top layer. The EL peak energy coincided with the photoluminescence peak energy of an equivalent p-type ZnO layer, indicating that the electron injection from the n-type layer to the p-type layer dominates the current, giving rise to the radiative recombination in the p-type layer. The imbalance in charge injection is considered to originate from the lower majority carrier concentration in the p-type layer, which is one or two orders of magnitude lower than that in the n-type one. The current-voltage characteristics showed the presence of series resistance of several hundreds ohms, corresponding to the current spread resistance within the bottom n-type ZnO. The employment of conducting ZnO substrates may solve the latter problem.

  356. High-mobility field-effect transistors based on single-crystalline ZnO channels 査読有り

    J Nishii, A Ohtomo, K Ohtani, H Ohno, M Kawasaki

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS & EXPRESS LETTERS 44 (37-41) L1193-L1195 2005年

    出版者・発行元:INST PURE APPLIED PHYSICS

    DOI: 10.1143/JJAP.44.L1193  

    ISSN:0021-4922

    詳細を見る 詳細を閉じる

    We have fabricated field-effect transistors with single-crystalline ZnO channels consisting of high-quality epitaxial films grown on lattice-matched (0001) ScAlMgO4 substrates by laser molecular-beam epitaxy. Amorphous alumina gate insulators are deposited on the top of the ZnO films using either RF magnetron sputtering or electron-beam evaporation. The field-effect mobility (mu(FE)) of the device prepared by the latter method is as high as 40cm(2.)V(-1.)s(-1), one order of magnitude higher than those typically observed for polycrystalline channel devices. However, hysteresis appears in transfer characteristics. This unfavorable effect is found to be eliminated by the thermal annealing of the entire devices in air. The much larger hysteresis and lower mu(FE) are observed for the device with sputtered gate insulators. This is presumably due to dense surface states created by ion or electron bombardment during the sputtering.

  357. Current-driven magnetization switching in CoFeB/MgO/CoFeB magnetic tunnel junctions 査読有り

    J Hayakawa, S Ikeda, YM Lee, R Sasaki, T Meguro, F Matsukura, H Takahashi, H Ohno

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS & EXPRESS LETTERS 44 (37-41) L1267-L1270 2005年

    出版者・発行元:JAPAN SOC APPLIED PHYSICS

    DOI: 10.1143/JJAP.44.L1267  

    ISSN:0021-4922

    詳細を見る 詳細を閉じる

    Current-driven magnetization switching in low-resistance Co40Fe40B20/MgO/Co40Fe40B20 magnetic tunnel junctions (MTJs) is reported. The critical-current densities J(c) requited for current-driven switching in samples annealed at 270 and 300 degrees C are found to be as low as 7.8 x 10(5) and 8.8 x 10(5) A/cm(2) with accompanying tunnel magnetoresistance (TMR) ratios of 49 and 73%, respectively. Further annealing of the samples at 350 degrees C increases TMR ratio to 160%, while accompanying J(c) increases to 2.5 x 10(6) A/cm(2). We attribute the low J(c) to the high spin-polarization of tunnel current and small MsV Product of the CoFeB single free layer, where M-s is the saturation magnetization and V the volume of the free layer.

  358. Dependence of tunnel magnetoresistance in MgO based magnetic tunnel junctions on Ar pressure during MgO sputtering 査読有り

    S Ikeda, J Hayakawa, YM Lee, R Sasaki, T Meguro, F Matsukura, H Ohno

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS & EXPRESS LETTERS 44 (46-49) L1442-L1445 2005年

    出版者・発行元:JAPAN SOC APPLIED PHYSICS

    DOI: 10.1143/JJAP.44.L1442  

    ISSN:0021-4922

    詳細を見る 詳細を閉じる

    We investigated dependence of tunnel magnetoresistance effect in CoFeB/MgO/CoFeB magnetic tunnel junctions on Ar pressure during MgO-barrier sputtering. Sputter deposition of MgO-barrier at high Ar pressure of 10 mTorr resulted in smooth surface and highly (001) oriented MgO. Using this MgO as a tunnel barrier, tunnel magnetoresistance (TMR) ratio as high as 355% at room temperature (578% at 5 K) was realized after annealing at 325 degrees C or higher, which appears to be related to a highly (001) oriented CoFeB texture promoted by the smooth and highly oriented MgO. Electron-beam lithography defined deep-submicron MTJs having a low-resistivity Au underlayer with the high-pressure deposited MgO showed high TMR ratio at low resistance-area product (RA) below 10 Omega mu m(2) as 27% at RA = 0.8 Omega mu m(2), 77% at RA = 1.1 Omega mu m(2), 130% at RA = 1.7 Omega mu m(2), and 165% at RA = 2.9 Omega mu m(2).

  359. Control of magnetization reversal in ferromagnetic semiconductors by electrical means 査読有り

    D Chiba, M Yamanouchi, F Matsukura, H Ohno

    JOURNAL OF PHYSICS-CONDENSED MATTER 16 (48) S5693-S5696 2004年12月

    出版者・発行元:IOP PUBLISHING LTD

    DOI: 10.1088/0953-8984/16/48/029  

    ISSN:0953-8984

    詳細を見る 詳細を閉じる

    A new scheme of magnetization reversal, an electrically assisted magnetization reversal, is realized in a carrier-induced ferromagnetic semiconductor (In, Mn)As structure. The demonstration has been done with field-effect transistors (FETs) having a thin (In, Mn)As channel by the application of a gate electric field to control the hole concentration p.

  360. Modulation of noise in submicron GaAs/AlGaAs hall devices by gating 査読有り

    YQ Li, C Ren, P Xiong, S von Molnar, Y Ohno, H Ohno

    PHYSICAL REVIEW LETTERS 93 (24) 246602-1-246602-4 2004年12月

    出版者・発行元:AMER PHYSICAL SOC

    DOI: 10.1103/PhysRevLett.93.246602  

    ISSN:0031-9007

    eISSN:1079-7114

    詳細を見る 詳細を閉じる

    We present a systematic characterization of fluctuations in submicron Hall devices based on GaAs/AlGaAs two-dimensional electron gas heterostructures at temperatures between 1.5 to 60 K. A large variety of noise spectra, from 1/f to Lorentzian, are obtained by gating the Hall devices. The noise level can be reduced by up to several orders of magnitude with a moderate gate voltage of 0.2 V, whereas the carrier density increases less than 60% in the same range. The significant dependence of the Hall noise spectra on temperature and gate voltage is explained in terms of the switching processes related to impurities in n-AlGaAs.

  361. Current-driven Magnetization Reversal in a Ferromagnetic Semiconductor (Ga,Mn)As/GaAs/(Ga,Mn)As Tunnel Junction 査読有り

    D. Chiba, Y. Sato, T. Kita, F. Matsukura, H. Ohno

    cond-mat 2004年11月19日

    DOI: 10.1103/PhysRevLett.93.216602  

    詳細を見る 詳細を閉じる

    &lt;RIEC&gt;&lt;DUMMY&gt;あ&lt;/DUMMY&gt;&lt;BIBID&gt;2003500756&lt;/BIBID&gt;&lt;/RIEC&gt;

  362. Hall and field-effect mobilities of electrons accumulated at a lattice-matched ZnO/ScAIMgO(4) heterointerface 査読有り

    TI Suzuki, A Ohtomo, A Tsukazaki, F Sato, J Nishii, H Ohno, M Kawasaki

    ADVANCED MATERIALS 16 (21) 1887-+ 2004年11月

    出版者・発行元:WILEY-V C H VERLAG GMBH

    DOI: 10.1002/adma.200401018  

    ISSN:0935-9648

    詳細を見る 詳細を閉じる

    At a lattice-matched ZnO/ScAIMgO(4) heterointerface, Hall and field-effect mobilities of grain-boundary-free ZnO channels have been simultaneously characterized under a gate electric field (E-G) applied through a ScAIMGO(4) dielectric gate. The field-effect mobility increased linearly with increasing EG (see Figure), clearly in contrast to the supralinear (exponential) dependence that has been previously reported for polycrystalline channels.

  363. Current-driven switching of exchange biased spin-valve giant magnetoresistive nanopillars using a conducting nanoprobe 査読有り

    J Hayakawa, K Ito, M Fujimori, S Heike, T Hashizume, J Steen, J Brugger, H Ohno

    JOURNAL OF APPLIED PHYSICS 96 (6) 3440-3442 2004年9月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.1769605  

    ISSN:0021-8979

    詳細を見る 詳細を閉じる

    An array of exchange biased spin-valve giant-magnetoresistance nanopillars was fabricated and the current I dependence of the resistance R was investigated using an electrically conducting atomic-force microscope (AFM) probe contact at room temperature. We observed current induced switching in a MnIr/CoFe/Cu/CoFe/NiFe nanopillar using the AFM probe contact. Current-driven switching using nanoprobe contact is a powerful method for developing nonvolatile and rewritable magnetic memory with high density. (C) 2004 American Institute of Physics.

  364. Molecular beam epitaxy and properties of Cr-doped GaSb 査読有り

    E Abe, K Sato, F Matsukura, JH Zhao, Y Ohno, H Ohno

    JOURNAL OF SUPERCONDUCTIVITY 17 (3) 349-352 2004年6月

    出版者・発行元:KLUWER ACADEMIC/PLENUM PUBL

    ISSN:0896-1107

    詳細を見る 詳細を閉じる

    Molecular beam epitaxy of GaSb films, with several percents of Cr, and their characterization are reported. Their electric and magnetic properties depend on their growth temperature and Cr composition. Although magnetization measurements reveal that all the films are ferromagnetic even at room temperature, this is most probably due to the precipitation of ferromagnetic zincblende CrSb. The magnetotransport measurements show that Cr spins may couple antiferromagnetically in GaSb host matrix.

  365. A Low Threshold Current Density InAs/AlGaSb Superlattice Quantum Cascade Laser Operating at 14um 査読有り

    K. Ohtani, K. Fujita, H. Ohno

    Jpn. J. Appl. Phys. 43 (7A) L879-L881 2004年6月

    DOI: 10.1143/JJAP.43.L879  

  366. Ferromagnetic semiconductor heterostructures 査読有り

    H Ohno

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 272 1-6 2004年5月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/j.jmmm.2003.12.961  

    ISSN:0304-8853

    eISSN:1873-4766

    詳細を見る 詳細を閉じる

    Ferromagnetic III-V semiconductors made it possible to integrate ferromagnetism with semiconductor heterostructures, allowing access to sturctures that exhibit magnetic/spin-related phenomena not previously accessible. This paper reviews the novel phenomena realized in such heterostructures the electric-field control of ferromagnetism, and a mean-field model developed to describe the ferromagnetism observed in magnetic III-V semiconductors. (C) 2004 Elsevier B.V. All rights reserved.

  367. Electrical properties of the patterned Co/Cu/Co sub-micron dots using a probe contact 査読有り

    J. Hayakawa, M. Fujimori, S. Heike, M. Ishibashi, T. Hashizume, K. Ito, H. Ohno

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 272 E1443-E1445 2004年5月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/j.jmmm.2003.12.730  

    ISSN:0304-8853

    詳細を見る 詳細を閉じる

    Using conductive atomic force microscopy, we investigated the electrical properties of patterned Co/Cu/Co submicron dots which were aligned at 200 nm intervals. As a result, we observed the I - V character having hysteresis behavior; it was apparently due to a magnetization reversal caused by the spin transfer torque. We demonstrated that the probe technique was able to be one of the candidates of the future high-areal-density magnetic recording devices. (C) 2003 Elsevier B. V. All rights reserved.

  368. Current-induced domain-wall switching in a ferromagnetic semiconductor structure 査読有り

    M Yamanouchi, D Chiba, F Matsukura, H Ohno

    NATURE 428 (6982) 539-542 2004年4月

    出版者・発行元:NATURE PUBLISHING GROUP

    DOI: 10.1038/nature02441  

    ISSN:0028-0836

    詳細を見る 詳細を閉じる

    Magnetic information storage relies on external magnetic fields to encode logical bits through magnetization reversal. But because the magnetic fields needed to operate ultradense storage devices are too high to generate, magnetization reversal by electrical currents is attracting much interest as a promising alternative encoding method. Indeed, spin-polarized currents can reverse the magnetization direction of nanometre- sized metallic structures through torque(1-4); however, the high current densities of 10(7)-10(8) A cm(-2) that are at present required exceed the threshold values tolerated by the metal interconnects of integrated circuits(5,6). Encoding magnetic information in metallic systems has also been achieved by manipulating the domain walls at the boundary between regions with different magnetization directions(7-13), but the approach again requires high current densities of about 10(7) A cm(-2). Here we demonstrate that, in a ferromagnetic semiconductor structure, magnetization reversal through domain-wall switching can be induced in the absence of a magnetic field using current pulses with densities below 10(5) A cm(-2). The slow switching speed and low ferromagnetic transition temperature of our current system are impractical. But provided these problems can be addressed, magnetic reversal through electric pulses with reduced current densities could provide a route to magnetic information storage applications.

  369. Magnetotransport properties of metallic (Ga,Mn)As films with compressive and tensile strain 査読有り

    F Matsukura, M Sawicki, T Dietl, D Chiba, H Ohno

    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES 21 (2-4) 1032-1036 2004年3月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/j.physe.2003.11.165  

    ISSN:1386-9477

    eISSN:1873-1759

    詳細を見る 詳細を閉じる

    Hall and sheet resistance of 200-nm thick metallic (Ga,Mn)As with compressive and tensile strain has been measured as a function of the magnetic field and temperature. The magnitude of resistance is found to depend rather strongly on relative orientations of magnetization and current and their directions in respect to crystal axes, the configuration corresponding to the highest resistance being different for compressive and tensile strain. Negative magnetoresistance, which is observed even if magnetization becomes saturated, is assigned to weak localization. (C) 2003 Elsevier B.V. All rights reserved.

  370. Electron spindynamics in InGaAs quantum wells 査読有り

    K Morita, H Sanada, S Matsuzaka, CY Hu, Y Ohno, H Ohno

    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES 21 (2-4) 1007-1011 2004年3月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/j.physe.2003.11.160  

    ISSN:1386-9477

    詳細を見る 詳細を閉じる

    Electron spin dynamics in strained In0.1Ga0.9As/Al0.4Ga0.6As quantum wells (QWs) on (100) and (110)-oriented substrates are investigated by time-resolved Faraday rotation. We find that the spin relaxation time in (I 10) QWs is 6 times longer than that in (100) QWs, at low temperatures, which is strongly reduced-by applying magnetic fields. The sign of g-factor is found positive and its magnitude decreases with increasing well width, in the well width range investigated here. (C) 2003 Elsevier B.V. All rights reserved.

  371. Tunneling magnetoresistance in (Ga,Mn)As-based heterostructures with a GaAs barrier 査読有り

    D Chiba, F Matsukura, H Ohno

    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES 21 (2-4) 966-969 2004年3月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/j.physe.2003.11.172  

    ISSN:1386-9477

    詳細を見る 詳細を閉じる

    We have investigated the properties of tunneling magnetoresistance (TMR) of (Ga,Mn)As trilayer structures with a GaAs intermediary barrier layer. TMR ratio of 290% is observed at 0.39 K around zero applied bias voltage. The bias dependence of TMR ratio as well as the temperature-dependent anisotropic behavior are presented. (C) 2003 Elsevier B.V. All rights reserved.

  372. Modeling of grain boundary barrier modulation in ZnO invisible thin film transistors 査読有り

    FM Hossain, J Nishii, S Takagi, T Sugihara, A Ohtomo, T Fukumura, H Koinuma, H Ohno, M Kawasaki

    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES 21 (2-4) 911-915 2004年3月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/j.physe.2003.11.149  

    ISSN:1386-9477

    詳細を見る 詳細を閉じる

    We model grain boundaries (GBs) for polycrystalline ZnO thin film transistors (TFTs). Experimental result shows a non-linear increase of drain current and gradual enhancement of field effect mobility with increasing gate bias. Our initial single GB model was unable to explain the experimentally obtained results, where we considered the peak defect distribution at the mid gap. Realizing from the experimentally obtained results, we remodeled the grain boundary considering the peak distribution close to the conduction band, which then better replicates the experimental observation. We describe here the transfer characteristic of experimental ZnO TFT in linear region with calculated potential profiles. Appropriate grain boundary modeling signifies that the slower decrease in potential barrier in grain boundary with applied gate voltage is responsible for such non-linear changes in drain current and gradual enhancement of mobility. (C) 2003 Elsevier B.V. All rights reserved.

  373. Hysteretic Dynamic Nuclear Polarization in GaAs/AlGaAs(110) Quantum Wells 査読有り

    H. Sanada, S. Matsuzaka, K. Morita, C. Y. Hu, Y. Ohno, H. Ohno

    Physical Review B 68 241303(R)-1-241303(R)-4 2003年12月15日

  374. Modeling and simulation of polycrystalline ZnO thin-film transistors 査読有り

    FM Hossain, J Nishii, S Takagi, A Ohtomo, T Fukumura, H Fujioka, H Ohno, H Koinuma, M Kawasaki

    JOURNAL OF APPLIED PHYSICS 94 (12) 7768-7777 2003年12月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.1628834  

    ISSN:0021-8979

    詳細を見る 詳細を閉じる

    Thin-film transistors (TFTs) made of transparent channel semiconductors such as ZnO are of great technological importance because their insensitivity to visible light makes device structures simple. In fact, there have been several demonstrations of ZnO TFTs achieving reasonably good field effect mobilities of 1-10 cm2/V s, but the overall performance of ZnO TFTs has not been satisfactory, probably due to the presence of dense grain boundaries. We modeled grain boundaries in ZnO TFTs and performed simulation of a ZnO TFT by using a two-dimensional device simulator in order to determine the grain boundary effects on device performance. Polycrystalline ZnO TFT modeling was started by considering a single grain boundary in the middle of the TFT channel, formulated with a Gaussian defect distribution localized in the grain boundary. A double Schottky barrier was formed in the grain boundary, and its barrier height was analyzed as a function of defect density and gate bias. The simulation was extended to TFTs with many grain boundaries to quantitatively analyze the potential profiles that developed along the channel. One of the main differences between a polycrystalline ZnO TFT and a polycrystalline Si TFT is that the much smaller nanoscaled grains in a polycrystalline ZnO TFT induces a strong overlap of the double Schottky barriers with a higher activation energy in the crystallite and a lower barrier potential in the grain boundary at subthreshold or off-state region of its transfer characteristics. Through the simulation, we were able to estimate the density of total trap states localized in the grain boundaries for polycrystalline ZnO TFT by determining the apparent mobility and grain size in the device. (C) 2003 American Institute of Physics.

  375. Zincblende CrSb/GaAs multilayer structures with room-temperature ferromagnetism 査読有り

    JH Zhao, F Matsukura, K Takamura, D Chiba, Y Ohno, K Ohtani, H Ohno

    MATERIALS SCIENCE IN SEMICONDUCTOR PROCESSING 6 (5-6) 507-509 2003年10月

    出版者・発行元:ELSEVIER SCI LTD

    DOI: 10.1016/j.mssp.2003.07.008  

    ISSN:1369-8001

    詳細を見る 詳細を閉じる

    CrSb (I ML)/GaAs (5 nm) multilayers with period up to 4 have been grown on GaAs substrates by solid-source molecular-beam epitaxy at 250degreesC. Reflection high-energy electron diffraction reveals zincblende characteristics throughout the growth of multilayer structures. High-resolution cross-sectional transmission electron microscopy also indicates that the crystal structure of the multilayers is zincblende and with no dislocations at the interfaces. The presence of room-tempera tu re ferromagnetism is confirmed by magnetization measurements. (C) 2003 Elsevier Ltd. All rights reserved.

  376. Ferromagnetic III-V and II-VI semiconductors 査読有り

    T Dietl, H Ohno

    MRS BULLETIN 28 (10) 714-719 2003年10月

    出版者・発行元:CAMBRIDGE UNIV PRESS

    ISSN:0883-7694

    eISSN:1938-1425

    詳細を見る 詳細を閉じる

    Recent years have witnessed extensive research aimed at developing functional, tetrahedrally coordinated ferromagnetic semiconductors that could combine the resources of semiconductor quantum structures and ferromagnetic materials systems and thus lay the foundation for semiconductor spintronics. Spin-injection capabilities and tunability of magnetization by light and electric field in Mn-based III-V and II-VI diluted magnetic semiconductors are examples of noteworthy accomplishments. This article reviews the present understanding of carrier-controlled ferromagnetism in these compounds with a focus on mechanisms determining Curie temperatures and accounting for magnetic anisotropy and spin stiffness as a function of carrier density, strain, and confinement. Materials issues encountered in the search for semiconductors with a Curie point above room temperature are addressed, emphasizing the question of solubility limits and self-compensation that can lead to precipitates and point defects. Prospects associated with compounds containing magnetic ions other that Mn are presented.

  377. Electrical Manipulation of Magnetization Reversal in a Ferromagnetic Semiconductor 査読有り

    D. Chiba, M. Yamanouchi, F. Matsukura, H. Ohno

    Science online 1086608 2003年7月

    DOI: 10.1126/science.1086608  

  378. Magnetization reversal of iron nanoparticles studied by submicron Hall magnetometry 査読有り

    YQ Li, P Xiong, S von Molnar, Y Ohno, H Ohno

    JOURNAL OF APPLIED PHYSICS 93 (10) 7912-7914 2003年5月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.1557827  

    ISSN:0021-8979

    詳細を見る 詳細を閉じる

    Magnetization of an array of 16 elongated iron nanoparticles with diameter of similar to7 nm and height of similar to100 nm has been studied with a submicron semiconductor Hall magnetometer. Details of the magnetization hysteresis curves and the angular dependence of switching fields are examined. The results indicate that the magnetization reversal in these cylindrical nanoparticles cannot be described with a single coherent rotation mode. (C) 2003 American Institute of Physics.

  379. Effect of low-temperature annealing on (Ga,Mn)As trilayer structures 査読有り

    D Chiba, K Takamura, F Matsukura, H Ohno

    APPLIED PHYSICS LETTERS 82 (18) 3020-3022 2003年5月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.1571666  

    ISSN:0003-6951

    eISSN:1077-3118

    詳細を見る 詳細を閉じる

    The effect of low-temperature annealing on (Ga,Mn)As/GaAs/(Ga,Mn)As trilayer structures is studied. Low-temperature annealing significantly increases the ferromagnetic transition temperature T-C of top (Ga,Mn)As layers, reaching as high as 160 K, whereas no apparent effect is observed on bottom (Ga,Mn)As layers. The annealing effect on Be-doped trilayers is also presented. (C) 2003 American Institute of Physics.

  380. High mobility thin film transistors with transparent ZnO channels 査読有り

    J Nishii, FM Hossain, S Takagi, T Aita, K Saikusa, Y Ohmaki, Ohkubo, I, S Kishimoto, A Ohtomo, T Fukumura, F Matsukura, Y Ohno, H Koinuma, H Ohno, M Kawasaki

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS 42 (4A) L347-L349 2003年4月

    出版者・発行元:INST PURE APPLIED PHYSICS

    DOI: 10.1143/JJAP.42.L347  

    ISSN:0021-4922

    詳細を見る 詳細を閉じる

    We have fabricated high performance ZnO thin film transistors (TFTs) using CaHfOx, buffer layer between ZnO channel and amorphous silicon-nitride gate insulator. The TFT structure, dimensions, and materials set are identical to, those of the commercial amorphous silicon (a-Si) TFTs in active matrix liquid crystal display, except for the channel and buffer layers replacing a-Si. The field effect mobility can be as high as 7 cm(2).V-1.s(-1) for devices with maximum process temperature of 300degreesC. The process temperature can be reduced to 150degreesC without much degrading the performance, showing the possibility of the use of polymer substrate.

  381. InAs-based quantum cascade light emitting structures containing a double plasmon waveguide 査読有り

    K Ohtani, H Sakuma, H Ohno

    JOURNAL OF CRYSTAL GROWTH 251 (1-4) 718-722 2003年4月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/S0022-0248(02)02314-X  

    ISSN:0022-0248

    詳細を見る 詳細を閉じる

    Molecular beam epitaxy and electroluminescence properties of InAs-based quantum cascade light emitting structure containing an InAs double plasmon waveguide are reported. Samples are prepared using low group-V flux and controlled interface bonds during molecular beam epitaxy resulting in high structural and optical qualities. Electroluminescence measurements indicate that it is necessary to reduce the operating electric fields to avoid band-to-band tunneling in narrow gap semiconductor cascade devices. (C) 2002 Elsevier Science B.V. All rights reserved.

  382. Molecular beam epitaxy and properties of ferromagnetic III-V semiconductors 査読有り

    H Ohno

    JOURNAL OF CRYSTAL GROWTH 251 (1-4) 285-291 2003年4月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/S0022-0248(02)02290-X  

    ISSN:0022-0248

    eISSN:1873-5002

    詳細を見る 詳細を閉じる

    Low-temperature molecular beam epitaxy has enabled synthesis of magnetic III-V semiconductors that can be epitaxially integrated into nonmagnetic III-V heterostructures. Carrier-induced ferromagnetism in these magnetic III-Vs has allowed us to explore spin-dependent phenomena previously not accessible in semiconductors. I review preparation and properties of ferromagnetic III-Vs together with isothermal and reversible electric field control of ferromagnetism. (C) 2002 Elsevier Science B.V. All rights reserved.

  383. Electrical Electron Spin Injection with a p-(Ga,Mn)As/n-GaAs Tunnel Junction 査読有り

    M. Kohda, Y. Ohno, K. Takamura, F. Matsukura, H. Ohno

    Journal of Superconductivity: Incorporating Novel Magnetism 16 (1) 167-170 2003年3月

    ISSN:1557-1939

    eISSN:1557-1947

    詳細を見る 詳細を閉じる

    &lt;RIEC&gt;&lt;DUMMY&gt;あ&lt;/DUMMY&gt;&lt;BIBID&gt;2003500333&lt;/BIBID&gt;&lt;/RIEC&gt;

  384. Electric field effect on the magnetic properties of III-V ferromagnetic semiconductor (In, Mn)As and ((Al),Ga,Mn)As 査読有り

    D Chiba, M Yamanouchi, F Matsukura, E Abe, Y Ohno, K Ohtani, H Ohno

    JOURNAL OF SUPERCONDUCTIVITY 16 (1) 179-182 2003年2月

    出版者・発行元:KLUWER ACADEMIC/PLENUM PUBL

    ISSN:0896-1107

    詳細を見る 詳細を閉じる

    We have investigated the magnetotransport properties of field-effect transistors (FET) having a III-V ferromagnetic semiconductor channel layer. One can control not only the ferromagnetic transition temperature T-C but also the magnetization and the coercive force of (In,Mn) As channel layers isothermally and reversibly by gate electric fields. A small change of the magnetization upon application of gate electric fields is also observed in FETs with a (Ga,Mn) As channel. Results on a (Al,Ga,Mn) As channel FET are also presented.

  385. Drift transport of spin-polarized electrons in GaAs 査読有り

    H Sanada, Arata, I, Y Ohno, K Ohtani, Z Chen, K Kayanuma, Y Oka, F Matsukura, H Ohno

    JOURNAL OF SUPERCONDUCTIVITY 16 (1) 217-219 2003年2月

    出版者・発行元:SPRINGER/PLENUM PUBLISHERS

    ISSN:0896-1107

    詳細を見る 詳細を閉じる

    We studied the transport properties of spin-polarized conduction electrons in GaAs by time-resolved photoinjection and photoluminescence polarization measurements. Under an electric field of a few kV/cm, the degree of the spin polarization considerably decreases during drift transport over the distance shorter than 4 mum. Spin relaxation by D'yakonov-Perel' mechanism is suggested to be the cause of such a rapid spin depolarization for hot electrons under a moderate electric field at low temperatures.

  386. InAs/AlSb quantum cascade lasers operating at 10um 査読有り

    K. Ohtani, H. Ohno

    Applied Physics Letters 82 (7) 1003-1005 2003年2月

    詳細を見る 詳細を閉じる

    &lt;RIEC&gt;&lt;DUMMY&gt;あ&lt;/DUMMY&gt;&lt;BIBID&gt;2003500339&lt;/BIBID&gt;&lt;/RIEC&gt;

  387. Ferromagnetic semiconductor spintronics 査読有り

    H Ohno

    PHYSICS OF SEMICONDUCTORS 2002, PROCEEDINGS 171 37-45 2003年

    出版者・発行元:IOP PUBLISHING LTD

    ISSN:0951-3248

    詳細を見る 詳細を閉じる

    Ferromagnetism in magnetic III-V semiconductors that can be integrated epitaxially into nonmagnetic heterostructures allows us to explore spin-dependent phenomena previously not accessible in semiconductors. Here, I review the properties of ferromagnetic III-V's and their heterostructures. Prospect of a new class of semiconductor electronics that utilizes both the charge and spin degrees of freedom (semiconductor spintronics) is also discussed.

  388. Spin degree of freedom in ferromagnetic semiconductor hetero structures 査読有り

    F Matsukura, D Chiba, Y Ohno, T Dietl, H Ohno

    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES 16 (1) 104-110 2003年1月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/S1386-9477(02)00596-9  

    ISSN:1386-9477

    eISSN:1873-1759

    詳細を見る 詳細を閉じる

    Ferromagnetic III-V semiconductors, such as (Ga,Mn)As and (In,Mn)As, are among the promising materials in the field of semiconductor spintronics because of their good compatibility with the high quality III-V heterostructures. We show several examples of the novel spin-related properties of heterostructures containing a ferroinagnetic component: (1) all-semiconductor (Ga,Mn)As/(Al.Ga)As/(Ga,Mn)As trilayers exhibiting spin-dependent scattering and tunneling magnetoresistance (2) resonant tunneling structures with (Ga,Mn)As emitter, where spontaneous spin-splitting of the valence band is probed; (3) spin-light emitting diodes, in which spin-injection can be observed and (4) field effect transistor structures with a (In,Mn)As channel layer, making it possible to control the ferromagnetism by an electric field. (C) 2002 Elsevier Science B.V. All rights reserved.

  389. Spin degree of freedom in ferromagnetic semiconductor hetero structures 査読有り

    F Matsukura, D Chiba, Y Ohno, T Dietl, H Ohno

    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES 16 (1) 104-110 2003年1月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/S1386-9477(02)00596-9  

    ISSN:1386-9477

    eISSN:1873-1759

    詳細を見る 詳細を閉じる

    Ferromagnetic III-V semiconductors, such as (Ga,Mn)As and (In,Mn)As, are among the promising materials in the field of semiconductor spintronics because of their good compatibility with the high quality III-V heterostructures. We show several examples of the novel spin-related properties of heterostructures containing a ferroinagnetic component: (1) all-semiconductor (Ga,Mn)As/(Al.Ga)As/(Ga,Mn)As trilayers exhibiting spin-dependent scattering and tunneling magnetoresistance (2) resonant tunneling structures with (Ga,Mn)As emitter, where spontaneous spin-splitting of the valence band is probed; (3) spin-light emitting diodes, in which spin-injection can be observed and (4) field effect transistor structures with a (In,Mn)As channel layer, making it possible to control the ferromagnetism by an electric field. (C) 2002 Elsevier Science B.V. All rights reserved.

  390. Intersubband absorption in n-doped InAs/AlSb multiple-quantum-well structures 査読有り

    K Ohtani, N Matsumoto, H Sakuma, H Ohno

    APPLIED PHYSICS LETTERS 82 (1) 37-39 2003年1月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.1534939  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    Well-thickness dependence of intersubband absorption energies is investigated in n-doped InAs/AlSb multiple-quantum-well structures grown by molecular-beam epitaxy. Decreasing the InAs well thickness from 18 to 9 monolayers, the absorption peak shifts from 3.31 mum (375 meV) to 1.98 mum (627 meV). These absorption energies are found to be larger than those of the corresponding spatially indirect band gap between the electron ground state in the InAs well and the heavy-hole ground state in the AlSb barrier. Intersubband transition energies are calculated self-consistently using multiband k.p calculation combined with Poisson equation, and compared with the experimental results. (C) 2003 American Institute of Physics.

  391. An InAs-based intersubband quantum cascade laser 査読有り

    K Ohtani, H Ohno

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS 41 (11B) L1279-L1280 2002年11月

    出版者・発行元:INST PURE APPLIED PHYSICS

    DOI: 10.1143/JJAP.41.L1279  

    ISSN:0021-4922

    詳細を見る 詳細を閉じる

    Quantum cascade laser structures using InAs quantum wells are designed, grown by molecular beam epitaxy, and processed into lasers. The intersubband transition is chosen to be bound-to-continuum and the double plasmon waveguide is employed as a cladding structure. Lasing at 10.1 mum has been observed at 4 K with a threshold current density of 5.2 kA/cm(2).

  392. Local electronic structures of GaMnAs observed by cross-sectional scanning tunneling microscopy 査読有り

    T Tsuruoka, N Tachikawa, S Ushioda, F Matsukura, K Takamura, H Ohno

    APPLIED PHYSICS LETTERS 81 (15) 2800-2802 2002年10月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.1512953  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    Using cross-sectional scanning tunneling microscopy (STM), we have investigated the local electronic properties of molecular-beam epitaxy grown GaMnAs layers on a p-GaAs substrate. The STM image shows light and dark areas with the average size on the order of nm. From conductance spectra measured with the STM, the bandgap of the GaMnAs is estimated to be 1.23+/-0.05 eV. An apparent conductance within the bandgap indicates the presence of hole states in the valence band, which are induced by Mn acceptors. A conductance peak at 0.7 eV above the valence band edge can be identified with electron tunneling into the ionization levels of As antisites. (C) 2002 American Institute of Physics.

  393. Relaxation of photoinjected spins during drift transport in GaAs 査読有り

    H Sanada, Arata, I, Y Ohno, Z Chen, K Kayanuma, Y Oka, F Matsukura, H Ohno

    APPLIED PHYSICS LETTERS 81 (15) 2788-2790 2002年10月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.1512818  

    ISSN:0003-6951

    eISSN:1077-3118

    詳細を見る 詳細を閉じる

    We studied the transport of photoinjected spins in GaAs by time-resolved photoluminescence measurements. At low temperatures, the spin polarization after drift transport of 4 mum is found to decrease as the applied electric field E increases to a few kV/cm, and it disappears when E exceeds 3 kV/cm. The origin of the field-dependent spin relaxation is discussed. (C) 2002 American Institute of Physics.

  394. Magnetic properties of (Al,Ga,Mn)As 査読有り

    K Takamura, F Matsukura, D Chiba, H Ohno

    APPLIED PHYSICS LETTERS 81 (14) 2590-2592 2002年9月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.1511540  

    ISSN:0003-6951

    eISSN:1077-3118

    詳細を見る 詳細を閉じる

    Epitaxial (Al,Ga,Mn)As films were prepared by low-temperature molecular-beam epitaxy and their magnetic properties were investigated. The Mn composition was fixed at approximately 0.05 while Al composition was varied up to 0.30. The results of magnetization and transport measurements for high Al composition samples show an out-of-plane magnetic easy axis and insulating behavior. This is quite different from those of (Ga,Mn)As films grown under the same growth conditions. The postgrowth annealing modified both the anisotropy and conductivity, indicating the presence of correlation between them. Preparation and characterization of the (Al,Ga,Mn)As-based heterostructures are also presented. (C) 2002 American Institute of Physics.

  395. Ferromagnetism of magnetic semiconductors: Zhang-Rice limit 査読有り

    T Dietl, F Matsukura, H Ohno

    PHYSICAL REVIEW B 66 (3) 033203 2002年7月

    出版者・発行元:AMER PHYSICAL SOC

    DOI: 10.1103/PhysRevB.66.033203  

    ISSN:1098-0121

    eISSN:1550-235X

    詳細を見る 詳細を閉じる

    It is suggested that p-d hybridization contributes significantly to the hole binding energy E-b of Mn acceptors in III-V compounds, leading in an extreme case to the formation of Zhang-Rice-like small magnetic polarons. The model explains both the strong increase of E-b and the evolution of a Mn spin-resonance spectrum with the magnitude of valence-band offsets. The high Curie temperature above room temperature is shown to be in accordance with the mean-field Zener model.

  396. Electric Field Control of Ferromagnetism in III-V Ferromagnetic Semiconductor 査読有り

    D. Chiba, M. Yamanouchi, F. Matsukura, Y. Ohno, K. Ohtani, H. Ohno

    Proceedings of the 26th International Conference on the Physics of Semiconductor F2.2 2002年7月

    詳細を見る 詳細を閉じる

    &lt;RIEC&gt;&lt;DUMMY&gt;あ&lt;/DUMMY&gt;&lt;BIBID&gt;2003500425&lt;/BIBID&gt;&lt;/RIEC&gt;

  397. Electric field effect on the spin transport in GaAs 査読有り

    H. Sanada, I. Arata, Y. Ohno, K. Ohtani, Z. Chen, K. Kayanuma, Y. Oka, F. Matsukura, H. Ohno

    Proceedings of the 26th International Conference on the Physics of Semiconductor H241 2002年7月

    詳細を見る 詳細を閉じる

    &lt;RIEC&gt;&lt;DUMMY&gt;あ&lt;/DUMMY&gt;&lt;BIBID&gt;2003500424&lt;/BIBID&gt;&lt;/RIEC&gt;

  398. Ferromagnetic semiconductor spintronics 査読有り

    H. Ohno

    Proceedings of the 26th International Conference on the Physics of Semiconductors 37-45 2002年7月

    詳細を見る 詳細を閉じる

    &lt;RIEC&gt;&lt;DUMMY&gt;あ&lt;/DUMMY&gt;&lt;BIBID&gt;2003500423&lt;/BIBID&gt;&lt;/RIEC&gt;

  399. Hall magnetometry on a single iron nanoparticle 査読有り

    YQ Li, P Xiong, S von Molnar, S Wirth, Y Ohno, H Ohno

    APPLIED PHYSICS LETTERS 80 (24) 4644-4646 2002年6月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.1487921  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    High-sensitivity magnetometry over a wide temperature range has been achieved using submicron GaAs/GaAlAs Hall gradiometry. The sensitivity and versatility of the technique was demonstrated by the successful measurement of the magnetization switching of a single Fe nanoparticle with msimilar to5x10(5) mu(B) (similar to5x10(-15) emu) at temperatures as high as 75 K. (C) 2002 American Institute of Physics.

  400. Ferromagnetic semiconductors for spin electronics 査読有り

    H Ohno

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 242 105-107 2002年4月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/S0304-8853(01)01210-0  

    ISSN:0304-8853

    eISSN:1873-4766

    詳細を見る 詳細を閉じる

    Modern information technology utilizes the charge degree of freedom of electrons to process information in semiconductors and the spin degree of freedom for mass storage of information in magnetic materials. If both charge and spin degrees of freedom are available in semiconductors, we expect to be able to create new functionalities and enhance the performance of existing devices. To do so, we need to be able to create, sustain, transport, control, and detect spins in semiconductors, which is a challenge for semiconductor physics, materials, and technology. Hole-induced ferromagnetism in transition metal doped III-V compounds offers integration of ferromagnetism with the existing nonmagnetic III-V heterostructures. These structures allow us to explore spin-dependent phenomena in semiconductor heterostructures, which may lead us to a new form of electronics, spin-electronics (spintronics), where both the spin and charge degrees of freedom play critical roles [1]. (C) 2002 Elsevier Science B.V. All rights reserved.

  401. Growth and properties of (Ga,Mn)As on Si (100) substrate 査読有り

    JH Zhao, F Matsukura, E Abe, D Chiba, Y Ohno, K Takamura, H Ohno

    JOURNAL OF CRYSTAL GROWTH 237 1349-1352 2002年4月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/S0022-0248(01)02181-9  

    ISSN:0022-0248

    詳細を見る 詳細を閉じる

    Ferromagnetic (Ga,Mn)As epitaxial layers with zincblende structure have been grown on Si (1 0 0) substrates employing a three-step method using molecular beam epitaxy. Magnetic measurements reveal that the ferromagnetic transition temperature is 48 K for a layer with a lattice constant of 0.567 nm, which corresponds to a nominal Mn composition of 2%. When grown directly on Si without the three-step method, the same set of growth parameters results in a (Ga,Mn)As layer with a ferromagnetic order below 25 K. The difference of magnetic property between these two samples is attributed to the quality of the (Ga,Mn)As layer which originates from the different growth methods. (C) 2002 Elsevier Science B.V. All rights reserved.

  402. Valence band barrier at (Ga,Mn)As/GaAs interfaces 査読有り

    Y Ohno, Arata, I, F Matsukura, H Ohno

    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES 13 (2-4) 521-524 2002年3月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/S1386-9477(02)00185-6  

    ISSN:1386-9477

    eISSN:1873-1759

    詳細を見る 詳細を閉じる

    Transport properties of (Ga,Mn)As/GaAs/p-GaAs p-i-p diodes were studied to manifest the potential barrier in the valence band at (Ga,Mn)As/GaAs junctions. The temperature dependences of the current-voltage characteristics exhibit typical thermionic emission behaviors, which gives the effective potential barrier height of 87-140 meV for holes injected from (Ga,Mn)As to undoped GaAs. (C) 2002 Elsevier Science B.V. All rights reserved.

  403. Semiconductor spintronics 査読有り

    H Akinaga, H Ohno

    IEEE TRANSACTIONS ON NANOTECHNOLOGY 1 (1) 19-31 2002年3月

    出版者・発行元:IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

    DOI: 10.1109/TNANO.2002.1005423  

    ISSN:1536-125X

    eISSN:1941-0085

    詳細を見る 詳細を閉じる

    We review recent, progress made in the field of semiconductor spintronics, a branch of semiconductor electronics where both charge and spin degrees of freedom play an important role in realizing unique functionalities. We first describe the new spin-dependent phenomena. found in semiconductors including carrier-induced ferromagnetism in III-V compounds, followed by an account of our current understanding of such spin-dependent phenomena. Then we summarize the challenges the semiconductor spintronics has to meet in order for it to be a success as "electronics."

  404. Anisotropic electrical spin injection in ferromagnetic semiconductor heterostructures 査読有り

    DK Young, E Johnston-Halperin, DD Awschalom, Y Ohno, H Ohno

    APPLIED PHYSICS LETTERS 80 (9) 1598-1600 2002年3月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.1458535  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    A fourteen-fold anisotropy in the spin transport efficiency parallel and perpendicular to the charge transport is observed in a vertically biased (Ga, Mn)As-based spin-polarized light emitting diode. The spin polarization is determined by measuring the polarization of electroluminescence from an (In, Ga)As quantum well placed a distance d (20-420 nm) below the p-type ferromagnetic (Ga, Mn)As contact. In addition, a monotonic increase (from 0.5% to 7%) in the polarization is measured as d decreases for collection parallel to the growth direction, while the in-plane polarization from the perpendicular direction (similar to0.5%) remains unchanged. (C) 2002 American Institute of Physics.

  405. chapter 1 III-V Ferromagnetic Semiconductors 査読有り

    F. Matsukura, H. Ohno, T. Dietl

    Handbook of Magnetic Materials 14 1-87 2002年

    DOI: 10.1016/S1567-2719(09)60005-6  

    ISSN:1567-2719

  406. Control of ferromagnetism in field-effect transistor of a magnetic semiconductor 査読有り

    F Matsukura, D Chiba, T Omiya, E Abe, T Dietl, Y Ohno, K Ohtani, H Ohno

    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES 12 (1-4) 351-355 2002年1月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/S1386-9477(01)00275-2  

    ISSN:1386-9477

    eISSN:1873-1759

    詳細を見る 詳細を閉じる

    Electric-field control of carrier-induced ferromagnetism is demonstrated for field-effect transistor structure of magnetic semiconductor (In,Mn)As. By varying the gate electric field one can control the ferromagnetic transition temperature isothermally and reversibly. (C) 2002 Elsevier Science B.V. All rights reserved.

  407. Semiconductor Spin Electronics 査読有り

    Hideo Ohno, Fumihiro Matsukura, Yuzo Ohno

    JSAP International 5 4-13 2002年

  408. Microscopic identification of dopant atoms in Mn-doped GaAs layers 査読有り

    T Tsuruoka, R Tanimoto, N Tachikawa, S Ushioda, F Matsukura, H Ohno

    SOLID STATE COMMUNICATIONS 121 (2-3) 79-82 2002年

    出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD

    DOI: 10.1016/S0038-1098(01)00471-9  

    ISSN:0038-1098

    詳細を見る 詳細を閉じる

    Using cross-sectional scanning tunneling microscopy (XSTM), we have identified the dopant atoms, in Mn-doped GaAs layers grown at 400 degreesC by molecular-beam epitaxy. The Mn-dopant atoms appeared as diffuse light areas superimposed on the background of As atomic rows, in the STM images. The Mn acceptor concentration deduced from the STM images agreed well with the hole concentration determined by Hall measurements. No As antisite and associated defects were observed. These results indicate that Mn atoms are incorporated into the GaAs layer as electrically activated acceptors. (C) 2002 Elsevier Science Ltd. All rights reserved.

  409. A Spin Esaki Diode 査読有り

    M. Kohda, Y. Ohno, K. Takamura, F. Matsukura, H. Ohno

    Japanese Journal of Applied Physics 40 (12A) L1274-L1276 2001年12月

    DOI: 10.1143/JJAP.40.L1274  

  410. Origin of enhanced dynamic neclear polarization and all-optical nuclear magnetic resonance in gaAs quantum wells 査読有り

    G. Salis, D. T. Fuchs, J. M. Kikkawa, D. D. Awschalom, Y. Ohno, H. Ohno

    Phys. Rev. B 64 195304-1-195304-10 2001年11月15日

  411. Spin Polarization dependent far infrared absorption in Ga1-xMnxAs 査読有り

    Y. Nagai, T. Kunimoto, K. Nagasaka, H. Nojiri, M. Motokawa, F. Matsukura, T. Dietl, H. Ohno

    Japanese Journal of Applied Physics 40 (11) 6231-6243 2001年11月

    DOI: 10.1143/JJAP.40.6231  

  412. Room-temperature ferromagnetism in zincblende CrSb grown by molecular-beam epitaxy 査読有り

    J. H. Zhao, F. Matsukura, K. Takamura, E. Abe, D. Chiba, H. Ohno

    Applied Physics Letters 79 2776-2779 2001年10月22日

    DOI: 10.1063/1.1413732  

  413. Spin-dependent properties of ferromagnetic/nonmagnetic GaAs heterostructures 査読有り

    H Ohno, F Matsukura, Y Ohno

    MATERIALS SCIENCE AND ENGINEERING B-SOLID STATE MATERIALS FOR ADVANCED TECHNOLOGY 84 (1-2) 70-74 2001年7月

    出版者・発行元:ELSEVIER SCIENCE SA

    DOI: 10.1016/S0921-5107(01)00572-4  

    ISSN:0921-5107

    詳細を見る 詳細を閉じる

    We review recent studies on spin-dependent properties of structures made of ferromagnetic GaAs, (Ga.Mn)As, aimed to lay the ground for semiconductor spin-electronics (spintronics). Introduction of magnetic ion, Mn. in CaAs leads to hole-induced ferromagnetism, the origin of which is explained in terms of a mean-field theory. Due to exchange interaction between spins of carriers and localized magnetic electrons, spin-splitting of the semiconductor bands takes place when ferromagnetism sets in, and carriers become spin polarized. This spontaneous spin polarization leads to spin-dependent scattering and tunnel magneto-resistance in semiconducting structures. Electrical spin injection across a ferromagnetic/nonmagnetic semiconductor heterojunction and into an InGaAs quantum well is also demonstrated using the spin polarized carriers in ferromagnetic (Ga,Mn)As. (C) 2001 Elsevier Science B.V. All rights reserved.

  414. Effect of barrier width on the performance of quantum well infrared photodetector 査読有り

    SKH Sim, HC Liu, A Shen, M Gao, KF Lee, M Buchanan, Y Ohno, H Ohno, EH Li

    INFRARED PHYSICS & TECHNOLOGY 42 (3-5) 115-121 2001年6月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/S1350-4495(01)00067-6  

    ISSN:1350-4495

    詳細を見る 詳細を閉じる

    We present a study on a set of AlGaAs/GaAs quantum well infrared photodetectors with various barrier widths from about 100 to 500 Angstrom. At 77 K and for a large field-of-view (FOV) 300-K background operation, measured results on dark current, responsivity, and detectivity indicate that detectors with barrier widths larger than about 200 Angstrom have similar performance. For 60-70 K and F/2 FOV, barriers need to be larger than about 300 Angstrom to suppress inter-well tunneling. (C) 2001 Elsevier Science B.V. All rights reserved.

  415. Dual-band photodetectors based on interband and intersubband transitions 査読有り

    HC Liu, CY Song, A Shen, M Gao, E Dupont, PJ Poole, ZR Wasilewski, M Buchanan, PH Wilson, BJ Robinson, DA Thompson, Y Ohno, H Ohno

    INFRARED PHYSICS & TECHNOLOGY 42 (3-5) 163-170 2001年6月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/S1350-4495(01)00072-X  

    ISSN:1350-4495

    詳細を見る 詳細を閉じる

    We present experimental results on quantum-well photodetectors for visible or near-infrared and middle- or far-infrared dual-band detection. We report on two types of devices based on (1) InGaAs/InP and (2) GaAs/AIGaAs quantum wells. In the first case, InGaAs/InP quantum-well infrared photodetectors (QWIPs) for both near and middle infrared spectra are shown. In the second case, large bandgap top contacts were used on standard GaAs/AlGaAs QWIPs so that visible light could reach the quantum-well region and be absorbed via interband transitions. Two large band gap top contacts were investigated, using a high Al fraction AlGaAs and a short period GaAs/AlAs superlattice. We evaluate and analyze the detector performance. We find that such devices are potentially useful for applications involving dual-band simultaneous detection and imaging. (C) 2001 Elsevier Science B.V. All rights reserved.

  416. Growth and properties of (Ga,Mn)As films with high Mn concentration 査読有り

    K Takamura, F Matsukura, Y Ohno, H Ohno

    JOURNAL OF APPLIED PHYSICS 89 (11) 7024-7026 2001年6月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.1357841  

    ISSN:0021-8979

    詳細を見る 詳細を閉じる

    (Ga, Mn)As films with high nominal Mn concentration (0 &lt;x &lt;0.55) are grown by low temperature molecular beam epitaxy (LT-MBE), growth temperature T-s = 180 degreesC. Reflection high energy electron diffraction patterns indicate epitaxial growth of (Ga, Mn)As for x &lt;0.1, whereas they show spotty patterns for x &gt;0.1, which turn to polycrystalline features when x &gt;0.3. X-ray diffraction shows the formation of MnAs together with the growth of (Ga, Mn)As. The lattice constant of the layers suggests that (Ga, Mn)As with high Mn composition as high as 17% can be grown by LT-MBE. (C) 2001 American Institute of Physics.

  417. Emission wavelength control by potential notch in type-II InAs/GaSb/AlSb intersubband light-emitting structures 査読有り

    K Ohtani, H Sakuma, H Ohno

    APPLIED PHYSICS LETTERS 78 (26) 4148-4150 2001年6月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.1381034  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    A potential notch in the well region is used to control the emission wavelength of type-II InAs/GaSb/AlSb intersubband light-emitting structures. Intersubband absorption measurements are performed to evaluate the subband structure of the active layers and are compared with theory. Type-II quantum cascade structures using these active layers are fabricated and midinfrared intersubband electroluminescence is observed. Calculation indicates that the active layer structure can emit electromagnetic waves in the THz region without employing a wide alloy well. (C) 2001 American Institute of Physics.

  418. Intersubband electroluminescence from InAs-based quantum cascade structures 査読有り

    K. Ohtani, H. Ohno

    IPAP Conference Series 2 129-130 2001年5月

  419. Electrical spin injection in ferromagnetic/nonmagnetic semiconductor heterostructures 査読有り

    Y Ohno, Arata, I, F Matsukura, H Ohno, DK Young, B Beschoten, DD Awschalom

    PHYSICA E 10 (1-3) 489-492 2001年5月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/S1386-9477(01)00143-6  

    ISSN:1386-9477

    詳細を見る 詳細を閉じる

    Magneto-electroluminescence properties of ferromagnetic/nonmagnetic semiconductor pn junction light emitting diodes (LEDs) are presented. A ferromagnetic p-type (Ca,Mn)As layer is grown on i-(In, Ga)As quantum well (QW)/n-GaAs so that the degree of spin polarization of holes injected from (Ga, Mn)As into GaAs can be probed by analyzing the polarization of light emitted from the LED structures. The EL polarization as a function of magnetic field exhibits clear hysteresis below the ferromagnetic transition temperature of(Ga, Mn)As, which is the evidence that spin-polarized electrical current is injected into nonmagnetic semiconductor. (C) 2001 Elsevier Science B.V. All rights reserved.

  420. Temperature dependence of electroluminescence and I-V characteristics of ferromagnetic/non-magnetic semiconductor pn junctions 査読有り

    Arata, I, Y Ohno, F Matsukura, H Ohno

    PHYSICA E 10 (1-3) 288-291 2001年5月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/S1386-9477(01)00101-1  

    ISSN:1386-9477

    詳細を見る 詳細を閉じる

    We investigated the temperature dependence of the electroluminescence and I-V characteristics of hybrid ferromagnetic/non-magnetic semiconductor pn junction light emitting diodes, which is used for spin-injection experiments reported earlier. The observed temperature dependence is found to be reproduced by a reference sample of non-magnetic p-GaAs/(In,Ga)As/n-GaAs with an undoped (Al,Ga)As spacer layer. This suggests the existence of potential barrier at the (Ga,Mn)As/GaAs interface. (C) 2001 Elsevier Science B.V. All rights reserved.

  421. Properties of (Ga,Mn)As/(Al,Ga)As/(Ga,Mn)As magnetic trilayer structures 査読有り

    D Chiba, N Akiba, F Matsukura, Y Ohno, H Ohno

    PHYSICA E 10 (1-3) 278-282 2001年5月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/S1386-9477(01)00100-X  

    ISSN:1386-9477

    詳細を見る 詳細を閉じる

    Magnetoresistance effect due to the spin-dependent scattering and the spin-polarized tunneling as well as the interlayer coupling in (Ga,Mn)As/(Al,Ga)As/(Ga,Mn)As semiconductor-based magnetic trilayer structures were studied. Both current-in-plane resistance and current-perpendicular-to-plane tunneling resistances are shown to depend on the relative magnetization directions of the two ferromagnetic (Ga,Mn)As layers. The interlayer coupling between the two (Ga,Mn)As layers is always ferromagnetic and the magnitude is weak (&lt; 0.5 muJ/m(2)). (C) 2001 Elsevier Science B.V. All rights reserved.

  422. Magnetic circular dichroism in Mn 2p core absorption of Ga1-xMnxAs 査読有り

    S Ueda, S Imada, T Muro, Y Saitoh, S Suga, F Matsukura, H Ohno

    PHYSICA E 10 (1-3) 210-214 2001年5月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/S1386-9477(01)00084-4  

    ISSN:1386-9477

    詳細を見る 詳細を閉じる

    We have measured the magnetic circular dichroism in the Mn 2p core absorption of ferromagnetic diluted magnetic semiconductor Ga1-xMnxAs with x = 0.025 in the Faraday configuration. The electronic structure parameters for Mn in Ga1-xMnxAs are obtained by fitting the experimental spectra on the basis of the cluster model calculation with considering the configuration interaction. The Mn 3d-As 4p hybridization and the negative weak p-d exchange constant are estimated. (C) 2001 Elsevier Science B.V. All rights reserved.

  423. Magnetotransport properties of (Ga,Mn)As grown on GaAs(411)A substrates 査読有り

    T Omiya, F Matsukura, A Shen, Y Ohno, H Ohno

    PHYSICA E 10 (1-3) 206-209 2001年5月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/S1386-9477(01)00083-2  

    ISSN:1386-9477

    詳細を見る 詳細を閉じる

    Properties of ferromagnetic (Ga,Mn)As layers grown epitaxially on a GaAs (4 1 1)A substrate were investigated. X-ray double-crystal diffraction showed the presence of shear strain due to lattice mismatch between substrate and the epitaxial layer. The magnetotransport measurements showed that the easy axis of magnetization was in the (1 0 0) plane. The results indicate that the origin of the magnetic anisotropy is dominated by the lattice strain. (C) 2001 Elsevier Science B.V. All rights reserved.

  424. Magnetic domain structure of a ferromagnetic semiconductor (Ga,Mn)As observed with scanning probe microscopes 査読有り

    T Fukumura, T Shono, K Inaba, T Hasegawa, H Koinuma, F Matsukura, H Ohno

    PHYSICA E 10 (1-3) 135-138 2001年5月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/S1386-9477(01)00068-6  

    ISSN:1386-9477

    詳細を見る 詳細を閉じる

    Magnetic domain structure of a ferromagnetic semiconductor, (Ga,Mn)As, is observed with a scanning Hall probe microscope and a scanning SQUID microscope at low temperature. The film with perpendicular magnetization has a maze pattern domain structure similar to those of conventional ferromagnetic materials, whereas the film with in-plane magnetization has unconventional domain structure that show random arrangement of the domains. (C) 2001 Elsevier Science B,V, All rights reserved.

  425. Spin relaxation in n-modulation doped GaAs/AlGaAs (110) quantum wells 査読有り

    T Adachi, Y Ohno, F Matsukura, H Ohno

    PHYSICA E 10 (1-3) 36-39 2001年5月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/S1386-9477(01)00049-2  

    ISSN:1386-9477

    詳細を見る 詳細を閉じる

    We measured the electron spin relaxation time tau (s) in n-modulation doped GaAs/AlGaAs(110) multiple quantum wills by pump probe method. The value of tau (s) exceeds 10 ns even at room temperature, which is two orders of magnitude longer than that in (001) GaAs quantum wells. The tau (s), dependence on quantized-electron energy, pump beam power and temperature can qualitatively be explained by the reduction of the electron-hole exchange interaction due to screening. (C) 2001 Elsevier Science B.V. All rights reserved.

  426. Optical manipulation of nuclear spin by a two-dimensional electron gas 査読有り

    G. Salis, D. T. Fuchs, J. M. Kikkawa, D. D. Awschalom, Y. Ohno, H. Ohno

    Phys. Rev. B 86 (12) 2677-2680 2001年3月19日

    DOI: 10.1103/PhysRevLett.86.2677  

  427. Fluorescence extended x-ray absorption fine structure study on local structures around Mn atoms in thin (In, Mn)As layer and (In, Mn)As quantum dots 査読有り

    H Ofuchi, T Kubo, M Tabuchi, Y Takeda, F Matsukura, SP Guo, A Shen, H Ohno

    JOURNAL OF APPLIED PHYSICS 89 (1) 66-70 2001年1月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.1330761  

    ISSN:0021-8979

    eISSN:1089-7550

    詳細を見る 詳細を閉じる

    We have investigated thin (In, Mn)As layer and (In, Mn)As quantum dots (with Mn mole fraction lower than 0.02) on GaAs(001) by fluorescence extended x-ray absorption fine structure (EXAFS) in order to study the local structures formed around the Mn atoms. The EXAFS analysis revealed that in a 10 nm thick (In, Mn)As layer, the In-site substitutional Mn and the NiAs-type MnAs coexisted, while the majority of the Mn atoms were substituted in the In-sites of InAs in (In, Mn)As quantum dots. It is considered that different growth modes for the thin layer and the quantum dots affect the local structures. (C) 2001 American Institute of Physics.

  428. Long wavelength intersubband light emitting structure based on type-II InAs/GaSb/AlSb hetero-structures 査読有り

    H Sakuma, O Keita, H Ohno

    PROCEEDINGS OF THE 10TH INTERNATIONAL CONFERENCE ON NARROW GAP SEMICONDUCTORS AND RELATED SMALL ENERGY PHENOMENA, PHYSICS AND APPLICATIONS 2 122-124 2001年

    出版者・発行元:INST PURE APPLIED PHYSICS

    詳細を見る 詳細を閉じる

    We propose intersubband light-emitting structures based on type-II InAs/GaSb/AlSb heterostructures with a potential "notch" to realize high injection efficiency even in the longer wavelength range such as in the Teraherz (THz) region. The design of the new active layers is based on an InAs quantum well (QW) with a notch, in which the conduction band of the middle part of QW is raised. The notch potential region is composed of the materials such as AlInAs. The subband structures with this active layer design are evaluated by intersubband absorption measurements. Type-II quantum cascade structures using this proposed active layer are fabricated and mid-infrared intersubband electroluminescence is observed. The long wavelength limit of the type-II InAs/GaSb/AlSb intersubband light emitting structure with notch potential is discussed.

  429. Spin-dependent phenomena in ferromagnetic/nonmagnetic III-V heterostructures 査読有り

    H Ohno, F Matsukura, Y Ohno

    SOLID STATE COMMUNICATIONS 119 (4-5) 281-289 2001年

    出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD

    DOI: 10.1016/S0038-1098(01)00175-2  

    ISSN:0038-1098

    詳細を見る 詳細を閉じる

    III-V ferromagnetic semiconductors allow epitaxial integration of ferromagnetism with nonmagnetic semiconductor heterostructures and offer opportunities to explore properties that combine conventional semiconductor physics with magnetic cooperative phenomena. Here, we review spin-dependent phenomena observed in III-V-based ferromagnetic semiconductor heterostructures, which include spin-dependent scattering, tunnel magnetoresistance, resonant tunneling with ferromagnetic emitter, spin injection, and electric field control of ferromagnetism. (C) 2001 Elsevier Science Ltd. All rights reserved.

  430. Hole-mediated ferromagnetismin tetrahedrally coordinated semiconductors tetrahedrally 査読有り

    T. Dietl, H. Ohno, F. Matsukura

    Physical Review B(/)- 63 (,19205-1-21) 2001年

  431. Toward functional spintronics 査読有り

    H. Ohno

    Science(/)- 840-841 2001年

  432. Ferromagnetism in III-V and II-Ⅵ semiconductor structures 査読有り

    T. Dietl, H. Ohno

    Physica E(/)- 9(1) 185-193 2001年

    DOI: 10.1016/S1386-9477(00)00193-4  

  433. A ferromagnetic III-V semiconductor: (Ga,Mn)As 査読有り

    H Ohno, F Matsukura

    SOLID STATE COMMUNICATIONS 117 (3) 179-186 2001年

    出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD

    DOI: 10.1016/S0038-1098(00)00436-1  

    ISSN:0038-1098

    詳細を見る 詳細を閉じる

    Magnetic and transport properties of ferromagnetic III-V semiconductor (Ga,Mn)As, an alloy between GaAs and transition element Mn, are reviewed. Results of direct magnetization measurements and magnetic properties obtained from transport are presented and compared. Origin of ferromagnetism and the prospects of magnetic III-V semiconductors are discussed. (C) 2001 Elsevier Science Ltd. All rights reserved.

  434. Electric-field control of ferromagnetism 査読有り

    H Ohno, D Chiba, F Matsukura, T Omiya, E Abe, T Dietl, Y Ohno, K Ohtani

    NATURE 408 (6815) 944-946 2000年12月

    出版者・発行元:MACMILLAN PUBLISHERS LTD

    DOI: 10.1038/35050040  

    ISSN:0028-0836

    詳細を見る 詳細を閉じる

    It is often assumed that it is not possible to alter the properties of magnetic materials once they have been prepared and put into use. For example, although magnetic materials are used in information technology to store trillions of bits (in the form of magnetization directions established by applying external magnetic fields), the properties of the magnetic medium itself remain unchanged on magnetization reversal. The ability to externally control the properties of magnetic materials would be highly desirable from fundamental and technological viewpoints, particularly in view of recent developments in magnetoelectronics and spintronics(1,2). In semiconductors, the conductivity can be varied by applying an electric field, but the electrical manipulation of magnetism has proved elusive. Here we demonstrate electric-field control of ferromagnetism in a thin-film semiconducting alloy, using an insulating-gate field-effect transistor structure. By applying electric fields, we are able to vary isothermally and reversibly the transition temperature of hole-induced ferromagnetism.

  435. Surface morphologies of III-V based magnetic semiconductor (Ga,Mn) As grown by molecular beam epitaxy 査読有り

    Yang, JR, H Yasuda, SL Wang, F Matsukura, Y Ohno, H Ohno

    APPLIED SURFACE SCIENCE 166 (1-4) 242-246 2000年10月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/S0169-4332(00)00429-3  

    ISSN:0169-4332

    詳細を見る 詳細を閉じる

    The influence of Mn flux intensity and growth temperature on surface morphologies of III-V based magnetic semiconductor (Ga,Mn)As layers grown by low temperature (LT) molecular beam epitaxy (MBE) on (001) GaAs is studied by atomic force microscopy (AFM). The results show that homogeneous (Ga,Mn)As grows two-dimensionally (2D), whereas 3D growth takes place when hexagonal second phase appears on the growth front. (C) 2000 Elsevier Science B.V. All rights reserved.

  436. Arsenic flux dependence of InAs nanostructure formation on GaAs (211) B surface 査読有り

    H Yasuda, F Matsukura, Y Ohno, H Ohno

    APPLIED SURFACE SCIENCE 166 (1-4) 413-417 2000年10月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/S0169-4332(00)00458-X  

    ISSN:0169-4332

    詳細を見る 詳細を閉じる

    We have studied the influence of As flux on InAs nanostructures on GaAs (211)B surfaces grown by molecular beam epitaxy (MBE) at various growth temperatures (T-S). It is shown that isotropic quantum dots (QDs) are formed at low Ts under high As pressure condition. However, non-isotropic nanostructures, quantum dashes (QDHs), are formed under low As flux conditions. It is also shown that the sizes of nanostructure become larger with increasing T-S. The shapes of nanostructure depend on As flux as well as T-S. (C) 2000 Elsevier Science B.V. All rights reserved.

  437. Magnetoresistance effect and interlayer coupling of (Ga, Mn)As trilayer structures 査読有り

    D Chiba, N Akiba, F Matsukura, Y Ohno, H Ohno

    APPLIED PHYSICS LETTERS 77 (12) 1873-1875 2000年9月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.1310626  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    We have investigated the magnetic and magnetotransport properties of (Ga, Mn)As/(Al, Ga)As/(Ga, Mn)As semiconductor-based magnetic trilayer structures. We observe a weak ferromagnetic interlayer coupling between the two ferromagnetic (Ga, Mn)As layers as well as magnetoresistance effects due to spin-dependent scattering and to spin-dependent tunneling. Both the coupling strength and the magnetoresistance ratio decrease with the increase of temperature and/or the increase of Al composition of the nonmagnetic (Al, Ga)As layer. (C) 2000 American Institute of Physics. [S0003-6951(00)00438-1].

  438. Observation of magnetic domain structure in a ferromagnetic semiconductor (Ga, Mn)As with a scanning Hall probe microscope 査読有り

    T Shono, T Hasegawa, T Fukumura, F Matsukura, H Ohno

    APPLIED PHYSICS LETTERS 77 (9) 1363-1365 2000年8月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.1290273  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    We have performed low-temperature scanning Hall probe microscopy on a ferromagnetic semiconductor (Ga0.957Mn0.043)As. The observed magnetic domain structure is a stripe-shaped pattern as has been observed in conventional nonsemiconductor ferromagnetic materials, and the measured magnetic field from the sample surface was small, reflecting the weak magnetization of (Ga, Mn)As. The domain width increased and the measured magnetic field decreased with raising temperature, which are consistent with calculated results, in which the exchange interaction between Mn spins deduced from the Curie temperature is assumed. (C) 2000 American Institute of Physics. [S0003-6951(00)04935-4].

  439. Magnetic domain structures of (Ga,Mn)As investigated by scanning Hall probe microscopy 査読有り

    T Shono, T Fukumura, M Kawasaki, H Koinuma, T Hasegawa, T Endo, K Kitazawa, F Matsukura, H Ohno

    PHYSICA B 284 1171-1172 2000年7月

    出版者・発行元:ELSEVIER SCIENCE BV

    ISSN:0921-4526

    詳細を見る 詳細を閉じる

    We have performed scanning Hall probe microscopy (SHPM) on III-V-based diluted magnetic semiconductors (Ga,Mn)Rs at low temperatures. The observed images clearly demonstrated stripe-shaped magnetic domains below T-c. The domain width was found to increase with temperature, and reached 3 mu m at 65 K, The temperature dependence of the domain size is consistent with the transport experiment, if we assume the RKKY interaction between Mn moments. (C) 2000 Published by Elsevier Science B.V. All rights reserved.

  440. Ferromagnetic III-V heterostructures 査読有り

    H Ohno

    JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B 18 (4) 2039-2043 2000年7月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1116/1.1305944  

    ISSN:1071-1023

    詳細を見る 詳細を閉じる

    Properties of the ferromagnetic III-V semiconductor (Ga,Mn)As and heterostructures based on it are reviewed. A model based on hole-mediated ferromagnetic interaction is shown to successfully describe the ferromagnetic transition temperature of (Ga,Mn)As. Spontaneous splitting of resonant tunneling spectra was compared with theory and shown to result from the spin splitting of the valence band. The first demonstration of spin-dependent scattering in magnetic semiconductor trilayers as well as electrical spin injection is also reviewed. (C) 2000 American Vacuum Society. [S0734-211X(00)06004-2].

  441. Molecular beam epitaxy of GaSb with high concentration of Mn 査読有り

    F Matsukura, E Abe, Y Ohno, H Ohno

    APPLIED SURFACE SCIENCE 159 265-269 2000年6月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/S0169-4332(00)00108-2  

    ISSN:0169-4332

    詳細を見る 詳細を閉じる

    Molecular-beam epitaxial growth and characterization of GaSb films with high concentration of Mn (several percents) are presented. The result shows that almost all Mn atoms in GaSb forms MnSb clusters at normal growth temperature (similar to 560 degrees C), and that low growth temperature (similar to 250 degrees C) suppresses the formation of MnSb and a few tens of percent of Mn are incorporated in the host GaSb. (C) 2000 Elsevier Science B.V. All rights reserved.

  442. Influence of interface bonds and buffer materials on optical properties of InAs/AlSb quantum wells grown on GaAs substrates 査読有り

    K Ohtani, A Sato, Y Ohno, F Matsukura, H Ohno

    APPLIED SURFACE SCIENCE 159 313-317 2000年6月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/S0169-4332(00)00106-9  

    ISSN:0169-4332

    詳細を見る 詳細を閉じる

    Optical properties of InAs/AlSb multiquantum wells (MQWs) epitaxially grown on GaAs substrates with a buffer laver are shown to be dependent on the type of the interface bond and the buffer layer material. Combinations of the two possible interface bond configurations (In-Sb and AI-As) with the two buffer layer materials (InAs and AlSb) were prepared by molecular beam epitaxy. The photoluminescence intensity (PL) of MQWs was considerably higher for two kinds of structures: (1) the In-Sb bond with the AlSb buffer or (2) the Al-As bond with the InAs buffer. The two other possible combinations resulted in a drastically reduced PL intensity. X-ray diffraction (XRD) measurements revealed that lattice matching between the average lattice constant of MQW and the buffer layer plays a key role in determining the PL intensity. (C) 2000 Published by Elsevier Science B.V. PACS: 81.10; 61.43; 78.60; 78.66; 61.10.N.

  443. MBE growth and electroluminescence of ferromagnetic/non-magnetic semiconductor pn junctions based on (Ga,Mn) As 査読有り

    Y Ohno, Arata, I, F Matsukura, K Ohtani, S Wang, H Ohno

    APPLIED SURFACE SCIENCE 159 308-312 2000年6月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/S0169-4332(00)00107-0  

    ISSN:0169-4332

    詳細を見る 詳細を閉じる

    Molecular beam epitaxial (MBE) growth of novel hybrid ferromagnetic/non-magnetic semiconductor pn junction Light emitting diodes (LEDs) is presented. The ferromagnetic p-type (Ga,Mn)As layers were grown on i-(In,Ga)As/n-GaAs structures to form LED structures. The current-voltage (I-V) characteristics and the electroluminescence (EL) spectra were measured at temperatures from 5 K to room temperature. In comparison to the properties of control samples consisting of all non-magnetic p-GaAs/(In,Ga)As/n-GaAs LEDs, the EL intensity of ferromagnetic/non-magnetic pn junction LEDs exhibited unique temperature dependence. (C) 2000 Published by Elsevier Science B.V.

  444. Molecular beam epitaxy of GaSb with high concentration of Mn 査読有り

    F Matsukura, E Abe, Y Ohno, H Ohno

    APPLIED SURFACE SCIENCE 159 265-269 2000年6月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/S0169-4332(00)00108-2  

    ISSN:0169-4332

    詳細を見る 詳細を閉じる

    Molecular-beam epitaxial growth and characterization of GaSb films with high concentration of Mn (several percents) are presented. The result shows that almost all Mn atoms in GaSb forms MnSb clusters at normal growth temperature (similar to 560 degrees C), and that low growth temperature (similar to 250 degrees C) suppresses the formation of MnSb and a few tens of percent of Mn are incorporated in the host GaSb. (C) 2000 Elsevier Science B.V. All rights reserved.

  445. Magnetic moment of Mn in the ferromagnetic semiconductor (Ga0.98Mn0.02)As 査読有り

    H Ohldag, Solinus, V, FU Hillebrecht, JB Goedkoop, M Finazzi, F Matsukura, H Ohno

    APPLIED PHYSICS LETTERS 76 (20) 2928-2930 2000年5月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.126519  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    We have studied the quasibinary ferromagnetic semiconductor (Ga0.98Mn0.02)As by magnetic circular dichroism in x-ray absorption. We find a richly structured Mn absorption spectrum typical for localized 3d electrons. An analysis of the magnetization-averaged and dichroism line shapes shows a local Mn moment of 4.6 mu(B), which is close to the Hund's rule moment for the half-filled 3d shell. The magnitude of the dichroism reveals that only about 1/7 of the Mn atoms participate in the ferromagnetic order. Our experiment does not show a distinction between the ferro- and paramagnetic Mn atoms. (C) 2000 American Institute of Physics. [S0003-6951(00)00720-8].

  446. Mobility dependence of electron spin relaxation time in n-type InGaAs/InAlAs multiple quantum wells 査読有り

    T Adachi, Y Ohno, R Terauchi, F Matsukura, H Ohno

    PHYSICA E 7 (3-4) 1015-1019 2000年5月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/S1386-9477(00)00107-7  

    ISSN:1386-9477

    詳細を見る 詳細を閉じる

    We have measured electron spin relaxation time (tau(e)) in undoped and n-type InGaAs/lnAlAs quantum wells (QWs) as a function of electron quantized energy (E-1e) and electron mobility (mu) at room temperature. For Ei, dependence, the trend can be explained either by the D'yakonov-Perel' (DP) theory or by the Elliott-Yafet (EY) theory. On the other hand, it is difficult to explain the complex mu-dependence of tau(e) by either of the theories. Our experimental results suggest that further improvement of the theories might be necessary to fully explain the relaxation mechanism in InGaAs QWs. (C) 2000 Elsevier Science B.V. All rights reserved.

  447. Molecular beam epitaxy of III-V diluted magnetic semiconductor (Ga,Mn)Sb 査読有り

    E Abe, F Matsukura, H Yasuda, Y Ohno, H Ohno

    PHYSICA E 7 (3-4) 981-985 2000年5月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/S1386-9477(00)00100-4  

    ISSN:1386-9477

    詳細を見る 詳細を閉じる

    (Ga,Mn)Sb with a few percent order of Mn was grown by molecular beam epitaxy. Two growth temperature ranges were studied; one is normal growth temperature of GaSb (similar to 560 degrees C) and the other is low temperature (250 degrees C or 300 degrees C). The properties of samples grown at these two growth temperatures were investigated by in situ reflection high-energy electron diffraction, atomic force microscopy, magnetization, and magnetotransport measurements. The results suggest the coexistence of two magnetic phases, (Ga,Mn)Sb and MnSb, for the samples grown at low temperature, whereas MnSb phase is dominant for the samples grown at high temperature. (C) 2000 Elsevier Science B.V. All rights reserved.

  448. Magnetotransport properties of (Ga,Mn)As investigated at low temperature and high magnetic field 査読有り

    T Omiya, F Matsukura, T Dietl, Y Ohno, T Sakon, M Motokawa, H Ohno

    PHYSICA E 7 (3-4) 976-980 2000年5月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/S1386-9477(00)00099-0  

    ISSN:1386-9477

    詳細を見る 詳細を閉じる

    Magnetotransport properties of ferromagnetic semiconductor (Ga,Mn)As have been investigated. Measurements at low temperature (50 mK) and high magnetic field (less than or equal to 27 T) have been employed in order to determine the hole concentration p = 3.5 x 10(20) cm(-3) of a metallic (Ga0.947Mn0.053)As layer. The analysis of the temperature and magnetic field dependencies of the resistivity in the paramagnetic region was performed using the above value of p, which gave the magnitude of p-d exchange energy \ N(0)beta \ similar to 1.5 eV. (C) 2000 Elsevier Science B.V. All rights reserved.

  449. Magnetotransport properties of (Ga, Mn)Sb 査読有り

    F Matsukura, E Abe, H Ohno

    JOURNAL OF APPLIED PHYSICS 87 (9) 6442-6444 2000年5月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.372732  

    ISSN:0021-8979

    詳細を見る 詳細を閉じる

    The preparation of dilute alloy of GaSb and Mn, (Ga, Mn)Sb, with a few percent of Mn by molecular beam epitaxy and its magnetotransport properties are reported. Magnetotransport measurements show a pronounced anomalous Hall effect and negative magnetoresistance below 50 K. The results suggest that Mn atoms are incorporated in the GaSb host, resulting in the formation of the ferromagnetic semiconductor, (Ga, Mn)Sb. (C) 2000 American Institute of Physics. [S0021-8979(00)91908-X].

  450. Spin-dependent scattering in semiconducting ferromagnetic (Ga,Mn)As trilayer structures 査読有り

    N Akiba, D Chiba, K Nakata, F Matsukura, Y Ohno, H Ohno

    JOURNAL OF APPLIED PHYSICS 87 (9) 6436-6438 2000年5月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.372730  

    ISSN:0021-8979

    詳細を見る 詳細を閉じる

    The spin-dependent scattering in ferromagnet/nonmagnet/ferromagnet (Ga,Mn)As/(Al,Ga)As/(Ga,Mn)As trilayer structures was studied. An increase of sheet resistance was observed when the magnetizations of the two ferromagnetic (Ga,Mn)As layers were aligned anti-parallel, which was realized by the different coercivity of the two (Ga,Mn)As layers with different compositions. This is the first demonstration of spin-dependent scattering in magnetic multilayer structures made of semiconductor-materials alone. (C) 2000 American Institute of Physics. [S0021-8979(00)81508-X].

  451. Mid-infrared intersubband electroluminescence in InAs/GaSb/AlSb type-II cascade structures 査読有り

    K Ohtani, H Ohno

    PHYSICA E 7 (1-2) 80-83 2000年4月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/S1386-9477(99)00282-9  

    ISSN:1386-9477

    詳細を見る 詳細を閉じる

    Mid-infrared intersubband light-emitting diodes based an InAs/GaSb/AlSb type-II cascade structure have been investigated: The observed emission energy is in good agreement with calculation based on the multi-band k . p theory. In contrast to interband cascade structures, dominant polarization of the emitted light is perpendicular to the quantum well layers. Structure dependence of intersubband electroluminescence is also presented. (C) 2000 Published by Elsevier Science B.V. All rights reserved.

  452. Zener model description of ferromagnetism in zinc-blende magnetic semiconductors 査読有り

    T Dietl, H Ohno, F Matsukura, J Cibert, D Ferrand

    SCIENCE 287 (5455) 1019-1022 2000年2月

    出版者・発行元:AMER ASSOC ADVANCEMENT SCIENCE

    DOI: 10.1126/science.287.5455.1019  

    ISSN:0036-8075

    詳細を見る 詳細を閉じる

    Ferromagnetism in manganese compound semiconductors not only opens prospects for tailoring magnetic and spin-related phenomena in semiconductors with a precision specific to III-V compounds but also addresses a question about the origin of the magnetic interactions that Lead to a Curie temperature (T-C) as high as 110 K for a manganese concentration of just 5%, Zener's model of ferromagnetism, originally proposed for transition metals in 1950, can explain T-C of Ga1-xMnxAs and that of its II-VI counterpart Zn1-xMnxTe and is used to predict materials with T-C exceeding room temperature, an important step toward semiconductor electronics that use both charge and spin.

  453. Electron spin relaxation beyond D'yakonov-Perel' interaction in GaAs/AlGaAs quantum wells 査読有り

    Y Ohno, R Terauchi, T Adachi, F Matsukura, H Ohno

    PHYSICA E 6 (1-4) 817-820 2000年2月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/S1386-9477(99)00251-9  

    ISSN:1386-9477

    詳細を見る 詳細を閉じる

    To study electron spin relaxation mechanisms in GaAs/AlGaAs quantum wells (QWs), undoped and n-doped (100) and (110) QWs with different well width and doping density are prepared and measured. The temperature dependence of electron spin relaxation time tau(s) in n-doped (100) QWs above 30 K is shown to be in good agreement with what is expected from the D'yakonov-Perel' (DP) mechanism. In (110) QWs, a 30-fold increase of tau(s), over (100) QWs at room temperature is observed. This dramatic increase is explained by the suppression of the DP mechanism. The remaining spin relaxation processes in (110) QWs are discussed. (C) 2000 Elsevier Science B.V. All rights reserved.

  454. Ferromagnetism and heterostructures of III-V magnetic semiconductors 査読有り

    H Ohno

    PHYSICA E 6 (1-4) 702-708 2000年2月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/S1386-9477(99)00177-0  

    ISSN:1386-9477

    詳細を見る 詳細を閉じる

    Ferromagnetism in III-V based magnetic semiconductors introduced a new degree of freedom associated with the magnetic cooperative phenomena to the low-dimensional heterostructures. This article reviews the preparation and the structure, magnetic, and transport properties of ferromagnetic III-V semiconductor (Ga,Mn)As, which can be grown pseudomorphically on GaAs, and heterostructures related to the ferromagnetic semiconductor. (C) 2000 Elsevier Science B.V. All rights reserved.

  455. Bilayer ν=2 quantum Hall state in parallel high magnetic field 査読有り

    A. Sawada, Z. F. Ezawa, H. Ohno, Y. Horikoshi, N. Kumada, Y. Ohno, S. Kishimoto, F. Matsukura, S. Nagahama

    Physica E 6 (1-4) 615-618 2000年2月

    出版者・発行元:None

    DOI: 10.1016/S1386-9477(99)00129-0  

    ISSN:1386-9477

  456. Ferromagnetism induced by free carriers in p-type structures of diluted magnetic semiconductors 査読有り

    T. Dietl, J. Chbert, P. Kossacki, D. Ferrand, S. Tatarenko, A. Waisiela, Y. Merle D'aubigne, F. Matsukura, N. Akiba, H. Ohno

    Physica E 7(nos.3-4) 967-975 2000年

    DOI: 10.1016/S1386-9477(00)00098-9  

  457. Surfactant effect of Mn on the formation of self-organized InAs nanostructures 査読有り

    SP Guo, A Shen, H Yasuda, Y Ohno, F Matsukura, H Ohno

    JOURNAL OF CRYSTAL GROWTH 208 (1-4) 799-803 2000年1月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/S0022-0248(99)00465-0  

    ISSN:0022-0248

    詳細を見る 詳細を閉じる

    The effect of Mn as a surfactant on the formation of InAs nanostructures was studied. The shape of the nanostructures changed drastically when a layer of Mn was added on the growth front before InAs growth. When 6 ML2 (1) (1) (6 monolayers in (2 1 1) plane) of InAs was grown on GaAs (2 1 1)B with an initial Mn coverage of 0.5 ML, quantum wire-like structures (QWRs) were formed at growth temperatures ranging from 450 to 510 degrees C, With the same initial coverage of Mn, two kinds of nanostructures, quantum dashes (QDHs) and quantum dots (QDs) were formed at 400 or 425 degrees C, whereas only QDs resulted at 380 degrees C. Nanostructures on (1 0 0) and (3 1 1)B surfaces were also investigated and compared. (C) 2000 Elsevier Science B.V. All rights reserved.

  458. Electrical spin injection in a ferromagnetic semiconductor heterostructure 査読有り

    Y Ohno, DK Young, B Beschoten, F Matsukura, H Ohno, DD Awschalom

    NATURE 402 (6763) 790-792 1999年12月

    出版者・発行元:MACMILLAN MAGAZINES LTD

    DOI: 10.1038/45509  

    ISSN:0028-0836

    詳細を見る 詳細を閉じる

    Conventional electronics is based on the manipulation of electronic charge. An intriguing alternative is the field of 'spintronics: wherein the classical manipulation of electronic spin in semiconductor devices gives rise to the possibility of reading and writing non-volatile information through magnetism(1,2) Moreover, the ability to preserve coherent spin states in conventional semiconductors' and quantum dots(4),ay eventually enable quantum computing in the solid state(5,6). Recent studies have shown that optically excited electron spins can retain their coherence over distances exceeding 100 micrometres (ref. 7). But to inject spin-polarized carriers electrically remains a formidable challenge(8,9), Here we report the fabrication of all-semiconductor, light-emitting spintronic devices using III-V heterostructures based on gallium arsenide. Electrical spin injection into a nonmagnetic semiconductor is achieved (in zero magnetic field) using a p-type ferromagnetic semiconductor(10) as the spin polarizer. Spin polarization of the injected holes is determined directly from the polarization of the emitted electroluminescence following the recombination of the holes with the injected (unpolarized) electrons.

  459. MOCVD growth and transport investigation of two-dimensional electron gas in AlGaN/GaN heterostructures on sapphire substrates 査読有り

    T Wang, Y Ohno, M Lachab, D Nakagawa, T Shirahama, S Sakai, H Ohno

    PHYSICA STATUS SOLIDI B-BASIC RESEARCH 216 (1) 743-748 1999年11月

    出版者・発行元:WILEY-V C H VERLAG GMBH

    DOI: 10.1002/(SICI)1521-3951(199911)216:1<743::AID-PSSB743>3.0.CO;2-G  

    ISSN:0370-1972

    詳細を見る 詳細を閉じる

    High quality AlGaN/GaN nominally undoped single heterostuctures (SH) with different Al contents have been fabricated on sapphire substrates. Magnetotransport investigations are performed on these samples at low temperature in a magnetic field up to 10 T. The existence of a two-dimensional electron gas (2DEG) at the AlGaN/GaN interface is confirmed by the observation of Shubnikov-de Hass oscillations in the magnetic field below 3 T and the integer quantum Hall effect. In particular, the Al0.18Ga0.82N/GaN SH shows a Hall mobility of 10300 cm(2)/Vs at 1.5 K, which to our knowledge is the highest carrier mobility on sapphire substrates grown by MOCVD. The mobility and carrier sheet density are enhanced by increasing Al composition. Based on the piezoelectric field effect, the Al composition dependence of 2DEG sheet density is calculated, which agrees well with the experimental result. This paper also investigates the effect of doping in the AlGaN layer on the properties of 2DEG. When the AlGaN layer is doped, the situation is changed. In the case of lightly doping in the AlGaN layer, the 2DEG cannot be observed. When the doping level in the AlGaN layer is increased, the 2DEG is demonstrated again together with an enhancement in the electron mobility. These behaviors are attributed to the strain-induced piezoelectric effect and silicon doping-induced screening effect. This result should be highly emphasized in designing GaN-based electrical devices.

  460. Magnetic circular dichroism studies of carrier-induced ferromagnetism in (Ga1-xMnx)As 査読有り

    B Beschoten, PA Crowell, Malajovich, I, DD Awschalom, F Matsukura, A Shen, H Ohno

    PHYSICAL REVIEW LETTERS 83 (15) 3073-3076 1999年10月

    出版者・発行元:AMERICAN PHYSICAL SOC

    DOI: 10.1103/PhysRevLett.83.3073  

    ISSN:0031-9007

    詳細を見る 詳細を閉じる

    Magnetic circular dichroism is used to investigate the evolution of ferromagnetism in the p-type magnetic semiconductor (Ga1-xMnx)As. Local Mn moments and holes produce two spectroscopically distinct contributions, whose properties reveal an antiferromagnetic Mn-hole alignment in the ferromagnetic state. These components are present in both metallic and insulating samples with different temperature and field dependences, suggesting that the holes play a mon active role in mediating the ferromagnetic exchange than in traditional RKKY systems.

  461. Properties of ferromagnetic III-V semiconductors 査読有り

    H Ohno

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 200 (1-3) 110-129 1999年10月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/S0304-8853(99)00444-8  

    ISSN:0304-8853

    詳細を見る 詳細を閉じる

    This review covers the experimental and theoretical results on III-V-based ferromagnetic semiconductors ((In,Mn)As and (Ga,Mn)As) accumulated to date. It was found in 1989 that low-temperature molecular beam epitaxy allows one to dope InAs. and later GaAs, with magnetic element Mn over its solubility limit, making it possible to realize an alloy of III-Vs and magnetic elements. Ferromagnetism in such alloys was discovered in (In,Mn)As and later in (Ga,Mn)As. Since ferromagnetic III-Vs can readily be incorporated in the existing semiconductor heterostructure systems, where a number of optical and electronic devices have been realized, they allow us to explore physics and application of previously not available combinations of quantum structures and magnetism in semiconductors. (C) 1999 Elsevier Science B.V. All rights reserved.

  462. Metal-insulator transition and magnetotransport in III-V compound diluted magnetic semiconductors 査読有り

    Y Iye, A Oiwa, A Endo, S Katsumoto, F Matsukura, A Shen, H Ohno, H Munekata

    MATERIALS SCIENCE AND ENGINEERING B-SOLID STATE MATERIALS FOR ADVANCED TECHNOLOGY 63 (1-2) 88-95 1999年8月

    出版者・発行元:ELSEVIER SCIENCE SA

    ISSN:0921-5107

    詳細を見る 詳細を閉じる

    Structural, magnetic and transport properties of diluted magnetic semiconductors, (Ga, Mn)As and (In, Mn)As, have been investigated. Manganese can be substitutionally doped into the group III site of the zincblend structure up to several percent. With Mn content of a few percent, these systems exhibit ferromagnetism at low temperatures. The highest Curie temperature so far achieved is similar to 100 K for (Ga, Mn)As. The saturated magnetization values are consistent with S = 5/2 local moment, suggesting divalent Mn which acts as an acceptor. The system becomes metallic with increasing Mn content, but a further increase of Mn content tends to decrease the hole density and increase disorder so that the system becomes nonmetallic again at higher Mn concentrations. Large negative magnetoresistance and highly anisotropic transport are observed in the semiconducting samples at low temperatures. The magnetic anisotropy in ultrathin films is found to be strongly affected by the lattice-mismatch-induced strain. (C) 1999 Elsevier Science B.V. All rights reserved.

  463. Interlayer coherence in nu=1 and nu=2 bilayer quantum Hall states 査読有り

    A Sawada, ZF Ezawa, H Ohno, Y Horikoshi, A Urayama, Y Ohno, S Kishimoto, F Matsukura, N Kumada

    PHYSICAL REVIEW B 59 (23) 14888-14891 1999年6月

    出版者・発行元:AMER PHYSICAL SOC

    DOI: 10.1103/PhysRevB.59.14888  

    ISSN:1098-0121

    eISSN:1550-235X

    詳細を見る 詳細を閉じる

    The presence of interlayer coherence in bilayer quantum Hall states was examined by magnetotransport experiments. Two macroscopic quantum conjugate observables, the phase difference and the electron density difference between the two layers, are experimentally addressed by tilting the sample in a magnetic field and applying gate bias voltages. Results strongly indicate the presence of interlayer coherence at the filling factor v = 1 and 2.

  464. Electron mobility exceeding 10(4) cm(2)/Vs in an AlGaN-GaN heterostructure grown on a sapphire substrate 査読有り

    T Wang, Y Ohno, M Lachab, D Nakagawa, T Shirahama, S Sakai, H Ohno

    APPLIED PHYSICS LETTERS 74 (23) 3531-3533 1999年6月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.124151  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    High-quality AlGaN/GaN undoped single heterostructures (SH) with different Al contents have been grown on sapphire substrates. The magnetotransport investigation was performed on these samples at a low temperature. The observation of Shubnikov-de Hass oscillations in the magnetic fields below 3 T and the integer quantum Hall effect confirmed the existence of the two-dimensional electron gas (2DEG) at the AlGaN/GaN interface. The Al0.18Ga0.82N/GaN SH shows a Hall mobility of 10 300 cm(2)/V s at a carrier sheet density of 6.19 X 10(12)/cm(2) measured at 1.5 K. To the best of our knowledge, this is the highest carrier mobility ever measured in GaN-based semiconductors grown on sapphire substrates. The Al composition dependence of the mobility and carrier sheet density were also investigated. Based on the piezoelectric field effect, the Al composition dependence of the 2DEG sheet density was calculated, which agreed well with the experimental result. The negative magnetoresistance with parabolic magnetic-field dependence in the low magnetic field was also observed in the sample with the highest 2DEG sheet density. (C) 1999 American Institute of Physics. [S0003-6951(99)03323-9].

  465. New 'coherent' bilayer quantum Hall systems 査読有り

    A. Sawada, Z. F. Ezawa, H. Ohno, Y. Horikoshi, Y. Ohno, S. KIshimoto, F. Matsukura, A. Urayama, N. Kumada

    Proc. of 6th Int. Symp. on Foundations of Quantum Mechanics in the Light of New Technology (ISQM-Tokyo '98) 207-210 1999年5月

  466. Mid-infrared intersubband electroluminescence in InAs AlSb cascade structures 査読有り

    K Ohtani, H Ohno

    ELECTRONICS LETTERS 35 (11) 935-936 1999年5月

    出版者・発行元:IEE-INST ELEC ENG

    DOI: 10.1049/el:19990624  

    ISSN:0013-5194

    詳細を見る 詳細を閉じる

    Mid-infrared intersubband electroluminescence is reported in InAs single quantum wells embedded in InAs/AlSb quantum cascade structures. The observed emission energy is in good agreement with calculations based on the multiband gp theory. The dominant polarisation of the emitted light is perpendicular to the quantum well layers.

  467. Monte Carlo simulation of reentrant reflection high-energy electron diffraction intensity oscillation observed during low-temperature GaAs growth 査読有り

    H Yasuda, H Ohno

    APPLIED PHYSICS LETTERS 74 (22) 3275-3277 1999年5月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.123318  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    Reentrant behavior of intensity oscillation of reflection high-energy electron diffraction (RHEED) observed during low-temperature GaAs homoepitaxy on GaAs (001) substrates is studied by a Monte Carlo simulation using cubic solid-on-solid configuration. By assuming that an excess As overlayer acts as surfactant which enhances the migration of Ga adatoms at low temperature, temperature as well as V/III ratio dependence of step density oscillation (i.e., RHEED intensity oscillation) is successfully reproduced. (C) 1999 American Institute of Physics. [S0003-6951(99)01822-7].

  468. Antiferromagnetic p-d exchange in ferromagnetic Ga1-xMnxAs epilayers 査読有り

    J Szczytko, W Mac, A Twardowski, F Matsukura, H Ohno

    PHYSICAL REVIEW B 59 (20) 12935-12939 1999年5月

    出版者・発行元:AMER PHYSICAL SOC

    DOI: 10.1103/PhysRevB.59.12935  

    ISSN:1098-0121

    eISSN:1550-235X

    詳細を見る 詳細を閉じる

    The s,p-d exchange interaction of p-type Ga1-xMnxAs (x&lt;0.05) epilayers is investigated by means of magnetoabsorption. The observed ferromagnetic-type splitting of fundamental absorption edge is explained by antiferromagnetic p-d exchange interaction, taking into account the Moss-Burstein effect, resulting from high hole concentration. [S0163-1829(99)05020-1].

  469. X-ray diffraction study of InAs AlSb interface bonds grown by molecular beam epitaxy 査読有り

    A Sato, K Ohtani, R Terauchi, Y Ohno, F Matsukura, H Ohno

    JOURNAL OF CRYSTAL GROWTH 201 861-863 1999年5月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/S0022-0248(98)01475-4  

    ISSN:0022-0248

    詳細を見る 詳細を閉じる

    Interface bond structures of InAs/AlSb superlattices (SLs) have been investigated by X-ray diffraction (XRD) and photoluminescence (PL) measurements. For heterointerfaces with different anion composition AsxSb1-x, XRD data are found to be in good agreement with simulation results assuming the presence of 1 monolayer InAsxSb1-x at the interfaces. For the sample with an AlAs interface bond, no good fit is obtained for XRD. This indicates that the growth of an InAs/AlSb SL is disrupted at the AlAs interfaces. Correlation between interface configurations and their optical properties is also discussed. (C) 1999 Elsevier Science B.V. All rights reserved.

  470. InAs and (In,Mn)As nanostructures grown on GaAs(100), (211)B, and (311)B substrates 査読有り

    SP Guo, A Shen, F Matsukura, Y Ohno, H Ohno

    JOURNAL OF CRYSTAL GROWTH 201 684-688 1999年5月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/S0022-0248(98)01442-0  

    ISSN:0022-0248

    詳細を見る 詳細を閉じる

    InAs and (In,Mn)As nanostructures grown on GaAs(1 0 0), (2 1 1)B and (3 1 1)B substrates have been studied. Quantum dots (QDs) were observed when InAs was grown on GaAs(1 0 0) (or (3 1 1)B). QDs with bimodal size distribution were formed when InAs was deposited on GaAs(2 1 1)B at lower growth temperatures(T-s) whereas quantum dashes (QDHs) were observed at higher T-s.(-)(In,Mn)As QDs grown on GaAs(1 0 0) showed a broad range of dot sizes with irregular shape, (In,Mn)As QDs with bimodal size distribution were observed for the structure grown on GaAs(3 1 I)B. (In,Mn)As QDs grown on GaAs(2 1 1)B showed improved size uniformity compared to those grown on GaAs(1 0 0) and (3 1 1)B. The effects of Mn as a surfactant on InAs nanostructures were also studied. (C) 1999 Elsevier Science B.V. All lights reserved.

  471. Low-temperature molecular beam epitaxial growth of GaAs and (Ga,Mn)As 査読有り

    A Shen, F Matsukura, SP Guo, Y Sugawara, H Ohno, M Tani, H Abe, HC Liu

    JOURNAL OF CRYSTAL GROWTH 201 679-683 1999年5月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/S0022-0248(98)01447-X  

    ISSN:0022-0248

    詳細を見る 詳細を閉じる

    GaAs and (Ga,Mn)As were grown by low-temperature (LT) MBE. In this paper we report the growth condition dependence of properties of LT GaAs and (Ga,Mn)As. Transient reflectivity measurements showed that the carrier lifetime in LT GaAs can be modified by changing the V/III ratio. The Curie temperature of (Ga,Mn)As, determined by magneto-transport measurements, was also shown to be a function of V/III ratio. (C) 1999 Elsevier Science B.V. All rights reserved.

  472. Carrier mobility dependence of electron spin relaxation in GaAs quantum wells 査読有り

    R Terauchi, Y Ohno, T Adachi, A Sato, F Matsukura, A Tackeuchi, H Ohno

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 38 (4B) 2549-2551 1999年4月

    出版者・発行元:JAPAN J APPLIED PHYSICS

    DOI: 10.1143/JJAP.38.2549  

    ISSN:0021-4922

    詳細を見る 詳細を閉じる

    We have investigated the electron mobility (mu) dependence and the electron quantized energy dependence of the electron spin relaxation time (tau(s)) in n-type and undoped GaAs/AlGaAs multiple quantum wells at room temperature, tau(s) proportional to mu(-1) obtained from the experimental results is consistent with the theoretical prediction based on the D'yakonov-Perel' theory.

  473. Intersubband electroluminescence in InAs/GaSb/AlSb type-II cascade structures 査読有り

    K Ohtani, H Ohno

    APPLIED PHYSICS LETTERS 74 (10) 1409-1411 1999年3月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.123566  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    Intersubband electroluminescence in InAs quantum wells embedded in InAs/GaSb/AlSb type-II cascade structures is reported. The observed emission energy is in good agreement with calculation based on the multiband k . p theory. Dominant polarization of the emitted light is perpendicular to the quantum well layers. Difference in the spectrum shape between intersubband and interband cascade transitions is also presented. (C) 1999 American Institute of Physics. [S0003-6951(99)01210-3].

  474. Magnetic and transport properties of the ferromagnetic semiconductor heterostructures (In,Mn)As/(Ga,Al)Sb 査読有り

    A Oiwa, A Endo, S Katsumoto, Y Iye, H Ohno, H Munekata

    PHYSICAL REVIEW B 59 (8) 5826-5831 1999年2月

    出版者・発行元:AMER PHYSICAL SOC

    DOI: 10.1103/PhysRevB.59.5826  

    ISSN:1098-0121

    eISSN:1550-235X

    詳細を見る 詳細を閉じる

    We have investigated the magnetic and transport properties of (In,Mn)As thin films grown on a (Ga,Al)Sb layer. Strong perpendicular magnetic anisotropy is observed for the (In,Mn)As layer, the thickness of which is less than the critical value required for relaxation of lattice-mismatch-induced strain. The anomalous Hall coefficient is found to be approximately proportional to the square of resistivity in the low-field region. Large negative magnetoresistance is found to occur over a magnetic field range significantly wider than that for the ferromagnetic hysteresis loop. [S0163-1829 (98)04344-6].

  475. Properties of (Ga,Mn)As and their dependence on molecular beam growth conditions 査読有り

    F. Matsukura, A. Shen, Y. Sugawara, T. Omiya, Y. Ohno, H. Ohno

    Proc. 25th Int. Symp. Compound Semiconductors, Institute of Physics Conference Series (162) 547-552 1999年

  476. 半導体結晶成長 査読有り

    大野英男

    コロナ社 1999年

  477. Ferromagnetic III-V semiconductors and their heterostructures 査読有り

    H. Ohno

    Proceedings of the 24th International Conference on the Physics of Semiconductors 139-146 1999年

  478. Spin relaxation in GaAs(110) quantum wells 査読有り

    Y. Ohno, R. Terachi, T. Adachi, F. Matsukura, H. Ohno

    Physical Review Letters 1999年

    DOI: 10.1103/PhysRevLett.83.4196  

  479. Integrated micromechanical cantilever magnetometry of Ga<SUB>1-x</SUB>Mn<SUB>x</SUB>As 査読有り

    J. G. E. Harris, D. D. Awshalom, F. Matsukura, H. Ohno, K. D. Maranowski, A. C. Gossard

    Applied Physics Letters 75 (8) 1140-1143 1999年

    DOI: 10.1063/1.124622  

  480. Spin-dependent tunneling and properties of ferromagnetic(Ga, Mn)As 査読有り

    H. Ohno, F. Matsukura, T. Omiya, N. Akiba

    J. Appl. Phys. 85 (8) 4277-4282 1999年

    DOI: 10.1063/1.370343  

  481. Magnetotransport properties of(Ga, Mn)As/GaAs/(Ga, Mn)As trilayer structures 査読有り

    F. Matsukura, N. Akiba, A. Shen, Y. Ohno, A. Oiwa, S. Katsumoto, Y. Iye, H. Ohno

    J. Magnetics Society of Japan 23 (1) 88-92 1999年

    出版者・発行元:The Magnetics Society of Japan

    DOI: 10.3379/jmsjmag.23.99  

    ISSN:0285-0192

    詳細を見る 詳細を閉じる

    All-semiconductor ferromagnet/nonmagnet/ferromagnet trilayer structures using (Ga, Mn)As as a ferromagnetic layer and GaAs a nonmagnetic layer were prepared and their magnetotransport properties were investigated. The results show that the interaction between the two (Ga, Mn)As layers decreases as the GaAs thickness increases. This shows that the carriers present in the nonmagnetic layer mediate the coupling between the two ferromagnetic layers in the present all-semiconductor system.

  482. III-V based ferromagnetic semiconductors 査読有り

    H. Ohno

    J. Magnetics Society of Japan 23 (1) 88-92 1999年

    出版者・発行元:The Magnetics Society of Japan

    DOI: 10.3379/jmsjmag.23.88  

    ISSN:0285-0192

    詳細を見る 詳細を閉じる

    Current status of III-V based ferromagnetic semiconductors, especially (Ga, Mn)As, a GaAs based diluted magnetic semiconductor, is reviewed. Low solubility of magnetic elements was overcome by low temperature nonequilibrium molecular beam epitaxial growth to realize successfully (Ga, Mn)As as well as (In, Mn)As. Magnetization measurements showed that GaAs based (Ga, Mn) As is ferromagnetic with Curie temperature <i>T</i><sub>C</sub> as high as 110 K. Magnetotransport measurements of (Ga, Mn) As epitaxial films revealed that the p-d exchange <i>N</i><sub>0</sub>β is 3 eV. This strong interaction was shown to be large enough to explain the high <i>T</i><sub>C</sub> by the RKKY interaction. Multilayer heterosturctures including superlattices and resonant tunneling diodes (RTD's) were also successfully fabricated. The magnetic coupling between two ferromagnetic (Ga, Mn)As films separated by a nonmagnetic GaAs (or AlGaAs) layer was found to be a function of thickness and composition of the intermediary layer, indicating the critical role of the holes on the magnetic coupling. This observation of magnetic coupling in all semiconductor ferromagnetic/nonmagnetic layered structures, together with the possibility of spin dependent tunneling in RTD's, showed the potential of the present material system for exploring new physics and for developing new functionality toward future electronics.

  483. ESR study of Mn doped II-Ⅵ and III-V DMS 査読有り

    H. Nojiri, M. Motokawa, S. Takeyama, F. Matsukura, H. Ohno

    Physica B 256 569-572 1998年12月

    出版者・発行元:None

    DOI: 10.1016/S0921-4526(98)00504-3  

    ISSN:0921-4526

  484. Cyclotron resonance in Cd1-xFexS and Ga1-xMnxAs at megagauss magnetic fields 査読有り

    YH Matsuda, H Arimoto, N Miura, A Twardowski, H Ohno, A Shen, F Matsukura

    PHYSICA B-CONDENSED MATTER 256 565-568 1998年12月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/S0921-4526(98)00673-5  

    ISSN:0921-4526

    詳細を見る 詳細を閉じる

    We have performed infrared and far-infrared magneto-transmission experiments for Cd1-xFexS (x=0.05) and Ga1-xMnxAs (x=0.00004, 0.053) at very high magnetic fields up to 500 T. The cyclotron mass of electrons in Cd1-xFexS (x=0.05) was found to be larger than that in CdS when we applied magnetic fields parallel to the c-axis of the crystal; the relative increase of the cyclotron mass shows anomalous temperature dependence at 85-300 K. Hole cyclotron resonance was observed in Ga1-xMnxAs (x=0.00004) at 119 mu m and 70.5 mu m. In Ga1-xMnxAs (x=0.053) far-infrared transmission does not show any resonance but a rapid decrease of transmission with magnetic field; the magneto-transmission spectrum depends strongly on temperature. (C) 1998 Elsevier Science B.V. All rights reserved.

  485. Magnetotunneling spectroscopy of resonant tunneling diode using ferromagnetic (Ga,Mn)As 査読有り

    N Akiba, F Matsukura, Y Ohno, A Shen, K Ohtani, T Sakon, M Motokawa, H Ohno

    PHYSICA B-CONDENSED MATTER 256 561-564 1998年12月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/S0921-4526(98)00490-6  

    ISSN:0921-4526

    詳細を見る 詳細を閉じる

    Tunneling and magnetotunneling properties of GaAs-based p-type double barrier resonant tunneling diodes (RTD's) with a ferromagnetic (Ga,Mn)As emitter layer are studied. Current-voltage characteristics of RTD's revealed the presence of spontaneous magnetization in the (Ga,Mn)As emitter. The transverse magnetic field results suggest that the valence band dispersion of (Ga,Mn)As is different from GaAs. (C) 1998 Published by Elsevier Science B.V. All rights reserved.

  486. Spin dependence of the interlayer tunneling in double quantum wells in the quantum Hall regime 査読有り

    S Kishimoto, Y Ohno, F Matsukura, H Ohno

    PHYSICA B-CONDENSED MATTER 256 535-539 1998年12月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/S0921-4526(98)00674-7  

    ISSN:0921-4526

    詳細を見る 詳細を閉じる

    We have studied the spin dependence of electron tunneling in GaAs/AlGaAs double quantum wells (DQWs) in the quantum Hall regime. One of the two-dimensional-electron layers (2DELs) is fully spin polarized by tuning a magnetic field while the spin orientation of the topmost Landau level (LL) in the other 2DEL is set in parallel or antiparallel by changing the carrier density. We have evaluated the interlayer tunnel dissipation (ITD) between the edge-channel in the bottom 2DEL and the half-filled LL in the top 2DEL. We observed that when the spin orientations of both layers are in alignment, ITD is enhanced as compared to the antiparallel alignment. The difference is found to disappear when tunnel coupling is reduced. (C) 1998 Elsevier Science B.V. All rights reserved.

  487. Interlayer exchange in (Ga,Mn)As/(Al,Ga)As/(Ga,Mn)As semiconducting ferromagnet/nonmagnet/ferromagnet trilayer structures 査読有り

    N Akiba, F Matsukura, A Shen, Y Ohno, H Ohno, A Oiwa, S Katsumoto, Y Iye

    APPLIED PHYSICS LETTERS 73 (15) 2122-2124 1998年10月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.122398  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    Magnetic properties of all-semiconductor (Ga,Mn)As/(Al,Ga)As/(Ga,Mn)As trilayer structures are studied. The interactions between the two ferromagnetic (Ga,Mn)As layers are investigated by magnetotransport measurements in a number of samples with different GaAs thickness or with different Al content in the intermediary nonmagnetic (Al,Ga)As layer. The results indicate that carriers present in the nonmagnetic layer mediate the coupling between the two ferromagnetic layers. (C) 1998 American Institute of Physics. [S0003-6951(98)01441-7].

  488. Light emission spectra of AlGaAs/GaAs multiquantum wells induced by scanning tunneling microscope 査読有り

    T Tsuruoka, Y Ohizumi, S Ushioda, Y Ohno, H Ohno

    APPLIED PHYSICS LETTERS 73 (11) 1544-1546 1998年9月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.122200  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    We have investigated the scanning-tunneling-microscope light emission (STM-LE) spectra of P-Al0.4Ga0.6As/p- GaAs multiquantum wells. The injection current level was kept as low as 0.1-0.5 nA to ensure that the sample is not damaged by the tunneling current. This is the current level ordinarily used for taking STM images. The peak energy of the emission shifts to the high energy side with decreasing well widths. A corresponding peak shift behavior was also observed in the photoluminescence (PL) spectra for the same samples. From comparisons of the STM-LE and the PL spectra, we find that although there is a difference in the excitation process, the final recombination process is identical in both cases. (C) 1998 American Institute of Physics.

  489. Magnetotransport and magnetic properties of (Ga,Mn)As and its heterostructures 査読有り

    H Ohno

    ACTA PHYSICA POLONICA A 94 (2) 155-164 1998年8月

    出版者・発行元:POLISH ACAD SCIENCES INST PHYSICS

    ISSN:0587-4246

    詳細を見る 詳細を閉じる

    Introduction of high density of Mn in GaAs by low temperature molecular beam epitaxy results in a homogeneous diluted magnetic semiconductor (Ga,Mn)As, which exhibits ferromagnetism at low temperatures. Temperature and magnetic field dependence of magnetotransport and magnetization of (Ga,Mn)As films revealed the Curie temperature Te which can be as high as 110 K and the p-d exchange, which explains To in the framework of the RKKY interaction. Multilayer heterostructures such as all-semiconductor ferromagnet/nonmagnet/ferromagnet trilayer structures and resonant tunneling diodes have been fabricated and studied. These heterostructure results show the potential of the present material system for exploring new physics and for developing new functionality toward future electronic and optical devices. PACS numbers: 73.61.Ey, 75.50.Pp, 75.70.Cn.

  490. Making nonmagnetic semiconductors ferromagnetic 査読有り

    H Ohno

    SCIENCE 281 (5379) 951-956 1998年8月

    出版者・発行元:AMER ASSOC ADVANCEMENT SCIENCE

    DOI: 10.1126/science.281.5379.951  

    ISSN:0036-8075

    詳細を見る 詳細を閉じる

    Semiconductor devices generally take advantage of the charge of electrons, whereas magnetic materials are used for recording information involving electron spin. To make use of both charge and spin of electrons in semiconductors, a high concentration of magnetic elements can be introduced in nonmagnetic III-V semiconductors currently in use for devices. Low solubility of magnetic elements was overcome by Low-temperature nonequilibrium molecular beam epitaxial growth, and ferromagnetic (Ca,Mn)As was realized. Magnetotransport measurements revealed that the magnetic transition temperature can be as high as 110 kelvin. The origin of the ferromagnetic interaction is discussed. Multilayer heterostructures including resonant tunneling diodes (RTDs) have also successfully been fabricated. The magnetic coupling between two ferromagnetic (Ga,Mn)As films separated by a nonmagnetic layer indicated the critical role of the holes in the magnetic coupling. The magnetic coupling in all semiconductor ferromagnetic/nonmagnetic Layered structures, together with the possibility of spin filtering in RTDs, shows the potential of the present material system for exploring new physics and for developing new functionality toward future electronics.

  491. Spontaneous splitting of ferromagnetic (Ga, Mn)As valence band observed by resonant tunneling spectroscopy 査読有り

    H Ohno, N Akiba, F Matsukura, A Shen, K Ohtani, Y Ohno

    APPLIED PHYSICS LETTERS 73 (3) 363-365 1998年7月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.121835  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    Current-voltage characteristics of AlAs/GaAs/AlAs double barrier resonant tunneling diodes with ferromagnetic p-type (Ga, Mn)As on one side and p-type GaAs on the other have been studied. A series of resonant peaks have been observed in both polarities, i.e., injecting holes from p-type GaAs and from (Ga, Mn)As. When holes are injected from the (Cia, Mn)As side, spontaneous resonant peak splitting has been observed below the ferromagnetic transition temperature of (Ga, Mn)As without magnetic field. The temperature dependence of the splitting is explained by the the spontaneous spin splitting in the valence band of ferromagnetic (Ga, Mn)As. (C) 1998 American Institute of Physics.

  492. Etched-backgate field-effect transistor structure for magnetotunneling study of low-dimensional electron systems 査読有り

    S Kishimoto, Y Ohno, F Matsukura, H Sakaki, H Ohno

    SOLID-STATE ELECTRONICS 42 (7-8) 1187-1190 1998年7月

    出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD

    DOI: 10.1016/S0038-1101(98)00001-X  

    ISSN:0038-1101

    詳細を見る 詳細を閉じる

    We fabricated field effect transistors having independent ohmic contacts to individual two-dimensional-electron gases in a double quantum well structure by etching the backgate (BG) area to 30 mu m-thick, while keeping the major part of the substrate thick for ease of handling (60 mu m). By this approach, it was made possible to form independent ohmic contacts with applied voltage to BG of about -60 V. We investigated the device by measuring the tunneling conductance as a function of temperature, in-plane magnetic field and carrier density. The temperature dependence showed that the broadening of resonant tunneling peak originated from the ionized impurity scattering and the electron-electron scattering. The in-plane magnetotunneling has shown two peaks at particular fields expected from the carrier densities in each well. These results indicate that the uniformity of the thick ness of the etched BG area is good enough to allow the study of 2D-2D tunneling spectroscopy. (C) 1998 Elsevier Science Ltd. All rights reserved.

  493. Well-width dependence of bound to quasi-bound intersubband transition in GaAs quantum wells with multi-quantum barriers 査読有り

    K Ohtani, Y Ohno, F Matsukura, H Ohno

    PHYSICA E 2 (1-4) 200-203 1998年7月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/S1386-9477(98)00043-5  

    ISSN:1386-9477

    詳細を見る 詳細を閉じる

    Well-width dependence of bound to quasi-bound intersubband transitions in GaAs quantum wells (QW) with multi-quantum barriers (MQB) is investigated. Narrowing the well width, the absorption peak shifts to higher energy while integrated absorption intensity decreases as the quasi-bound state energy increases. The transition energies are in good agreement with the calculation, whereas the observed decrease of integrated absorption is found to be larger than the decrease in oscillotor strength due to the spread to quasi-bound wave function. Using a simple rate equation, the decrease of the integrated absorption is discussed. (C) 1998 Elsevier Science B.V. All rights reserved.

  494. InAs quantum dots and dashes grown on (100), (211)B, and (311)B GaAs substrates 査読有り

    SP Guo, A Shen, Y Ohno, H Ohno

    PHYSICA E 2 (1-4) 672-677 1998年7月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/S1386-9477(98)00137-4  

    ISSN:1386-9477

    詳細を見る 詳細を閉じる

    InAs self-organized quantum dots (QDs) and quantum dashes (QDHs) grown on GaAs (100), (211)B and (311)B substrates by molecular beam epitaxy at different growth temperatures (T-s) have been investigated. QDs were observed after deposition of 2ML(100) (or 4ML(311)) of InAs on GaAs (100) (or (311)B) at T-s ranging from 450 degrees C to 530 degrees C, The average density decreases and the average size increases monotonically with increasing T-s. QDs with bimodal size distribution were formed when 6ML(211) of InAs was deposited on GaAs (211)B at lower T-s. When the same amount of InAs was deposited at higher T-s, however, QDHs were observed. The photoluminescence intensity of the QDs and QDHs showed similar temperature dependence, whereas the excitation density dependence showed quite different behaviors. (C) 1998 Elsevier Science B.V. All rights reserved.

  495. Ferromagnetic (Ga, Mn)As and its heterostructures 査読有り

    H Ohno, F Matsukura, A Shen, Y Sugawara, N Akiba, T Kuroiwa

    PHYSICA E 2 (1-4) 904-908 1998年7月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/S1386-9477(98)00184-2  

    ISSN:1386-9477

    詳細を見る 詳細を閉じる

    Magnetotransport measurements have been performed to clarify the origin of ferromagnetism in a new III-V-based diluted magnetic semiconductor, (Ga, Mn)As. Hall resistance was dominated by the anomalous Hall effect proportional to the magnetization, allowing one to determine the magnetic properties such as Curie temperature and Curie constant as well as the conduction type (p-type) and carrier concentration. Negative resistance above Curie temperature was shown to be well accounted for by the spin disorder scattering, from which the exchange between conduction holes and localized Mn moments was determined. This exchange interaction is shown to be responsible for the observed ferromagnetism in (Ga, Mn)As through the RKKY interaction. The magnetic coupling between two ferromagnetic (Ga, Mn)As films separated by a nonmagnetic (Al, Ga)As layer was controlled by the composition of the intermediary layer, indicating the critical role of the holes in the intermediary layer on the coupling. (C) 1998 Elsevier Science B.V. All rights reserved.

  496. Interlayer quantum coherence and anomalous stability of v-1 bilayer quantum Hall state 査読有り

    A. Sawada, Z. F. Eazawa, H. Ohno, Y. Horikoshi, S. Kishimoto, F. Matsukura, Y. Ohno, M. Yasumoto, A. Urayama

    Physica B 249-251 836-840 1998年6月17日

    DOI: 10.1016/S0921-4526(98)00326-3  

  497. Low-temperature GaAs grown by molecular-beam epitaxy under high As overpressure: A reflection high-energy electron diffraction study 査読有り

    A. Shen, H. Ohno, Y. Horikoshi, S. P. Guo, Y. Ohno, F. Matsukura

    Applied Surface Science 130-132 382-397 1998年6月

    DOI: 10.1016/S0169-4332(98)00087-7  

  498. Self-organized (In, Mn) as diluted magnetic semiconductor nanostructures on GaAs substrates 査読有り

    SP Guo, H Ohno, A Shen, F Matsukura, Y Ohno

    APPLIED SURFACE SCIENCE 130 797-802 1998年6月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/S0169-4332(98)00157-3  

    ISSN:0169-4332

    詳細を見る 詳細を閉じる

    We have grown (In,Mn)As quantum dots (QDs) on GaAs (100), (211)B and (311)B substrates. The observation of reflection high energy electron diffraction pattern and atomic force microscopy measurement confirmed the formation of the (In,Mn)As QDs. The structure grown on GaAs (100) showed a broad range of dot sizes with irregular shape. For the structure grown on GaAs (311)B, (In,Mn)As QDs with bimodal size distribution were observed. The (In,Mn)As QDs grown on GaAs (211)B showed improved size uniformity compared to those grown on GaAs (100) and (311)B. The effect of Mn as a surfactant on InAs nanostructures was also studied. (C) 1998 Elsevier Science B.V. All rights reserved.

  499. Photoluminescence study of InAs quantum dots and quantum dashes grown on GaAs (211)B 査読有り

    SP Guo, H Ohno, AD Shen, Y Ohno, F Matsukura

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 37 (3B) 1527-1531 1998年3月

    出版者・発行元:JAPAN J APPLIED PHYSICS

    DOI: 10.1143/JJAP.37.1527  

    ISSN:0021-4922

    詳細を見る 詳細を閉じる

    InAs self-organized quantum dots (QDs) and quantum dashes (QDHs) were grown by molecular beam epitaxy on GaAs (211)B substrates. QDs with bimodal size distribution were formed at lower growth temperatures, whereas QDHs were observed at higher growth temperatures. Photoluminescence (PL) intensity and peak position of QDs and QDHs showed similar temperature dependence, whereas the excitation density dependence of the Pi, peak intensity and the PL peak energy of the two nanostructures was different. The blue shift in QDH peak energy with the increase of the excitation density is suggested to be due to the existence of the piezoelectric field in InAs QDHs.

  500. Giant negative magnetoresistance of (Ga, Mn)As/GaAs in the vicinity of a metal-insulator transitions 査読有り

    A. Oiwa, S. Katsumoto, A. Endo, M. Hirasawa, Y. Iye, H. Ohno, F. Matsukura, A. Shen, Y. Sugawara

    physica status solidi (b) 205 (1) 167-171 1998年1月

    DOI: 10.1002/(SICI)1521-3951(199801)205:1<167::AID-PSSB167>3.0.CO;2-O  

  501. Strongly anisotropic hopping conduction in (Ga, Mn)As/GaAs 査読有り

    S Katsumoto, A Oiwa, Y Iye, H Ohno, F Matsukura, A Shen, Y Sugawara

    PHYSICA STATUS SOLIDI B-BASIC RESEARCH 205 (1) 115-118 1998年1月

    出版者・発行元:WILEY-V C H VERLAG GMBH

    DOI: 10.1002/(SICI)1521-3951(199801)205:1<115::AID-PSSB115>3.0.CO;2-F  

    ISSN:0370-1972

    詳細を見る 詳細を閉じる

    We report magnetotransport of (Ga, Mn)As below 1 K in the reentrant insulating phase. The external magnetic Field drove the samples from the strongly insulating regime to the variable range hopping one. Below 1 K, the resistivity was strongly anisotropic (by about two orders of magnitude). The conduction along the highly resistive direction ([1(1) over bar0$]) was well described by variable range hopping in the soft Coulomb gap regime while that along the lower resistive direction ([1(1) over bar0$]) seemed to undergo an insulator-to-metal transition by the external magnetic Field. The result may be a key to solve the problem of reentrant metal-to-insulator transition in (Ga, Mn) As with increasing Mn content.

  502. Properties of(Ga, Mn)As and their dependence on molecular beam growth conditions 査読有り

    F. Matsukura, A. Shen, Y. Sugawara, T. Omiya, Y. Ohno, H. Ohno

    Inst. Phys. Conf. Ser. (162) 547-552 1998年

  503. Magnetotransport properties of all semiconductor(Ga, Mn)As/(Al, Ga)As/(Ga, Mn)As tri-layer structure 査読有り

    F. Matsukura, N. Akiba, A. Shen, Y. Ohno, A. Oiwa, S. Katsumoto, Y. Iye, H. Ohno

    Physica B 256-258 573-576 1998年

    DOI: 10.1016/S0921-4526(98)00495-5  

  504. υ=1 bilayer quantum Hall state at arbitrary electron distribution in a double qrantum well 査読有り

    Y. Ohno, A. Sawada, Z. F. Ezawa, H. Ohno, Y. Horikoshi, S. Kishimoto, F. Matsukura, M. Yasumoto, A. Urayama

    Solid-State Electronics 42 (7-8) 1183-1185 1998年

    DOI: 10.1016/S0038-1101(97)00326-2  

  505. Phase transition in the υ=2 bilayer quantum Hall state 査読有り

    A. Sawada, Z. F. Ezawa, H. Ohno, Y. Horikoshi, Y. Ohno, S. Kishimoto, F. Matsukura, M. Yasumoto, A. Urayama

    Physical Review Letters 80 (20) 4534-4537 1998年

    DOI: 10.1103/PhysRevLett.80.4534  

  506. Low-temperature GaAs grown by molecular-beam epitaxy under high As overpressure : A reflection high-energy electron diffraction study 査読有り

    A. Shen, H. Ohno, Y. Horikoshi, S. P. Guo, Y. Ohno, F. Matsukura

    Applied Surface Science 130-132 382-397 1998年

    DOI: 10.1016/S0169-4332(98)00087-7  

  507. Superlattice and maltilayer structures based on ferromagnetic semiconductor(Ga, Mn)As 査読有り

    A. Shen, H. Ohno, F. Matsukura, H. C. Liu, N. Akiba, Y. Sugawara, T. Kuroiwa, Y. Ohno

    Physica B 249-251 809-813 1998年

    DOI: 10.1016/S0921-4526(98)00319-6  

  508. Transport properties and origin of ferromagnetism in(Ga, Mn)As 査読有り

    F. Matsukura, H. Ohno, A. Shen, Y. Sugawara

    Physical Review B 57 (4) R2037-R2040 1998年

    DOI: 10.1103/PhysRevB.57.R2037  

  509. Faraday rotation of ferromagnetic (Ga, Mn)As 査読有り

    T Kuroiwa, T Yasuda, F Matsukura, A Shen, Y Ohno, Y Segawa, H Ohno

    ELECTRONICS LETTERS 34 (2) 190-192 1998年1月

    出版者・発行元:IEE-INST ELEC ENG

    DOI: 10.1049/el:19980128  

    ISSN:0013-5194

    詳細を見る 詳細を閉じる

    Faraday rotation of (Ga, Mn)As, with an Mn composition of 0.043, is presented. The measurements were performed in the Fundamental aborption edge region (1.24-1.8eV) at 10K (ferromagnetic phase) and at room temperature (paramagnetic phase). The magnetic behaviour of(Gal Mn)As manifests itself in the magnetic field dependence of Faraday rotation, which was found to be proportional to the magnetisation of the sample. A large Faraday rotation of 6 x 10(4) deg/cm (at 0.1 T, 1.55eV) at 10K is observed. The Verdet constant at room temperature is 8 x 10(-2) deg/G.cm (1.49eV).

  510. Preparation and properties of III-V based new diluted magnetic semiconductors 査読有り

    H Ohno

    ADVANCES IN COLLOID AND INTERFACE SCIENCE 71-2 61-75 1997年9月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/S0001-8686(97)00010-9  

    ISSN:0001-8686

    詳細を見る 詳細を閉じる

    Preparation and properties of a new class of diluted magnetic semiconductors (DMS's) based on III-V compounds are reviewed. Epitaxial films of (In,Mn)As and (Ga,Mn)As, the new III-V based DMS's, are now possible by low temperature molecular beam epitaxial growth (&lt; 300 degrees C). The magnetic properties of the epitaxial layers were revealed by the use of the anomalous Hall effect with the assistance of SQUID magnetization measurements. The epitaxial films showed antiferromagnetic, superparamagnetic, and ferromagnetic behaviors depending on the Mn-Mn interaction, which was modified by the presence of carriers and strain in the layers. These new III-V based DMS's will open up new fields in semiconductor technology, where both semiconducting and magnetic properties play critical roles. (C) 1997 Elsevier Science B.V.

  511. Reflection high-energy electron diffraction oscillations during growth of GaAs at low temperatures under high As overpressure 査読有り

    A Shen, Y Horikoshi, H Ohno, SP Guo

    APPLIED PHYSICS LETTERS 71 (11) 1540-1542 1997年9月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.119973  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    Reflection high-energy electron diffraction oscillations were observed during molecular beam epitaxy of GaAs at temperatures as low as 150 degrees C under various V/III beam equivalent pressure ratios using As-4 as an arsenic source. At the As/Ga beam equivalent pressure ratio of 40, the amplitude of the oscillations was shown to first decrease with the decrease of substrate temperature and then increase when the temperature was further lowered to below 300 degrees C. The oscillation characteristics at 200 degrees C were comparable to those recorded at around 600 degrees C. At fixed temperatures in the low temperature region (&lt;350 degrees C), the oscillations were shown to be greatly affected by the V/III ratio, with the maximum amplitude at a certain V/III ratio which depends on the substrate temperature used. The strong oscillations at low temperatures and at high V/III ratios were tentatively explained by assuming that the migration of Ga atoms is enhanced on the surface passivated by excess As. (C) 1997 American Institute of Physics.

  512. Anomalous stability of nu=1 bilayer quantum Hall state 査読有り

    A Sawada, ZF Ezawa, H Ohno, Y Horikoshi, O Sugie, S Kishimoto, F Matsukura, Y Ohno, M Yasumoto

    SOLID STATE COMMUNICATIONS 103 (8) 447-451 1997年8月

    出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD

    DOI: 10.1016/S0038-1098(97)00221-4  

    ISSN:0038-1098

    詳細を見る 詳細を閉じる

    We have studied the fractional and integer quantum Hall (QH) effects in a high-mobility double-layer two-dimensional electron system. We have compared the ''stability'' of the QH state in balanced and unbalanced double quantum wells. The behavior of the nu = 1 QH state is found to be strikingly different from all others. It is anomalously stable, though all other states decay, as the electron density is made unbalanced between the two quantum wells. We interpret the peculiar features of the nu = 1 state as consequences of the interlayer quantum coherence developed spontaneously on the basis of the composite-boson picture. (C) 1997 Elsevier Science Ltd.

  513. Nonmetal-metal-nonmetal transition and large negative magnetoresistance in (Ga, Mn)As/GaAs 査読有り

    A Oiwa, S Katsumoto, A Endo, M Hirasawa, Y Iye, H Ohno, F Matsukura, A Shen, Y Sugawara

    SOLID STATE COMMUNICATIONS 103 (4) 209-213 1997年7月

    出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD

    DOI: 10.1016/S0038-1098(97)00178-6  

    ISSN:0038-1098

    詳細を見る 詳細を閉じる

    We have studied magnetic and transport properties of a series of Ga1-xMnxAs/GaAs samples with different Mn concentrations (x = 0.015-0.071). For Mn content higher than about 0.02, carrier(hole)-induced ferromagnetism is observed. Samples with x = 0.035 and 0.043 behave as ferromagnetic dirty metals. With further increase of Mn content above x similar to 0.05, the zero-field resistivity turns a semiconducting temperature dependence. Very large negative magnetoresistance is observed in nonmetallic samples near the metal-nonmetal transitions both in the low and the high Mn content regimes. (C) 1997 Elsevier Science Ltd.

  514. Epitaxy of (Ga, Mn)As, a new diluted magnetic semiconductor based on GaAs 査読有り

    A Shen, H Ohno, F Matsukura, Y Sugawara, N Akiba, T Kuroiwa, A Oiwa, A Endo, S Katsumoto, Y Iye

    JOURNAL OF CRYSTAL GROWTH 175 1069-1074 1997年5月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/S0022-0248(96)00967-0  

    ISSN:0022-0248

    詳細を見る 詳細を閉じる

    GaAs-based diluted magnetic semiconductor, (Ga, Mn)As, with Mn composition x up to 0.07 was prepared by molecular-beam epitaxy on GaAs substrate at temperatures ranging from 160 to 320 degrees C. Clear reflection high-energy electron diffraction oscillations were observed at the initial growth stage, indicating that the growth mode is two-dimensional. The lattice constant of (Ga, Mn)As films determined by X-ray diffraction showed a linear increase with the increase of Mn composition. Well-aligned in-plane ferromagnetic order was observed by magnetization measurements. Magnetotransport measurements also revealed the presence of ferromagnetic order in the (Gz, Mn)As layer. The easy axis of magnetization can be reversed by changing the strain direction in (Ga, Mn)As. GaAs/(Ga, Mn)As superlattice structures with high crystal perfection and good interface quality were also prepared.

  515. Electric field dependence of intersubband transitions in GaAs/AlGaAs single quantum wells 査読有り

    A Mathur, Y Ohno, F Matsukura, K Ohtani, N Akiba, T Kuroiwa, H Nakajima, H Ohno

    APPLIED SURFACE SCIENCE 113 90-96 1997年4月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/S0169-4332(96)00879-3  

    ISSN:0169-4332

    詳細を見る 詳細を閉じる

    The effects of applied electric fields on intersubband (ISB) transitions in modulation-doped n-i-n and p-i-n type GaAs/AlGaAs single quantum well (SQW) structures an studied experimentally using Fourier Transform InfraRed (FTIR) spectroscopy. The n-i-n SQW devices exhibit a red shift of 0.7 meV in the ISB transition energy and a 12% decrease in the integrated absorbance at the maximum applied bias of 3.2 V with reference to their zero bias values, most of which is attributed to a rise in the device temperature due to Joule heating owing to the current flowing through the device. The p-i-n SQW devices exhibit strong quenching of the absorption when a negative bios is applied, while there was no observable shift in the ISB transition energy.

  516. Epitaxy and properties of InMnAs/AlGaSb diluted magnetic III-V semiconductor heterostructures 査読有り

    A Shen, F Matsukura, Y Sugawara, T Kuroiwa, H Ohno, A Oiwa, A Endo, S Katsumoto, Y Iye

    APPLIED SURFACE SCIENCE 113 183-188 1997年4月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/S0169-4332(96)00865-3  

    ISSN:0169-4332

    詳細を見る 詳細を閉じる

    InMnAs/AlGaSb diluted magnetic semiconductor heterostructures have been grown by molecular-beam epitaxy on GaAs substrates. Three epitaxial procedures were employed for the growth of InMnAs, which resulted in three-dimensional or two-dimensional nucleation. Low-temperature magnetotransport measurements reveal that while some of the samples show well-aligned ferromagnetic ordering some others show ferromagnetic behavior with no magnetic anisotropy or, in the extreme case, superparamagnetic behavior. The transport properties were correlated to the growth modes.

  517. Growth and properties of (Ga, Mn) As: A new III-V diluted magnetic semiconductor 査読有り

    F Matsukura, A Oiwa, A Shen, Y Sugawara, N Akiba, T Kuroiwa, H Ohno, A Endo, S Katsumoto, Y Iye

    APPLIED SURFACE SCIENCE 113 178-182 1997年4月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/S0169-4332(96)00790-8  

    ISSN:0169-4332

    詳細を見る 詳細を閉じる

    A new III-V diluted magnetic semiconductor, (Ga, Mn)As, was prepared by low-temperature molecular beam epitaxy. The lattice constant oi (Ga, Mn)As films determined by X-ray diffraction showed a linear increase with increase of Mn composition, suggesting homogeneous incorporation of Mn in the film. Magnetization measurements revealed ferromagnetic order al low temperature, while magnetotransport measurements showed the anomalous Hall effect and negative magnetoresistance associated with the ferromagnetic order in the (Ga, Mn)As films.

  518. InAs self-organized quantam dashes grown on GaAs(211)B 査読有り

    S. P. Guo, H. Ohno, A. Shen, F. Matsukura, Y. Ohno

    Appl. Phys. Lett 71 (11) 1540-1542 1997年

    DOI: 10.1063/1.119007  

  519. Electvical and magnetic properties of (In, Mn)AS/(A1, Ga)Sb heterostructures and bulk(Ga, Mn)AS 査読有り

    A. Oiwa, Y. Iye, S. Katsumoto, A. Endo, M. Hirasawa, H. Ohno, F. Matsukura, A. Shen, H. Munekata

    Proc, 12th Int, Conf on High Magnetic Fields in the Physics of SemiconductorsII 885-888 1997年

  520. (Ga, Mn)As/GaAs diluted megnetic semiconductor superlattice Structures prepared by molecular beam epitaxy 査読有り

    A. Shen, H. Ohno, F. Matsukura, Y. Sugawara, Y. Ohno, N. Akiba, T. Kuroiwa

    Jpn. J. Appl. Phys. 36 (2A) 273-275 1997年

  521. (Ga,Mn)As: A new diluted magnetic semiconductor based on GaAs 査読有り

    H Ohno, A Shen, F Matsukura, A Oiwa, A Endo, S Katsumoto, Y Iye

    APPLIED PHYSICS LETTERS 69 (3) 363-365 1996年7月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.118061  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    A new GaAs-based diluted magnetic semiconductor, (Ga,Mn)As, was prepared by molecular beam epitaxy. The lattice constant of (Ga,Mn)As films was determined by x-ray diffraction and shown to increase with the increase of Mn composition, x. Well-aligned in-plane ferromagnetic order was observed by magnetization measurements. Magnetotransport measurements revealed the occurrence of anomalous Hall effect in the (Ga,Mn)As layer. (C) 1996 American Institute of Physics.

  522. Ferromagnetic order in(Ga, Mn)As/GaAs heterostructures. 査読有り

    H. Ohno, F. Matsukura, A. Shen, Y. Sugawara, A. Oiwa, A. Endo, S. Katsumoto, Y. Iye

    Proc. 23rd. Int. Conf. Physics of Semiconductors 405-408 1996年

  523. Mn-based III-V diluted magnetic(semimagnetic) semiconductors 査読有り

    H. Ohno

    Materials Science Forum (182-184) 443 1995年

  524. Growth of GaAs by molecular-beam epitaxy using trisdinethylaminoarsine 査読有り

    S. Goto, Y. Nomura, Y. Morishita, Y. Katayama, H. Ohno

    J.Crystal Growth 143 1995年

    DOI: 10.1016/0022-0248(95)00031-3  

  525. Temperature dependence of anomalous Hall effect and magnetism of (In, Mn)Asl(Al,Ga)Sb heterostructures

    H. Ohno, F. Matsukura, H. Munekata, Y. Iye, J. Nakahara

    Proc.22nd Int.Conf.Physics of Semiconductors 2605 1995年

  526. Kinetics and mechanism of atomic layer epitaxy of GaAs using trimethylgallium 査読有り

    H. Ohno, S. Goto, Y. Nomura, Y. Morishita, Y. Katayama

    Applied Surface Science 82-83 (C) 164-170 1994年12月2日

    DOI: 10.1016/0169-4332(94)90213-5  

    ISSN:0169-4332

    詳細を見る 詳細を閉じる

    The desorption time constant of carbon-related species from clean GaAs surfaces exposed to trimethylgallium (TMGa), measured by in situ Auger electron spectroscopy, is of the order of 100 s in the temperature range where atomic layer epitaxy of GaAs takes place. A set of rate equations based on the adsorbate-inhibition model using this desorption time constant is shown to reproduce atomic layer epitaxy growth results: the GaAs growth rate dependence on the TMGa supply duration and the growth rate of the double TMGa pulse experiments with purge time in between two TMGa pulses. The origin of the remaining discrepancies is discussed. © 1994.

  527. MINIMUM LIGHT POWER FOR OPTICAL INTERCONNECTION IN INTEGRATED-CIRCUITS 査読有り

    H OHNO

    OPTOELECTRONICS-DEVICES AND TECHNOLOGIES 9 (1) 131-136 1994年3月

    出版者・発行元:MITA PRESS

    ISSN:0912-5434

    詳細を見る 詳細を閉じる

    Minimum light power and the corresponding minimum number of photons required for the operation of on-chip optical interconnection are discussed. The minimum light power to realize the designed error rate is compared to the minimum light power needed to output sufficient voltage to drive the following electronic circuits. It has been shown from the study that the limiting factor would be the circuit restriction rather than the error rate constraint.

  528. ADSORPTION OF CARBON-RELATED SPECIES ONTO GAAS(001), (011), AND (111) SURFACES EXPOSED TO TRIMETHYLGALLIUM 査読有り

    S GOTO, H OHNO, Y NOMURA, Y MORISHITA, Y KATAYAMA

    JOURNAL OF CRYSTAL GROWTH 136 (1-4) 104-108 1994年3月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/0022-0248(94)90391-3  

    ISSN:0022-0248

    詳細を見る 詳細を閉じる

    The adsorption/desorption process of carbon-related species on GaAs surfaces exposed to trimethylgallium (TMGa) was studied using in situ Auger electron spectroscopy (AES) and reflection high-energy electron diffraction (RHEED) as a function of the various surface reconstructions and orientations. The adsorption of C originating from TMGa and its transient behavior were observed on Ga-stabilized (001)-4 X 6 and (111)B-square-root 19 x square-root 19 surfaces. On the other hand, the C KLL (273 eV) signal intensity on (011) and (111)A surfaces was extremely low, even just after exposure to TMGa. The growth rates of GaAs grown by chemical beam epitaxy using an alternating supply of TMGa and arsine depended strongly on the substrate orientations, corresponding to the adsorption of the C-containing species on the surfaces. The results indicated that the self-limiting monolayer growth (atomic-layer epitaxy) of GaAs is caused by the adsorbed alkyls, which terminate surfaces and block all of the decomposition sites for TMGa.

  529. Inter-subbard population inversion in tunneling heterostructures 査読有り

    H. Ohno

    Transactions of the Materials Research Society of Japan 19A 47 1994年

  530. トリメチルガリウムを用いたGaAsの原子層エピタキシと表面カイネティクス 査読有り

    大野英男

    日本結晶成長学会誌 21 (1) 24-31 1994年

    DOI: 10.19009/jjacg.21.1_24  

  531. DILUTED MAGNETIC III-V SEMICONDUCTORS AND ITS TRANSPORT-PROPERTIES 査読有り

    H OHNO

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 32 (Suppl.32-2) 459-461 1993年

    出版者・発行元:JAPAN J APPLIED PHYSICS

    ISSN:0021-4922

    詳細を見る 詳細を閉じる

    A new class of diluted magnetic semiconductor (DMS) based on III-V compounds and its transport properties are presented. While the new DMS, (In, Mn)As, films exhibiting n-type conduction were all paramagnetic with the Mn-Mn interaction being antiferromagnetic, ferromagnetic interaction between the Mn ions in p-type films manifested itself in the hysteresis in the magnetic field dependence of the Hall resistivity at low temperatures, indicating the presence of ferromagnetic order. This ferromagnetic order was accompanied by paramagnetic response extending to high magnetic fields. The coexistence of remanent magnetization and unsaturated spins (partial ferromagnetic order; asperomagnetism) can be explained by the formation of bound magnetic polarons with partially aligned spins. The ferromagnetic order observed in the (In, Mn)As based heterojunctions is also discussed.

  532. In situ Auger electron spectroscopy of carbon transient behavior on GaAs surfaces exposed to trimethylgallium 査読有り

    S. Goto, H. Ohno, Y. Nomura, Y. Morishita, A. Watanabe, Y. Katayama

    Journal of Crystal Growth 127,1005-1009 1993年

    DOI: 10.1016/0022-0248(93)90777-T  

  533. Auger electron spectroscopy of molecular beam epitaxially grown GaAs surfaces exposed to trimethylgallium 査読有り

    H. Ohno, S. Goto, Y. Nomura, Y. Morishita, A. Watanabe, Y. Katayama

    Applied Physics Letters 62 (18) 2248 1993年

    DOI: 10.1063/1.109635  

  534. Partial ferromagnetic order in p-type(In, Mn)As diluted magnetic III-V semiconductors 査読有り

    H. Ohno, H. Munekata, T. Penney, S. von Moln, L.L. Chang

    Material Science Forum 117-118,297-302 1993年

  535. Optoelectronic devices based on type II polytype tunnel heterostructures 査読有り

    H. Ohno, L. Esaki, E.E. Mendez

    Applied Physics Letters 60 (25) 1992年

    DOI: 10.1063/1.106726  

  536. Magnetotransport properties of p-type(In, Mn)As diluted magnetic III-V semiconductors 査読有り

    H. Ohno, H. Munekata, T. Penney, S. von Moln, L.L. Chang

    Physical Review Letters 68 (16) 2664 1992年

    DOI: 10.1103/PhysRevLett.68.2664  

  537. New diluted magnetic III-V semiconductors 査読有り

    H. Ohno, H. Munekata, S. von Moln, L.L. Chang

    Japanese of Applied Physics 69 (8) 6103 1991年

    DOI: 10.1063/1.347780  

  538. Effect of carrier mass differences on the current-voltage characterics of resonant tunneling structures 査読有り

    H. Ohno, E.E. Mendez, W.I. Wang

    Applied Physics Letters 56 (18) 1793 1990年

    DOI: 10.1063/1.103102  

  539. Observation of 'Tamm states' in superlattices 査読有り

    H. Ohno, E.E. Mendez, J.A. Brum, J.M. Hong, F. AgullRueda, L.L. Chang, L. Esaki

    Physical Review Letters 64 (21) 2555 1990年

    DOI: 10.1103/PhysRevLett.64.2555  

  540. Effect of exposure to group III alkyls on compound semiconductor surfaces observed by X-ray photoelectron spectroscopy 査読有り

    H. Ishii, H. Ohno, K. Matsuzaki, H. Hasegawa

    J. Crystal Growth 95 1989年

    DOI: 10.1016/0022-0248(89)90365-5  

  541. Low temperature mobility of two dimensional electron gas in selectively doped pseudomorphic N-AlGaAs/GaInAs/GaAs structures 査読有り

    H. Ohno, J.K. Luo, K. Matsuzaki, H. Hasegawa

    Appl. Phys. Lett. 54 (1) 1989年

    DOI: 10.1063/1.100826  

  542. Absence of growth sequence dependence of AlAs/GaAs heterojunction band discontinuity determined by X-ray photoelection spectroscopy 査読有り

    H. Ohno, H. Ishii, K. Matsuzaki, H. Hasegawa

    J Crystal Growth 95 1989年

    DOI: 10.1016/0022-0248(89)90420-X  

  543. Quantum Hall effect of two dimensional electron gas in AlyGa<SUB>1-y</SUB>As/Ga<SUB>1-x</SUB>In<SUB>x</SUB>As/GaAs pseudomorphic structures 査読有り

    J. K. Luo, H. Ohno, K. Matsuzaki, H. Hasegawa

    J. Appl Phys 66 (9) 1989年

    DOI: 10.1063/1.344473  

  544. Self-limiting deposition of Ga on a GaAs surface by thermal decomposition of diethylgalliumchloride observed by X-ray photoelectron spectroscopy 査読有り

    H. Ohno, H. Ishii, K. Matsuzaki, H. Hasegawa

    Appl Phys Lett 54 (12) 1989年

    DOI: 10.1063/1.100776  

  545. Magnetoconductivity of two-dimensional electron gas in Al<SUB>0.3</SUB>Ga<SUB>0.7</SUB>As/Ga<SUB>1-x</SUB>In<SUB>x</SUB> As/GaAs pseudomorphic heterostructure in quantum Hall regime 査読有り

    J. K. Luo, H. Ohno, K. Matsuzaki, T. Umeda, J. Nakahara, H. Hasegawa

    Physical Review B 40 (5) 1989年

    DOI: 10.1103/PhysRevB.40.3461  

  546. Atomic layer epitaxy of GaAs using triethylgallium and arsine 査読有り

    H. Ohno, S. Ohtsuka, H. Ishii, Y. Matsubara, H. Hasegawa

    Applied Physics Letters 54 (20) 1989年

    DOI: 10.1063/1.101195  

  547. Diluted magnetic III-V semiconductors 査読有り

    H. Munekata, H. Ohno, S. von Moln, A. Segmler, L.L. Chang, L. Esaki

    Physical Review Letters 63 (17) 1989年

    DOI: 10.1103/PhysRevLett.63.1849  

  548. Dark current in selectively doped N-AlGaAs/GaAs CCDs 査読有り

    Y. Akatsu, H. Ohno, H. Hasegawa, N. Sano

    Japanese J. Applied Physics 27 (1) 1988年

    DOI: 10.1143/JJAP.27.78  

  549. MBE growth of GaAs/InAs structures on (001)InP by alternating III-V fluxes 査読有り

    R. Katsumi, H. Ohno, H. Ishii, K. Matsuzaki, Y. Akatsu, H. Hasegawa

    J. Vacuum Science and Technology B B6 (2) 1988年

    DOI: 10.1116/1.584405  

  550. Growth of GaAs, InAs, and GaAs/InAs superlattice structures at low substrate temperature by MOVPE 査読有り

    H. Ohno, S. Ohtsuka, A. Ohuchi, T. Matsubara, H. Hasegawa

    J. Crystal Growth 93 1988年

    DOI: 10.1016/0022-0248(88)90550-7  

  551. Low-field transport properties of two dimensional electron gas in selectively doped N-AlGaAs/GaInAs/GaAs pseudomorphic structures 査読有り

    J.K. Luo, H. Ohno, K. Matsuzaki, H. Hasegawa

    Japanese J. Applied Physics 27 (10) 1988年

  552. Effect of a coincident Pb flux during MBE growth on the electrical properties of GaAs 査読有り

    Y. Akatsu, H. Ohno, H. Hasegawa, T. Hashizume

    J. Crystal growth 81 1987年

    DOI: 10.1016/0022-0248(87)90411-8  

  553. Correlation between the location of the interface state minimum at insulator-semiconductor interfaces and Schottky barrier heights 査読有り

    H. Ohno, H. Hasegawa

    Japanese J. Appl Physics 25 (5) 1986年

  554. Deep level characterization of AlGaAs and selectively doped N-AlGaAs/GaAs heterojunctions 査読有り

    H. Ohno, Y. Akatsu, T. Hashizume, H. Hasegawa, N. Sano, H. Kato, M. Nakayama

    J. Vacuum Science and Technology B B3 (4) 1985年

    DOI: 10.1116/1.583018  

  555. Growth of a (GaAs)n/(InAs)n superlattice semiconductor by molecular beam epitaxy 査読有り

    H. Ohno, R. Katsumi, T. Takama, H. Hasegawa

    Japanese J. Appl Physics 24 (9) 1985年

    DOI: 10.1143/JJAP.24.L682  

  556. Mechanism of high gain in GaAs photoconductive detectors under low excitation 査読有り

    N. Matsuo, H. Ohno, H. Hasegawa

    Japanese J. Appl Phys 23 (5) 1984年

  557. Free-carrier profile synthesis in MOCVD grown GaAs by 'atomic-plane'doping 査読有り

    H. Ohno, E. Ikeda, H. Hasegawa

    Japanese J. Applied Physics 23 (6) 1984年

  558. Planer doping by interrupted MOVPE growth of GaAs 査読有り

    H. Ohno, E. Ikeda, H. Hasegawa

    J. Crystal Growth 68 (1) 1984年

    DOI: 10.1016/0022-0248(84)90390-7  

  559. Monolithic integration of GaAs photoconductive detectors and GaAs MESFETs with distributed coupling to optical fibers 査読有り

    N. Matsuo, H. Ohno, H. Hasegawa

    Japanese J. Appl Plays 23 (8) 1984年

  560. Effect of tangential magnetic field on the two-dimensional electron transport in N-AlGaAs/GaAs superlattices and hetero-interfaces 査読有り

    H. Sakaki, H. Ohno, S. Nishi, J.. Yoshino

    Physica 117B&118B 1983年

    DOI: 10.1016/0378-4363(83)90629-0  

  561. Dependence of electron mobility on spacer layer thickness and electron density in modulation doped Ga<SUB>0.47</SUB>In<SUB>0.53</SUB>As/Al<SUB>0.48</SUB> In<SUB>0.52</SUB> As heterojunction 査読有り

    K. Hsieh, H. Ohno, G. Wicks, L.F. Eastman

    Electronics Letters 19 (5) 1983年

    DOI: 10.1049/el:19830112  

  562. A new GaAs/AlGaAs heterojunction FET with insulated gate structure (MISSFET) 査読有り

    T. Hotta, H. Ohno, H. Sakaki

    Japanese Journal of Applied Physics 21 (2) L122-L124 1982年6月

    DOI: 10.1143/JJAP.21.L122  

  563. Transport properties of electrons at n-AlGaAs/GaAs heterojunction interface and their dependence on GaAs buffer-layer thickness and substrates 査読有り

    Y. Sekiguchi, H. Sakaki, T. Tanoue, T. Hotta, H. Ohno

    Collected Papers of MBE-CST-2 139-142 1982年6月

  564. OPTICAL-QUALITY GAINAS GROWN BY MOLECULAR-BEAM EPITAXY 査読有り

    G WICKS, CEC WOOD, H OHNO, LF EASTMAN

    JOURNAL OF ELECTRONIC MATERIALS 11 (2) 435-440 1982年

    出版者・発行元:MINERALS METALS MATERIALS SOC

    DOI: 10.1007/BF02654681  

    ISSN:0361-5235

  565. STABILIZATION OF SCHOTTKY-BARRIER PROPERTIES OF SINGLE-CRYSTAL AL/GAAS AND AL/ALGAAS/GAAS CONTACTS PREPARED BY MOLECULAR-BEAM EPITAXY 招待有り 査読有り

    DC SUN, H SAKAKI, H OHNO, Y SEKIGUCHI, T TANOUE

    INSTITUTE OF PHYSICS CONFERENCE SERIES 63 (63) 311-316 1982年

    出版者・発行元:PLENUM PUBL CORP

    ISSN:0951-3248

  566. Tangential magnetoresistance of two-dimensional electron gas at a selectively doped n-GaAlAs/GaAs heterojunction interface grown by molecular beam epitaxy 査読有り

    H. Ohno, H. Sakaki

    Appl Phys Lett 40 (10) 1982年

    DOI: 10.1063/1.92938  

  567. Characterisation of Al/AlInAs/GaInAs heterostructures 査読有り

    D.V. Morgan, H. Ohno, C.E.C. Wood, W.J. Schaff, K. Board, L.F. Eastman

    IEEE Proceedings 128 (4) 141-143 1981年9月

  568. Schottky-barrier properties of nearly-ideal (n=1) Al contact on MBE-and heat cleaned-GaAs surfaces 査読有り

    H. Sakaki, Y. Sekiguchi, D.C. Sun, M. Taniguchi, H. Ohno, A. Tanaka

    Japanese Journal of Applied Physics 20 (2) L107-L110 1981年9月

  569. ON THE ORIGIN AND ELIMINATION OF MACROSCOPIC DEFECTS IN MBE FILMS 査読有り

    CEC WOOD, L RATHBUN, H OHNO, D DESIMONE

    JOURNAL OF CRYSTAL GROWTH 51 (2) 299-303 1981年

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/0022-0248(81)90314-6  

    ISSN:0022-0248

    eISSN:1873-5002

  570. CHANNELING ANALYSIS OF MBE INALAS-INGAAS INTERFACES 査読有り

    DV MORGAN, CEC WOOD, H OHNO, LF EASTMAN

    JOURNAL OF VACUUM SCIENCE & TECHNOLOGY 19 (3) 596-598 1981年

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1116/1.571136  

    ISSN:0022-5355

  571. ION-BEAM ANALYSIS OF MOLECULAR-BEAM EPITAXY INALAS-INGAAS LAYER STRUCTURES 査読有り

    DV MORGAN, H OHNO, CEC WOOD, LF EASTMAN, JD BERRY

    JOURNAL OF THE ELECTROCHEMICAL SOCIETY 128 (11) 2419-2424 1981年

    出版者・発行元:ELECTROCHEMICAL SOC INC

    DOI: 10.1149/1.2127262  

    ISSN:0013-4651

  572. Integrated double heterostructure Ga<SUB>0.47</SUB>In<SUB>0.53</SUB>As photoreceiver with automatic gain control 査読有り

    J. Barnard, H. Ohno, C.E.C. Wood, L.F. Eastman

    IEEE Electron Device Letters 2 (1) 1981年

    DOI: 10.1109/EDL.1981.25320  

  573. High speed photoconductive detectors using GaInAs 査読有り

    J. Gammel, H. Ohno, J.M. Ballantyne

    IEEE J. Quantum Electronics QE-17 (2) 1981年

    DOI: 10.1109/JQE.1981.1071056  

  574. GaInAs-AlInAs structures grown by molecular beam epitaxy 査読有り

    H. Ohno, C.E.C. Wood, L. Rathbun, D.V. Morgan, G.W. Wicks, L.F. Eastman

    J Appl Phys 52 (6) 1981年

    DOI: 10.1063/1.329212  

  575. Arsenic stabilization of InP substrates for growth of GaxIn1-xAs layers by molecular beam epitaxy 査読有り

    G.J. Davies, R. Heckingbottom, H. Ohno

    Applied Physics Letters 37 (3) 290-293 1980年6月

    DOI: 10.1063/1.91910  

  576. Double heterostructure Ga<SUB>0.47</SUB> In<SUB>0.53</SUB> As MESFET'S by MBE 査読有り

    H. Ohno, J. Barnard, C.E.C. Wood, L.F. Eastman

    IEEE Electron Device Letters 1 (8) 1980年

  577. Thermal conversion mechanism in semi-insulating GaAs 査読有り

    H. Ohno, A. Ushirokawa, T. Katoda

    J. Appl Phys 50 (12) 1979年

    DOI: 10.1063/1.325921  

︎全件表示 ︎最初の5件までを表示

MISC 33

  1. 確率ビット向け微細磁性体の熱ゆらぎ 招待有り 査読有り

    金井駿, 深見俊輔, 大野英男

    日本物理学会誌 78 (5) 256-261 2023年5月

    DOI: 10.11316/butsuri.78.5_256  

  2. Coherent antiferromagnetic spintronics

    Jiahao Han, Ran Cheng, Luqiao Liu, Hideo Ohno, Shunsuke Fukami

    Nature Materials 2023年

    DOI: 10.1038/s41563-023-01492-6  

    ISSN:1476-1122

    eISSN:1476-4660

    詳細を見る 詳細を閉じる

    Antiferromagnets have attracted extensive interest as a material platform in spintronics. So far, antiferromagnet-enabled spin–orbitronics, spin-transfer electronics and spin caloritronics have formed the bases of antiferromagnetic spintronics. Spin transport and manipulation based on coherent antiferromagnetic dynamics have recently emerged, pushing the developing field of antiferromagnetic spintronics towards a new stage distinguished by the features of spin coherence. In this Review, we categorize and analyse the critical effects that harness the coherence of antiferromagnets for spintronic applications, including spin pumping from monochromatic antiferromagnetic magnons, spin transmission via phase-correlated antiferromagnetic magnons, electrically induced spin rotation and ultrafast spin–orbit effects in antiferromagnets. We also discuss future opportunities in research and applications stimulated by the principles, materials and phenomena of coherent antiferromagnetic spintronics.

  3. 招待講演 アナログスピントロニクス素子とその人工神経回路網応用 (磁気記録・情報ストレージ)

    秋間 学尚, BORDERS William, 深見 俊輔, 守谷 哲, 栗原 祥太, KURENKOV Aleksandr, 堀尾 喜彦, 佐藤 茂雄, 大野 英男

    電子情報通信学会技術研究報告 = IEICE technical report : 信学技報 117 (247) 7-12 2017年10月19日

    出版者・発行元:電子情報通信学会

    ISSN:0913-5685

  4. 招待講演 アナログスピントロニクス素子とその人工神経回路網応用 (マルチメディアストレージ)

    秋間 学尚, BORDERS William, 深見 俊輔, 守谷 哲, 栗原 祥太, KURENKOV Aleksandr, 堀尾 喜彦, 佐藤 茂雄, 大野 英男

    映像情報メディア学会技術報告 = ITE technical report 41 (34) 7-12 2017年10月

    出版者・発行元:映像情報メディア学会

    ISSN:1342-6893

  5. Spintronics Materials and Devices for Working Memory Technology FOREWORD

    Hideo Ohno, Masafumi Yamamoto, Tetsuo Endoh, Yasuo Ando, Takahiro Hanyu, Kohei M. Itoh, Masaaki Tanaka, Seiji Mitani, Hitoshi Wakabayashi

    JAPANESE JOURNAL OF APPLIED PHYSICS 56 (8) 2017年8月

    出版者・発行元:IOP PUBLISHING LTD

    DOI: 10.7567/JJAP.56.080201  

    ISSN:0021-4922

    eISSN:1347-4065

  6. C-12-1 スピン注入磁化反転メモリの大容量化回路技術(C-12.集積回路,一般セッション)

    竹村 理一郎, 河原 尊之, 大野 英男

    電子情報通信学会ソサイエティ大会講演論文集 2014 (2) 53-53 2014年9月9日

    出版者・発行元:一般社団法人電子情報通信学会

  7. 27aKF-1 垂直磁化Co/Ni細線中の磁壁電流駆動におけるスピンホール効果の影響(スピントロニクス(磁化ダイナミクス),領域3(磁性,磁気共鳴))

    吉村 瑶子, 小山 知弘, 森山 貴広, Kim Kab-Jin, 千葉 大地, 仲谷 栄伸, 深見 俊輔, 山ノ内 路彦, 大野 英男, 小野 輝男

    日本物理学会講演概要集 68 (2) 415-415 2013年8月26日

    出版者・発行元:一般社団法人日本物理学会

    ISSN:1342-8349

  8. High-speed and reliable domain wall motion device: Material design for embedded memory and logic application

    S. Fukami, M. Yamanouchi, T. Koyama, K. Ueda, Y. Yoshimura, K. J. Kim, D. Chiba, D. Chiba, H. Honjo, N. Sakimura, R. Nebashi, Y. Kato, Y. Tsuji, A. Morioka, K. Kinoshita, S. Miura, T. Suzuki, H. Tanigawa, S. Ikeda, S. Ikeda, T. Sugibayashi, N. Kasai, T. Ono, H. Ohno, H. Ohno

    Digest of Technical Papers - Symposium on VLSI Technology 61-62 2012年9月27日

    DOI: 10.1109/VLSIT.2012.6242461  

    ISSN:0743-1562

    詳細を見る 詳細を閉じる

    High-speed capability and excellent reliability of a magnetic domain wall (DW) motion device required for embedded memory and logic-in-memory applications were achieved by optimizing the film stack structure of Co/Ni wire. Low-current with high-speed writing, high heat resistance, low error rate, wide operation range for temperature and magnetic field, high retention, and high endurance features were confirmed. © 2012 IEEE.

  9. スピン注入RAM(SPRAM)の動向および多値化技術

    石垣 隆士, 河原 尊之, 竹村 理一郎, 小埜 知夫, 伊藤 顕知, 大野 英男

    電子情報通信学会技術研究報告. ICD, 集積回路 111 (6) 1-5 2011年4月11日

    出版者・発行元:一般社団法人電子情報通信学会

    ISSN:0913-5685

    詳細を見る 詳細を閉じる

    本稿では、スピン注入型磁性体メモリの最新動向と多値スピン注入RAM(MLC-SPRAM)について述ペる。2つの直列接続した磁気トンネル接合を用いてメモリセルを構成することで、その磁化反転による抵抗変化の組み合わせにより4レべルの抵抗値、すなわち2bit/cellを実現した。多値化のための必要条件は、2つのSPRAM素子が互いに平面面積のみ異なっていればよい。書き換え・読み出し動作としては、2段階のシーケンスを用いる方式を考案した。また、セルサイズ設計の一例を述べ、4F^2/bitが見込めることを示した。

  10. 依頼講演 Fabrication of a nonvolatile lookup-table circuit chip using magneto/semiconductor-hybrid structure for an immediate-power-up field programmable gate array (集積回路)

    鈴木 大輔, 夏井 雅典, 池田 正二, 長谷川 晴弘, 三浦 勝哉, 早川 純, 遠藤 哲郎, 大野 英男, 羽生 貴弘

    電子情報通信学会技術研究報告. ICD, 集積回路 110 (9) 47-52 2010年4月15日

    出版者・発行元:一般社団法人電子情報通信学会

    ISSN:0913-5685

    詳細を見る 詳細を閉じる

    本稿では,磁気トンネル接合素子(MTJ:Magnetic Tunnel Junction)素子特性を活用することで, FPGA (Field-Programmable Gate Array)におけるLUT (lookup table)演算機能と不揮発性記憶機能を一体化させた回路を提案する.提案回路は電流モード論理に基づき構成され, MTJ素子の記憶に応じた電流値の変化を直接論理値として扱うことが可能である.したがって,演算結果のみを増幅して出力すればよく,結果としてコンパクトな回路を実現可能である.実際,提案方式により設計された2入力LUT試作チップでは従来CMOS方式と比較して2/3の素子数削減を達成している.

  11. 強磁性半導体における磁壁の電流駆動

    千葉 大地, 山ノ内 路彦, 松倉 文[ヒロ], 大野 英男

    まぐね = Magnetics Japan 4 (8) 390-395 2009年8月1日

    出版者・発行元:日本磁気学会

    ISSN:1880-7208

  12. 22aWB-7 強磁性半導体(Ga,Mn)Asにおける磁壁のクリープ運動(実験)(微小領域磁性,領域3,磁性,磁気共鳴)

    松倉 文礼, 山ノ内 路彦, 大野 英男

    日本物理学会講演概要集 62 (2) 452-452 2007年8月21日

    出版者・発行元:一般社団法人日本物理学会

    ISSN:1342-8349

  13. 積層フェリ自由層トンネル磁気抵抗効果素子を備えたSPRAMのリードディスターブ耐性と書き込み電流のばらつきの低減

    三浦 勝哉, 河原 尊之, 竹村 理一郎, 早川 純, 山ノ内 路彦, 池田 正二, 佐々木 龍太郎, 伊藤 顕知, 高橋 宏昌, 松岡 秀行, 大野 英男

    電子情報通信学会技術研究報告. SDM, シリコン材料・デバイス 107 (194) 135-138 2007年8月16日

    出版者・発行元:一般社団法人電子情報通信学会

    ISSN:0913-5685

    詳細を見る 詳細を閉じる

    磁性体メモリの一つであるSPin-transf torque RAM(SPRAM)は,高速動作,低電力化が可能な不揮発メモリとして期待されている.SPRAMはメモリセルとして,MgO障壁層を備えたトンネル磁気抵抗(TMR)素子を用いる.このTMR素子は,自由層に用いる磁性体の熱安定性を大きくすることによって,読み出しの際の誤書き込み(ディスターブ)および書き込み電流のばらつきを低減することができる.熱安定性の大きいと期待される積層フェリ(SyF)自由層を用いた場合,他の構造と比べて読み出しディスターブと書き込み電流のばらつきがともに抑制されており,読み出しと書き込み動作が安定化することが明らかとなった.さらに,syF自由層の記録保持時間,読み出し電流,読み出し時間の関係を調査した結果,1.5ns以下の高速な読み出しが可能であることがわかった.

  14. 強磁性半導体における磁壁と伝導

    千葉大地, 山之内路彦, 松倉文礼, T. Dietl, 大野英男

    固体物理 42 (2) 99-106 2007年2月

    出版者・発行元:アグネ技術センタ-

    ISSN:0454-4544

    詳細を見る 詳細を閉じる

    通研インポート200703

  15. (Ga,Mn)As・(In,Mn)Asにおける磁性の電界制御

    千葉 大地, 松倉 文礼, 大野 英男

    日本応用磁気学会研究会資料 150 29-34 2006年10月18日

    ISSN:1340-7562

  16. Electrical magnetization reversal in ferromagnetic III-V semiconductors

    D. Chiba, F. Matsukura, H. Ohno

    JOURNAL OF PHYSICS D-APPLIED PHYSICS 39 (13) R215-R225 2006年7月

    出版者・発行元:IOP PUBLISHING LTD

    DOI: 10.1088/0022-3727/39/13/R01  

    ISSN:0022-3727

    詳細を見る 詳細を閉じる

    Introduction of a high concentration of manganese in III-V semiconductors, such as InAs and GaAs, results in carrier-induced ferromagnetism, which allows us to integrate ferromagnetism in nonmagnetic heterostructures and which modifies their magnetic properties through electric-field control of carrier concentration. The properties of ferromagnetism can in many cases be semi-quantitatively understood by the p-d Zener model, which is qualitatively different from conventional ferromagnetic metals. These ferromagnetic III-V semiconductors also offer the unique opportunity of examining spin-dependent phenomena observed so far only in metallic systems. Here, we review our experimental study on electrical manipulation of magnetization in these ferromagnetic III-V semiconductors. We first describe the results of electrically assisted magnetization reversal in ferromagnetic semiconductor (In, Mn) As field-effect transistor structures. The coercivity as well as ferromagnetic transition temperature can be controlled through the modification of carrier concentration by applied electric fields in a gated structure. We then present electrical magnetization reversal by spin-transfer torque exerted by spin-polarized currents at low threshold current density (similar to 10(5) A cm(-2)) in (Ga, Mn) As-based magnetic tunnel junctions.

  17. 注入層のドーピング濃度がInAs量子カスケードレーザーの特性に及ぼす影響

    大西 秀和, 森安 嘉貴, 大谷 啓太, 大野 英男

    電子情報通信学会技術研究報告. ED, 電子デバイス 105 (629) 49-52 2006年2月23日

    出版者・発行元:一般社団法人電子情報通信学会

    ISSN:0913-5685

    詳細を見る 詳細を閉じる

    InAs/AlSb量子カスケードレーザーの注入層におけるドーピング濃度がレーザーの特性に及ぼす影響について検討した。InAs量子カスケードレーザーには、短波長化に伴い動作電界が大きくなると高電界効果によってホールが生成され、ゲインが減少するという問題がある。そこで我々は動作電界を小さくするために注入層のドーピング濃度を上げる方法に注目した。エレクトロルミネッセンスの測定結果から、注入層のドーピング濃度を上げることで動作電界が減少し、ホールの生成が抑えられることがわかった。また注入層のドーピング濃度と閾値電流密度の温度依存性及び最高動作温度について検討した。

  18. (Ga, Mn)As MTJにおけるスピン注入磁化反転

    千葉 大地, 北 智洋, 山ノ内 路彦, 松倉 文〓, 大野 英男

    日本応用磁気学会研究会資料 145 7-12 2006年1月30日

    ISSN:1340-7562

  19. 強磁性半導体トンネル接合におけるスピン注入磁化反転

    千葉 大地, 松倉 文礼, 大野 英男

    日本応用磁気学会誌 = JOURNAL OF THE MAGNETICS SOCIETY OF JAPAN 29 (5) 514-522 2005年5月1日

    出版者・発行元:日本応用磁気学会

    ISSN:0285-0192

    詳細を見る 詳細を閉じる

    Electrical magnetization reversal in the absence of magnetic fields is attracting great interest on account of its potential the application to high-density magnetic memories. Experimental confirmations of the theoretical predictions of current-driven magnetization reversal due to spin-transfer torque exerted by spinpolarized currents have mostly been carried out on metal CPP-GMR structures. The critical current density J_c required for magnetization reversal in these systems is of the order of 10^7 A/cm^2 or even higher, and its reduction is a current focus of research. In this article, we demonstrate current-driven magnetization reversal in a ferromagnetic semiconductor system, a (Ga, Mn)As/GaAs/(Ga, Mn)As magnetic tunnel junction (MTJ), at J_c=1-2×10^5 A/cm^2. The basic properties of (Ga, Mn)As itself and its MTJ are also described.

  20. 27aYP-5 強磁性半導体保磁力パターニング構造における電流誘起磁壁移動(主題:磁性ナノ構造における電流誘起磁壁移動,領域3シンポジウム,領域3(磁性,磁気共鳴))

    山ノ内 路彦, 千葉 大地, 松倉 文礼, 大野 裕三, 大野 英男

    日本物理学会講演概要集 60 (1) 481-481 2005年3月4日

    出版者・発行元:一般社団法人日本物理学会

    ISSN:1342-8349

  21. 27pXJ-7 半導体へのスピン注入(領域3シンポジウム : スピン注入現象の新展開)(領域3)

    好田 誠, 大野 裕三, 松倉 文, 大野 英男

    日本物理学会講演概要集 59 (1) 465-465 2004年3月3日

    出版者・発行元:一般社団法人日本物理学会

    ISSN:1342-8349

  22. 30pWD-5 III-V 族強磁性半導体とそのヘテロ構造ベースのデバイス創製

    松倉 文礼, 千葉 大地, 篁 耕司, 大野 英男

    日本物理学会講演概要集 58 (1) 464-464 2003年3月6日

    出版者・発行元:一般社団法人日本物理学会

    ISSN:1342-8349

  23. 7pWA-5 強磁性半導体を用いた非磁性半導体へのスピン注入(主題:強磁性体/半導体ヘテロ接合・界面におけるスピン偏極電子伝導,領域3,領域4合同シンポジウム,領域4)

    大野 裕三, 好田 誠, 篁 耕司, 松倉 文〓, 大野 英男

    日本物理学会講演概要集 57 (2) 576-576 2002年8月13日

    出版者・発行元:一般社団法人日本物理学会

    ISSN:1342-8349

  24. 磁性/非磁性半導体ヘテロ構造におけるスピン注入

    大野 裕三, 大野 英男

    日本応用磁気学会誌 = Journal of Magnetics Society of Japan 25 (7) 1355-1360 2001年7月1日

    出版者・発行元:日本応用磁気学会

    ISSN:0285-0192

    詳細を見る 詳細を閉じる

    Injection and probing of spin-polarized currents in ferromagnetic/nonmagnetic semiconductor pn junctions are reviewed. A ferromagnetic p-type semiconductor (Ga, Mn)As layer, which produces a spinpolarized hole current, is grown on i-GaAs/i-(In, Ga)As quantum well (QW)/n-GaAs to form pn junction light emitting diode structures. The electroluminescence spectra and their polarization are measured at temperatures from 5 K to above the ferromagnetic transition temperature (T_c) of (Ga, Mn)As with or without magnetic fields. The EL polarization as a function of the magnetic field exhibits clear hysteresis below T_c, which is considered to be evidence that a spin-polarized electrical current is injected into nonmagnetic semiconductors.

  25. 28aTB-2 希薄磁性半導体GaMnAsの磁場下における遠赤外吸収スペクトル

    永井 康之, 長坂 啓吾, 野尻 浩之, 本河 光博, 松倉 文礼, 大野 英男

    日本物理学会講演概要集 56 (1) 607-607 2001年3月9日

    出版者・発行元:一般社団法人日本物理学会

    ISSN:1342-8349

  26. 半導体スピントロニクス素子・材料のスピン制御 (強誘電体メモリとスピントロニクス素子)

    大野 裕三, 大野 英男

    FEDジャ-ナル 12 (2) 29-32 2001年

    出版者・発行元:新機能素子研究開発協会

    ISSN:0918-2772

  27. 強磁性半導体を用いたスピン偏向発光ダイオード

    大野 裕三, 大野 英男

    光学 29 (12) 734-739 2000年12月10日

    出版者・発行元:応用物理学会分科会日本光学会

    ISSN:0389-6625

  28. 22aK-5 希薄磁性半導体GaMnAsにおける遠赤外吸収スペクトルの温度変化II

    永井 康之, 長坂 啓吾, 野尻 浩之, 本河 光博, 松倉 文礼, 大野 英男

    日本物理学会講演概要集 55 (1) 562-562 2000年3月10日

    出版者・発行元:一般社団法人日本物理学会

    ISSN:1342-8349

  29. 24aC-8 希薄磁性半導体GaMnAsにおける遠赤外吸収スペクトルの温度変化

    永井 康之, 長坂 啓吾, 野尻 浩之, 本河 光博, 松倉 文〓, 大野 英男

    日本物理学会講演概要集 54 (2) 588-588 1999年9月3日

    出版者・発行元:一般社団法人日本物理学会

    ISSN:1342-8349

  30. 24aC-3 希薄磁性半導体(Ga, Mn)Asの磁区構造観察

    庄野 知至, 福村 知昭, 松倉 文礼, 大野 英男, 長谷川 哲也

    日本物理学会講演概要集 54 (2) 587-587 1999年9月3日

    出版者・発行元:一般社団法人日本物理学会

    ISSN:1342-8349

  31. k・p摂動法による(Ga,Mn)Asバンド構造の計算

    秋葉教充, 松倉文礼, 大野裕三, DIETL T, 大野英男

    応用物理学会学術講演会講演予稿集 60th (3) 1999年

  32. 強磁性半導体(Ga,Mn)Asとそのヘテロ接合の物性 (文部省S)

    大野英男, 大野裕三, WANG S, 秋葉教充, 岸本修也, 寺内亮太, 安達太郎, 大宮忠志, 中田健一

    スピン制御による半導体超構造の新展開 平成10年度研究成果報告書 スピン制御半導体 研究成果報告会論文集 1999年

  33. III-V族希薄磁性半導体(In,Mn)Asの電流磁気効果

    大岩顕, 家泰弘, 勝本信吾, 遠藤彰, 大野英男, 宗片比呂夫

    物性研だより 35 (3) 1995年

    ISSN:0385-9843

︎全件表示 ︎最初の5件までを表示

書籍等出版物 11

  1. 半導体ストレージ2012

    羽生貴弘, 池田正二, 杉林直彦, 笠井直記, 遠藤哲郎, 大野英男

    日経BP社 2011年7月29日

  2. Semiconductors and Semimetals, (Spintronics)

    T. Dietl, D. Awschalom, M. Kaminska, H. Ohno

    Elsevier Academic Press 2008年11月

  3. Semiconductors and Semimetals (Spintronics)

    T. Dietl, D. Awschalom, M. Kaminska, H. Ohno

    Elsevier Academic Press 2008年10月

    ISBN: 9780080449562

  4. Surface kinetics and mechanism of atomic layer epitaxy of GaAs using trimethylgallium

    H. Ohno

    1997年

  5. 物性科学辞典(分担執筆)

    大野英男

    1996年

  6. III-V族化合物半導体

    大野英男

    1994年

  7. 先端デバイス材料ハンドブック

    大野英男

    1993年

  8. 薄膜作成ハンドブック

    大野英男

    1991年

  9. 超高速化合物半導体デバイス

    大野英男

    1986年

  10. 化合物半導体デバイス

    生駒俊明, 大野英男

    1984年

  11. Field-effect transistors

    H. Ohno, J. Barnard

    1982年

︎全件表示 ︎最初の5件までを表示

講演・口頭発表等 821

  1. Spintronics Gateway to Green Society –For smarter, longer, and less - 招待有り

    H. Ohno

    World Materials Forum (online) 2021年6月19日

  2. Spintronics a Gateway to Green Society 招待有り

    H. Ohno

    2021 Spintronics Workshop on LSI (online) 2021年6月13日

  3. What Spintronics Tells You About Future Information Processing 招待有り

    H. Ohno

    NSF Future of Semiconductors and Beyond Workshop, Materials, Devices, and Integration (online) 2021年3月2日

  4. Spintronics nanodevice – From SMALL to SMART 招待有り

    H. Ohno

    6th International Conference on Nanoscience and Nanotechnology (ICONN 2021) (online) 2021年2月1日

  5. Spintronics Nanodevice – How small can we make it and what else can we use it for 招待有り

    H. Ohno

    On-line SPICE-SPIN+X Seminars (online) 2020年9月20日

  6. Spintronics Device – Scaling to Single Digit nm and More 招待有り

    H. Ohno

    78th Device Research Conference (DRC) (online) 2020年6月22日

  7. Nano Spintronics Devices –From Digital to Bio-inspired Computing- 国際会議

    International Symposium for Bio-Convergence Spin System 2017年2月9日

  8. Nano Spintronics Devices for Integrated Circuit Applications 国際会議

    International Conference on Magnetic Materials and Applications (ICMAGMA-2917) 2017年2月1日

  9. Spin on Integrated Circuits: An Emerging Feld of Spintronics 国際会議

    Conference on 90 Years of Quantum Mechanics 2017年1月23日

  10. High-speed & external-magnetic-field free spin-orbit switching devices for VLSI 国際会議

    8th MRAM Global Innovation Forum 2016年10月26日

  11. Two-and three terminal spintronics devices for VLSI-progress in spin-orbit-torque devices 国際会議

    Nanomaterials 2016, International Workshop and School on Spin Transfer 2016年9月23日

  12. Spin-orbit switching of magnetization 国際会議

    2nd Marie Curie School on Domain Walls and Spintronics 2016年9月12日

  13. Spintronics devices for nonvolatile VLSI

    40th Annual Conference on Magnetics in Japan 2016年9月5日

  14. Nanoscale Spintronics Devices 国際会議

    16th International Conference on Nanotechnology (IEEE NANO) 2016年8月22日

  15. Spintronics Nano-Devices for VLSI Integration 国際会議

    8th Joint European Magnetics Symposium (JEMS2016) 2016年8月21日

  16. Spintronics Nano-Devices for VLSIs Applications 国際会議

    20th Int. Vacuum Congress (IVC-20) 2016年8月21日

  17. Three-Terminal Spintronics Devices for CMOS Integration 国際会議

    The 4th International Conference of Asian Union of Magnetics Societies (ICAUMS 2016) 2016年8月1日

  18. Spintronics I 国際会議

    IEEE Magnetic Society Summer School 2016年7月10日

  19. Spintronics II 国際会議

    IEEE Magnetic Society Summer School 2016年7月10日

  20. Three-Terminal Spintronics Devices for VLSI 国際会議

    International Union of Materials Research Societies-International Conference on Electronic Materials (IUMRS-ICEM 2016) 2016年7月4日

  21. Spintronics nano-devices for VLSIs 国際会議

    Nothwestern University Materials Science and Engineering Seminar 2016年6月30日

  22. Spin-orbit torque switching of magnetization 国際会議

    University of Chicago IME Seminar 2016年6月28日

  23. Matreial Efficiency: The case of devices for IoT 国際会議

    World Materials Forum 2016年6月9日

  24. Nano spintronics devices for CMOS integration 国際会議

    5th International Conference Smart and Multifunctional Materials, Structures and Systems (CIMTEC) 2016年6月5日

  25. Spintronics nano-devices for VLSIs 国際会議

    5th International Conference on Superconductivity and Magnetism (ICSM) 2016年4月24日

  26. Efficiency of spintronics nanodevices 国際会議

    Spintronics Meeting in Lanna 2016年3月30日

  27. 垂直磁気異方性CoFeB-MgO磁気トンネル接合の高速中性子耐性評価(III)

    成田克, 高橋豊, 原田正英, 大井元貴, 及川健一, 小林大輔, 廣瀬和之, 佐藤英夫, 池田正二, 遠藤哲郎

    第63回応用物理学会春季学術講演会、 2016年3月19日

  28. Electric-field effect on domain structure in MgO/CoFeB/Ta

    T. Dohi, S. Kanai, A. Okada, S. Fukami, F. Matsukura

    第63回応用物理学会春季学術講演会、 2016年3月19日

  29. Spin-orbit torque induced magnetization switching in W/CoFeB/MgO

    C. Zhang, S. Fukami, S. DuttaGupta, H. Sato, F. Matsukura

    第63回応用物理学会春季学術講演会、 2016年3月19日

  30. Dot size dependence of magnetization switching by spin-orbit torque in antiferromagnet/ferromagnet structures

    A. Kurenkov, C. Zhang, S. Fukami, S. DuttaGupta

    第63回応用物理学会春季学術講演会、 2016年3月19日

  31. スピントロニクス最前線-集積回路応用を中心に

    電子デバイス界面テクノロジー研究会 2016年1月22日

  32. Control of the skyrmion structure in a nano disk by electric field pulses at room temperature 国際会議

    Y. Nakatani, S. Kanai, S. Fukami, M. Hayashi

    13th Joint MMM-Intermag Conference 2016年1月11日

  33. Current induced magnetization switching of CoFeB/Ta/[Co/Pd(Pt)]-multilayer in magnetic tunnel junctions with perpendicular anisotropy 国際会議

    S. Ishikawa, H. Sato, S. Fukami, F. Matsukura

    13th Joint MMM-Intermag Conference 2016年1月11日

  34. Electric field control of magnetism and magnetization switching in CoFeB-MgO 国際会議

    S. Kanai, Y. Nakatani, H. Sato, F. Matsukura

    13th Joint MMM-Intermag Conference 2016年1月11日

  35. Optimum boron composition difference between single and double CoFeB/MgO interface perpendicular magnetic tunnel junctions (MTJs) with high thermal tolerance and its mechanism 国際会議

    H. Honjo, H. Sato, S. Ikeda, S. Sato, T. Watanabe, S. Miura, T. Natsuno, Y. Noguchi, M. Yasuhira, T. Tanigawa, H. Koike, M. Muraguchi, M. Niwa, K. Ito, T. Endoh

    13th Joint MMM-Intermag Conference 2016年1月11日

  36. Dependence of magnetic properties of CoFeB-MgO on buffer layer materials 国際会議

    K. Watanabe, H. Sato, S. Fukami, F. Matsukura

    13th Joint MMM-Intermag Conference 2016年1月11日

  37. 強磁性体の電界制御とその記録素子応用

    金井駿, 仲谷栄伸, 岡田篤, 佐藤英夫, 松倉文礼

    第20回スピン工学の基礎と応用(PASPS-20) 2015年12月3日

  38. Ta/CoFeB/MgO構造における磁気異方性とダンピング定数の電気的制御 国際会議

    岡田篤, 橋本祥斉, 金井駿, 松倉文礼

    第20回スピン工学の基礎と応用(PASPS-20) 2015年12月3日

  39. Magnetization Switching in Ta/CoFeB/MgO Nanodot Driven by Spin-Orbit Torque

    C. Zhang, S. Fukami, H. Sato, F. Matsukura

    第20回スピン工学の基礎と応用(PASPS-20) 2015年12月3日

  40. CoFeB/MgO垂直磁化容易磁気トンネル接合における電界誘起非線形強磁性共鳴

    平山絵里子, 金井駿, 大江純一郎, 佐藤英夫, 松倉文礼

    第20回スピン工学の基礎と応用(PASPS-20) 2015年12月3日

  41. Perpendicular Anisotropy and Damping Constant of Single and Double CoFeB-MgO Interface Structures with Various CoFeB Thicknesses

    E. C. I. Enobio, H. Sato, S. Fukami, F. Matsukura

    第20回スピン工学の基礎と応用(PASPS-20) 2015年12月3日

  42. (Ga,Mn)As:Liの面内異方性磁気抵抗効果の温度依存性

    都澤章平, 陳林, 松倉文礼

    第20回スピン工学の基礎と応用(PASPS-20) 2015年12月3日

  43. Spi-Orbit Torque Switching for Three-Terminal Spintronics Devices 国際会議

    S. Fukami, C. Zhang, S. DuttaGupta, A. Kurenkov

    13th RIEC International Workshop on Spintronics 2015年11月18日

  44. Different Universality Classes for Current and Field Driven Domain Wall Creep in a Magnetic Metal 国際会議

    S. DuttaGupta, S. Fukami, C. Zhang, H. Sato, M. Yamanouchi, F. Matsukura

    13th RIEC International Workshop on Spintronics 2015年11月18日

  45. Layer Thicknesses and Annealing Condition Dependence of Magnetic Properties of CoFeB-MgO Structure 国際会議

    K. Watanabe, H. Sato, S. Fukami, F. Matsukura

    13th RIEC International Workshop on Spintronics 2015年11月18日

  46. Temperature Dependence of Magnetotransport Properties in (Ga,Mn)As: Li 国際会議

    S. Miyakozawa, L. Chan, F. Matsukura

    13th RIEC International Workshop on Spintronics 2015年11月18日

  47. Magnetization Switching via Spin-Orbit Torque in Nano-Scale Ta/CoFeB/MgO 国際会議

    C. Zhang, S. Fukami, H. Sato, F. Matsukura

    13th RIEC International Workshop on Spintronics 2015年11月18日

  48. A Three-Terminal Spin-Orbit Torque Device with a New Configuration 国際会議

    T. Anekawa, C. Zhang, S. Fukami

    13th RIEC International Workshop on Spintronics 2015年11月18日

  49. Electrical Modulation of Damping Constant in Ta/CoFeB/MgO with Perpendicular Easy Axis 国際会議

    A. Okada, Y. Hashimoto, S. Kanai, F. Matsukura

    13th RIEC International Workshop on Spintronics 2015年11月18日

  50. CoFeB Thickness Dependence of Damping Constant for Single and Double CoFeB-MgO Interface Structures 国際会議

    E. C. I. Enobio, H. Sato, S. Fukami, F. Matsukura

    13th RIEC International Workshop on Spintronics 2015年11月18日

  51. Spintronics materials and devices for nonvolatile CMOS VLSIs 国際会議

    16th RIES-Hokudai International Symposium 2015年11月10日

  52. Improving the Sensitivity of Vector-Network-Analyzer Ferromagnetic Resonance Measurement by Varying the Coplanar Waveguide Size 国際会議

    E. C. I. Enobio, H. Sato, S. Fukami, F. Matsukura

    2015 International Conference on Applied Materials and Optical Systems (ICAMOS) 2015年10月22日

  53. Spintronics Nano-Devices for Nonvolatile VLSIs 国際会議

    Electronic and Photonics Workshop 2015年10月15日

  54. Challenge of MTJ-based Nonvolatile Logic-Memory Architecture for Ultra Low-Power and Highly Dependable VLSI Computing 国際会議

    T. Hanyu, M. Natsui, D. Suzuki, A. Mochizuki, N. Onizawa, S. Ikeda, T. Endoh

    IEEE SOI-3D-Subthreshold Microelectronics Technology Unifield Conference 2015年10月5日

  55. Properties of Perpendicular-Anistropy Magnetic Tunnel Junctions with Single and Double CoFeB-MgO Interface 国際会議

    H. Sato, E. C. I, Enobio, S. Fukami, F. Matsukura

    6th Annual Conference on Magnetics 2015年10月2日

  56. Nonvolatile VLSI Made Possible by Spintronics 国際会議

    4th Winton Symposium 2015年9月28日

  57. Optimization of CoFeB Capping Layer Thickness for Characterization of Leakage Spot in MgO Tunneling Barrier of Magnetic Tunnel Junction 国際会議

    H. Sato, H. Honjo, S. Ikeda, H. Ohno, T. Endoh, M. Niwa

    2015 International Conference on Solid State Devices and Materials (SSDM) 2015年9月27日

  58. A600-μ W Ultroa-Low-Power Associative Processor for Image Pattern Recognition Employing Magnetic Tunnel Junction (MTJ) Based Nonvolatile Memories with Novel Intelligent Power-Gating (|IPG) Scheme 国際会議

    Y. Ma, S. Miura, H. Honjo, S. Ikeda, T. Hanyu, T. Shibata, T. Endoh

    2015 International Conference on Solid State Devices and Materials (SSDM) 2015年9月27日

  59. Spintronics Memory Devices for Ultralow-Power and High-performance Integrated Circuits 国際会議

    S. Fukami, H. Sato

    2015 International Conference on Solid State Devices and Materials (SSDM) 2015年9月27日

  60. Spintronics Nano-Devices for Nonvolatile VLSIs 国際会議

    12th Sweden-Japan QNANO Workshop 2015年9月24日

  61. Wire Width Depencence of Current-Induced Domain Wall Motion Properties

    T. Iwabuchi, S. Fukami

    第76回応用物理学会秋季学術講演会 2015年9月13日

  62. Pulse Width Dependence of a Spin-Orbit Torque Induced Magnetization Switching

    T. Anekawa, C. Zhang, S. Fukami

    第76回応用物理学会秋季学術講演会 2015年9月13日

  63. In-Plane Aspect Ratio Dependence of Thermal Stability and Intrinsic Critical Current in CoFeB/MgO Magnetic Tunnel Junctions with Perpendicular Anisotropy

    E. Hirayama, S. Kanai, H. Sato, F. Matsukura

    第76回応用物理学会秋季学術講演会 2015年9月13日

  64. CoFeB Thickness Dependence of Electric-Field Effects on Magnetic Anistropy and Damping Constant in Ta/CoFeB/MgO Structures

    A. Okada, Y. Hashimoto, S. Kanai, F. Matsukura

    第76回応用物理学会秋季学術講演会 2015年9月13日

  65. Spin-Orbit Torque Induced Switching in an Antiferromgnet/Ferromagnet Heterostructure

    S. Fukami, C. Zhang, S. DuttaGupta

    第76回応用物理学会秋季学術講演会 2015年9月13日

  66. Temperature Dependence of In-Plane Anistropic Magnetoresistance in (Ga, Ma)As:Li

    S. Miyakozawa, L. Chen, F. Matsukura

    第76回応用物理学会秋季学術講演会 2015年9月13日

  67. Switching Characteristics of CoFeB-MgO Magnetic Tunnel Junctions in the ns Reqime

    N. Ohshima, S. Kubota, H. Sato, S. Fukami, F. Matsukura

    第76回応用物理学会秋季学術講演会 2015年9月13日

  68. Magnetization Reversal Induced by Spin-Orbit Torque in a Nanoscale Ta/CoFeB/MgO Dot

    C. Zhang, S. Fukami, H. Sato, F. Matsukura

    第76回応用物理学会秋季学術講演会 2015年9月13日

  69. 垂直磁気異方性CoFeB-MgO磁気トンネル接合の高速中性子耐性評価(II)

    成田克, 高橋豊, 原田正英, 大井元貴, 及川健一, 小林大輔, 廣瀬和之, 石川慎也, E. C. I. Enobio, 佐藤英夫, 池田正二, 遠藤哲郎

    第76回応用物理学会秋季学術講演会 2015年9月13日

  70. Spin-Orbit Torque Induced Magnetization Switching for Three-Terminal Spintronics Devices 国際会議

    S. Fukami

    2nd Spin Waves and Interactions 2015年9月9日

  71. dc-bias Depencence of Ferromagnetic Resonance Spectra of a CoFeB-MgO based Magnetic Tunnel Junction 国際会議

    S. Kanai, M. Gajek, D. C. Worledge, F. Matsukura

    International School and Conference (SPINTECH VIII) 2015年8月10日

  72. Nano-Spintronics Devices for VLSI Integration 国際会議

    Spin Dynamics in Nanostructures, Gordon Research Conference (GRC) 2015年7月26日

  73. Effect of Li Codoping on In-Plane Uniaxial Magnetic Anisotropy in (Ga,Mn)As 国際会議

    S. Miyakozawa, L. Chen, F. Matsukura

    21st International Conference on Electronic Properties of Two-Dimensional Systems and 17th International Conference on Modulated Semiconductor Structures, (EP2DS-21/MSS-17) 2015年7月26日

  74. 電界による強磁性金属薄膜の磁気特性の変調

    岡田篤

    平成27年度ナノ・スピン実験施設研究発表会 2015年7月23日

  75. ナー共添加が強磁性半導体の諸特性に与える影響

    都澤章平

    平成27年度ナノ・スピン実験施設研究発表会 2015年7月23日

  76. 磁化ダイナミクスを利用したナノ磁性体の特性評価

    平山絵里子

    平成27年度ナノ・スピン実験施設研究発表会 2015年7月23日

  77. Temperature Dependence of Intrinsic Critical Current of CoFeB-MgO Magnetic Tunnel Junctions with Perpendicular Easy Axis 国際会議

    Y. Takeuchi, E. C. I. Enobio, H. Sato, S. Fukami, F. Matsukura

    Internationa Colloquium on Magnetic Films and Survaces (ICMFS) 2015年7月12日

  78. Width Dependence of Threshold Current Density for Domain Wall Motion in Co/Ni Wire

    T. Iwabuchi, S. Fukami

    34th Electronic Materials Symposium (EMS) 2015年7月8日

  79. Junction Size Dependence of Switching Current in CoFeB-MgO Magnetic Tunnel Junctions with Perpendicular Easy Axis

    N. Ohshima, S.Kubota, H. Sato, S. Fukami, F. Matsukura

    34th Electronic Materials Symposium (EMS) 2015年7月8日

  80. Building Blocks of Artificial Square Spin Ice: Stray-Field Studies of Thermal Dynamics and Tuned Interactions 国際会議

    M. Pohlit, F. Porrati, M. Huth, Y. Ohno, J. Muller

    20th International Conference on Magnetism (ICM) 2015年7月5日

  81. Ultra-High Frequency Tunability in Low-Current and Low-Field Spin Torque Oscillators based on Perpendicular Magnetic Tunnel Junctions 国際会議

    T. Le, A. Eklund, S. Chung, H. Mazraati, A. Nguyen, M. Yamanouchi, E. Enobio, S. Ikeda, J. Akerman

    20th International Conference on Magnetism (ICM) 2015年7月5日

  82. Spin-Orbit Torque Switching in a Ferromagnet / Antiferromagnet Bilayer System 国際会議

    S. Fukami, C. Zhang, S. DuttaGupta

    20th International Conference on Magnetism (ICM) 2015年7月5日

  83. Spin-Orbit Torque Induced Magnetization Switching in Ta/CoFeB/MgO Heterostructure with a Diameter Down to 30 nm 国際会議

    C. Zhang, S. Fukami, H. Sato, F. Matsukura

    20th International Conference on Magnetism (ICM) 2015年7月5日

  84. Spintronics for Stand-by Power Free VLSI 国際会議

    8th International Conference on Materials for Advanced Technologies and 16th IUMRS International Conference in Asia (ICMAT2015-IUMRS-ICA2015) 2015年6月28日

  85. Nanoscale Spintronics Materials and Devices 国際会議

    8th International Conference on Materials for Advanced Technologies and 16th IUMRS International Conference in Asia (ICMAT2015-IUMRS-ICA2015) 2015年6月28日

  86. Electric-Field Dependence of Magnetic Anisotropy and Damping Constant in Ta/CoFeB/MgO Structures 国際会議

    A. Okada, Y. Hashimoto, S. Kanai, F. Matsukura

    8th International Conference on Materials for Advanced Technologies and 16th IUMRS International Conference in Asia (ICMAT2015-IUMRS-ICA2015) 2015年6月28日

  87. Vector Network Analyzer –Ferromagnetic Resonance Measurements on CoFeB-MgO Stack with Perpendicular Easy Axis 国際会議

    E. C. Enobio, H. Sato, S. Fukami, F. Matsukura

    8th International Conference on Materials for Advanced Technologies and 16th IUMRS International Conference in Asia (ICMAT2015-IUMRS-ICA2015) 2015年6月28日

  88. Toward Ultra-Low Power Microprocessor Using Spintronics Technology 国際会議

    1st ImPACT International Symposium on Spintronic Memory, Circuit and Storage 2015年6月21日

  89. 10nmφ Perpendicular-Anistropy CoFeB-MgO Magnetic Tunnel Junctions with Over 400℃ High Thermal Tolerance by Boron Diffusion Control 国際会議

    H. Honjo, H. Sato, S. Ikeda, S. Sato, T. Watanabe, S. Miura, T. Nasuno, Y. Noguchi, M. Yasuhira, T. Tanigawa, H. Koike, M. Muraguchi, M. Niwa, K. Ito, T. Endoh

    2015 Symposium on VLSI Technology and Circuits 2015年6月15日

  90. Fabrication of a 3000-6-Input-LUTs Embedded and Block-Level Power-Gated Nonvolatile FPGA Chip Using p-MTJ-Based Logic-in-Memory Structure 国際会議

    D. Suzuki, M. Natsui, A. Mochizuki, S. Miura, H. Honjo, H. Sato, S. Fukami, S. Ikeda, T. Endoh, T. Hanyu

    2015 Symposium on VLSI Technology and Circuits 2015年6月15日

  91. Properties of CoFeB-MgO Magnetic Tunnel Junctions with Perpendicular Easy Axis for Spintronics Based VLSI Applications 国際会議

    H. Sato, Y. Takeuchi, N. Ohshima, S. Kubota, M. Yamanouchi, S. Ikeda, S. Fukami, F. Matsukura

    2015 Spintronics Workshop on LSI 2015年6月15日

  92. Nanoscale Magnetic Tunnel Junction 国際会議

    York-Tohoku-Kaiserslautern Symposium on New-Concept Spintronics Devices 2015年6月11日

  93. Domain Wall Creep Driven by Adiabatic Spin Transfer Torque in Magnetic Metals 国際会議

    S. DuttaGupta

    York-Tohoku-Kaiserslautern Symposium on New-Concept Spintronics Devices 2015年6月11日

  94. 強磁性薄膜における電界効果と磁気ダイナミクス

    金井駿, 仲谷栄伸, 岡田篤, 松倉文礼

    第54回スピントロニクス専門研究会「スピンの電界制御の現状と将来展望」 2015年6月10日

  95. Nano-Scale Magnetic Tunnel Junction Materials and Devices –Toward Nonvolatile VLSI- 国際会議

    International Conference on Spin Physics, Spin Chemistry and Spin Technology 2015年6月1日

  96. Nanoscale Magnetic Tunnel Junction 国際会議

    5th STT-MRAM Global Innovation Forum 2015年5月27日

  97. Spintronic Nano-Devices for Nonvolatile VLSIs 国際会議

    Frontiers in Quantum Materials and Devices Workshop and Tohoku-Harvard Workshop 2015年5月21日

  98. Nanoscale Magnetic Tunnel Junction –Materials Science and Device Physics- 国際会議

    Intel Seminar 2015年5月19日

  99. Nanoscale Magnetic Tunnel Junction –Materials Science and Device Physics 国際会議

    Intel Seminar 2015年5月19日

  100. 1T1MTJ STT-MRAM Cell Array Design with an Adaptive Reference Voltage Generator for Improving Device Variation Tolerance 国際会議

    H. Koike, S. Miura, H. Honjo, T. Watanabe, H. Sato, S. Sato, T. Nasuno, Y. Noguchi, M. Yasuhira, T. Tanigawa, M. Muraguchi, M. Niwa, K. Ito, S. Ikeda, T. Endoh

    International Memory Workshop (IMW) 2015年5月17日

  101. Proposal and Demonstration of a New Spin-Orbit Torque Induced Switching Device 国際会議

    S. Fukami, T. Anekawa, C. Zhang

    International Magnetic Conference (INTERMAG) 2015年5月11日

  102. Three-Terminal Spointronics Memory Devices with Perpendicular Anistropy 国際会議

    S. Fukami

    International Magnetic Conference (INTERMAG) 2015年5月11日

  103. Diffusion Behaviors Observed on the Surface of CoFeB Film after the Natural Oxidation and the Annealing 国際会議

    S. Sato, H. Honjo, S. Ikeda, T. Endoh, M. Niwa

    International Magnetic Conference (INTERMAG) 2015年5月11日

  104. Diffusion Behaviors Observed on the Surface of CoFeB Film after the Natural Oxidation and the Annealing 国際会議

    S. Sato, H. Honjo, S. Ikeda, T. Endoh, M. Niwa

    International Magnetic Conference (INTERMAG) 2015年5月11日

  105. 不揮発ロジックインメモリアーキテクチャとその低電力VLSIシステムへの応用

    羽生貴弘, 鈴木大輔, 望月明, 夏井雅典, 鬼沢直哉, 杉林直彦, 池田正二, 遠藤哲郎

    電子情報通信学会・集積回路研究会 2015年4月17日

  106. 磁場および電流によって制御された磁壁発信器

    平松亮, K. K.Jin, 谷口卓也, 東野隆之, 森山貴広, 深見俊輔, 山ノ内路彦, 仲谷栄伸, 小野輝男

    第70回日本物理学会春季年次大会 2015年3月21日

  107. Spintronics Devices for Integrated Circuits – An Overview 国際会議

    1st CIES Technology Forum 2015年3月19日

  108. 垂直磁気異方性CoFeB-MgO磁気トンネル接合の高速中性子耐性評価

    Narita

    第62回応用物理学会学術講演会 2015年3月11日

  109. 新規3端子スピン軌道トルク素子の動作実証

    T. Anekawa

    第62回応用物理学会学術講演会 2015年3月11日

  110. 垂直磁気異方性CoFeB-MgO磁気トンネル接合における閾値電流の温度依存性

    Y. Takeuchi

    第62回応用物理学会学術講演会 2015年3月11日

  111. dc Bias Voltage Dependence of Magnetic Anisotropy in CoFeB/MgO Investigated by Electric Field-Induced Ferromagnetic Resonance

    S. Kanai

    第62回応用物理学会学術講演会 2015年3月11日

  112. Universality Classes for Current-and Field-Induced Domain Wall Creep in a Ta/CoFeB/MgO/Ta Wire

    S. DuttaGupta

    第62回応用物理学会学術講演会 2015年3月11日

  113. Device size Dependence of Switching Current for Magnteization Reversal Induced by Spin-Orbit Torque in Ta/CoFeB/MgO Structures Down to 30nm

    C. Zhang

    第62回応用物理学会学術講演会 2015年3月11日

  114. Ferromagnetic Resonance Induced Electrical Signals in Pt/(Ga,Mn)As

    H. Nakayama

    第62回応用物理学会学術講演会 2015年3月11日

  115. rf Power Dependence of Homodyne-Detected Ferromagnetic Resonance Spectra of a CoFeB/MgO Magnetic Tunnel Junction

    E. Hirayama

    第62回応用物理学会学術講演会 2015年3月11日

  116. Temperature Dependent Direction of in-plane Uniaxial Magnetic Anisotropy in (Ga,Mn)As Codoped with Li

    S. Miyakozawa

    第62回応用物理学会学術講演会 2015年3月11日

  117. AlInAs/GaInAsから強磁性半導体GaMnAsまで

    第62回応用物理学会学術講演会 2015年3月11日

  118. 先端スピントロニクス素子・材料のブレークスルーと評価技術

    SPRUC分野融合型研究ワークショップ「新たな分野融合型研究の開拓に向けて」 2015年2月19日

  119. Nanoscale Magnetic Tunnel Junction 国際会議

    Nanyang Technological University Seminar 2014年12月18日

  120. 磁気ランダムアクセスメモリ(MRAM)の最新技術動向

    小池洋紀, 池田正二, 羽生貴弘, 大野英男, 遠藤哲郎

    第60回CVD研究会 2014年12月18日

  121. 東北大学におけるスピントロニクス

    東北大学電気通信研究所共同プロジェクト研究S「スピントロニクス学術研究基礎と連携ネットワーク構築に向けて」 2014年12月17日

  122. Temperature dependence of in-plane magnetic anisotropy in (Ga,Mn)As codoped with Li

    S. Miyakozawa

    19th Physics and Applications of Spin-related Phenomena in Semiconductors (PASPS-19) 2014年12月15日

  123. DC voltages in Pt/(Ga,Mn)As under ferromagnetic resonance

    H. Nakayama

    19th Physics and Applications of Spin-related Phenomena in Semiconductors (PASPS-19) 2014年12月15日

  124. Challenge of MOS/MTJ-Hybrid Nonvolatile Logic-in Memory Architecture in Dark-Silicon Era 国際会議

    T. Hanyu

    2014 International Electron Devices Meeting (IEDM) 2014年12月15日

  125. Perpendicular-Anisotropy CoFeB-MgO Based Magnetic Tunnel Junctions Scaling Down to 1X nm 国際会議

    S. Ikeda

    2014 International Electron Devices Meeting (IEDM) 2014年12月15日

  126. ナノデバイス科学からの放射光への期待

    大野英男, 松倉文礼

    東北大学金属材料研究所共同利用ワークショップ「3GeV中型高輝度放射光(SLiT-J)の実現に向けて」 2014年12月15日

  127. Properties of Nanoscale Magnets Investigated by Homodyne-Detected Ferromagnetic Resonance

    E. Hirayama, S. Kanai, H. Sato, F. Matsukura, H. Ohno

    8th High-Tech Research Center Symposium, “New Frontiers in Functional Materials” 2014年12月6日

  128. Korea University Special Seminar 国際会議

    Korea University Special Seminar 2014年12月4日

  129. 面内磁化容易3端子スピン軌道トルク素子の反転電流

    T. Anekawa

    第69回応用物理学会東北支部学術講演会 2014年12月4日

  130. Pt/(Ga,Mn)As構造における強磁性共鳴下の直流電圧信号

    H. Nakayama

    第69回応用物理学会東北支部学術講演会 2014年12月4日

  131. MgO/CoFeB/Ta積層膜の磁気特性のCoFeBおよびTa膜厚依存性

    K Watanabe

    第69回応用物理学会東北支部学術講演会 2014年12月4日

  132. ize Dependence of Magnetic Properties of Nanoscale CoFeB/MgO Magnetic Tunnel Junctions

    E. Hirayama, S. Kanai, H. Sato, F. Matsukura, H. Ohno

    応用物理学会東北支部大会Student Chapter 2014年12月2日

  133. Temperature Dependence of Thermal Stability Factor of CoFeB-MgO Perpendicular-Anisotropy

    Y. Takeuchi, S. Ishikawa, H. Sato, M. Yamanouchi, S. Ikeda, S. Fukami, F. Matsukura, H. Ohno

    応用物理学会東北支部大会Student Chapter 2014年12月2日

  134. Magnetic Tunnel Junctions with CoFeB/Ta/[Co/Pt] Multilayer Ferromagnetic Electode

    S. Ishikawa, H. Sato, M. Yamanouchi, S. Ikeda, S. Fukami, F. Matsukura, H. Ohno

    応用物理学会東北支部大会Student Chapter 2014年12月2日

  135. Nano-scale magnetic tunnel junction for nonvolatile VLSIs 国際会議

    2nd Internaional Symposium on Functionality of Organized Nanostructures 2014 (FON14) 2014年11月26日

  136. Spintronics materials and devices for nonvolatile VLSIs 国際会議

    1st International Symposium on Interactive Materials Science Cadet Program (iSIMSC) 2014年11月16日

  137. 微細スピントロニクス素子

    平成26年度東北大学電気通信研究所共同プロジェクト研究会「非平衡スピン・ゆらぎの精緻な制御と観測による新規ナノデバイスの開拓研究」 2014年11月13日

  138. Domain wall creep in Ta/CoFeB/MgO wire induced by current field 国際会議

    S. DuttaGupta

    59th Annual Magnetism and Magnetic Materials Conference (MMM) 2014年11月3日

  139. In-plane magnetic field angle dependence of ferromagnetic resonance frequency in a nanoscale CoFeB-MgO magnetic tunnel junction 国際会議

    E. Hirayama

    59th Annual Magnetism and Magnetic Materials Conference (MMM) 2014年11月3日

  140. Device size dependence of magnetization reversal by spin-orbit torque in Ta/CoFeB/MgO structure down to sub 100 nm 国際会議

    C. Zhang

    59th Annual Magnetism and Magnetic Materials Conference (MMM) 2014年11月3日

  141. Intrinsic critical current and thermal stability factor of MgO/CoFeB/Ta/CoFeB/MgO recording structure scaling down to 11 nm 国際会議

    H. Sato

    59th Annual Magnetism and Magnetic Materials Conference (MMM) 2014年11月3日

  142. ナノデバイス科学からの期待

    日本学術会議公開シンポジウム「中型高輝度放射光源に期待するこれからの科学技術」 2014年10月31日

  143. Spintronics – recent advances 国際会議

    4th imec-Stanford International Workshop on Resistive Memories 2014年10月27日

  144. Three-Terminal Nonvolatile Spintronics Memory Device using Spin-Transfer Torque and Spin-Orbit Torque 国際会議

    S. Fukami

    14th Non-Volatile Memory Technology Symposium (NVMTS 2014) 2014年10月27日

  145. Three-Terminal Spintronics Devices for Nonvolatile Memory and Logic 国際会議

    S. Fukami

    11th International Conference on Flow Dynamics (ICFD) 2014年10月8日

  146. スピントロニクス-電界制御と界面効果を中心に-

    新学術領域「超低速ミュオン顕微鏡が拓く物質・生命・素粒子科学のフロンティア」領域会議 2014年9月23日

  147. Spintronic Nano-Devices for Nonvolatile VLSIs 国際会議

    1st University of Chicago/AIMR Joint Research Center Workshop 2014年9月18日

  148. Magnetic anisotropy in Ta/CoFeB/MgO investigated by x-ray magnetic circular dichroism and first-principles calculation

    H. Kanai

    第75回応用物理学会秋季学術講演会 2014年9月17日

  149. Junction size dependence of intrinsic critical current and thermal stability factor of MgO/CoFeB/Ta/CoFeB/MgO recording structure

    H. Sato

    第75回応用物理学会秋季学術講演会 2014年9月17日

  150. In-plane anisotropy in a CoFeB-MgO magnetic tunnel junction detected by magnetoresistance

    E. Hirayama

    第75回応用物理学会秋季学術講演会 2014年9月17日

  151. Modulation of spin precession frequency by spin relaxation anisotropy in a (110) GaAs/AlGaAs quantum wall

    A. Aoki, J. Nitta

    第75回応用物理学会秋季学術講演会 2014年9月17日

  152. Thermal stability and critical current for domain wall motion in nanowire

    S. Fukami

    第75回応用物理学会秋季学術講演会 2014年9月17日

  153. Device size dependence of magnetization switching by spin-orbit torque in Ta/CoFeB/MgO structure

    C. Zhang

    第75回応用物理学会秋季学術講演会 2014年9月17日

  154. Current and field induced domain wall creep in Ta/CoFeB/MgO/Ta wire

    S. DuttaGupta

    第75回応用物理学会秋季学術講演会 2014年9月17日

  155. Thermal stability and threshold current of nanoscale magnetic tunnel junctions 国際会議

    International Workshop on Nanomaterials (M-SNOWS) 2014年9月8日

  156. In-Plane Anisotropy of a CoFeB-MgO Magnetic Tunnel Junction with Perpendicular Magnetic Easy Axis 国際会議

    E. Hirayama

    International Conference on Solid State Devices and Materials (SSDM) 2014年9月8日

  157. Dependence of Magnetic Properties of MgO/CoFeB/Ta Stacks on CoFeB and Ta Thicknesses 国際会議

    K. Watanabe

    International Conference on Solid State Devices and Materials (SSDM) 2014年9月8日

  158. Properties of Perpendicular-Anisotropy Magnetic Tunnel Junctions Fabricated over The Cu Via 国際会議

    S. Miura

    International Conference on Solid State Devices and Materials (SSDM) 2014年9月8日

  159. A Power-Gated 32bit MPU with a Power Controller Circuit Activated by Deep-Sleep-Mode Instruction Achieving Ultra-Low-Power Operation 国際会議

    H. Koike

    International Conference on Solid State Devices and Materials (SSDM) 2014年9月8日

  160. Switching Current and Thermal Stability of Perpendicular Magnetic Tunnel Junction with MgO/CoFeB/Ta/CoFeB/MgO Recording Structure Scaling Down to IX nm 国際会議

    H. Sato

    International Conference on Solid State Devices and Materials (SSDM) 2014年9月8日

  161. A 500ps/8.5ns Array Read/Werite Latency 1MB Twin ITIMTJ STT-MRAM designed in 90 nm CMOS/40 nm MTJ Process with Novel Positive Feedback S/A Circuit 国際会議

    T. Ohsawa

    International Conference on Solid State Devices and Materials (SSDM) 2014年9月8日

  162. 最先端研究開発支援プログラム(FIRST)「省エネルギー・スピントロニクス論理集積回路の研究開発」での論理集積回路研究について

    革新的研究開発推進プログラム(ImPACT)[無充電で長時間使用できる究極のエコIT機器の実現」 2014年8月28日

  163. スピントロニクスと集積回路 日の丸半導体復活への道

    産学連携セミナー・寺子屋せんだい 2014年8月25日

  164. Properties of CoFeB-MgO magnetic tunnel junctions down to 11nm 国際会議

    SPIE NanoScience +Engineering 2014年8月19日

  165. The effect of electric-field on damping constant of ferromagnetic semiconductor (Ga,Mn)As 国際会議

    L. Chen

    32nd International Conference on the Physics of Semiconductors (ICPS) 2014年8月10日

  166. From compound semiconductors to spintronics 国際会議

    Lester Eastman Conference on High Performance Devices 2014年8月5日

  167. Magnetic domain wall motion and spin-orbit torque induced magnetization switching for three-terminal spintronics devices 国際会議

    S. Fukami

    IEEE International Nanoelectronics Conference (INEC) 2014年7月28日

  168. Spintronics for VLSI 国際会議

    8th International Conference on the Physics and Applications of Spin Phenomena in Solids (PASPS 8) 2014年7月28日

  169. Spintronics for nonvolatile VLSIs 国際会議

    Tsukuba Nanotechnology Symposium (TNS’14) 2014年7月25日

  170. Magnetization reversal mode switching and its application

    S. Kanai

    33rd Electronic Materials Symposium (EMS-33) 2014年7月9日

  171. Ferromagnetic resonance spectra of CoFeB-MgO magnetic tunnel junction measured by homodyne detection

    E. Hirayama

    33rd Electronic Materials Symposium (EMS-33) 2014年7月9日

  172. CoFeB and Ta capping layer thicknesses dependence of magnetic properties for MgO/CoFeB/Ta stacks

    K. Watanabe

    33rd Electronic Materials Symposium (EMS-33) 2014年7月9日

  173. Current induced domain wall motion in Co/Ni wires for nonvolatile memories and logic circuits 国際会議

    S. Fukami

    12th RIEC International Workshop on Spintronics 2014年6月25日

  174. Current induced spin orbit torques and chiral magnetic texture in magnetic heterostructures 国際会議

    M. Hayashi

    12th RIEC International Workshop on Spintronics 2014年6月25日

  175. Magnetization switching induced by electric field 国際会議

    S. Kanai

    12th RIEC International Workshop on Spintronics 2014年6月25日

  176. In-plane current-induced effective fields and magnetization switching in Ta/CoFeB/MgO structures 国際会議

    C. Zhang

    12th RIEC International Workshop on Spintronics 2014年6月25日

  177. Current and field induced domain wall creep in Ta/CoFeB/MgO wire 国際会議

    S. Duttagupta

    12th RIEC International Workshop on Spintronics 2014年6月25日

  178. Electrical detection and control of magnetization dynamics in (Ga,Mn)As 国際会議

    L. Chen

    12th RIEC International Workshop on Spintronics 2014年6月25日

  179. Temperature dependence of thermal stability factor in CoFeB-MgO magnetic tunnel junction 国際会議

    Y. Takeuchi

    12th RIEC International Workshop on Spintronics 2014年6月25日

  180. MgO cap thickness dependence of interfacial anisotropy of MgO/FeB/MgO structure 国際会議

    Y. Horikawa

    12th RIEC International Workshop on Spintronics 2014年6月25日

  181. High thermal stability of magnetic tunnel junction with CoFeB/Ta/[Co/Pt] multilayer ferromagnetic electrode 国際会議

    S. Ishikawa

    12th RIEC International Workshop on Spintronics 2014年6月25日

  182. In-plane anisotropy in CoFeB magnetic tunnel junction 国際会議

    E. Hirayama

    12th RIEC International Workshop on Spintronics 2014年6月25日

  183. dc voltage measured in Py/ZnO bilayer under ferromagnetic resonance 国際会議

    S. D'Ambrosio

    12th RIEC International Workshop on Spintronics 2014年6月25日

  184. Current status and prospects of magnetoresistive random access memory technology 国際会議

    6th Forum on New Materials (CIMTEC 2014) 2014年6月15日

  185. Material stack design with high tolerance to process induced damage in domain wall motion device 国際会議

    H. Honjo

    IEEE International Magnetics Conference (INTERMAG) 2014年5月4日

  186. Temperature dependence of current induced spin-orbit torques 国際会議

    J. Kim

    IEEE International Magnetics Conference (INTERMAG) 2014年5月4日

  187. Thermal stability and critical current for domain wall motion in nanowires with reduced dimensions 国際会議

    S. Fukami

    IEEE International Magnetics Conference (INTERMAG) 2014年5月4日

  188. Thermal stability and critical current for domain wall motion in nanowires with reduced dimensions 国際会議

    J. Torrejon

    IEEE International Magnetics Conference (INTERMAG) 2014年5月4日

  189. Three-terminal spintronics cells for high-speed and nonvolatile VLSIs 国際会議

    N. Sakimura

    IEEE International Magnetics Conference (INTERMAG) 2014年5月4日

  190. 強磁性金属薄膜における電流誘起有効磁場の膜厚依存性

    河口真志

    日本物理学会秋季大会 2014年3月27日

  191. Ta and CoFeB thickness dependence of sheet resistance in Ta/CoFeB/MgO heterostructures

    C. Zhang

    第61回応用物理学会春季学術講演会 2014年3月17日

  192. 電流誘起磁壁移動素子のしきい電流と熱安定性の素子サイズ依存性

    S. Fukami

    第61回応用物理学会春季学術講演会 2014年3月17日

  193. スピントロニクス技術を用いた論理集積回路

    第61回応用物理学会春季学術講演会 2014年3月17日

  194. 電界誘起磁化ダイナミクスの実時間観測

    S. Kanai

    第61回応用物理学会春季学術講演会 2014年3月17日

  195. Ferromagnetic resonance spectra of CoFeB-MgO magnetic tunnel junctions measured by homodyne detection

    E. Hirayama

    第61回応用物理学会春季学術講演会 2014年3月17日

  196. CoFeB/Ta/[Co/Pd]強磁性電極を用いた磁気トンネル接合

    S. Ishikawa

    第61回応用物理学会春季学術講演会 2014年3月17日

  197. Current-induced switching properties under perpendicular magnetid field magnetic tunnel junctions with perpendicular magnetic easy axis

    ハンジャン

    第61回応用物理学会春季学術講演会 2014年3月17日

  198. MgO/FeB/MgO積層膜における磁気異方性の上部MgO層厚依存性

    堀川喜久

    第61回応用物理学会春季学術講演会 2014年3月17日

  199. Two-barrier stability that allows low-power operation in current-induced domain-wall

    K. J. Kim

    第61回応用物理学会春季学術講演会 2014年3月17日

  200. Current induced domain wall creep in Ta/CoFeB/MgO/Ta wire

    S. Duttagupta

    第61回応用物理学会春季学術講演会 2014年3月17日

  201. Electric field effects on Li codoped (Ga,Mn)As

    S. Miyakozawa

    第61回応用物理学会春季学術講演会 2014年3月17日

  202. Temperature dependence of electric-field on magnetic properties of Ta/CoFeB/MgO structures investigated by ferromagnetic resonance

    A. Okada

    第61回応用物理学会春季学術講演会 2014年3月17日

  203. Magnetization switching by two successive voltage pulses

    S. Kanai

    第61回応用物理学会春季学術講演会 2014年3月17日

  204. Spintronics: Materials throuth devices to integrated circuits 国際会議

    International Meeting on Spintronics for Integrated Ciucuits Applications and Beyond 2014年3月13日

  205. Nanoscale magnetic tunnel junction 国際会議

    American Physical Society, March Meeting 2014年3月3日

  206. スピントロニクスが拓く新しい集積回路の世界

    平成25年度最先端研究開発戦略的強化事業・最先端研究開発支援プログラムFIRST EXPO 2014年2月28日

  207. A90nm 20MHz fully nonvolatile microcontroller for standby-power-critical applications 国際会議

    N. Sakimura

    International Solid-State Circuits Conference (ISSCC) 2014年2月22日

  208. Electric-field modulation of damping constant in (Ga,Mn)As 国際会議

    L. Chen

    AIMR International Symposium 2014 (AMIS) 2014年2月17日

  209. ZnO as a spintronics material 国際会議

    S. D'Ambrosio

    AIMR International Symposium 2014 (AMIS) 2014年2月17日

  210. スピントロニクスが拓く新しい集積回路の世界

    FIRST研究成果ビジネスマッチングシンポジウム --日本の電子産業、復活の狼煙(のろし)-- 2014年1月22日

  211. Advances in spintronics devices for microelectronics –from spin-transfer torque 国際会議

    S. Fukami

    19th Asia and South Pacific Design Automation Conference (ASP-DAC) 2014年1月20日

  212. スピントロニクス

    北海道学力向上推進事業・札幌南高等学校講演会 2014年1月5日

  213. スピントロニクス素子と材料 -磁気トンネル接合の最近の進展-

    顕微ナノ材料研究会 2013年12月26日

  214. Magnetic property of Li codoped (Ga,Mn)As

    S. Miyakozawa, L. Chen, F. Matsukura, H. Ohno

    Physics and Applications of Spin-related Phenomena in Semiconductors (PASPS-18) 2013年12月9日

  215. Temperature dependence of electric-field effects on magnetic anisotropies in Ta-CoFeB-MgO

    A. Okada, S. Kanai, M. Yamanouchi, S. Ikeda, F. Matsukura, H. Ohno

    Physics and Applications of Spin-related Phenomena in Semiconductors (PASPS-18) 2013年12月9日

  216. 20-nm magnetic domain wall motion memory with ultralow-power operation 国際会議

    S. Fukami, M. Yamanouchi, K.-J. Kim, T. Suzuki, N. Sakimura, D. Chiba, S. Ikeda, T. Sugibayashi, N. Kasai, T. Ono, H. Ohno

    2013 IEEE International Electron Devices Meeting (IEDM) 2013年12月9日

  217. Comprehensive study of CoFeB-MgO magnetic tunnel junction characteristics with single- and double-interface scaling down to 1X nm 国際会議

    H. Sato, T. Yamamoto, M. Yamanouchi, S. Ikeda, S. Fukami, K. Kinoshita, F. Matsukura, N. Kasai, H. Ohno

    2013 IEEE International Electron Devices Meeting (IEDM) 2013年12月9日

  218. 垂直磁化容易CoFeB-MgO磁気トンネル接合における電流誘起磁化反転の面内磁場依存性

    久保田修司, 山ノ内路彦, 佐藤英夫, 池田正二, 松倉文礼, 大野英男

    応用物理学会東北支部講演会 2013年12月5日

  219. MgO/Fe(B)/MgO積層膜の磁気特性

    堀川喜久, 石川慎也, 池田正二, 佐藤英夫, 山ノ内路彦, 深見俊輔, 松倉文礼, 大野英男

    応用物理学会東北支部講演会 2013年12月5日

  220. Three-terminal magnetic domain wall motion device for spintronics VLSIs 国際会議

    S. Fukami, H. Ohno

    International Japanese-French Workshop on Spintronics 2013年11月27日

  221. Cuベースチャネル3端子磁気トンネル接合

    山ノ内路彦, 陳林, 金俊延, 林将光, 佐藤英夫, 深見俊輔, 池田正二, 松倉文礼, 大野英男

    応用物理学会スピントロニクス研究会・日本磁気学会スピンエレクトロニクス専門研究会共同主催研究会「元素戦略、環境調和を視野に入れたスピントロニクスの新展開」 2013年11月11日

  222. Material Status and Outlook of STT-Based Memory Technology 国際会議

    58th Magnetism and Magnetic Materials (MMM) 2013年11月4日

  223. Distribution of critical current density for magnetic domain wall motion 国際会議

    S. Fukami, M. Yamanouchi, K. J. Kim, T. Koyama, D. Chiba, S. Ikeda, N. Kasai, T. Ono, H. Ohno

    58th Magnetism and Magnetic Materials (MMM) 2013年11月4日

  224. Magnetization reversal induced by in-plane current in Ta/CoFeB/MgO structures with perpendicular magnetic easy axis 国際会議

    C. Zhang, M. Yamanouchi, H. Sato, S. Fukami, S. Ikeda, F. Matsukura, H. Ohno

    58th Magnetism and Magnetic Materials (MMM) 2013年11月4日

  225. Co/Pt multilayer-based magnetic tunnel junctions with thin Ta spacer layer 国際会議

    S. Ishikawa, H. Sato, M. Yamanouchi, S. Ikeda, S. Fukami, F. Matsukura, H. Ohno

    58th Magnetism and Magnetic Materials (MMM) 2013年11月4日

  226. Temperature dependence of thermal stability factor of CoFeB-MgO magnetic tunnel junctions with perpendicular easy-axis 国際会議

    H. Sato, Y. Takeuchi, K. Mizunuma, S. Ishikawa, M. Yamanouchi, S. Ikeda, S. Fukami, F. Matsukura, H. Ohno

    58th Magnetism and Magnetic Materials (MMM) 2013年11月4日

  227. Process induced damage by C-O based etching chemistries and its recovery for a CoFeB-MgO magnetic tunnel junction with perpendicular magnetic easy-axis 国際会議

    K. Kinoshita, H. Honjo, K. Tokutome, S. Miura, M. Murahata, K. Mizunuma, H. Sato, S. Fukami, S. Ikeda, N. Kasai, H. Ohno

    58th Magnetism and Magnetic Materials (MMM) 2013年11月4日

  228. Fabrication of a perpendicular-MTJ-Based compact nonvolatile programmable switch using shared-writecontrol-transistor structure 国際会議

    D. Suzuki, M. Natsui, A. Mochizuki, S. Miura, H. Honjo, K. Kinoshita, H. Sato, S. Fukami, S. Ikeda, T. Endoh, H. Ohno, T. Hanyu

    58th Magnetism and Magnetic Materials (MMM) 2013年11月4日

  229. Three-terminal magnetic tunneling junction device with perpendicular anisotropy CoFeB sensing layer 国際会議

    H. Honjo, S. Fukami, K. Ishihara, R. Nebashi, K. Kinoshita, K. Tokutome, M. Murahata, S. Miura, N. Sakimura, T. Sugibayashi, N. Kasai, H. Ohno

    58th Magnetism and Magnetic Materials (MMM) 2013年11月4日

  230. Analysis of single-event upset in MTJ/MOS-Hybrid circuits employing calculation of switching probability by radiation-induced corrent 国際会議

    N. Sakimura, R. Nebashi, M. Natsui, T. Hanyu, H. Ohno, T. Sugibayashi

    58th Magnetism and Magnetic Materials (MMM) 2013年11月4日

  231. MTJ resistance distribution of 1-kbit 1T-1MTJ STT-MRAM cell arrays fabricated on a 300-mm wafer 国際会議

    H. Koike, T. Ohsawa, S. Miura, H. Honjo, S. Ikeda, T. Hanyu, H. Ohno, T. Endoh

    58th Magnetism and Magnetic Materials (MMM) 2013年11月4日

  232. Trend of TMR and variation in Vth for keeping data load robustness of MOS/MTJ hybrid latches 国際会議

    T. Ohsawa, S. Ikeda, T. Hanyu, H. Ohno, T. Endoh

    58th Magnetism and Magnetic Materials (MMM) 2013年11月4日

  233. Two-barrier stability in current-induced domain-wall motion device 国際会議

    K. Kim, R. Hiramatsu, T. Koyama, K. Ueda, Y. Yoshimura, D. Chiba, K. Kobayashi, Y. Nakatani, S. Fukami, M. Yamanouchi, H. Ohno, H. Kohno, G. Tatara, T. Ono

    58th Magnetism and Magnetic Materials (MMM) 2013年11月4日

  234. Spintronics Devices for Nonvolatile CMOS VLSIs 国際会議

    150 years diplomatic relation Japan-Switzerland, Swiss-Japanese Nanoscience Workshop, Materials Phenomena at Small Scale 2013年10月9日

  235. Current-induced magnetic domain wall motion in Co/Ni wire and its application to nonvolatile memory devices 国際会議

    S. Fukami, H. Ohno

    150 years diplomatic relation Japan-Switzerland, Swiss-Japanese Nanoscience Workshop, Materials Phenomena at Small Scale 2013年10月9日

  236. 垂直磁化Co/Ni細線中の磁壁電流駆動におけるスピンホール効果の影響

    吉村瑶子, 小山知弘, 森山貴広, K. J. Kim, 千葉大地, 仲谷栄伸, 深見俊輔, 山ノ内路彦, 大野英男, 小野輝男

    日本物理学会秋季大会 2013年9月25日

  237. 強磁性金属薄膜における電流誘起有効磁場の直流ホール測定による決定

    河口真志, 島村一利, 深見俊輔, 松倉文礼, 大野英男, 森山貴広, 千葉大地, 小野輝男

    日本物理学会秋季大会 2013年9月25日

  238. Co/Pt multilayer based reference layers in magnetic tunnel junction for novolatile spintronics VLSIs 国際会議

    H. Sato, S. Ikeda, S. Fukami, H. Honjo, S. Ishikawa, M. Yamanouchi, K. Mizunuma, F. Matsukura, H. Ohno

    International Conference on Solid State Devices and Materials (SSDM) 2013年9月24日

  239. Properties of perpendicular-anisotropy magnetic tunnel junctions prepared by different MTJ etching process 国際会議

    S. Miura, H. Honjo, K. Tokutome, N. Kasai, S. Ikeda, T. Endoh, H. Ohno

    International Conference on Solid State Devices and Materials (SSDM) 2013年9月24日

  240. Mapping of photoexcited local spins in a modulation-doped GaAs/AlGaAs wires 国際会議

    J. Ishihara, Y. Ohno, H. Ohno

    International Conference on Solid State Devices and Materials (SSDM) 2013年9月24日

  241. A 4x4 nonvolatile multiplier using novel MTJ-CMOS hybrid latch and flip-flop 国際会議

    T. Ohsawa, S. Miura, H. Honjo, K. Kinoshita, S. Ikeda, T. Hanyu, H. Ohno, T. Endoh

    International Conference on Solid State Devices and Materials (SSDM) 2013年9月24日

  242. Strategy of STT-MRAM cell design and its power gating technique for low-voltage and low-power cache memoroes 国際会議

    T. Ohsawa, S. Ikeda, T. Hanyu, H. Ohno, T. Endoh

    International Conference on Solid State Devices and Materials (SSDM) 2013年9月24日

  243. Wide operational margin capability of 1kbit STT-MRAM array chip with 1-PMOS and 1-bottom-pin-MTJ type cell 国際会議

    H. Koike, T. Ohsawa, S. Miura, H. Honjo, S. Ikeda, T. Hanyu, H. Ohno, T. Endoh

    International Conference on Solid State Devices and Materials (SSDM) 2013年9月24日

  244. Demonstration of a nonvolatile processor core chip with software-controlled trhee-terminal MRAM cells for standby-power critical applications 国際会議

    R. Nebashi, Y. Tsuji, H. Honjo, N. Sakimura, A. Morioka, K. Tokutome, S. Miura, S. Fukami, M. Yamanouchi, K. Kinoshita, T. Hanyu, T. Endoh, N. Kasai, H. Ohno, T. Sugibayashi

    International Conference on Solid State Devices and Materials (SSDM) 2013年9月24日

  245. Studies on selective devices for spin-transfer-torque magnetic tunnel junctions 国際会議

    T. Ohsawa, S. Ikeda, T. Hanyu, H. Ohno, T. Endoh

    International Conference on Solid State Devices and Materials (SSDM) 2013年9月24日

  246. Tuneable chiral domain wall motion by intertwined spin Hall effect and spin transfer torque in ultrathin TaN/CoFeB/MgO 国際会議

    J. Torrejon, J. Kim, J. Sinha, S. Mitani, M. Hayashi, M. Yamanouchi, H. Ohno

    Donostia International Conference on Nanoscaled Magnetism and Applications (ICNMA) 2013年9月9日

  247. 反応性イオンエッチングを用いた磁気トンネル接合の作製

    山本直志, 佐藤英夫, 木下啓蔵, 池田正二, 大野英男

    第37回日本磁気学会学術講演会 2013年9月3日

  248. 垂直磁気異方性CoNi超格子膜の作製と磁気特性の評価

    深見俊輔, 佐藤英夫, 山ノ内路彦, 池田正二, 大野英男

    第37回日本磁気学会学術講演会 2013年9月3日

  249. Co/Ni細線における磁壁デピニング確率の測定と計算

    深見俊輔, 山ノ内路彦, 池田正二, 大野英男

    第37回日本磁気学会学術講演会 2013年9月3日

  250. 急峻なFe/GaAs(001)を介したスピン偏極電子の注入特性

    ルークフリート, 吉田健太, 小林裕臣, 金子雄基, 松坂俊一郎, 大野裕三, 大野英男, 本多周太, 井上順一郎, 廣畑貴文

    第37回日本磁気学会学術講演会 2013年9月3日

  251. Magnetic Tunnel Junction Technology: Materials and Performance 国際会議

    International Conference on Nanoscale Magnetism (ICNM) 2013年9月2日

  252. Introduction to Spintronics for Integrated Circuit Applications 国際会議

    7th International School and Conference on Spintronics and Quantum Information Technology 2013年7月29日

  253. Introduction to Spintronics for integrated circuit applications 国際会議

    J. Ishihara, Y. Ohno, H. Ohno

    7th International School and Conference on Spintronics and Quantum Information Technology (SPINTECH7) 2013年7月29日

  254. Wire width dependence of suppressed spin dephasing in modulation-doped GaAs/AlGaAs wires 国際会議

    J. Ishihara, Y. Ohno, H. Ohno

    7th International School and Conference on Spintronics and Quantum Information Technology (SPINTECH7) 2013年7月29日

  255. Two and three terminal non-volatile spintronics devices for VLSI applications 国際会議

    International Symposium on Advanced Magnetic Materials and Applications (ISAMMA) 2013年7月21日

  256. Electric-field induced magnetization switching in CoFeB-MgO with different magnetic field angles 国際会議

    S. Kanai, M. Yamanouchi, S. Ikeda, Y. Nakatani, F. Matsukura

    International Symposium on Advanced Magnetic Materials and Applications (ISAMMA) 2013年7月21日

  257. Electrical reliability of Co/Ni wire for domain wall motion devices 国際会議

    S. Fukami, M. Yamanouchi, H. Honjo, K. Kinoshita, K. Tokutome, S. Miura, S. Ikeda, N. Kasai

    International Symposium on Advanced Magnetic Materials and Applications (ISAMMA) 2013年7月21日

  258. Two and three terminal non-volatile spintronics devices for VLSI application 国際会議

    International Symposium on Advanced Magnetic Materials and Applications (ISAMMA) 2013年7月21日

  259. Liを共添加した(Ga,Mn)Asの作製と評価

    都澤章平, 陳林, 松倉文礼, 大野英男

    第32回電子材料シンポジウム(EMS32) 2013年7月10日

  260. Ta/CoFeB/MgO構造における磁気特性の電界効果の強磁性共鳴による検出

    岡田篤, 金井駿, 山ノ内路彦, 池田正二, 松倉文礼, 大野英男

    第32回電子材料シンポジウム(EMS32) 2013年7月10日

  261. 垂直磁気異方性CoFeB-MgO磁気トンネル接合のトンネル磁気抵抗特性の温度依存性

    竹内祐太郎, 水沼広太朗, 石川慎也, 佐藤英夫, 池田正二, 山ノ内路彦, 深見俊輔, 松倉文礼, 大野英男

    第32回電子材料シンポジウム(EMS32) 2013年7月10日

  262. Current status and prospect of magnetic tunnel junction 国際会議

    H. Ohno

    7th International Conference on Materials for Advanced Technologies (ICMAT) 2013年6月30日

  263. What we can learn from ferromagnetism in semiconductors 国際会議

    H. Ohno

    4th International Symposium on Organic and Inorganic Electronic Materials and Related Nanotechnologies (EM-NANO 2013) 2013年6月17日

  264. Fabrication of a 99%-Energy-Less Nonvolatile Multi-Functional CAM Chip Using Hierarchical Power Gating for a Massively-Parallel Full-Text-Search Engine 国際会議

    S. Matsunaga, N. Sakimura, R. Nebashi, Y. Tsuji, A. Morioka, T. Sugibayashi, S. Miura, H. Honjo, K. Kinoshita, H. Sato, S. Fukami, M. Natsui, A. Mochizuki, S. Ikeda, T. Endoh, H. Ohno, T. Endoh

    2013 Symposia on VLSI Circuits 2013年6月12日

  265. A 1.5nsec/2.1nsec Random Read/Write Cycle 1Mb STT-RAM Using 6T2MTJ Cell with Background Write for Nonvolatile e-Memories 国際会議

    T. Ohsawa, S. Miura, K. Kinoshita, H. Honjo, S. Ikeda, T. Hanyu, H. Ohno, T. Endoh

    2013 Symposia on VLSI Circuits 2013年6月12日

  266. Low-Current Domain Wall Motion MRAM with Perpendicularly Magnetized CoFeB/MgO Magnetic Tunnel Junction and Underlying Hard Magnets 国際会議

    T. Suzuki, H. Tanigawa, Y. Kobayashi, K. Mori, Y. Ito, Y. Ozaki, K. Suemitsu, T. Kitamura, K. Nagahara, E. Kariyada, N. Ohshima, S. Fukami, M. Yamanouchi, S. Ikeda, M. Hayashi, M. Sakao, H. Ohno

    2013 Symposia on VLSI Circuits 2013年6月12日

  267. Low-Current Domain Wall Motion MRAM with Perpendicularly Magnetized CoFeB/MgO Magnetic Tunnel Junction and Underlying Hard Magnets 国際会議

    T. Suzuki, H. Tanigawa, Y. Kobayashi, K. Mori, Y. Ito, Y. Ozaki, K. Suemitsu, T. Kitamura, K. Nagahara, E. Kariyada, N. Ohshima, S. Fukami, M. Yamanouchi, S. Ikeda, M. Hayashi, M. Sakao, H. Ohno

    2013 Symposia on VLSI Technology 2013年6月11日

  268. MgO/CoFeB/Ta/CoFeB/MgO recording structure with low critical current and high thermal stability 国際会議

    H. Sato, M. Yamanouchi, S. Ikeda, S. Fukami, F. Matsukura, H. Ohno

    JSPS York-Tohoku Symposium on Magnetic Materials and Spintronic Devices 2013年6月10日

    詳細を見る 詳細を閉じる

    H. Satoによる講演

  269. A 1-Mb STT-MRAM with Zero-Array Standby Power and 1.5-ns Quick Wake-Up by 8-b Fine-Grained Power Gating 国際会議

    T. Ohsawa, S. Ikeda, T. Hanyu, H. Ohno, T. Endoh

    5th IEEE International Memory Workshop (IMW) 2013年5月26日

  270. Quantitative determination of intrinsic energy barrier for current induced domain wall motion 国際会議

    K. J. Kim, R. Hiramatsu, T. Koyama, K. Ueda, Y. Yoshimura, D. Chiba, K. Kobayashi, Y. Nakatani, S. Fukami, M. Yamanouchi, H. Ohno, T. Ono

    The 8th International Symposium on Metallic Multilayers (MML2013) 2013年5月19日

  271. Influence of in-plane magnetic fields on current-induced domain wall motion in a perpendicularly magnetized Co/Ni nanowire 国際会議

    Y. Yoshimura, T. Koyama, D. Chiba, Y. Nakatani, S. Fukami, M. Yamanouchi, H. Ohno, T. Ono

    The 8th International Symposium on Metallic Multilayers (MML2013) 2013年5月19日

  272. Current-induced effective field vector in Ta│CoFeB│MgO with various layer thicknesses 国際会議

    J. Kim, J. Sinha, M. Hayashi, M. Yamanouchi, S. Fukami, T. Suzuki, S. Mitani, H. Ohno

    The 8th International Symposium on Metallic Multilayers (MML2013) 2013年5月19日

  273. Electric field effect on magnetic properties in Fe ultra-thin film 国際会議

    M. Kawaguchi, K. Shimamura, S. Ono, S. Fukami, F. Matsukura, H. Ohno, D. Chiba, T. Ono

    The 8th International Symposium on Metallic Multilayers (MML2013) 2013年5月19日

  274. Temperature dependence of spin polarization in Co/Ni nanowires with different Co and Ni thicknesses determined from magnetic domain wall dynamics 国際会議

    K. Ueda, R. Hiramatsu, D. Chiba, H. Tanigawa, T. Suzuki, S. Fukami, M. Yamanouchi, H. Ohno, Y. Nakatani, T. Ono

    The 8th International Symposium on Metallic Multilayers (MML2013) 2013年5月19日

  275. Monoatomically-layered CoNi film with perpendicular magnetic anisotropy 国際会議

    S. Fukami, H. Sato, M. Yamaguchi, S. Ikeda, H. Ohno

    The 8th International Symposium on Metallic Multilayers (MML2013) 2013年5月19日

  276. (Co100-xFex)80B20 composition dependence of interface anisotropy in MgO/CoFeB/Ta stack structure 国際会議

    H. Sato, R. Koizumi, S. Ikeda, M. Yamanouchi, F. Matsukura, H. Ohno

    The 8th International Symposium on Metallic Multilayers (MML2013) 2013年5月19日

  277. Quantitative determination of intrinsic energy barrier for current induced domain wall motion 国際会議

    K. J. Kim, R. Hiramatsu, T. Koyama, K. Ueda, Y. Yoshimura, D. Chiba, K. Kobayashi, Y. Nakatani, S. Fukami, M. Yamanouchi, H. Ohno, T. Ono

    8th International Symposium on Metallic Multilayers (MML2013) 2013年5月19日

  278. Influence of in-plane magnetic fields on current-induced domain wall motion in a perpendicularly magnetized Co/Ni nanowire 国際会議

    Y. Yoshimura, T. Koyama, D. Chiba, Y. Nakatani, S. Fukami, M. Yamanouchi, H. Ohno, T. Ono

    8th International Symposium on Metallic Multilayers (MML2013) 2013年5月19日

  279. Current-induced effective field vector in Ta│CoFeB│MgO with various layer thicknesses 国際会議

    J. Kim, J. Sinha, M. Hayashi, M. Yamanouchi, S. Fukami, T. Suzuki, S. Mitani, H. Ohno

    8th International Symposium on Metallic Multilayers (MML2013) 2013年5月19日

  280. Electric field effect on magnetic properties in Fe ultra-thin film 国際会議

    M. Kawaguchi, K. Shimamura, S. Ono, S. Fukami, F. Matsukura, H. Ohno, D. Chiba, T. Ono

    8th International Symposium on Metallic Multilayers (MML2013) 2013年5月19日

  281. Temperature dependence of spin polarization in Co/Ni nanowires with different Co and Ni thicknesses determined from magnetic domain wall dynamics 国際会議

    K. Ueda, R. Hiramatsu, D. Chiba, H. Tanigawa, T. Suzuki, S. Fukami, M. Yamanouchi, H. Ohno, Y. Nakatani, T. Ono

    8th International Symposium on Metallic Multilayers (MML2013) 2013年5月19日

  282. Monoatomically-layered CoNi film with perpendicular magnetic anisotropy 国際会議

    S. Fukami, H. Sato, M. Yamaguchi, S. Ikeda, H. Ohno

    8th International Symposium on Metallic Multilayers (MML2013) 2013年5月19日

  283. (Co100-xFex)80B20 composition dependence of interface anisotropy in MgO/CoFeB/Ta stack structure 国際会議

    H. Sato, R. Koizumi, S. Ikeda, M. Yamanouchi, F. Matsukura, H. Ohno

    8th International Symposium on Metallic Multilayers (MML2013) 2013年5月19日

  284. 不揮発性集積回路応用に向けた CoFeB-MgO磁気トンネル接合の開発状況

    池田正二, 佐藤英夫, 山ノ内路彦, 深見俊輔, 水沼広太朗, 金井駿, 石川慎也, 松倉文礼, 笠井直記, 大野英男

    独立行政法人 日本学術振興会 先端ナノデバイス・材料テクノロジー第151委員会 平成25年度 第1回研究会「最先端スピンデバイスと新しいスピン制御技術」 2013年5月9日

  285. Ta|CoFe|MgOにおける電流誘起実効磁場

    金俊延, J. Sinha, 林将光, 山ノ内路彦, 深見俊輔, 鈴木哲広, 三谷誠司, 大野英男

    第60回応用物理学会春季学術講演会 2013年3月27日

  286. CoFeB-MgO垂直磁化容易磁気トンネル接合における反転閾値電流密度の素子サイズ依存性

    水沼広太朗, 山ノ内路彦, 佐藤英夫, 池田正二, 松倉文礼, 大野英男

    第60回応用物理学会春季学術講演会 2013年3月27日

  287. 変調ドープ(001)GaAs/AlGaAs細線における電子スピンダイナミクスの細線幅依存性

    石原淳, 大野裕三, 大野英男

    第60回応用物理学会春季学術講演会 2013年3月27日

  288. CoFeB-MgO接合における電界誘起磁化スイッチングの磁界角度依存性

    金井駿, 山ノ内路彦, 池田正二, 仲谷栄伸, 松倉文礼, 大野英男

    第60回応用物理学会春季学術講演会 2013年3月27日

  289. Co/Pt多層膜とCoFeBの積層膜を用いたMgO障壁磁気トンネル接合

    石川慎也, 佐藤英夫, 山ノ内路彦, 池田正二, 深見俊輔, 松倉文礼, 大野英男

    第60回応用物理学会春季学術講演会 2013年3月27日

  290. Enhanced interface perpendicular magnetic anisotropy in nitrogen doped Ta underlayer with CoFeB|MgO

    ジャンバルダン・シンハ, 林将光, 小塚雅也, 山ノ内路彦, 深見俊輔, 三谷誠司, 宝野和博, 大野英男

    第60回応用物理学会春季学術講演会 2013年3月27日

  291. 3端子磁壁移動デバイスの開発

    深見俊輔, 山ノ内路彦, 池田正二, 大野英男

    第60回応用物理学会春季学術講演会 2013年3月27日

  292. 非対称な膜構成を持つ強磁性金属薄膜における異常磁気抵抗効果

    河口真志, 島村一利, 深見俊輔, 松倉文礼, 大野英男, 千葉大地, 小野輝男

    日本物理学会第68回年次大会 2013年3月26日

  293. Helicity-dependent photocurrent in a (110) GaAs quantum well stack 国際会議

    D.C.Schmadel, M. –H. Kim, A. B. Sushkov, G. S. Jenkins, J. D. Koralek, J. E. Moore, J. Orenstein, Y. Ohno, H. Ohno, H. D. Drew

    American Physical Society, March Meeting 2013年3月18日

  294. スピントロニクス材料・デバイス基盤技術の創出

    伊藤公平, 吉田博, 大野英男

    東北大学電気通信研究所平成24年共同プロジェクト研究発表会 2013年2月28日

  295. 半導体量子ナノ構造の電子・核スピン物性の研究

    石原淳, 大野裕三, 大野英男

    東北大学電気通信研究所平成24年共同プロジェクト研究発表会 2013年2月28日

  296. Spintronics makes CMOS VLSI nonvolatile 国際会議

    5th Int. Symp. on Advanced Plasma Science and its Applications for Nitrides and Nanomaterials (ISPlasma) 2013年1月28日

  297. Physics and Materials of Perpendicular CoFeB-MgO Magnetic Tunnel Junction 国際会議

    Tohoku-Harvard Joint Workshop 2013年1月15日

  298. Anisotropic Spin Dephasing Dynamics of Quasi-one Dimensional Electron Gas in Modulation-doped GaAs/AlGaAs Wire 国際会議

    J. Ishihara, Y. Ohno, H. Ohno

    Tohoku-Harvard Joint Workshop 2013年1月15日

  299. Magnetization Switching in CoFeB/MgO by electric Fields 国際会議

    S. Kanai, M. Yamanouchi, S. Ikeda, Y. Nakatani, F. Matsukura, H. Ohno

    Tohoku-Harvard Joint Workshop 2013年1月15日

  300. Ferromagnetic Resonance Measurement in CoFeB-MgO Magnetic Tunnel Junctions with Perpendicular Magnetic Easy Axis 国際会議

    K. Mizunuma, M. Yamanouchi, H. Sato, S. Ikeda, S. Kanai, F. Matsukura, H. Ohno

    Tohoku-Harvard Joint Workshop 2013年1月15日

  301. Magnetic properties of MgO-[Co/Pt] multilayer with a CoFeB insertion layer 国際会議

    S. Ishikawa, H. Sato, M. Yamanouchi, S. Ikeda, S. Fukami, F. Matsukura, H. Ohno

    12th Joint Magnetism and Magnetic Materials/International Magnetics Conference 2013年1月14日

  302. MgO/CoFeB/Ta/CoFeB/MgO recording structure in magnetic tunnel junctions with perpendicular magnetic easy axis 国際会議

    H. Sato, M. Yamanouchi, S. Ikeda, S. Fukami, K. Mizunuma, F. Matsukura, H. Ohno

    12th Joint Magnetism and Magnetic Materials/International Magnetics Conference 2013年1月14日

  303. High speed switching by pulse current with duration down to subnanoseconds in CoFeB/MgO based magnetic tunnel junctions with perpendicular easy axis 国際会議

    K. Miura, M. Yamanouchi, H. Sato, S. Ikeda, F. Matsukura, H. Ohno

    12th Joint Magnetism and Magnetic Materials/International Magnetics Conference 2013年1月14日

  304. Determination of the current induced effective field vector in Ta|CoFeB|MgO 国際会議

    J. Kim, J. Sinha, M. Hayashi, M. Yamanouchi, S. Fukami, T. Suzuki, S. Mitani, H. Ohno

    12th Joint Magnetism and Magnetic Materials/International Magnetics Conference 2013年1月14日

  305. Enhanced perpendicular magnetic anisotropy in Ta|CoFeB|MgO by nitrogen doping the Ta underlayer 国際会議

    J. Sinha, M. Hayashi, M. Kodzuka, M. Yamanouchi, S. Fukami, S. Mitani, K. Hono, H. Ohno

    12th Joint Magnetism and Magnetic Materials/International Magnetics Conference 2013年1月14日

  306. Transport and structural properties of the abrupt Fe/GaAs(001) interface 国際会議

    L. R. Fleet, K. Yoshida, H. Kobayashi, Y. Kaneko, S. Matsuzaka, Y. Ohno, S. Honda, J. Inoue, A. Hirohata

    12th Joint Magnetism and Magnetic Materials/International Magnetics Conference 2013年1月14日

  307. Electric-field manipulation of magnetization 国際会議

    Sweden-Japan Workshop on Quantum Nano-Physics and Electronics (QNANO2013) 2013年1月13日

  308. 垂直磁化CoFeB-MgO接合における電界誘起磁化反転

    金井駿, 山ノ内路彦, 池田正二, 仲谷栄伸, 松倉文礼, 大野英男

    第17回半導体スピン工学の基礎と応用(PASPS, Physics and Applications of Spin-related Phenomena in Semiconductors) 2012年12月19日

  309. 垂直磁化Co/Ni細線中の磁壁電流駆動に対する面内磁場の影響

    吉村瑶子, 小山知弘, 千葉大地, 深見俊輔, 山ノ内路彦, 大野英男, 仲谷栄伸, 小野輝男

    第17回半導体スピン工学の基礎と応用(PASPS, Physics and Applications of Spin-related Phenomena in Semiconductors) 2012年12月19日

  310. スピントロニクス素子の将来展望

    東北大学電気通信研究所共同プロジェクト研究会「ナノスケールのゆらぎ・電子相関制御に基づく新規ナノデバイス」 2012年12月14日

  311. Magnetic tunnel junctions of MgO-[Co/Pt] multilayers with a CoFeB insertion layer

    S. Ishikawa, H. Sato, M. Yamanouchi, S. Ikeda, S. Fukami, F. Matsukura, H. Ohno

    スピントロニクス入門セミナー・若手研究会 2012年12月11日

  312. Spintronics-based Nanovolatile CMOS VLSI 国際会議

    Advanced Metallization Conference 2012 (ADMETA) 2012年10月23日

  313. Bridging Semiconductors and Magnetism – Toward Stand-by Power Free VLSIs 国際会議

    International Conference on Hot-Wire Chemical Vapor Depositon (HWCVD7) 2012年10月8日

  314. Domain Wall Motion by Current In a Co/Ni Nanowire with Perpendicular Magnetization under In-Plane Magnetic Fields 国際会議

    Y. Yoshimura

    International Conference of the Asian Union of Magnetics Societies (ICAUMS) 2012年10月2日

  315. Magnetic Anisotropy in CoFe(B)/MgO Stack Structures 国際会議

    S. Ikeda

    International Conference of the Asian Union of Magnetics Societies (ICAUMS) 2012年10月2日

  316. Physics and Materials of Perpendicular CoFeB-MgO Magnetic Tunnel Junction 国際会議

    21th International Colloquium on Magnetic Films and Surfaces (ICMFS) 2012年9月24日

  317. Domain wall depinning probability - Experiment and Theory 国際会議

    S. Fukami

    21th International Colloquium on Magnetic Films and Surfaces (ICMFS) 2012年9月24日

  318. Ferromagnetic resonance by means of homodyne detection technique in CoFeB/MgO magnetic tunnel junctions with perpendicular easy axis 国際会議

    K. Mizunuma

    21th International Colloquium on Magnetic Films and Surfaces (ICMFS) 2012年9月24日

  319. Electric-field magnetization switching in CoFeB-MgO with perpendicular anisotropy 国際会議

    S. Kanai, M. Yamanouchi, S. Ikeda, F. Matsukura, H. Ohno

    21th International Colloquium on Magnetic Films and Surfaces (ICMFS) 2012年9月24日

  320. Electric-field manipulation and switching of magnets 国際会議

    International Workshop on Spin Phenomena in Reduced Dimensions 2012年9月19日

  321. CoFeB-MgO垂直磁化容易磁気トンネル接合における強磁性共鳴のホモダイン検出

    水沼広太朗

    第73回応用物理学会学術講演会 2012年9月11日

  322. MgO/CoFeB/Ta/CoFeB/MgO構造を用いた垂直磁気容易磁気トンネル接合

    佐藤英夫

    第73回応用物理学会学術講演会 2012年9月11日

  323. 細線加工した(001)GaAs/AlGaAs量子井戸における動的核スピン分極

    石原淳

    第73回応用物理学会学術講演会 2012年9月11日

  324. 垂直磁気異方性CoFeB-MgO接合における電界誘起磁化反転

    金井駿

    第73回応用物理学会学術講演会 2012年9月11日

  325. Magnetism for Nonvolatile Memories and Beyond 国際会議

    Joint European Magnetic Symposia (JEMS 2012) 2012年9月9日

  326. 材料科学が拓く新たな論理集積回路のパラダイム

    東北大-産総研合同シンポジウム「材料科学で日本を元気にする」 2012年8月31日

  327. Spintronics Meets CMOS VLSI 国際会議

    Samsung the Future Technology Seminar 2012年8月28日

  328. Perpendicular CoFeB-MgO magnetic tunnel junction 国際会議

    H. Sato, K. Miura, H. D. Gan, K. Mizunuma, S. Fukami, S. Kanai, F. Matsukura, N, Kasai

    SPIE Nanoscience+Engineering 2012 2012年8月12日

  329. Magnetic Tunnel Junction: A Spintronic Nonvolatile Device for VLSI Applications 国際会議

    2012 IEEE Lester Eastman Conference on High Performance Devices 2012年8月7日

  330. Magnetic Semiconductors: Materials, Physics and Devices 国際会議

    7th International Conference on Physics and Applications of Spin-related Phenomena in Semiconductors (PASPS-VII) 2012年8月5日

  331. Bridging Semiconductor and Magnetism 国際会議

    31st International Conference on the Physics of Semiconductors (ICPS 2012) 2012年7月29日

  332. Electrical and Optical Detection of Spin Injection in CoFe/MgO/n-GaAs Junctions 国際会議

    Y. Ohno

    31st International Conference on the Physics of Semiconductors (ICPS 2012) 2012年7月29日

  333. Ferromagnetism in Semiconductors 国際会議

    4th WUN International Conference on Spintronics (WUN-SPIN) 2012年7月23日

  334. 核電気共鳴によるn-GaAs/GaAlAs(110)量子井戸中の核スピンコヒーレンスの制御

    張超亮

    第31回電子材料シンポジウム 2012年7月11日

  335. 垂直磁気トンネル接合におけるCo/Pt電極の磁気異方性のPt膜厚および熱処理温度依存性

    石川慎也

    第31回電子材料シンポジウム 2012年7月11日

  336. Perpendicular CoFeB-MgO for Spintronics Devices 国際会議

    19th International Conference on Magnetism (ICM2012) 2012年7月8日

  337. CoFeB-MgO Perpendicular Magnetic Tunnel Junction 国際会議

    Tohoku University-IMEC Seminar 2012年6月21日

  338. A 3.14um2 4T-2MTJ-Cell Fully Parallel TCAM Based on Nonvolatile Logic-in-Memory Architecture 国際会議

    S. Matsunaga

    2012 Symposium on VLSI Circuits 2012年6月13日

  339. 1Mb 4T-2MTJ Nonvolatile STT-RAM for Embedded Memories Using 32b Fine-Grained Power Gating Technique with 1.0ns/200ps Wake-up/Power-off Times 国際会議

    T. Ohsawa

    2012 Symposium on VLSI Circuits 2012年6月13日

  340. High-Speed and Reliable Domain Wall Motion Device: Material Design for Embedded Memory and Logic Application 国際会議

    S. Fukami

    2012 Symposium on VLSI Technology 2012年6月12日

  341. Spintronics Primitive Gate with High Error Correction Efficiency 6(P<SUB>error</SUB>)2 for Logic-in Memory Architecture 国際会議

    Y. Tsuji

    2012 Symposium on VLSI Technology 2012年6月12日

  342. Restructuring of Memory Hierarchy in Computing System with Spintronics-Based Technologies 国際会議

    T. Endoh

    2012 Symposium on VLSI Technology 2012年6月12日

  343. Ultrafast Parallel Reconfiguration of 3D-Stacked Reconfigurable Spin Logic Chip with On-chip SPRAM(SPin-transfer torque RAM) 国際会議

    T. Tanaka

    2012 Symposium on VLSI Technology 2012年6月12日

  344. Magnetic Tunnel Junction for Magnetoresistive Random Access memory and Beyond 国際会議

    Silicon Nanoelectronics Workshop (SNW) 2012年6月10日

  345. CMOS VLSI Meets Spintronics 国際会議

    Qualcomm Technology Forum 2012年6月7日

  346. Factors Determining Thermal Stability in CoFeB-MgO Perpendicular Junctions 国際会議

    H. Sato

    9th RIEC International Workshop on Spintronics 2012年5月31日

  347. Electromotive Forces in (Ga, Mn)As-based Structures 国際会議

    F. Matsukura

    9th RIEC International Workshop on Spintronics 2012年5月31日

  348. Coherent Control of Nuclear Spins in a (110) GaAs/GaAlAs Quantum Well by Nuclear Electric Resonance 国際会議

    C. Zhang

    9th RIEC International Workshop on Spintronics 2012年5月31日

  349. Electrical and Optical Detection of Spin Polarized Electrons in n-GaAs/MgO/CoFe Junctions 国際会議

    Y. Kaneko

    9th RIEC International Workshop on Spintronics 2012年5月31日

  350. Coherent Manipulation of Nuclear Spins in Semiconductors with an Electric Field 国際会議

    Y. Ohno

    9th RIEC International Workshop on Spintronics 2012年5月31日

  351. Magnetic Anisotropy of Co/Pt based Electrodes for Magnetic Tunnel Junctions with perpendicular Magnetic Easy Axis 国際会議

    S. Ishikawa

    9th RIEC International Workshop on Spintronics 2012年5月31日

  352. Electrical Signal Related to Ferromagnetic Resonance in (Ga, Mn)As/p-GaAs bilayer Structure 国際会議

    L. Chen

    9th RIEC International Workshop on Spintronics 2012年5月31日

  353. Perpendicular Magnetic Tunnel Junction for Nonvolatile Electronics 国際会議

    E-MRS & Nature Materials Workshop, “Frontiers in Materials: Spintronics” 2012年5月13日

  354. Spin injection across abrupt Fe/GaAs(001) interfaces 国際会議

    L. Fleet

    International Magnetics Conference (INTERMAG) 2012年5月7日

  355. Thickness dependence of thermal stability factor in CoFeB/MgO perpendicular magnetic tunnel junctions 国際会議

    H. Sato

    International Magnetics Conference (INTERMAG) 2012年5月7日

  356. CoFeB composition dependence of magnetic anisotropy and tunnel magnetoresistance in CoFeB/MgO stack structures 国際会議

    International Magnetics Conference (INTERMAG) 2012年5月7日

  357. MTJ based non volatile SRAM and low power non volatile logic-in-memory architecture 国際会議

    T. Endoh

    International Magnetics Conference (INTERMAG) 2012年5月7日

  358. Physics and Materials Science of Perpendicular MgO-CoFeB 国際会議

    Korean Physical Society, Spring Meeting 2012年4月25日

  359. 半導体と磁性体に橋を架ける

    第59回応用物理学会学術講演会 2012年3月15日

  360. 超薄膜を用いた垂直磁化型強磁性トンネル接合

    第59回応用物理学会学術講演会 2012年3月15日

  361. CoFeB/MgO/CoFeB垂直磁化トンネル磁気抵抗素子のスピントルクダイオード効果

    井波暢人

    第59回応用物理学会学術講演会 2012年3月15日

  362. 垂直CoFeB/MgO磁気トンネル接合の熱安定性の記録層膜厚依存性

    佐藤英夫

    第59回応用物理学会学術講演会 2012年3月15日

  363. CoFeB/MgO積層構造における磁気特性のCoFeB組成依存性

    小泉遼平

    第59回応用物理学会学術講演会 2012年3月15日

  364. 歪(110)GaAs/AlGaAs量子井戸における四重極分裂の磁場依存性

    石原 淳

    第59回応用物理学会学術講演会 2012年3月15日

  365. 歪(110)GaAs/AlGaAs量子井戸における核スピン共鳴線幅の磁場依存性

    石原 淳

    第59回応用物理学会学術講演会 2012年3月15日

  366. Spintronics Device for Stand-by Power Free Nonvolatile CMOS VLSI 国際会議

    American Physical Society, March Meeting 2012 2012年2月27日

  367. Recent Progress in Spintronics Technology for Nonvolatile VLSIs 国際会議

    5th International Symposium and 4th Student Organizing International Mini-Conference on Information Electronics Systems 2012年2月22日

  368. Ferromagnetism in Semiconductors 国際会議

    19th Korean Conference on Semiconductors 2012年2月15日

  369. Spintronics makes integrated circuits low-power and high performance 国際会議

    Presentation of the "Guardian Angeles" flagship by EPFL Prof. A. Ionescu 2012年2月15日

  370. Perpendicular CoFeB-MgO for Spintronics Applications 国際会議

    Magnetic Single Nano-Object Workshop & School (M-SNOWS 2012) 2012年2月5日

  371. Tunnel stability factor of CoFeB/MgO perpendicular magnetic tunnel junctions 国際会議

    H. Sato

    2nd CSIS Int. Symposium on Spintronics-based VLSIs and 8th RIEC International Workshop on Spintronics 2012年2月2日

  372. Current induced magnetization dynamics in CoFeB/MgO nanostructures 国際会議

    M. Hayashi

    2nd CSIS Int. Symposium on Spintronics-based VLSIs and 8th RIEC International Workshop on Spintronics 2012年2月2日

  373. Proposal of new MTJ-based nonvolatile memories 国際会議

    T. Ohsawa

    2nd CSIS Int. Symposium on Spintronics-based VLSIs and 8th RIEC International Workshop on Spintronics 2012年2月2日

  374. A content addressable memory using three-terminal magnetic domain wall motion cells 国際会議

    R. Nebashi

    2nd CSIS Int. Symposium on Spintronics-based VLSIs and 8th RIEC International Workshop on Spintronics 2012年2月2日

  375. Annealing temperature dependence of tunnel magnetoresistance in MgO magnetic tunnel junctions with thin CoFeB electrodes 国際会議

    H. Gan

    2nd CSIS Int. Symposium on Spintronics-based VLSIs and 8th RIEC International Workshop on Spintronics 2012年2月2日

  376. B concentration dependence of magnetic anisotropy in MgO/CoFeB/Ta stack structure 国際会議

    R. Koizumi

    2nd CSIS Int. Symposium on Spintronics-based VLSIs and 8th RIEC International Workshop on Spintronics 2012年2月2日

  377. Energy-assisted oxidation process of Mg layer for MgO-MTJs 国際会議

    H. Yamamoto

    2nd CSIS Int. Symposium on Spintronics-based VLSIs and 8th RIEC International Workshop on Spintronics 2012年2月2日

  378. Spin torque diode effect of perpendicularly magnetized CoFeB/MgO/CoFeB magnetic tunnel junctions 国際会議

    N. Inami

    2nd CSIS Int. Symposium on Spintronics-based VLSIs and 8th RIEC International Workshop on Spintronics 2012年2月2日

  379. Hole concentration dependence of the Curie temperature of (Ga,Mn)Sb channel in field-effect structure 国際会議

    S. Akita

    2nd CSIS Int. Symposium on Spintronics-based VLSIs and 8th RIEC International Workshop on Spintronics 2012年2月2日

  380. 半導体における強磁性

    MLFシンポジウム 2012年1月19日

  381. A 600MHz MTJ-based nonvolatile latch making use of incubation time in MTJ switching 国際会議

    T. Endoh

    2011 IEEE International Electron Devices Meeting(IEDM) 2011年12月5日

  382. CoFeB-MgO system for spintronic devices 国際会議

    山ノ内路彦

    The 7th Taiwan International Conference on Spintronics 2011年12月2日

  383. (Ga,Mn)Sb電界効果素子におけるキュリー温度の正孔濃度依存性

    金子雄基

    第16回半導体スピン工学の基礎と応用(PASPS-16) 2011年11月28日

  384. GaAs/AlGaAs量子井戸における電子スピンダイナミクスの細線方向依存性

    石原 淳

    第16回半導体スピン工学の基礎と応用(PASPS-16) 2011年11月28日

  385. Spintronics-based Nonvolatile CMOS VLSI 国際会議

    Joint Polish-Japanese Workshop Spintronics –from New Materials to Applications 2011年11月15日

  386. Nonvolatile CMOS Circuits Using Magnetic Tunnel Junction 国際会議

    2nd Berkeley Symposium on Energy Efficient Electronic Systems 2011年11月3日

  387. 垂直磁気異方性電極磁気トンネル接合の進展

    応用電子物性分科会・スピントロニクス研究会「スピントロニクスデバイスの新展開」 2011年11月2日

  388. Spin orbit field assisted current driven domain wall motion in perpendicularly magnetized ultrathin CoFeB/MgO nanowires 国際会議

    M. Hayashi

    56th Annual Conference on Magnetism and Magnetic Materials 2011年10月30日

  389. Domain patterns in demagnetized CoFeB/MgO structures with perpendicular anisotropy 国際会議

    M. Yamanouchi

    56th Annual Conference on Magnetism and Magnetic Materials 2011年10月30日

  390. Annealing stability of perpendicular anisotropy CoFeB/MgO magnetic tunnel junctions with various junction sizes 国際会議

    H Gan

    56th Annual Conference on Magnetism and Magnetic Materials 2011年10月30日

  391. Decrease in intrinsic critical current density under magnetic field along hard in-plane axis of free layer in magnetic tunnel junctions with in-plane anisotropy 国際会議

    K. Miura

    56th Annual Conference on Magnetism and Magnetic Materials 2011年10月30日

  392. Eigenmode analysis and thermal stability of magnetic tunnel junctions with synthetic antiferromagnet free layers 国際会議

    D. Marko

    56th Annual Conference on Magnetism and Magnetic Materials 2011年10月30日

  393. The MTJ with NiFeB/Fe free layer for magnetic logic 国際会議

    H. Honjo

    56th Annual Conference on Magnetism and Magnetic Materials 2011年10月30日

  394. Design of a 270ps-access 7T-2MTJ-cell nonvolatile ternary content-addressable memory 国際会議

    S. Matsunaga

    56th Annual Conference on Magnetism and Magnetic Materials 2011年10月30日

  395. 50%-transistor-less standby-power-free 6-input LUT circuit using redundant MTJ-based nonvolatile logic-in-memory architecture 国際会議

    D. Suzuki

    56th Annual Conference on Magnetism and Magnetic Materials 2011年10月30日

  396. Spintronics-based LSI: A Route to Stand-by Power Free Society 国際会議

    Tohoku University 4th International Symposium 2011年10月27日

  397. Photocurrent Measurements on a Quantum Cascade Laser Device byFourier Transform Infrared Microscope 国際会議

    E. C. Enobio

    24th International Microprocesses and Nanotechnology Conference (MNC2011) 2011年10月24日

  398. Electrical Control of the Exciton Fine Structure splitting in GaAs Island Quantum Dots for the Generation of Polarization-entangled Photons 国際会議

    M. Ghali

    24th International Microprocesses and Nanotechnology Conference (MNC2011) 2011年10月24日

  399. スピントロニクス構造の熱的安定性

    東北大学電気通信研究所共同プロジェクト研究会「ナノスケールのゆらぎ・電子相関制御に基づく新規ナノデバイス」 2011年10月21日

  400. Magnetoresistive Random Access Memory with Spin Transfer Torque Write (Spin RAM) –Present and Future- 国際会議

    International Conference on Solid State Devices and Materials (SSDM) 2011年9月28日

  401. Studies on Static Noise Margin and Scalability for Low-Power and High-Density Nonvolatile SRAM using Spin-Transfer-Torque (STT) MTJs 国際会議

    T. Ohsawa

    International Conference on Solid State Devices and Materials (SSDM) 2011年9月28日

  402. Novel 2step writing method for STT-RAM to improve switching probability and write speed 国際会議

    F. Iga

    International Conference on Solid State Devices and Materials (SSDM) 2011年9月28日

  403. High-speed-search nonvolatile TCAM using MTJ devices 国際会議

    S. Matsunaga

    International Conference on Solid State Devices and Materials (SSDM) 2011年9月28日

  404. A compact nonvolatile logic element using an MTJ/MOS-hybrid structure 国際会議

    D. Suzuki

    International Conference on Solid State Devices and Materials (SSDM) 2011年9月28日

  405. Time-resolved switching characteristic in magnetic tunnel junction with spin transfer torque write 国際会議

    F. Iga

    International Conference on Solid State Devices and Materials (SSDM) 2011年9月28日

  406. 垂直CoFeB/MgO 磁気トンネル接合のスイッチング電流と熱安定性

    佐藤英夫

    第35回日本磁気学会学術講演会 2011年9月27日

  407. 垂直磁化CoFeB/MgO 細線における電流誘起磁壁移動

    深見俊輔

    第35回日本磁気学会学術講演会 2011年9月27日

  408. 磁性材料のリアクティブイオンエッチング

    山本直志

    第35回日本磁気学会学術講演会 2011年9月27日

  409. Nonvolatile Spintronic-based CMOS VLSI 国際会議

    Nanoscience and Nanotechnology Conference (n&n11) 2011年9月19日

  410. MgO-CoFeB Perpendicular Magnetic Tunnel Junction 国際会議

    Seminar of Center for Materials for Information Technology, University of Alabama 2011年9月9日

  411. 磁性半導体を出発点として

    応用物理学会スクール 2011年8月29日

  412. 磁気トンネル接合素子のプラズマプロセス誘起ダメージとリカバリーの試み

    木下啓蔵

    第72回応用物理学会学術講演会 2011年8月29日

  413. 3端子磁壁移動素子のスケーラビリティー

    深見俊輔

    第72回応用物理学会学術講演会 2011年8月29日

  414. Ta/Co20Fe60B20/MgO 接合における電界による垂直磁気異方性変調の膜厚及び熱処理温度依存性

    金井駿

    第72回応用物理学会学術講演会 2011年8月29日

  415. n-GaAs/MgO/CoFe接合を用いたスピン蓄積と拡散の光学的検出

    金子雄基

    第72回応用物理学会学術講演会 2011年8月29日

  416. 細線加工したGaAs/AlGaAs量子井戸における電子スピン緩和時間の磁場依存性

    石原 淳

    第72回応用物理学会学術講演会 2011年8月29日

  417. 垂直磁化細線における電流誘起磁壁移動

    深見俊輔

    第36回スピンエレクトロニクス専門研究会 2011年8月22日

  418. Electric field control of ferromagnetism in III-V ferromagnetic semiconductor structures 国際会議

    千葉大地

    Moscow International Symposium on Magnetism 2011年8月21日

  419. Electric-field Effects on Magnetic Semiconductors and Metals 国際会議

    Workshop on Spin Transport in Solids 2011年8月8日

  420. Diluted Magnetic Semiconductors –An Introduction- 国際会議

    International Conference and School on Spintronics and Quantum Information Technology (SPINTECH VI) 2011年8月1日

  421. Annealing stability of perpendicular anisotropy CoFeB/MgO magnetic tunnel junctions 国際会議

    H. Gan

    International Conference and School on Spintronics and Quantum Information Technology (SPINTECH VI) 2011年8月1日

  422. Strong spin relaxation anisotropy of electrons in modulation-doped GaAs/AlGaAs wires 国際会議

    J. Ishihara

    International Conference and School on Spintronics and Quantum Information Technology (SPINTECH VI) 2011年8月1日

  423. Magnetic anisotropy direction switching in Ta/CoFeB/MgO by electric fields 国際会議

    S. Kanai

    International Conference and School on Spintronics and Quantum Information Technology (SPINTECH VI) 2011年8月1日

  424. Scalability of critical current in perpendicular anisotropy CoFeB/MgO magnetic tunnel junction 国際会議

    H. Sato

    International Conference and School on Spintronics and Quantum Information Technology (SPINTECH VI) 2011年8月1日

  425. Electrical and optical detection of spin injection in ferromagnetic metal/semiconductor junctions 国際会議

    5th International Workshop on Spin Currents 2011年7月25日

  426. Magnetic field dependence of quadrupole interaction in a stralined (110) GaAs quantum well 国際会議

    小野真証

    5th International Workshop on Spin Currents 2011年7月25日

  427. Manipulating Magnetism in Semiconductors 国際会議

    UK Semiconductors 2011 2011年7月6日

  428. Spintroncs Meets Semiconductor Integrated Circuits 国際会議

    JSPS York-Tohoku Research Symposium on -Magnetic Materials and Spintroncs- 2011年6月27日

  429. MgO-CoFeB Interface Perpendicular Anisotropy for Spintronics Devices 国際会議

    European Conference on Physics of Magnetism 2011(PM’11) 2011年6月27日

  430. Nonvolatile CMOS VLSI with Spintronics 国際会議

    International Conference on Materials for Advanced Technologies (ICMAT2011) 2011年6月26日

  431. Electric-Field Effects on Magnetic Materials ?From Ferromagnetic Semiconductors to CoFeB- 国際会議

    Magnetics and Optics Research International Symposium for New Storage Technology(MORIS2011) 2011年6月21日

  432. Fully parallel 6T-2MTJ nonvolatile TCAM with single-transistor-based self match-line discharge control 国際会議

    松永翔雲

    2011 Symposia on VLSI Circuits 2011年6月15日

  433. A content addressable memory using magnetic domain wall motion cells 国際会議

    R. Nebashi

    2011 Symposia on VLSI Circuits 2011年6月15日

  434. CoFeB/MgO based perpendicular magnetic tunnel junctions with stepped structure for symmetrizing different retention times of “0” and “1” information 国際会議

    三浦勝哉

    2011 Symposia on VLSI Technology 2011年6月14日

  435. スピントロニクスによる不揮発性VLSI

    SEMI Forum Japan 2011年5月31日

  436. 半導体スピントロニクス-強磁性半導体を中心として-

    日本磁気学会 2011年5月20日

  437. Perpendicular Easy-Axis MgO-CoFeB Magnetic Tunnel Junctions 国際会議

    IEEE International Magnetics Conference (INTERMAG 2011) 2011年4月25日

  438. Size Dependence of CoFeB/MgO Perpendicular Anisotropy Magnetic Tunnel Junctions on Critical Current and Thermal Stability 国際会議

    佐藤英夫

    IEEE International Magnetics Conference (INTERMAG 2011) 2011年4月25日

  439. Dependence of tunnel magnetoresistance in CoFeB-MgO based perpendicular anisotropy magnetic tunnel junctions on sputtering conditions and stack structures 国際会議

    水沼広太朗

    IEEE International Magnetics Conference (INTERMAG 2011) 2011年4月25日

  440. Post-annealing effect on perpendicular magnetic anisotropy in CoFeB/MgO structure 国際会議

    小泉遼平

    IEEE International Magnetics Conference (INTERMAG 2011) 2011年4月25日

  441. A Perpendicular-anisotropy CoFeB-MgO magnetic tunnel junction with natural oxidation process 国際会議

    H. Yamamoto

    IEEE International Magnetics Conference (INTERMAG 2011) 2011年4月25日

  442. Domain wall motion induced by electric current in CoFeB/MgO wire with perpendicular magnetic anisotropy 国際会議

    S. Fukami

    IEEE International Magnetics Conference (INTERMAG 2011) 2011年4月25日

  443. Spintronics based Nonvolatile Electronics 国際会議

    2011 Frontier of Spintronics/Nanoelectronics Workshop 2011年4月24日

  444. Perpendicular Anisotropy at MgO-CoFeB Interface for High Performance Spintronics Devices 国際会議

    Korean Physical Society 2011年4月13日

  445. 電界による(Ga,Mn)As強磁性ナノドット配列の形成

    千葉大地

    第58回応用物理学会学術講演会 2011年3月24日

  446. Ta/Co40Fe40B20/MgO接合における電界による垂直磁気異方性変調の膜厚及び熱処理温度による最適化

    金井駿

    第58回応用物理学会学術講演会 2011年3月24日

  447. 積層フェリ自由層を有するトンネル接合の面直磁場印加スピントルクダイオード効果

    井波暢人

    第58回応用物理学会学術講演会 2011年3月24日

  448. 垂直CoFeB/MgO磁気トンネル抵抗素子の書き込み電流と熱安定性の素子サイズ依存性

    佐藤英夫

    第58回応用物理学会学術講演会 2011年3月24日

  449. BリッチなCo-Fe-B/MgO/Co-FeB擬スピンバルブの微細組織解析

    小塚雅也

    第58回応用物理学会学術講演会 2011年3月24日

  450. CoFeB-MgO垂直磁気異方性MTJのTMR特性に及ぼす成膜条件の影響

    水沼広太朗

    第58回応用物理学会学術講演会 2011年3月24日

  451. 垂直磁気異方性CoFeB/MgO積層構造における磁区構造

    山ノ内路彦

    第58回応用物理学会学術講演会 2011年3月24日

  452. CoFeB層厚の異なるMgO/CoFeB構造における磁気特性の熱処理温度依存性

    小泉遼平

    第58回応用物理学会学術講演会 2011年3月24日

  453. AlGaAs/GaAsダブルヘテロ構造における電子スピン緩和時間の細線方向に対する依存性

    石原 淳

    第58回応用物理学会学術講演会 2011年3月24日

  454. MgO-MTJs with Application to VLSI 国際会議

    American Physical Society 2011年3月21日

  455. Perpendicular 40 nm MgO-CoFeB Magnetic Tunnel Junctions 国際会議

    German Physical Society 2011年3月14日

  456. Toward new paradigm for semiconductor LSI of the "Post-Moore" ear 国際会議

    8th ITEC Int. Conf. on Overcoming Two "Ends" 2011年3月4日

  457. Spintronics Meets VLSI, toward nonvolatile electronics 国際会議

    First Outreach Program, Int. Symp. on Innovative Nanoelectronics & Systems 2011年2月16日

  458. Materials design and science of magnetic tunnel junctions with perpendicular anisotropy electrodes for VLSIs 国際会議

    1st CSIS Int. Symp. on Spintronics-based VLSIs and 7th RIEC Int. Workshop on Spintronics 2011年2月3日

  459. Temperature dependence of domain patterns observed in demagnetized CoFeB/MgO films with perpendicular anisotropy 国際会議

    山ノ内路彦

    1st CSIS Int. Symp. on Spintronics-based VLSIs and 7th RIEC Int. Workshop on Spintronics 2011年2月3日

  460. A post oxidation process of Mg layer for MgO barrier magnetic tunnel junctions 国際会議

    H. Yamamoto

    1st CSIS Int. Symp. on Spintronics-based VLSIs and 7th RIEC Int. Workshop on Spintronics 2011年2月3日

  461. Spin torque diode effect of magnetic tunnel junction with synthetic ferrimagnetic free layer 国際会議

    N. Inami

    1st CSIS Int. Symp. on Spintronics-based VLSIs and 7th RIEC Int. Workshop on Spintronics 2011年2月3日

  462. Influences of Boron composition on tunnel magnetoresistance properties of double-MgO-barrier magnetic tunnel junctions 国際会議

    甘華東

    1st CSIS Int. Symp. on Spintronics-based VLSIs and 7th RIEC Int. Workshop on Spintronics 2011年2月3日

  463. Annealing effect on perpendicular magnetic anisotropy of CoFeB/MgO structure 国際会議

    佐藤英夫

    1st CSIS Int. Symp. on Spintronics-based VLSIs and 7th RIEC Int. Workshop on Spintronics 2011年2月3日

  464. Annealing stability for tunnel magnetoresistance in MgO-CoFeB based magnetic tunnel junctions with perpendicular anisotropy CoFe/Pd multilayers 国際会議

    水沼広太朗

    1st CSIS Int. Symp. on Spintronics-based VLSIs and 7th RIEC Int. Workshop on Spintronics 2011年2月3日

  465. Modulation of magnetic anisotropy in Ta/Co40Fe40B20/MgO by electric fields: thickness and annealing temperature dependences 国際会議

    金井 駿

    1st CSIS Int. Symp. on Spintronics-based VLSIs and 7th RIEC Int. Workshop on Spintronics 2011年2月3日

  466. Buffer layer dependence of magnetic domain wall creep in (Ga,Mn)As 国際会議

    鈴木淳士

    1st CSIS Int. Symp. on Spintronics-based VLSIs and 7th RIEC Int. Workshop on Spintronics 2011年2月3日

  467. Perpendicular Magnetic Anisotropy at the Interface of MgO-CoFeB 国際会議

    38th Conf on the Physics & Chemistry of Surface & Interfaces (PCSI38) 2011年1月16日

  468. 歪(110)GaAs量子井戸中における四重極分裂幅の磁場依存性

    特定領域「スピン流の創出と制御」研究会 2011年1月6日

  469. n-GaAs/MgO/CoFe接合におけるスピン蓄積とその電気的検出

    小林裕臣, L. Fleet, 廣畑貴文

    第15回半導体スピン工学の基礎と応用(PASPS-15) 2010年12月20日

  470. 電界による(Ga,Mn)As強磁性ナノドットの形成

    千葉大地

    第15回半導体スピン工学の基礎と応用(PASPS-15) 2010年12月20日

  471. (110)GaAs量子井戸における電界誘起の四重極分裂

    小野真証, 佐藤源輝, 石原淳, 松坂俊一郎

    第15回半導体スピン工学の基礎と応用(PASPS-15) 2010年12月20日

  472. CoFeB/MgO/CoFeB接合にける垂直磁気異方性とスピン注入磁化反転

    東北大学 電気通信研究所 共同プロジェクト研究 (H22/A03) 研究会 2010年12月17日

  473. Magnetic Tunnel Junction for Nonvolatile CMOS Logic 国際会議

    2010 Int. Electron Devices Meeting (IEDM) 2010年12月6日

  474. Perpendicular MgO-CoFeB Magnetic Tunnel Junction 国際会議

    6th Taiwan Int. Conf. on Spintronics (TICSpin) 2010年12月1日

  475. 40nm垂直異方性磁気トンネル接合

    東北大学電気通信研究所共同プロジェクト研究会「ナノスケールのゆらぎ・電子相関制御に基づく新規ナノデバイス」 2010年11月26日

  476. MgO/CoFeB構造における磁気異方性の熱処理温度依存性

    小泉遼平, 佐藤英夫, 山ノ内路彦, 水沼広太郎, 三浦勝哉, 甘華東

    第65回応用物理学会東北支部学術講演会 2010年11月25日

  477. Magnetic Tunnel Junction for Integrated Circuits: Scaling and Beyond 国際会議

    55th Annual Conf. on Magnetims & Magnetic Materials (MMM2010) 2010年11月14日

  478. Stack structures for realization of high annealing stability in perpendicular magnetic tunnel junctions with CoFe/Pd multilayer electrodes 国際会議

    水沼広太朗

    55th Annual Conf. on Magnetims & Magnetic Materials (MMM2010) 2010年11月14日

  479. The dependence of the magnetic anisotropy on buffer layer and MgO thickness in Co20Fe60B20/MgO structures for magnetic tunnel junction 国際会議

    山ノ内路彦

    55th Annual Conf. on Magnetims & Magnetic Materials (MMM2010) 2010年11月14日

  480. Electrical detection of spin polarized electrons in n-GaAs/MgO/CoFe junctions 国際会議

    H. Kobayashi

    55th Annual Conf. on Magnetims & Magnetic Materials (MMM2010) 2010年11月14日

  481. Control of magnetic anisotropy in CoFeB by capping layer for current induced magnetization switching 国際会議

    H. Yamamoto, J. Hayakawa, K. Ito, K. Miura, H. Matsuoka

    55th Annual Conf. on Magnetims & Magnetic Materials (MMM2010) 2010年11月14日

  482. Spin-torque diode effect in magnetic tunnel junctions with synthetic ferrimagnetic layers 国際会議

    N. Inami, H. Naganuma, M. Oogane, Y. Ando

    55th Annual Conf. on Magnetims & Magnetic Materials (MMM2010) 2010年11月14日

  483. High tunnel magnetoresistance, low current switching and high thermal stability in 40-nm-diameter CoFeB/MgO-based magnetic tunnel junctions with perpendicular anisotropy 国際会議

    K. Miura, M. Yamanouchi, H. Yamamoto, K. Mizunuma, H. Gan, J. Hayakawa, R. Koizumi, M. Endo, S. Kanai

    55th Annual Conf. on Magnetims & Magnetic Materials (MMM2010) 2010年11月14日

  484. n型GaAsにおけるスピンホール効果の光学的評価ドーピング濃度依存性

    松坂俊一郎

    物性科学領域横断研究会 凝縮系科学の最前線 2010年11月13日

  485. 垂直磁気異方性電極磁気トンネル接合の進展

    応用物理学会応用電子物性分科会スピントロニクス研究会 2010年11月2日

  486. スピントロニクスデバイスの原理と最新動向

    日本学術振興会 未踏・ナノデバイステクノロジー第151委員会、シリコン超集積化システム第165委員会合同研究会 2010年10月29日

  487. MgO-based Magnetic Tunnel Junctions for Integrated Cuicuit Applications 国際会議

    Int. Conf. on Magnetic Materials (ICMM2010) 2010年10月25日

  488. Spin-orbit effective field in (Ga,Mn)As 国際会議

    遠藤将起

    The 3rd Student Organizing International Mini-Conference on Information Electronics Systems 2010年10月19日

  489. Quadrupolar splitting dependence of nuclear spin coherence in an n-(110) GaAs quantum well 国際会議

    小野真証

    The 3rd Student Organizing International Mini-Conference on Information Electronics Systems 2010年10月19日

  490. Intersubband optical transition measurement in InAs/AlSb quantum cascade laser using fourier-transform photocurrent spectrscopy 国際会議

    Eli Christopher Inocencio Enobio

    The 3rd Student Organizing International Mini-Conference on Information Electronics Systems 2010年10月19日

  491. Control of the exciton fine structure splitting in GaAs single quantum dots using vertical gate voltage 国際会議

    Mohsen Ghali

    The 3rd Student Organizing International Mini-Conference on Information Electronics Systems 2010年10月19日

  492. Electric-field dependence of magnetic anisotropy in as-deposited and annealed CoFeB/MgO structures 国際会議

    金井 駿

    The 3rd Student Organizing International Mini-Conference on Information Electronics Systems 2010年10月19日

  493. TMR properties and annealing stability in MgO barrier MTJs with CoFe/Pd perpendicular anisotropy multilayer electrodes 国際会議

    水沼広太朗

    The 3rd Student Organizing International Mini-Conference on Information Electronics Systems 2010年10月19日

  494. Nonvolatile CMOS VLSI with Spintronics 国際会議

    8th Int. Workshop on Future Information Processing Technologies (IWFIPT) 2010年10月18日

  495. Recent Progress on MgO-barrier Magnetic Tunnel Junctio 国際会議

    Seminar at National Taiwan University 2010年10月1日

  496. MgO-based Magnetic Tunnel Junction for CMOS VLSI Integration 国際会議

    Int. Conf. on Nanoscale Magnetism 2010年9月28日

  497. Magnetic field dependence of quadrupoar splitting and nuclear spin coherence in a (110) GaAs/AlGaAs quantum well 国際会議

    J. Ishihara, M. Ono, G. Sato, S. Matsuzaka

    Intl Conf. on Solid State Devices and Materials 2010年9月21日

  498. Physics and Material Science of MgO-CoFeB Structures 国際会議

    Int. Symp. on Metallic Multilayers(MML) 2010年9月19日

  499. Tunnel magnetoresistance properties of double MgO-barrier magnetic tunnel junctions with different free-layer alloy compositions and structures 国際会議

    甘華東

    Int. Symp. on Metallic Multilayers(MML) 2010年9月19日

  500. CoFeBにおける磁気異方性電界変調に及ぼすアニールの影響

    金井駿

    第71回応用物理学会学術講演会 2010年9月14日

  501. 抵抗極プロットを用いた(Ga,Mn)AsにおけるSOI有効磁界の検出

    遠藤将起

    第71回応用物理学会学術講演会 2010年9月14日

  502. (Ga,Mn)Asにおける電流誘起磁壁移動の膜厚依存性

    鈴木淳士

    第71回応用物理学会学術講演会 2010年9月14日

  503. n-GaAs/MgO/CoFe接合を用いたスピン蓄積の電気的検出

    小林裕臣

    第71回応用物理学会学術講演会 2010年9月14日

  504. MgO障壁磁気トンネル接合における磁化反転磁場のバイアス電圧依存性

    三浦勝哉

    第71回応用物理学会学術講演会 2010年9月14日

  505. 積層フェリ構造を有するトンネル接合のスピントルクダイオード効果

    井波暢人

    第71回応用物理学会学術講演会 2010年9月14日

  506. 垂直磁気異方性CoFe/Pd多層膜電極を用いたMgO障壁磁気トンネル接合のトンネル磁気抵抗特性と積層構造

    水沼広太朗

    第71回応用物理学会学術講演会 2010年9月14日

  507. n型GaAsにおけるスピンホール効果の光学的評価

    松坂俊一郎

    第71回応用物理学会学術講演会 2010年9月14日

  508. n-(110)GaAs単一量子井戸中における四重極分裂幅のゲート電圧依存性

    小野真証

    第71回応用物理学会学術講演会 2010年9月14日

  509. GaAs量子井戸における核スピン四重極分裂幅とコヒーレンス時間の磁場依存性

    石原 淳

    第71回応用物理学会学術講演会 2010年9月14日

  510. スピントロニクス: More and Beyond

    第71回応用物理学会学術講演会 2010年9月14日

  511. 垂直磁気異方性電極MTJにおける強磁性層構造のTMR特性に及ぼす影響

    水沼広太朗, 山ノ内路彦, 甘華東, 三浦勝哉, 小泉遼平

    第34回日本磁気学会学術講演会 2010年9月4日

  512. Ferromagnetic III-V Semiconductor Spintronics 国際会議

    16th International Conference on Molecular Beam Epitaxy (MBE2010) 2010年8月22日

  513. Electric field induced magnetization switching in a (Ga,Mn)As field effect structure 国際会議

    千葉大地

    6th Int. Conf. on the Physics and Applications of Spin Related Phenomena in Semiconductors 2010年8月1日

  514. Inverse spin Hall effect in a (Ga,Mn)As/p-GaAs bilayer structure 国際会議

    6th Int. Conf. on the Physics and Applications of Spin Related Phenomena in Semiconductors 2010年8月1日

  515. Spin resonance and spin-orbit coupling effects in two dimensional hole systems in GaAs/AlGaAs(311)A heterostructures 国際会議

    S. Teraoka

    6th Int. Conf. on the Physics and Applications of Spin Related Phenomena in Semiconductors 2010年8月1日

  516. Strain dependence of nuclear spin coherent time in a GaAs quantum well 国際会議

    佐藤源輝

    6th Int. Conf. on the Physics and Applications of Spin Related Phenomena in Semiconductors 2010年8月1日

  517. Magnetic field dependence of nuclear quadrupole interaction in a (110)GaAs quantum well 国際会議

    石原淳

    6th Int. Conf. on the Physics and Applications of Spin Related Phenomena in Semiconductors 2010年8月1日

  518. Characterization of spin-orbit interaction induced effectivev magnetic fields in (Ga,Mn)As by resistance polar plot 国際会議

    M. Endo

    Int. Conf. on Physics of Semiconductors (ICPS) 2010年7月25日

  519. Nuclear spin coherence time in a strained GaAs quantum well 国際会議

    M. Ono, G. Sato, J. Ishihara, S. Matsuzaka

    Int. Conf. on Physics of Semiconductors (ICPS) 2010年7月25日

  520. GaAs量子井戸における核スピンコヒーレンスの磁場依存性

    石原淳

    第29回電子材料シンポジウム 2010年7月14日

  521. 面内磁場中におけるInAs/AlSb量子カスケードレーザの発振特性

    佐藤啓貴

    第29回電子材料シンポジウム 2010年7月14日

  522. (Ga,Mn)Asにおける電流誘起磁壁移動の膜厚依存性

    鈴木淳士

    第29回電子材料シンポジウム 2010年7月14日

  523. 電子材料とスピントロニクス

    第29回電子材料シンポジウム 2010年7月14日

  524. Current-induced magnetization switching in MTJs with high TMR ratio 国際会議

    甘華東

    Int. Symp. on Advanced Magnetic Materials and Applications 2010年7月12日

  525. TMR Properties of Perpendicular MTJs with Thin Pd Based Multilayers 国際会議

    水沼広太朗

    Int. Symp. on Advanced Magnetic Materials and Applications 2010年7月12日

  526. High spin-filter efficiency in a Co ferrite fabricated by a thermal oxidation 国際会議

    金井 駿

    Int. Symp. on Advanced Magnetic Materials and Applications 2010年7月12日

  527. Magnetization reversal in (Ga,Mn)As by using spin-orbit interaction effective magnetic field 国際会議

    遠藤将起

    Int. Symp. on Advanced Magnetic Materials and Applications 2010年7月12日

  528. 歪GaAs量子井戸中における核スピンコヒーレンスの磁場依存性

    小野真証, 石原淳, 佐藤源輝, 松坂俊一郎

    特定領域「スピン流の創出と制御」研究会 2010年6月23日

  529. GaAs量子井戸中における核スピンコヒーレンスの四重極分裂幅依存性

    石原淳, 佐藤源輝, 松坂俊一郎

    特定領域「スピン流の創出と制御」研究会 2010年6月23日

  530. Gating Ferromagnetic Semiconductor (Ga,Mn)As 国際会議

    9th Int. Workshop on Surface, Interface and Thin Film Physics 2010年6月16日

  531. Spintronics for Nonvolatile Silicon Nanoelectronics 国際会議

    International Symposium on Technology Evolution for Silicon Nano-Electronics (ISTESNE) 2010年6月3日

  532. Exploring Magnetism with Ferromagnetic III-V Semiconductors 国際会議

    International Conference on Core Research and Engineering Science of Advanced Materials (Global COE Program) & 3rd International Conference on Nanospintronics Design and Realization (3rd-ICNDR) 2010年5月30日

  533. Gating Magnetism of Ferromagnetic Semiconductors 国際会議

    International Conference on Core Research and Engineering Science of Advanced Materials (Global COE Program) & 3rd International Conference on Nanospintronics Design and Realization (3rd-ICNDR) 2010年5月30日

  534. Electrical Gating of Magnetism in (Ga,Mn)As and Beyond 国際会議

    Huangkun Semiconductor Science and Technology Forum 2010年5月21日

  535. Experimentalist of the Week: Magnetic Semiconductors 国際会議

    Progress in Spintronics and Graphene Research (Beijing, Kavli Institute for Theoretical Physics 2010年5月20日

  536. Experimentalist of the Week: Magnetic Random (Access Memories + discussion) 国際会議

    Progress in Spintronics and Graphene Research 2010年5月20日

  537. Spintronics: Nanoscience and Nanoelectronics 国際会議

    IEEE Magnetics Society Distinguished Lecture for 2009 2010年5月19日

  538. Spintronics Meets CMOS VLS 国際会議

    Tohoku University, Japan-National Chiao Tung University & National Nano Device Laboratories, Taiwan Joint Workshop on Nano-Process and Nano-Device 2010年4月23日

  539. (Ga,Mn)AsにおけるDresselhausスピン軌道相互作用有効磁界

    遠藤将起

    第57回応用物理学会 2010年3月17日

  540. 2重MoO障壁CoFeB電極MTJのトンネル磁気抵抗特性と積層構造

    第57回応用物理学会 2010年3月17日

  541. CoFe/Pd多層膜を電極に用いた垂直MTJにおけるTMR特性と熱処理耐性

    水沼広太朗

    第57回応用物理学会 2010年3月17日

  542. キャパシタ構造を用いたCoFeBの磁気特性の電界制御

    金井駿

    第57回応用物理学会 2010年3月17日

  543. 金属プラズモン導波路構造を有するテラヘルツ量子カスケードレーザ

    第57回応用物理学会 2010年3月17日

  544. 電子濃度の異なるn型GaAsにおけるスピンホール効果の評価

    第57回応用物理学会 2010年3月17日

  545. 半導体量子井戸中における核スピン緩和時間の歪依存性

    小野真証

    第57回応用物理学会 2010年3月17日

  546. Nanoelectronics Meets Spintronics 国際会議

    3rd GCOE International Symposium on Photonics and Electronics Science and Engineering 2010年3月12日

  547. 金属導波路構造GaAsテラヘルツ量子カスケードレーザの発振特性

    テラヘルツ電磁波技術研究会「テラヘルツ電子デバイスの新展開」 2010年2月25日

  548. Electric-field Effects on Magnetic and Transport Properties of (Ga,Mn)As 国際会議

    16th International Winterschool, New Developments in Solid State Physics 2010年2月22日

  549. Carrier Concentration Dependence of Spin Hall Effect in n-GaAs 国際会議

    6th RIEC International Workshop on Spintronics 2010年2月5日

  550. Change of Magnetic Properties in Co40Fe40B20 Induced by Electric Field 国際会議

    遠藤将起

    6th RIEC International Workshop on Spintronics 2010年2月5日

  551. Effect of CoFeB Insertion and Pd Layer Thicknesses on TMR Properties in Perpendicular MTJs with MgO Barrier and CoFe/Pd Multilayers 国際会議

    水沼広太朗

    6th RIEC International Workshop on Spintronics 2010年2月5日

  552. Effect of Free Layer Structures on Tunnel Magnetoresistance for Double MgO Barrier Magnetic Tunnel Junctions 国際会議

    6th RIEC International Workshop on Spintronics 2010年2月5日

  553. Electric-field Effect on Thin (Ga,Mn)As Layers 国際会議

    6th RIEC International Workshop on Spintronics 2010年2月5日

  554. Hole Spin Resonance and Spin-orbit Interaction in p-GaAs/AlGaAs(311)A Heterostructure 国際会議

    寺岡総一郎

    6th RIEC International Workshop on Spintronics 2010年2月5日

  555. Spin Transfer Torque Switching in Magnetic Tunnel Junctions with CoFeB-based Synthetic Ferrimagnetic Free Layers 国際会議

    伊藤顕知

    6th RIEC International Workshop on Spintronics 2010年2月5日

  556. Strain Dependence of Nuclear Spin Relaxation Time in a GaAs Quantum Well 国際会議

    小野真証

    6th RIEC International Workshop on Spintronics 2010年2月5日

  557. Thickness Dependence of Magnetic Anistropy in CoFeB under Electric Fields 国際会議

    金井駿

    6th RIEC International Workshop on Spintronics 2010年2月5日

  558. Tunneling Spectroscopy of CoFeB/MgO/CoFeB Pseudo Spin-Valve MTJs with Ultrahigh TMR Ratio 国際会議

    6th RIEC International Workshop on Spintronics 2010年2月5日

  559. Intersubband transitions in ZnO quantum wells 国際会議

    SPIE Photonics West 2010年1月23日

  560. Effect of synthetic ferrimagnetic free layer structure on the thermal stability in MgO-barrier magnetic tunnel junctions 国際会議

    11th Joint MMM-Intermag Conference 2010年1月18日

  561. Material Science and Physics of Large TMR and Spin-transfer Switching in MgO-based MTJs for CMOS logic integration 国際会議

    11th Joint MMM-Intermag Conference 2010年1月18日

  562. GaAs量子井戸中における核スピン緩和の四重極分裂幅依存性

    特定領域成果報告会「スピン流の創出と制御」 2010年1月13日

  563. (Ga,Mn)Asにおけるスピン軌道有効磁界を用いた磁化方向制御

    遠藤将起

    第14回半導体スピン工学の基礎と応用(PASPS-14) 2009年12月21日

  564. GaAs量子井戸中における核スピン緩和の四重極分裂幅依存性

    小野真証

    第14回半導体スピン工学の基礎と応用(PASPS-14) 2009年12月21日

  565. n型GaAsにおけるスピンホール効果のキャリア濃度依存性

    第14回半導体スピン工学の基礎と応用(PASPS-14) 2009年12月21日

  566. ゲート付きGaAs/AlGaAs単一量子井戸を用いたゼロ磁場における高移動度2次元電子スピン歳差運動の光学検出

    高橋卓也

    第14回半導体スピン工学の基礎と応用(PASPS-14) 2009年12月21日

  567. 二次元正孔系のスピン共鳴とゼロ磁場スピン分裂

    寺岡総一郎

    第14回半導体スピン工学の基礎と応用(PASPS-14) 2009年12月21日

  568. A Disturbance-Free Read Scheme and a Compact Stochastic-Spin-Dynamics-Based MTJ Circuit Model for Gb-scale SPRAM 国際会議

    K. Ono(Hitachi

    International Electron Devices meeting 2009年12月7日

  569. n-(110)GaAs/AlGaAs単一量子井戸における核スピンダイナミクスのゲート電圧依存性

    小林裕臣

    応用物理学会東北支部学術講演会 2009年12月3日

  570. 磁性積層構造における逆スピンホール効果の温度依存性

    小池 奨

    応用物理学会東北支部学術講演会 2009年12月3日

  571. Multi pulse operation and optical detection of nuclear spin coherence in a quantum well 国際会議

    Sweden-Japan Workshop on Quantum Nanoelectronics (QNANO) 2009年11月13日

  572. 金属導波路構造GaAsテラヘルツ量子カスケードレーザの発振特性

    東北大学電気通信研究所共同プロジェクト研究会「量子カスケードレーザの高性能化と応用に関する研究」 2009年11月4日

  573. Electrical control of properties of (Ga,Mn)As using electric-double layer transistor 国際会議

    遠藤将起

    The 2nd RIEC-CNSI Workshop on Nanoelectronics, Spintronics and Photonics 2009年10月22日

  574. Multi-pulse control and optical detection of nuclear spin coherence in GaAs/AlGaAs quantum well 国際会議

    The 2nd RIEC-CNSI Workshop on Nanoelectronics, Spintronics and Photonics 2009年10月22日

  575. Nuclear spin coherence in a Schottky gated n-GaAs quantum well 国際会議

    小野真証

    The 2nd RIEC-CNSI Workshop on Nanoelectronics, Spintronics and Photonics 2009年10月22日

  576. Properties of Cu-based metal-metal waveguide THz quantum cascade lasers fabricated by radio frequency sputtering method 国際会議

    The 2nd RIEC-CNSI Workshop on Nanoelectronics, Spintronics and Photonics 2009年10月22日

  577. Spin resonance and zero field spin splitting of two dimensional hole system in (311)A GaAs/GaAs heterostructure 国際会議

    寺岡総一郎

    The 2nd RIEC-CNSI Workshop on Nanoelectronics, Spintronics and Photonics 2009年10月22日

  578. スピントロニクス素子を用いた論理集積回路

    東北大学電気通信研究所共同プロジェクト研究会「半導体サイエンスと半導体テクノロジーの融合~技術を先導する半導体サイエンスを目指して~」 2009年10月16日

  579. Annealing Temperature Dependence of Critical Current and Thermal Stability Factor in MgO-Barrier Magnetic Tunnel Junctions with CoFeB based Synthetic Ferrimagnetic Recording Layer 国際会議

    早川 純

    2009 International Conference on Solid State Devices and Materials (SSDM) 2009年10月7日

  580. CoFeB Inserted Perpendicular Magnetic Tunnel Junctions with CoFe/Pd Multilayers for High Tunnel Magnetoresistance Ratio 国際会議

    水沼広太朗

    2009 International Conference on Solid State Devices and Materials (SSDM) 2009年10月7日

  581. CoFeB/MgO/CoFeB Magnetic Tunnel Junctions with Low Resistance-Area Product and High Magnetoresistance 国際会議

    2009 International Conference on Solid State Devices and Materials (SSDM) 2009年10月7日

  582. Dielectric breakdown in MgO-barrier magnetic tunnel junctions with a CoFeB based synthetic ferrimagetic recording layer 国際会議

    山ノ内路彦

    2009 International Conference on Solid State Devices and Materials (SSDM) 2009年10月7日

  583. Electrical Control of the Magnetic Properties in (Ga,Mn)As Channel in Electric Double Layer Transistor 国際会議

    遠藤将起

    2009 International Conference on Solid State Devices and Materials (SSDM) 2009年10月7日

  584. Fine-Grain Power-Gating Scheme of a CMOS/MTJ-Hybrid Bit-Serial Ternary Content-Addressable Memory 国際会議

    松永翔雲

    2009 International Conference on Solid State Devices and Materials (SSDM) 2009年10月7日

  585. ThePerformance of Magnetic Tunnel Junction Integrated on the Back-end Metal Line of CMOS Circuits 国際会議

    遠藤哲郎

    2009 International Conference on Solid State Devices and Materials (SSDM) 2009年10月7日

  586. Spintronics: Nanoscience and Nanoelectronics 国際会議

    IEEE Magnetics Society Distinguished Lecture for 2009 (Yorktown Heights) 2009年10月6日

  587. Spintronics: Nanoscience and Nanoelectronics 国際会議

    IEEE Magnetics Society Distinguished Lecture for 2009 (Tallahasse) 2009年10月5日

  588. Spintronics: Nanoscience and Nanoelectronics 国際会議

    IEEE Magnetics Society Distinguished Lecture for 2009 (Paris) 2009年10月2日

  589. Spintronics: Nanoscience and Nanoelectronics 国際会議

    IEEE Magnetics Society Distinguished Lecture for 2009 (Grenoble) 2009年10月1日

  590. Magnets of Ferromagnetism in Semiconductors 国際会議

    The Royal Society Scientific Discussion Meeting -The Spin on Electronics- 2009年9月28日

  591. Spintronics: Nanoscience and Nanoelectronics 国際会議

    IEEE Magnetics Society Distinguished Lecture for 2009 (Madrid) 2009年9月25日

  592. Spintronics: Electrical Control of Magnetization 国際会議

    10th International Conference on Atomically Controlled Surfaces, Interfaces, and nanostructures (ACSIN 10) 2009年9月21日

  593. Spintronics: Nanoscience and Nanoelectronics 国際会議

    IEEE Magnetics Society Distinguished Lecture for 2009 (York) 2009年9月11日

  594. Spintronics: Nanoscience and Nanoelectronics 国際会議

    IEEE Magnetics Society Distinguished Lecture for 2009 (Southampton) 2009年9月9日

  595. (Ga,Mn)Sb薄膜における強磁性の電界制御

    西谷 雄

    第70回応用物理学会 2009年9月8日

  596. 2DEG移動度100,000cm2V-1s-1を越えるMgZnO/ZnO界面の実現

    塚崎敦

    第70回応用物理学会 2009年9月8日

  597. CoFe/Pd多層膜電極を用いた垂直MTJのTMR特性に及ぼす強磁性層挿入の影響

    水沼広太朗

    第70回応用物理学会 2009年9月8日

  598. Fabrication of a Nonvolatile Full Adder Based on Logic-in-Memory Architecture Using Magnetic Tunnel Junctions

    松永翔雲

    第70回応用物理学会 2009年9月8日

  599. 磁気トンネル接合における電流誘起フィールドトルクの直接測定

    伊藤顕知

    第70回応用物理学会 2009年9月8日

  600. 高反平行結合強度を有する積層フェリ構造を用いたMTJにおけるスピン注入磁化反転

    西村真之

    第70回応用物理学会 2009年9月8日

  601. 銅をベースとした金属・金属導波路テラヘルツ量子カスケードレーザの製作

    林宗澤

    第70回応用物理学会 2009年9月8日

  602. 半導体量子井戸中における核スピンダイナミクスの歪依存性

    小野真証

    第70回応用物理学会 2009年9月8日

  603. Spintronics: Nanoscience and Nanoelectronics 国際会議

    19th Soft Magnetic Materials Conference (SMM19) 2009年9月6日

  604. Conduction to valence band offset ratio of ZnO/MgZnO Quantum Wells 国際会議

    10th International Conference on Intersubband Transitions in Quantum Wells 2009年9月6日

  605. Fabrication of Copper Metal-Metal THz Waveguide by Radio Frequency Sputtering Method 国際会議

    10th International Conference on Intersubband Transitions in Quantum Wells 2009年9月6日

  606. Spintronics: Nanoscience and Nanoelectronics 国際会議

    IEEE Magnetics Society Distinguished Lecture for 2009 (Tuscaloosa) 2009年9月4日

  607. Spintronics: Nanoscience and Nanoelectronics 国際会議

    IEEE Magnetics Society Distinguished Lecture for 2009 (Argonne) 2009年9月3日

  608. Ferromagnetism in III-V Semiconductors 国際会議

    36th International Symposium on Compound Semiconductors (ISCS2009) 2009年8月30日

  609. Magnetic Tunnel Junctions: Beyond Nonvolatile Memories 国際会議

    Nano and Giga Challenges in Electronics, Photonics and Renewable Energy Simposium and Summer School (NGC200) 2009年8月10日

  610. 不純物ドープ半導体量子井戸中における核スピン緩和時間の電界制御

    特定領域「スピン流の創出と制御」研究会 2009年8月9日

  611. Transport properties of double MgO barrier magnetic tunnel junctions with CoFeB electrodes 国際会議

    International Conference on Magnetism 2009年7月26日

  612. Effects of annealing temperature on giant tunnel magnetoresistance ratio and tunneling spectroscopy of CoFeB/MgO/CoFeB magnetic tunnel junctions 国際会議

    20th International Colloquium on Magnetic Films and Surfaces 2009年7月20日

  613. SQUID magnetometry of the effect of electric-field on magnetization of (Ga,Mn)As 国際会議

    18th Electronic Properties of 2 Dimensional Systems and 14th Modulated Semiconductor Structures 2009年7月19日

  614. Epitaxy and characterization of Co doped ZnO on ZnO substrate 国際会議

    18th Electronic Properties of 2 Dimensional Systems and 14th Modulated Semiconductor Structures 2009年7月19日

  615. Optical detection of zero-field spin precession of high mobility two dimensional electron gas in a gated GaAs/AlGaAs quantum well 国際会議

    18th Electronic Properties of 2 Dimensional Systems and 14th Modulated Semiconductor Structures 2009年7月19日

  616. Multi pulse operation and optical detection of nuclear spin coherence in a quantum well 国際会議

    18th Electronic Properties of 2 Dimensional Systems and 14th Modulated Semiconductor Structures 2009年7月19日

  617. Detection of local electron and nuclear spin dynamics by time-resolved Kerr microscopy 国際会議

    18th Electronic Properties of 2 Dimensional Systems and 14th Modulated Semiconductor Structures 2009年7月19日

  618. Fabrication and operation of a metal-metal waveguide GaAs terahertz quantum cascade laser 国際会議

    18th Electronic Properties of 2 Dimensional Systems and 14th Modulated Semiconductor Structures 2009年7月19日

  619. Magnetic anisotropy in a ferromagnetic (Ga,Mn)Sb thin film 国際会議

    西谷

    18th Electronic Properties of 2 Dimensional Systems and 14th Modulated Semiconductor Structures 2009年7月19日

  620. Width and temperature dependences of lithographically induced magnetic anisotropy in (Ga,Mn)As wires 国際会議

    小川(新田研

    18th Electronic Properties of 2 Dimensional Systems and 14th Modulated Semiconductor Structures 2009年7月19日

  621. Electric-field control of the anomalous Hall effect in (Ga,Mn)As thin films 国際会議

    千葉

    18th Electronic Properties of 2 Dimensional Systems and 14th Modulated Semiconductor Structures 2009年7月19日

  622. Two-color pump-probe measurements of intersubband excitonic interactions in GaAs/AlGaAs quantum wells 国際会議

    森田健

    18th Electronic Properties of 2 Dimensional Systems and 14th Modulated Semiconductor Structures 2009年7月19日

  623. Electric-field manipulation of magnetization vector in (Ga,Mn)As 国際会議

    千葉

    18th Electronic Properties of 2 Dimensional Systems and 14th Modulated Semiconductor Structures 2009年7月19日

  624. Spin resonance of two dimensional hole system 国際会議

    寺岡総一郎

    18th Electronic Properties of 2 Dimensional Systems and 14th Modulated Semiconductor Structures 2009年7月19日

  625. Control of Spin States in Semiconductors 国際会議

    The 3rd International Symposium on Information Electronics Systems 2009年7月13日

  626. Thermally activated longitudinal optical phonon scattering time of a GaAs/AlGaAs THz quantum cascade laser emitting at 3.8 THz 国際会議

    14th International Conference on Narrow Gap Semiconductors and Systems 2009年7月13日

  627. Control of Spin States in Semiconductors 国際会議

    3rd International Symposium on Information Electronics Systems 2009年7月13日

  628. n-(110)GaAs単一量子井戸における核スピン緩和時間のゲート電圧依存性

    第28回電子材料シンポジウム 2009年7月8日

  629. 磁性積層構造における逆スピンホール効果の温度異存性

    第28回電子材料シンポジウム 2009年7月8日

  630. 薄層MgO障壁CoFeB/MgO/CoFeB MTJのTMR特性と構造

    第28回電子材料シンポジウム 2009年7月8日

  631. 20 Years of III-V DMS – An Introduction 国際会議

    5th International School and Conference on Spintronics and Quantum Information Technology (SPINTECH V) 2009年7月7日

  632. Spintronics: Nanoscience and Nanoelectronics 国際会議

    21th Annual Conference on Magnetics and Cross-Strait Magnetism Conference (TAMT), IEEE Magnetic Society Distinguished Lecture for 2009 2009年6月24日

  633. Hybrid CMOS/Magnetic Tunnel Junction Approach for Nonvolatile Integrated Circuits 国際会議

    2009 Symposia on VLSI Technology and Circuits 2009年6月15日

  634. 32-Mb 2T1R SPRAM with Localized Bi-Directional Write Driver and ‘1’/‘0’ Dual-Array Equalized Reference Cell 国際会議

    R. Takemura(Hitachi

    2009 Symposia on VLSI Technology and Circuits 2009年6月15日

  635. SPRAM with Large Thermal Stability for High Immunity to Read Disturbance and Long Retention for High-Temperature Operation 国際会議

    K.Ono(Hitachi

    2009 Symposia on VLSI Technology and Circuits 2009年6月15日

  636. Magnetic Tunnel Junction for Next Generation Intergrated Circuits 国際会議

    2009 Advanced Research Workshop, Future Trends in Microelectronics 2009年6月14日

  637. Spintronics: Nanoscience and Nanoelectronics 国際会議

    IEEE Magnetic Society Distinguished Lecture for 2009 2009年6月8日

  638. Electrical Magnetization Vector manipulation in (Ga,Mn)As 国際会議

    Spin-Up 2009 2009年5月31日

  639. Electric-Field Manipulation of Magnetization Direction 国際会議

    Frontiers in Nanoscale Science and Technology, Nanoelectronics & Nanophotonics, Spintronics & Quantum Information 2009年5月29日

  640. Electric Field Manipulation of Magnetic Anisotropy in Ferromagnetic Semiconductors 国際会議

    IEEE International Magnetics Conference 2009年5月4日

  641. Perpendicular magnetic tunnel junctions with CoFe/Pd multilayer electrodes and MgO barrier 国際会議

    IEEE International Magnetics Conference 2009年5月4日

  642. Tunneling spectroscopy of CoFeB/MgO/CoFeB MTJs with ultrahigh TMR ratio 国際会議

    IEEE International Magnetics Conference 2009年5月4日

  643. Spintronics: Nanoscience and Nanoelectronics 国際会議

    IEEE Magnetic Society Distinguished Lecture for 2009 (Danver) 2009年4月23日

  644. Spintronics: Nanoscience and Nanoelectronics 国際会議

    IEEE Magnetic Society Distinguished Lecture for 2009 (San Diego) 2009年4月22日

  645. Spintronics: Nanoscience and Nanoelectronics 国際会議

    IEEE Magnetic Society Distinguished Lecture for 2009 (San Jose) 2009年4月21日

  646. Spintronics: Nanoscience and Nanoelectronics 国際会議

    IEEE Magnetic Society Distinguished Lecture for 2009 (Santa Clara) 2009年4月21日

  647. Spintronics: Nanoscience and Nanoelectronics 国際会議

    IEEE Magnetic Society Distinguished Lecture for 2009 2009年4月20日

  648. Manipulation of Magnetization Direction by Electric Fields 国際会議

    Spin Current 2009(SpinAps) 2009年4月17日

  649. Spintronics: Nanoscience and Nanoelectronics 国際会議

    IEEE Magnetic Society Distinguished Lecture for 2009 (Carvallis) 2009年4月16日

  650. Spintronics: Nanoscience and Nanoelectronics 国際会議

    IEEE Magnetic Society Distinguished Lecture for 2009 (Sendai) 2009年4月13日

  651. 垂直磁化トンネル接合電極としてのCoFe/Pd多層膜の検討

    第56回応用物理学会 2009年3月30日

  652. CoFeB/MgO/CoFeB保磁力差型MTJの低RA領域でのTMR特性

    第56回応用物理学会 2009年3月30日

  653. 高移動度2次元電子の内部有効磁場によるスピン歳差運動の光学検出

    第56回応用物理学会 2009年3月30日

  654. 不純物ドープ半導体量子井戸中における核スピン緩和時間の電界制御

    第56回応用物理学会 2009年3月30日

  655. (Ga,Mn)As薄膜における強磁性転移温度の電界制御

    第56回応用物理学会 2009年3月30日

  656. (Ga,Mn)Asの異常ネルンスト効果

    第56回応用物理学会 2009年3月30日

  657. (Ga,Mn)As中の磁壁の磁場誘起クリープ

    第56回応用物理学会 2009年3月30日

  658. (Ga,Mn)Sbの低温MBE成長と磁気特性評価

    第56回応用物理学会 2009年3月30日

  659. Electric-Field Manipulation of Magnetization Vector Direction 国際会議

    American Physical Society, March Meeting 2009年3月16日

  660. 不揮発性論理素子実現のための課題

    科学技術未来戦略ワークショップ「次世代を拓くナノエレクトロニクス」 2009年3月9日

  661. n-GaAs/AlGaAs量子井戸構造における核スピンの量子ゲート操作とその光検出

    特定領域研究会「スピン流の創出と制御」 2009年1月7日

  662. Ferromagnetic III-V Semiconductors: Electrical Manipulation of Magnetism and Magnetization 国際会議

    Twenty Years of Spintronics Retrospective and Perspective 2008年12月8日

  663. Electrical Control of Magnetism and Magnetization 国際会議

    D. Chiba

    Magnetic Single Nano-Object International School and Workshop (M-SNOW) 2008年11月23日

  664. Electrical Manipulation of Magnetization Vector 国際会議

    Asian Conf. on Nanoscience and Nanotechnology (AsiaNano) 2008年11月3日

  665. Exploring Ferromagnetism in III-V Semiconductors 国際会議

    23rd Nishinomiya-Yukawa Memorial Int. Workshop, Spin Transport in Condensed Matter (STCM) 2008年10月27日

  666. Electric-Field Munipulation of Magnetization Vector -Toward Electric-Field Reversal- 国際会議

    D. Chiba

    CNSI-RIEC Workshop on Nanoelectronics, Spintronics and Photonics 2008年10月9日

  667. Magnetic Tunnel Junction for Next Generation Integrated Circuits 国際会議

    4th Taiwan Int. Spintronics Conf. on Spintronics (TICSpin) 2008年10月2日

  668. Electric-field manipulation of magnetization vector - Toward electric-field reversal- 国際会議

    The 4th Taiwan International Conference on Spintronics 2008年10月2日

  669. Current-induced Magnetization Switching for Next Generation Integrated Circuits 国際会議

    SPINSWITCH Workshop "Spin Momentum Transfer" 2008年9月3日

  670. Current Induced Magnetic Domain Wall Creep in Semiconductors 国際会議

    9th Int. Symp. on Foundations of Quantum Mechanics, In the Light of New Technology (ISQM-TOKYO 08) 2008年8月25日

  671. Spintronics: Nanoscience and Nanoelectronics 国際会議

    Seminar on Magnetic Semiconductors 2008年8月15日

  672. Electrically driven domain wall in (Ga,Mn)As 国際会議

    SPIE Optics + Photonics 2008, Nano Science + Engineering 2008年8月10日

  673. Ferromagnetic III-V Semiconductors Physics and Material Science 国際会議

    5th Int. Conf. on Physics and Applications of Spin-related Phenomena in Semiconductors (PASPS V) 2008年8月3日

  674. Control of Spins in Semiconductor Structures 国際会議

    2nd Int. Symp. on Information Electronics Systems 2008年7月14日

  675. Control of Spins in Semiconductor Structures 国際会議

    2nd International Symposium on Information Electronics Systems 2008年7月14日

  676. Ferromagnetic Semiconductors - Physics and Material Science 国際会議

    Summer School of Advanced Functional Materials 2008年7月8日

  677. Spintronics: Nanoscience and Nanoelectronics 国際会議

    UCSB Seminar 2008年5月29日

  678. Ferromagnetic III-V Semiconductors 国際会議

    CNSI/FENA Seminar 2008年5月27日

  679. Domain Wall in (Ga,Mn)As 国際会議

    Workshop on Spin and Charge Transport in Nanostructures(SPINOR2008) 2008年5月14日

  680. Spin Manipulation in Semiconductors and Metals 国際会議

    IEEE International Magnetic Conference (INTERMAG08) 2008年5月4日

  681. Electrical Manipulation of Magnetic Properties in (Ga,Mn)As 国際会議

    D. Chiba

    Workshop on Recent Advances of Low Dimensional Structures and Devices (WRA-LDSD) 2008年4月7日

  682. Coherent Control of Nuclear Spins in GaAs Quantum Wells

    NIMS&東工大合同シンポジウム「凝縮系の超高速現象とコヒーレント制御」 2008年2月21日

  683. Spin Current-Induced Domain Wall Motion in (Ga,Mn)As 国際会議

    11th Sanken International Symposium, Sanken Nanotech Symposim, Sanken MSTEC Symposium 2008年2月4日

  684. Ferromagnetic III-V Semiconductors 国際会議

    International Workshop and Conference on Photonics and Nanotechnology (ICPN) 2007年12月16日

  685. University-Classes Domain Wall Creep Motion in (Ga,Mn)As 国際会議

    International Symposium, the Winter Conference of Korean Magnetic Society 2007年12月6日

  686. Ferromagnetic Semiconductors for Spintronics 国際会議

    9th Northeastern Asian Symposium on Advanced Material 2007年12月5日

  687. Spin-current induced dynamics in a ferromagnetic semiconductor domain wall 国際会議

    3rd Seeheim Conference on Magnetism 2007年8月26日

  688. Ferromagnetism in III-V semiconductors 国際会議

    10th Asia Pacific Physics Conference (APPC10) 2007年8月21日

  689. 半導体スピントロニクスの全て

    第45回茅コンファレンス -最近のスピン科学とスピン技術- 2007年8月19日

  690. Spin-current induced domain wall creep motion in ferromagnetic semiconductors 国際会議

    1st WUN INternational Conference on Spintronic Materials and Technology (WUN-SPIN07) 2007年8月7日

  691. Ferromagnetism in III-V semiconductors 国際会議

    1st NIMS Conference on Recent Breakthroughts in Materials Science and Technology 2007年7月11日

  692. Materials science and physics of ferromagnetism in semiconductors 国際会議

    12th International Conference on Intergranular and Interphase Boundaries in Materials (IIB2007) 2007年7月10日

  693. スピントロニクス -材料からデバイス・回路へ-

    電子情報通信学会 2007年6月29日

  694. Spin-current induced dynamics in ferromagnetic semiconductor structures 国際会議

    4th International School and Conference on Spintronics and Quantum Inoformation Technology (SPINTECH IV) 2007年6月17日

  695. Spin-Current Induced Dynamics in Ferromagnetic Semiconductor Structures 国際会議

    4th International School and Conference on Spintronics and Quantum Information Technology (SPINTECH IV) 2007年6月17日

  696. Ferromagnetism in semiconductors 国際会議

    International Center for Quantum Structures Workshop on Nanomagnetism and Spintronics (ICQS) 2007年6月14日

  697. Manipulation of magnetism and magnetization in ferromagnetic semiconductors 国際会議

    International Center for Quantum Structures Workshop on Nanomagnetism and Spintronics (ICQS) 2007年6月11日

  698. The world of spintronics 国際会議

    International Symposium on Advanced Magnetic Materials and Applications (ISAMMA) 2007年5月28日

  699. Domain wall motion in (Ga,Mn)As induced by spin-polarized current 国際会議

    Research Center for Spin Dynamics and Spin-Wave Devices Workshop 2007年5月25日

  700. Spin spin-current induced domain wall dynamics in ferromagnetic semiconductors 国際会議

    M. Yamanouchi, D. Chiba, T. Dietl, F. Matsukura, J. Ieda, S. Maekawa, S. Barnes

    CERC International Symposium, Highlights and Perspectives of Correlated Electron Systems - From Physics to Applications 2007年5月22日

  701. Control of magnetizaion in ferromagnetic semiconductors by spin-current 国際会議

    Frontiers in Nanoscale Science and Technology Workshop(FNST2007) 2007年3月29日

  702. Spin current induced dynamics in ferromagnetic semiconductors 国際会議

    UK-Japan Workshop on Advance Materials 2007年2月27日

  703. Spin-current effects observed by current-induced domain wall motion in (Ga,Mn)As 国際会議

    ATI and IFCAM International Workshop on Spin Current 2007年2月19日

  704. Recent development in magnetic tunnel junctions for magnetic random access memories and beyond 国際会議

    SEMICON KOREA 2007 2007年1月31日

  705. Spintronics -From materials to circuits 国際会議

    The 1st JUNBA Symposium on Nanomaterial Science 2007年1月11日

  706. Giant tunnel-magnetoresistance in rf-sputter deposited CoFeB/MgO/CoFeB magnetic tunnel junctions 国際会議

    International Symposium, the Winter Conference of Korean Magnetic Society 2006年11月23日

  707. MgO-based Magnetic Tunnel Junctions for Spin-Injection Magnetic Random Access Memories 国際会議

    International Workshop on New Non-Volatile Memory 2006年11月20日

  708. Ferromagnetic Semiconductor Spintronics 国際会議

    Japan-German Joint Workshop 2006 2006年10月30日

  709. Spin Current in Ferromagnetic Semiconductor Structures 国際会議

    The Semiconductor Spintronics Workshop 2006年10月12日

  710. Current Induced Domain Wall Motion in (Ga, Mn)As 国際会議

    International Workshop on Spin Transfer 2006 (IWST) 2006年10月2日

  711. Physics of Current-induced Domain Wall Motion in a Ferromagnetic Semiconductor (Ga, Mn)As 国際会議

    Workshop on Current Trends in Nanoscopic and Mesoscopic Magnetism 2006年9月6日

  712. Physics and Materials of Spintronics with Semiconductors 国際会議

    4th International Conference on Physics and Applications of Spin-related Phenomena in Semiconductors (PASPS-IV) 2006年8月15日

  713. Integrating Spins in Electronics 国際会議

    Device Research Conference 2006年6月26日

  714. Ferromagnetic III-V Semiconductors: Progress and Prospects 国際会議

    III Joing European Magnetic Symposia 2006年6月26日

  715. Ferromagnetic III-V Semiconductors 国際会議

    International Conference on Modern Materials & Technologies (CIMTEC) 2006年6月4日

  716. Electrical Manipulation of Magnetization in Ferromagnetic III-V Semiconductors 国際会議

    Spintronics Workshop 2006年5月8日

  717. Magnetization manipulation in ferromagnetic semiconductors 国際会議

    Bio Nano Robo Seminar Series 2006年4月27日

  718. Interaction between spin polarized current and localized spins in ferromagnetic semiconductors 国際会議

    KITP Conference of Spintronics 2006年3月20日

  719. Progress and porspects of spintronics 国際会議

    15th International Conference on Ternary and Multinary Compounds 2006年3月6日

  720. Domain wall motion induced by electrical current in (Ga,Mn)As 国際会議

    International Symposium on Mesoscopic Superconductivity and Spintronics 2006 (MS+S2006) 2006年2月27日

  721. Current induced domain wall motion in ferromagnetic semiconductors 国際会議

    14th International Winterschool on New Developments in Solid State Physics, Charges and spins in nanostructures: basics and devices 2006年2月13日

  722. Physics of ferromagnetic in semiconductors and their Heterostructures (I), (II) 国際会議

    Workshop on Mesoscopic and Spin Physics 2006 2006年1月5日

  723. Electrical control of domain wall motion in ferromagnetic semiconductors 国際会議

    50th Magnetism and Magnetic Materials Conference 2005年10月30日

  724. Electrical Magnetism and Magnetization Manipulation in Ferromagnetic Semiconductor Heterostructures 国際会議

    D. Chiba, M. Yamanouchi, F. Matsukura

    2005 Workshop on Materials with Novel Electronic Properties 2005年9月26日

  725. Mid-infrared InAs/AlGaSb quantum cascade lasers 国際会議

    K. Otani

    20th Congress of International Commission for Optics, Challenging Optics in Science and Technology (ICO20) 2005年8月21日

  726. Electrical Manipulation of Domain Walls in Semiconductors 国際会議

    Advanced Study Institute-Science and Application of Spin Electronics 2005年8月15日

  727. Ferromagnetic Semiconductors for Spintronics 国際会議

    The 23rd International Conference on Defects in Semiconductors (ICDS-23) 2005年7月24日

  728. Synthesis, Properties and Functionalities of Ferromagnetic Semiconductors 国際会議

    13th European Physical Society 2005 2005年7月10日

  729. Electrical Magnetization Manipulation in Semiconductors 国際会議

    3rd International Conference on Materials for Advanced Technologies (ICMAT 2005) 2005年7月3日

  730. Spin-based Electronics 国際会議

    1st International Nanotechnology Conference on Communication and Cooperation 2005年6月1日

  731. InAs/AlSb quantum cascade lasers 国際会議

    K. Otani

    Conference on Lasers and Electro-Optics Quantum Electronics and Laser Science Conference (CLEO/QELS 2005) 2005年5月22日

  732. High Temperature Ferromagnetism in Semiconductors: Issues 国際会議

    AFOSR Wide Band Gap Ferromagnetic Semiconductors Workshop 2005年5月15日

  733. Magnetization Manipulation in Ferromagnetic Semiconductor Structures 国際会議

    Int. Workshop on Nanoscale Fluctuations in Magnetic and Superconducting Systems 2005年5月10日

  734. Mid-infrared InAs-based quantum cascade lasers 国際会議

    K. Otani

    17th Indium Phosphide and Related Materials Conference (IPRM2005) 2005年5月8日

  735. Magnetization reversal in ferromagnetic semiconductor structures 国際会議

    Japan – Sweden International Workshop on Quantum Nano Physics and Electronics 2005年4月7日

  736. Current Induced Magnetization Reversal in Semiconductors 国際会議

    M. Yamanouchi, F. Matsukura

    International Magnetics Conference, "INTERMAG2005" 2005年4月4日

  737. Electrical Control of Magnetization in Semiconductors 国際会議

    2005 March Meeting of the American Physical Society 2005年3月21日

  738. Ferromagnetic III-V Semiconductors Spintronics 国際会議

    Deutsche Physikalsche Gesellschaft (German Physical Society) 2005年3月4日

  739. Electrical Magnetization Control in Semiconductors 国際会議

    32nd Conf. on Physics and Chemistry of Semiconductor Interfaces (PCSI-32) 2005年1月23日

  740. Electrical magnetization control in ferromagnetic semiconductors 国際会議

    The 2004 Conference on Optoelectronic and Microelectronic Materials and Devices (COMMAD 2004) 2004年12月8日

  741. Electrical Magnetization reversal in ferromagnetic semiconductors 国際会議

    Australia-Japan Workshop 2004年12月6日

  742. Magnetic Semiconductor Spintronics 国際会議

    13th Semi-conducting and iusulating Materials Conference (SIMC-XIII-2004) 2004年9月20日

  743. Electrical Manipulation of Magnetization in Ferromagnetic Semiconductors 国際会議

    31st International Symposium on Compound Semiconductors (ISCS2004) 2004年9月12日

  744. Magnetism and Magnetization Manipulation in Semiconductors 国際会議

    Gordon Research Conference: Magnetic Nanostructures 2004年8月22日

  745. Electrical Magnetization Reversal in Ferromagnetic Semiconductor Structures 国際会議

    4th IEEE Conference on Nanotechnology 2004年8月16日

  746. Ferromagnetism in III-V and III-N Semiconductors 国際会議

    International Workshop on NItride Semiconductors, IWNS 2004 2004年7月19日

  747. Manipulation of magnetism in semiconductors 国際会議

    1st Taiwan International Conference on Nanoscience and Technology 2004年6月30日

  748. Electrical manipulation of magnetization in semiconductors 国際会議

    12th International Conference on Solid Films and Surfaces, ICSFS-12 2004年6月21日

  749. Electrical manipulation of magnetism in ferromagnetic semiconductors 国際会議

    International Conference on Nanospintronics Design and Realization, ICNDR 2004 2004年5月24日

  750. Manipulation of ferromagnetism in magnetic semiconductors 国際会議

    International Symposium on Mesoscopic Superconductivity and Spintronics MS+S2004 2004年3月1日

  751. Ferromagnetic Semiconductor Materials and Devices for Spintronics 国際会議

    9th Joint MMM-Intermag Conference, MMM2004 2004年1月5日

  752. Elecrrical manipulation of ferromagnetism in magnetic semiconductors 国際会議

    Aspen Winter Conference 2004-Spins in Nanostructures: From Atoms and Quantum Dots to Magnets 2004年1月4日

  753. Spintronics Based on Ferromagnetic Semiconductors 国際会議

    3rd International Conference on Advanced Materials and Devices ICAMD2003 2003年12月10日

  754. Ferromagnetic Semiconductor Spintronic Devices 国際会議

    New Phenomena in Mesoscopic Systems 6 and Surfaces and Interfaces in Mesoscopic Devices 4, NPMS6-SIMD4 2003年11月30日

  755. Ferromagnetic Semiconductor Spintronic Materials and Devices 国際会議

    International Symposium on Clusters and Nano-Assemblies: Physical and Biological Systems, ISCANA 2003 2003年11月10日

  756. Semiconductor Spintronics 国際会議

    1st Student-organizing International Mini-Conference on Information Electronics System 2003年11月4日

  757. Spintronic Semiconductor Materials and Devices 国際会議

    International Symposium on Photonics and Spintronics in Semiconductors Nanostructures, PSSN 2003 2003年11月2日

  758. Spintronics by Ferromagnetic Semiconductors 国際会議

    International Union of Materials Reserach Societies - International Conference on Advanced Materials IUMRS-ICAM 2003 2003年10月8日

  759. Type-II InAs-based Quantum Cascade Lasers 国際会議

    Int. Conf. on Solid State Devices and Materials 2003年9月16日

  760. Ferromagnetic III-V Semiconductor Materials and Devices 国際会議

    24th Riso Int. Symp. on Materials Science 2003年9月10日

  761. Semiconductor Spintronics 国際会議

    2nd Int. Conf. on Semiconductor Spintronics and Quantum Information Technology, SPINTECH II 2003年8月4日

  762. Ferromagnetic Semiconductor Heterostructures 国際会議

    Int. Conf. on Magnetism (ICM2003) 2003年7月27日

  763. Properties and Manipulation of Ferromagnetism in III-V Semiconductors 国際会議

    Int. Conf. on Magnetism (ICM2003) 2003年7月27日

  764. Manipulation of Spins in Semiconductors 国際会議

    8th Int. Symp. on Advanced Physical Fields 2003年1月14日

  765. Ferromagnetism in III-V Semiconductor Heterostructures 国際会議

    the WE-Heraus Seminar on Frontiers in Nanomagnetism 2003年1月6日

  766. Ferromagnetism and Spintronics in Semiconductors 国際会議

    Materials Research Society 2002 Fall Meeting 2002年12月2日

  767. Manipulation of Spin States in Semiconductors 国際会議

    6th Symp. on Spin-Charge-Photon(SCP) Coupled Systems 2002年11月18日

  768. Ferromagnetic Semiconductors for Spintronic Heterostructures 国際会議

    Asia-Pacific Surface and Interface Analysis Conference (APSIAC '02) 2002年10月1日

  769. Molecular Beam Epitaxy and Properties of Ferromagnetic III-V Semiconductors 国際会議

    12th Int. Conf. on Molecular Beam Epitaxy (MBE XII) 2002年9月15日

  770. Ferromagnetic Semiconductor Spintronics 国際会議

    26th Int. Conf. on Physics of Semiconductors (ICPS2002) 2002年7月29日

  771. Manipulation of Ferromagnetism in Magnetic Semiconductor Field Effect Transistors 国際会議

    Device Research Conference 2002年6月24日

  772. Magnetic semiconductors and manipulation of spin states 国際会議

    The 8th Int. Conf. on Electronic Materials(IUMRS-ICEM2002) 2002年6月10日

  773. 49.H. Ohno, "Semiconductor Spintronics Using Ferromagnetic Semiconductor Heterostructures," 国際会議

    Intermag Europe 2002 2002年4月28日

  774. 48.H. Ohno, "Spin-dependent Phenomena in Ferromagnetic Semiconductor Heterostructures," 国際会議

    The 17th International Colloquium on Magnetic Films and Surfaces 2002年3月5日

  775. 47.H. Ohno, "Manipulation of Ferromagnetism in Semiconductors," 国際会議

    Mesoscopic Superconductivity and Spintronics 2002 (MS S 2002) 2002年3月4日

  776. 46.H. Ohno, "Manipulation of Ferromagnetism and Spin-dependent Phenomena in Semiconductors," 国際会議

    The 28th International Symposium on Compound Semiconductors 2001 2001年10月1日

  777. 44.H. Ohno, "Ferromagnetic Semiconductors for Spintronics," 国際会議

    The First Joint European Magnetic Symposia (JEMS01) 2001年8月28日

  778. 45.H. Ohno, "Electric Field Control of Ferromagnetism in Semiconductors," 国際会議

    The 2001 International Conference on Solid State Devices and Materials (SSDM2001) 2001年8月28日

  779. 43.H. Ohno, "Ferromagnetism in III-V Semiconductors," 国際会議

    The ERATO-JST Mini-Symposium on Quantum Computing: Priciples and Implementations 2001年8月24日

  780. 42.H. Ohno, "Polarization, Transport and Manipulation of Spins in Semiconductors," 国際会議

    Spintronics 2001 (International Conference on Novel Aspects of Spin-Polarized Transport and Spin Dynamics) 2001年8月9日

  781. 41.H. Ohno, "Ferromagnetic/nonmagnetic III-V Semiconductor Structures," 国際会議

    The 2nd Stig Lundqvist Research Conference on the Advancing Frontiers in Condensed Matter Physics: "Non-Conventional Systems and New Directions" 2001年7月2日

  782. 40.H. Ohno, "Spin Manipulation in Ferromagnetic Semiconductor Structures," 国際会議

    The 4th Swedish-Japanese Quantum Nanostructure Workshop 2001年6月14日

  783. 39.H. Ohno, "Spin Manipulation in Ferromagnetic/Nonmagnetic Semiconductor Heterostructures," 国際会議

    The 1st International Conference and School on Spintronic and Quantum Information Technology (SPINTECH-I) 2001年5月13日

  784. 38.H. Ohno, "Spin Manipulation in Ferromagnetic Semiconductor Heterostructures," 国際会議

    The 10th Brazilian Workshop on Semiconductor Physics 2001年4月22日

  785. 37.H. Ohno, "Ferromagnetic/Nonmagnetic Semiconductor Heterostructures," 国際会議

    2001 March Meeting of The American Physical Society 2001年3月12日

  786. 36.H. Ohno, "Ferromagnetic III-V Semiconductors for Spintronics," 国際会議

    2001 March Meeting of The American Physical Society 2001年3月11日

  787. 35.H. Ohno, "Electrical Spin Injection from Ferromagnetic Semiconductors," 国際会議

    The 8th Joint MMM-Intermag Conference 2001年1月7日

  788. 34.H. Ohno, "Magnetic Semiconductor Heterostructures for Spintronics," 国際会議

    4th International Workshop on Quantum Functional Devices 2000年11月15日

  789. 33.H. Ohno, "Spin-dependent Phenomena in Ferromagnetic/Nonmagnetic Semiconductor Structures," 国際会議

    Japanese-German Symposium on Nanotechnology 2000年10月29日

  790. 32.H. Ohno, "Polarization, injection and relaxation of spins in magnetic/nonmagnetic III-V heterostructures," 国際会議

    The 8th NEC Symposium on Fundamental Approaches to New Material Phases – Spin-related Quantum Transport in Mesoscopic Systems 2000年10月22日

  791. 31.H. Ohno, "Ferromagnetism and Spin Related Phenomena in Semiconductor Heterostructures," 国際会議

    American Vacuum Society 47th International Symposium 2000年10月2日

  792. 30.H. Ohno, "Magnetism and Heterostructures of (Ga,Mn)As," 国際会議

    The 14th International Conference on High Magnetic Fields in Semiconductor Physics 2000年9月24日

  793. 29.Y. Ohno, R. Terauchi, T. Adachi, F. Matsukura, and H. Ohno, "Probing and controlling spin-relaxation in semiconductor heterostructures," 国際会議

    25th International Conference on Physics of Semiconductors 2000年9月17日

  794. 28.Y. Ohno, D. K. Young, B. Beschoten, F. Matsukura, H. Ohno, and D. D. Awschalom, "Spin-polarized Current Injection in Ferromagnetic Semiconductor Heterostructures," 国際会議

    Solid State Devices and Materials 2000 2000年8月29日

  795. 27.H. Ohno, "Ferromagnetic Heterostructures for Semiconductor Spintronics," 国際会議

    8th Asia Pacific Physics Conference 2000年8月7日

  796. 26.H. Ohno, "Ferromagnetism and Heterostructures of Magnetic III-V Semiconductors," 国際会議

    Electronic Structure and Magnetism in Complex Materials 2000年7月26日

  797. 25.F. Matsukura and H. Ohno, "Manganese Based Ferromagnetic III-V Semiconductors," 国際会議

    Symposium on Spin Electronics 2000年7月2日

  798. 24.H. Ohno, "Ferromagnetic III-V Heterostructures," 国際会議

    27th Conference on the Physics and Chemistry of Semiconductor Interfaces 2000年1月16日

  799. 23.H. Ohno, "Ferromagnetic Semiconductor (Ga,Mn)As," 国際会議

    Frontiers in Magnetism 1999年8月12日

  800. 22.H. Ohno, "Ferromagnetism and Heterostructures of III-V Magnetic Semiconductors," 国際会議

    13th International Conference on the Electronic Properties of Two-Dimensional Systems 1999年8月1日

  801. 21.H. Ohno, "Magnetism and Transport Properties of Ferromagnetic Semiconductor (Ga,Mn)As," 国際会議

    The Fall 1998 Materials Resaerch Society Meeting 1998年11月30日

  802. 20.H. Ohno, "Spin-Dependent Tunneling and Magnetic Properties of Ferromagnetic (Ga,Mn)As," 国際会議

    43rd Annual Conference on Magnetism and Magnetic Materials 1998年11月9日

  803. 19.H. Ohno, "Spin-Dependent Phenomena in Semiconductor Heterostructures," 国際会議

    International Workshop on Physics and Applications of Semicondcutor Quantum Structures 1998年10月18日

  804. 18.H. Ohno, "Spin Dependent Phenomena in Magnetic and Non-Magnetic III-V's," 国際会議

    International Conference on Solid State Devices and Materials 1998年9月7日

  805. 17.H. Ohno, "III-V Based Ferromagnetic Semiconductors," 国際会議

    Fourth International Symposium on Physics of Magnetic Materials 1998年8月23日

  806. 16.H. Ohno, “Ferromagnetic III-V Semiconductors and their Heterostructures” 国際会議

    24th International Conference on Physics of Semiconductors 1998年8月2日

  807. 15.H. Ohno, “Ferromagnetism and Heterostructures of (Ga,Mn)As,” 国際会議

    FED-PDI Joint Conference on 21st Century Electron Devices 1998年6月29日

  808. 14.H. Ohno, ”Magnetotransport and Magnetic Properties of (Ga,Mn)As and Its Heterostructures” 国際会議

    XXVII International School on Physics of Semiconducting Compounds 1998年6月7日

  809. 12.H. Ohno, “Spin Dependent Transport in Ferromagnetic (Ga,Mn)As” 国際会議

    1998 March Meeting of The American Physical Society 1998年3月16日

  810. 13.H. Ohno, “Spin and Charge Transport in III-V Magnetic Semiconductors” 国際会議

    JSPS Asian Science Seminar on Physics and Control of Defects in Semiconductors 1998年3月15日

  811. 11.H. Ohno, “Properties of Ferromagnetic (Ga,Mn)As” 国際会議

    2nd Gordon Research Conference on Magnetic Nanostructures 1998年1月25日

  812. 10.H. Ohno, “Carrier Induced Ferromagnetism in Diluted Magnetic Semiconductors” 国際会議

    The Second BUTSUKO Symposium Spin-Charge-Photon Coupled Systems 1997年11月25日

  813. 9.H. Ohno, “Origin of Ferromagnetism in (Ga,Mn)As” 国際会議

    Japanese-Polish Symposium on Diluted Magnetic Semiconductors 1997年9月11日

  814. 8.H. Ohno, “Ferromagnetic Semiconductor (Ga,Mn)As for Semiconductor Spin Electronics” 国際会議

    JRCAT Workshop on Phase Control of Colossal Magnetoresistive Oxides 1997年6月25日

  815. 7.H. Ohno, “Mn-based III-V Diluted Magnetic (Semimagnetic) Semiconductors,” 国際会議

    International Workshop on Semimagnetic (Diluted Magnetic) Semiconductors 1994年9月28日

  816. 6.H. Ohno, “Inter-Subband Population Inversion in Tunneling Heterostructures,” 国際会議

    The 3rd International Union of Materials Research Society International Conference on Advanced Materials 1993年8月31日

  817. 5.H. Ohno, "Diluted Magnetic III-V Semiconductors and Its Transport Properties," 国際会議

    The 9th International Conference on Ternary and Multinary Compounds 1993年8月8日

  818. 4.H. Ohno, E.E. Mendez, A. Alexandrou, and J.M. Hong, "Tamm States in Superlattices," 国際会議

    The 5th International Conference on Modulated Semiconductor Structures 1991年7月8日

  819. 3.H. Ohno, "Tamm States in Superlattices," 国際会議

    1991 March Meeting of The American Physical Society 1991年3月18日

  820. 2.H. Ohno, H. Munekata, S. von Molnar, and L.L. Chang, "New Diluted Magnetic III-V Semiconductors," 国際会議

    35th Annual Conference on Magnetism and Magnetic Materials 1990年10月29日

  821. 1.H. Ohno, J. Barnard, C.E.C. Wood, L. Rathbun and L.F. Eastman, "Double Heterojunction GaInAs Devices by MBE," 国際会議

    1980 International Electron Device Meeting 1980年12月8日

︎全件表示 ︎最初の5件までを表示

産業財産権 37

  1. 磁気抵抗効果素子及び磁気メモリ

    大野英男, 池田正二, 松倉文礼, 遠藤将起, 金井駿, 山本浩之, 三浦勝哉

    産業財産権の種類: 特許権

  2. 磁気抵抗効果素子、それを用いた磁気メモリセル及びランダムアクセスメモリ

    池田正二, 大野英男, 山本浩之, 伊藤顕知, 高橋宏昌

    産業財産権の種類: 特許権

  3. 共鳴トンネル磁気抵抗効果素子、磁気メモリセル及び磁気ランダムアクセスメモリ

    大野英男

    産業財産権の種類: 特許権

  4. 量子カスケードレーザ

    森安嘉貴, 大野英男, 大谷啓太

    産業財産権の種類: 特許権

  5. 磁気メモリセル及びランダムアクセスメモリ

    大野英男, 池田正二, 早川純

    産業財産権の種類: 特許権

  6. 半導体集積回路装置及びその製造方法

    羽生貴弘, 望月明, 白濱弘勝, 三浦成友, 大野英男

    産業財産権の種類: 特許権

  7. 磁気デバイスの製造方法、及び磁気デバイスの製造装置

    小野一修, 大野英男, 池田正二

    産業財産権の種類: 特許権

  8. 磁気抵抗効果素子、それを用いた磁気メモリセル及び磁気ランダムアクセスメモリ

    大野英男, 池田正二, 李 永珉, 早川純

    産業財産権の種類: 特許権

  9. 磁気デバイスの製造方法、及び磁気デバイスの製造装置

    小野一修, 大野英男, 池田正二

    産業財産権の種類: 特許権

  10. 磁気メモリセル及び磁気ランダムアクセスメモリ

    大野英男, 池田正二, 早川純

    産業財産権の種類: 特許権

  11. トランジスタおよび電子デバイス

    西井潤弥, 大友明, 大谷啓太, 川崎雅司, 大野英男

    産業財産権の種類: 特許権

  12. 低消費電力磁気メモリ及び磁化情報書き込み装置

    早川純, 大野英男

    産業財産権の種類: 特許権

  13. 混晶二酸化チタン、多層膜構造体、及び素子構造

    川崎雅司, 豊崎秀海, 山田康博, 大野英男, 松倉文礼

    産業財産権の種類: 特許権

  14. コバルトドープ二酸化チタン膜の作製方法、コバルトドープ二酸化チタン膜、及び多層膜構造

    川崎雅司, 大野英男

    産業財産権の種類: 特許権

  15. 電流注入磁壁移動素子

    大野英男, 松倉文礼, 千葉大地, 山ノ内路彦

    産業財産権の種類: 特許権

  16. 半導体装置およびその製造方法ならびに電子デバイス

    杉原利典, 大野英男

    産業財産権の種類: 特許権

  17. ツェナートンネル効果を用いた半導体発光素子

    大野英男, 大谷啓太

    産業財産権の種類: 特許権

  18. トランジスタの製造方法

    原猛, 大野英男

    産業財産権の種類: 特許権

  19. アクティブマトリクス基板およびその製造方法

    藤田達也, 大野英男

    産業財産権の種類: 特許権

  20. 半導体装置およびその製造方法

    藤田達也, 大野英男

    産業財産権の種類: 特許権

  21. InAs/AlSb量子カスケードレーザー及びその作製方法

    大野英男, 大谷啓太

    産業財産権の種類: 特許権

  22. III-V族強磁性半導体とその製造方法

    大野英男, 白井正文, 松倉文礼, 千葉大地

    特許第3817204

    産業財産権の種類: 特許権

  23. 不揮発性固体磁気メモリ、不揮発性固体磁気メモリの保磁力制御方法、及び不揮発性固体磁気メモリの記録方法

    大野英男, 松倉文礼, 千葉大地

    産業財産権の種類: 特許権

  24. 不揮発性固体磁気メモリの記録方法

    大野英男

    産業財産権の種類: 特許権

  25. 不揮発性固体磁気メモリの記録方法

    大野英男, 松倉文礼, 千葉大地

    特許第3932356

    産業財産権の種類: 特許権

  26. 強磁性半導体素子、強磁性半導体のスピン分極方法

    大野英男, 松倉文礼, 篁耕司

    産業財産権の種類: 特許権

  27. 半導体装置およびそれを用いる表示装置

    川崎雅司, 大野英男, シャープ株式会社

    産業財産権の種類: 特許権

  28. スピンフィルタ

    大野英男, 大谷啓太

    特許第3834616

    産業財産権の種類: 特許権

  29. 閃亜鉛鉱型CrSb、閃亜鉛鉱型CrSbの製造方法、及び多層膜構造

    大野英男, 松倉

    3849015

    産業財産権の種類: 特許権

  30. 薄膜トランジスタおよびマトリクス表示装置

    川崎雅司, 大野英男

    産業財産権の種類: 特許権

  31. スピン偏極伝導電子生成方法および半導体素子

    大野英男, 松倉文礼

    特許第3284239

    産業財産権の種類: 特許権

  32. 核スピン制御素子及びその制御方法

    大野英男, 大野裕三, 岸本修也

    特許第3427179

    産業財産権の種類: 特許権

  33. サブバンド間発光素子

    大野英男, 大谷啓太

    特許第3412007

    産業財産権の種類: 特許権

  34. 半導体デバイス

    川崎雅司, 大野英男

    産業財産権の種類: 特許権

  35. 量子閉じ込め構造を有する素子

    大野英男, 大野裕三

    特許第3438020

    産業財産権の種類: 特許権

  36. 半導体光集積回路

    秋永広幸, 大野英男

    産業財産権の種類: 特許権

  37. トランジスタ及び半導体装置

    川崎雅司, 大野英男

    産業財産権の種類: 特許権

︎全件表示 ︎最初の5件までを表示

共同研究・競争的資金等の研究課題 35

  1. スピントロニクスを用いた人工知能ハードウェアパラダイムの創成

    大野 英男, 遠藤 哲郎, 鈴木 大輔, 佐藤 茂雄, 堀尾 喜彦, 深見 俊輔

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Specially Promoted Research

    研究機関:Tohoku University

    2017年4月25日 ~ 2022年3月31日

    詳細を見る 詳細を閉じる

    本研究課題は、人工知能(AI)ハードウェアパラダイムの創成を念頭に、不揮発性スピン素子を用いたAIハードウェアとしての集積回路を設計実現することを目指して進めてきた。当初の計画に従い、3つの主要課題、①AIコンピューティングハードウェア向けスピントロニクス素子の開拓、②ノイマン型AIコンピューティングハードウェアの実現、③非ノイマン型AIコンピューティングハードウェアの実現、に対して研究を進めた。 ①については、アナログスピントロニクス素子のダイナミクスを利用することでスパイクタイミング依存可塑性やリーキー・インテグレート・アンド・ファイアなどの非ノイマン型ニューラルネットワークで必要とされるニューロン、シナプスの特性をスピン素子で再現できることなどが分かった。その他、反強磁性/強磁性ヘテロ構造におけるジャロシンスキー・守谷相互作用やスピン軌道トルクなどを評価し、人工知能ハードウェア応用に向けた有用な知見を得た。②については、基本回路の検討、ならびにハードウェアアルゴリズム検討のためのプラットフォーム構築に取り組み、スピン素子ベース多機能・再構成可能演算回路の設計や学習アルゴリズム評価のためのプラットフォーム構築などを進めノイマン型AIハードウェア実現の土台を形成した。③については、非ノイマン型・脳型コンピューティングアーキテクチャの検討、アナログスピンシナプス特性を考慮した学習則、アナログスピンメモリ素子を組み込んだアナログニューラルネットワーク集積回路の構築に向けた詳細な検討を行った。

  2. InAs量子カスケードレーザの次元性の制御とその効果

    大野 英男, 大谷 啓太, 林 宗澤, ベルムバーリック モハッマド, 佐藤 啓貴

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Scientific Research (A)

    研究機関:Tohoku University

    2007年 ~ 2009年

    詳細を見る 詳細を閉じる

    InAs中赤外量子カスケードレーザ(QCL)の磁場によるキャリアの閉じ込め効果を調べるために、量子井戸の面内に平行方向、及び垂直方向に磁場を印加し、特性を評価した。磁場を面内垂直方向に印加すると、ランダウ準位形成により閾値電流密度が減少した。一方で面内平行方向では閾値電流密度は変化せず、スロープ効率のみが増加するという特異な振る舞いを観測した。又テラヘルツ(THz)帯においても磁場の効果を調べるため、GaAs THz QCLを開発した。加えてTHz帯で高性能化が期待できるZnO量子井戸においてサブバンド間遷移を初めて観測した。

  3. InAs量子カスケードレーザーの高性能化に関する研究

    大野 英男, 大谷 啓太

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Scientific Research (A)

    研究機関:Tohoku University

    2005年 ~ 2006年

    詳細を見る 詳細を閉じる

    本研究ではInAs量子カスケードレーザーの活性領域におけるバンド構造と電気・光学特性の関係を明らかにすると同時に、どのように構造設計すれば特性の向上につながるかを理論、実験の両面から検討を行い、レーザーの高性能化を進めた。具体的には1.低温低閾値電流密度化、2.室温動作化、3.室温高出力化、及び4.高温動作を目指した。以下にその成果の概要を示す。 1.低温低或閾値電流密度化 振動子強度の大きいInAs/Al_<0.2>Ga_<0.8>Sb超格子構造を用いて、0.4kA/cm^2というこれまで報告されている最低閾値電流密度(液体窒素温度)に近い電流密度を実現した。又観測された発振波長(10.1μm)は設計値とほぼ一致した。 2.室温動作化 熱活性型のフォノン散乱による励起サブバンドへの注入効率の減少を抑えるために、励起サブバンドの波動関数が局在した発光層構造を用い室温パルス発振に成功した。このとき観測された室温(300K)における閾値電流密度は12kA/cm^2であり、発振波長は8.9μmで設計値にほぼ一致した。又最高動作温度は305Kであった。 3.室温高出力化 注入層のドーピング濃度を増大させ、注入電流のダイナミックレンジを増大させることで、室温においてピーク出力100mW以上の高出力化に成功した(発振波長12μm)。又室温における閾値電流密度を4.OkA/cm^2まで低減させることに成功した。観測された最高動作温度は340Kであった。 4.高温動作化 発光層として結合量子井戸を用いた構造に注目し構造と利得係数及び最高動作温度の関係について調べた結果、利得係数が最大となる構造で最高動作温度+100℃を実現した。このとき観測された発振波長は6μmで、閾値電流密度は15.5kA/cm^2であった。

  4. 半導体ナノスピントロニクス

    宗片 比呂夫, 田中 雅明, 伊藤 公平, 勝本 信吾, 白井 正文, 大野 英男

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Scientific Research on Priority Areas

    研究機関:Tokyo Institute of Technology

    2002年 ~ 2006年

    詳細を見る 詳細を閉じる

    本領域が主催するオープンな国際会議「半導体中のスピンが関連する現象とその応用に関する国際会議」(会議議長:宗片)(英語名:Intrn'l Conf.Phys.Appl.Spin-Related Phenomena in Semiconductors ; PASPS)を、2006年8月15日から18日の4日間、仙台市国際センターで実施した。本研究領域が中心となって得られた研究成果を世界に発信するとともに、物性物理学や電子工学において重要な研究分野と国際的に認知されつつあるスピントロニクスにおけるわが国の先導的な立場をあらためて強固にしつつ、世界の理工学に貢献した。 半導体中のスピン関連現象は、様々な構造において異なる形で現れる。それらは、非磁性半導体や磁性半導体あるいは関連のナノ構造におけるスピンと電荷の間の相互作用であり、電荷移動を伴わないスピンの伝播や蓄積、ホール効果、局在・非局在キャリア系におけるスピン位相の保存と破壊など、スピンを活用する素子の実現にとって極めて重要な問題を多く含んでいる。本会議では、これらを解き明かすべき共通の諸問題と位置づけた上で、スピン依存光学遷移、スピン依存電気伝導、スピン制御と位相、同位体スピン、スピントロニクス材料とその理論、スピン電子デバイス・スピン光デバイスとその応用、量子情報処理におけるスピン、などに関する最先端の研究成果144件を、19カ国から201名の参加者を得て検討した。会議録は学術雑誌physica status solidi(c)から出版された。 さらに、2006年12月14,15日には「半導体スピン工学」研究会を東大・物性研究所で開催し、わが国における半導体スピントロニクス研究の基盤の更なる強化と本領域の今後の発展について、現状と展望を交えて検討した。

  5. 磁性/非磁性半導体量子構造におけるスピン注入とスピン制御

    大野 裕三, 大野 英男, 松倉 文礼, 大谷 啓太

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Scientific Research (A)

    研究機関:Tohoku University

    2002年 ~ 2004年

    詳細を見る 詳細を閉じる

    本研究では,(1)磁性/非磁性半導体量子構造の設計と形成を行い,(2)磁性/非磁性半導体量子構造におけるキャリア,核,励起子,磁性イオンなどのスピンを電気的または光学的に制御し、それらの相互作用の制御及びその結果もたらされる光・電子・磁気スピン物性を調べ、スピンを情報担体とする"スピントロニクス"デバイスの基盤技術を確立することを目的とする。当該研究期間に得られた成果は以下の通りである。 ・強磁性半導体(Ga, Mn)Asとn^+-GaAsトンネル接合からなるスピン注入素子について、注入される電流のスピン偏極率がn^+-GaAs層の厚さ・ドーピング濃度に強く依存することを系統的な実験により明らかにしその最適条件を示した。 ・スピン軌道相互作用を抑制しスピン緩和時間を長くできるGaAs(110)基板上に形成したn-GaAs/AlGaAs(110)単一量子井戸構造において、g因子の異方性に起因する核スピン分極の双安定性とヒステリシスを時間分解ファラデー回転法により観測した。g因子の異方性と超微細相互作用による自己無撞着を考慮してラーモア周波数の磁場依存性を計算したところ、実験結果とよく一致する結果を得た。また、実験結果より核スピン分極率は最大で30%であることを示した。 ・ゲート電極を有するn-GaAs/AlGaAs(110)単一量子井戸構造において、ゲート電圧を印加して電子密度を制御することにより、超微細相互作用と動的核スピン分極を大きく変調できることを示した。また、その原因として電子密度の変化によって金属一絶縁体遷移が生じ、電子の波動関数の局在・非局在の変化により超微細相互作用の大きさが変調されているモデルを示した。

  6. 希薄磁性半導体量子構造スピン読み出し素子

    大谷 啓太, 大野 英男

    2002年 ~ 2002年

    詳細を見る 詳細を閉じる

    本研究課題では希薄磁性半導体スピン読み出し素子を提案し、次世代の量子情報処理・通信技術の基幹となる量子状態読み出し素子のプロトタイプを作製することを目指して研究を進めた。具体的には平成14年度の1年の研究期間で希薄磁性半導体量子井戸構造スピンフィルタを用いたスピン読み出し素子を提案し、その構造と期待される性能について理論的検討を行った。本年度に得られた主な研究成果は以下の通りである。 (1)II-VI族希薄半導体量子井戸構造スピンフィルタの設計 ZnMnSe/ZnSe及びZnCdMnSe/ZnSe量子井戸構造を用いたスピンフィルタに注目し、フィルタリング特性について計算を行ったところ、スピンをフィルタリングできるエネルギー及びその帯域が井戸や障壁層の厚さや組成などの構造をによって制御可能であることがわかった。 (2)II-VI族希薄磁性半導体量子井戸構造スピンフィルタを用いたスピン読み出し素子の提案 ZnMnSe/ZnSe及びZnCdMnSe/ZnSe量子井戸構造スピンフィルタを用いた3種類のスピン読み出し素子を提案した。これらの素子ではスピン状態の読み出しに光を用いるが、この光のエネルギーが量子井戸内のサブバンドのエネルギーに一致したとき、スピンの方向を効率良く光電流の流れる方向に変換できることがわかった。 (3)II-VI族希薄磁性半導体量子井戸スピン読み出し素子を用いた高周波発生器の検討 スピン読み出し素子と微小アンテナをカップリングさせた高周波発生器を提案し理論検討を行ったところ、円偏光バンド間光とサブバンド間光を用いれば、印加磁場によりギガヘルツからテラヘルツの周波数領域で可変な高周波発生器が作製可能であることがわかった。

  7. 半導体ナノスピントロニクス

    宗片 比呂夫, 勝本 信吾, 伊藤 公平, 田中 雅明, 大野 英男, 白井 正文

    2002年 ~ 2002年

    詳細を見る 詳細を閉じる

    従来の半導体物性に「スピン」という新しい自由度をもたらす様々な材料や構造が作製されるようになり、スピン機能を利用したデバイス実現へ向けた多くの基礎研究が行われるなど、これまで半導体ではあまり意識されなかったスピンを積極的に利用しようという研究が、ここ数年急速に進展している。本企画調査は、「半導体ナノスピントロニクス」分野およびその関連分野の研究者を集め、半導体や磁性体と半導体の複合構造中のスピンが関与する物性・機能およびその応用に関する研究成果について、集中的に討議することにより「半導体ナノスピントロニクス」の基本的な理解を深め,新しいスピン制御デバイスヘの応用の可能性を拓くことを目的として行われた。具体的には、平成14年12月19,20日に仙台国際センターにおいて「半導体中のスピン現象とその応用」に関する総合的な研究会(Physics and Application of Spin-related Phenomena in Semiconductors ; PASPS-8)を開催し、磁性原子を添加した半導体のバルク結晶や薄膜、磁性体と半導体から成る複合構造、非磁性半導体の量子構造、それらを微細加工した「スピントロニクスナノ構造」を対象に、(1)材料・構造の作製に関する材料科学、(2)キャリアスピン、磁性原子のスピン、光の間の相互作用に起因した光・電子物性,(3)キャリアあるいは磁性原子のスピンと伝導電子との相互作用に起因した電気伝導物性、(4)非磁性半導体中に注入・励起されたキャリアスピンのスピン緩和・スピンコヒーレンスなどのスピン物性、(5)以上述べた種々のスピン依存現象の応用可能性、に関して理論、実験、デバイス応用など様々な面からの研究課題を、口頭発表・ポスター発表形式で議論し、「半導体ナノスピントロニクス」と呼ばれる新分野の基盤技術を固めるとともに、21世紀の新しいエレクトロニクスに向けた我が国における研究コミュニティーを形成することができた。

  8. 半導体超構造における電子のスピンコヒーレンスとその制御

    大野 英男, 大野 裕三, 松倉 文礼

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Scientific Research (A)

    研究機関:Tohoku University

    2000年 ~ 2002年

    詳細を見る 詳細を閉じる

    本研究では、従来の半導体量子構造と新たに創生されつつある強磁性半導体との融合構造に基礎を置き、そこでの(1)電子のスピンコヒーレンスの顕示と外場による制御、(2)核スピンや磁性イオンとの相互作用の解明と制御、さらに(3)スピンに依存する電子・光物性を活用した新しいデバイスの作製を目的として研究を進め、以下のような成果を得た。 1.強磁性半導体(In,Mn)Asをチャネルとする電界効果トランジスタ構造を作製し、その正孔密度のゲート制御を確認した。さらに、正孔濃度を変化させることにより、温度を一定に保ったまま、磁性を制御することに初めて成功した。 2.低温分子線エピタキシ法によって、自然界には存在しない閃亜鉛鉱型CrSbをGaAs上にエピタキシャル成長させることに成功し、それが室温で強磁性体であることを明らかにした。 3.強磁性半導体(Ga,Mn)Asをベースとする(Ga,Mn)As/(Al,Ga)As/(Ga,Mn)As3層構造を作製し、巨大磁気抵抗効果やトンネル磁気抵抗(TMR)など、磁気エレクトロニクスデバイスに応用されている現象を全て半導体で構成されたデバイスにおいて観測した。特に、TMRでは100%を超える大きな磁気抵抗比を得た。 4.(110)変調ドープGaAs/AlGaAs量子井戸構造を作製し、時間分解ファラデー回転測定によってスピンコヒーレンス時間を調べたところ、共鳴スピン増幅を観測し、低温でスピン位相緩和時間が10ns程度であることを確認した。さらに、レーザーパルスによって生成されたスピン偏極電子と核スピンの相互作用の共鳴現象を観測した。 5.p型強磁性半導体(Ga,Mn)Asとn^+-GaAsからなるスピンエサキダイオードを作製し、(Ga,Mn)Asの価電子帯から非磁性GaAsの伝導帯へのバンド間トンネルを用いたスピン偏極電子注入を確認した。

  9. スピン制御による半導体超構造の新展開

    大野 英男, 嶽山 正二郎, 吉田 博, 岡 泰夫, 西澤 潤一, 吉野 淳二, 望月 和子

    2000年 ~ 2000年

    詳細を見る 詳細を閉じる

    特定領域研究「スピン制御による半導体超構造の新展開」では、平成9-11年度の3年間、スピン物性を顕著に発現する半導体超構造の作製法の確立とそのスピン物性の解明・制御、およびそれらのデバイス応用の観点から4つの研究班を組織し研究を進めた。特定領域研究が終了した本年度、総括班は、(1)特定領域研究の研究成果を発表し世界に情報発信をするとともに、内外の研究者が研究成果を発表することができる国際会議を開催、(2)和文の研究報告書のとりまとめ、(3)英文の研究報告書と論文集の作成、(4)報告書の主要部分のインターネット上への公開を行った。 具体的には、以下の通りである。平成12年9月13-15日の3日間、仙台国際センターにおいて17カ国から162名(うち69名は海外から)の参加者を集め、「半導体中のスピン関連現象の物理と応用に関する国際シンポジウム(PASPS2000)」と題して国際会議を開催した。会議では、17件の招待講演を含む132件の論文が発表された。プロシーディングスは学術雑誌Physica Eに発表される。会議中に海外からの参加者の要請で急遽第2回目の会議を2002年にドイツ・ウルツブルグ大学で開催する運びとなった。報告書に関しては、和文171ページ、英文700ページ(論文別刷含む)の2冊をまとめ、主要部分を http://www.ohno.riec.tohoku.ac.jp/projectreport/japanese/indexJ.htm及び http://www.ohno.riec.tohoku.ac.jp/projectreport/english/indexE.htmにて公開した。 本特定領域研究では、Nature,Scienceに4件の論文を発表したのをはじめ、半導体中のスピン応用に関する多くの知見を得た。米国では本領域研究に範を取り、新たにSpins in Semiconductorsなるプロジェクトが10倍の研究費規模で開始された。このように本領域は「半導体中のスピン」を一つの領域として国内外において確立することに成功した。同時に、本特定領域研究が先駆けて開拓した領域において、世界的にリードし続ける組織的対応が求められている。

  10. InAs/GaSbを用いた量子カスケード型遠赤外〜テラヘルツ帯発光素子

    大野 英男, 水田 正志, 大野 裕三, 松倉 文禮

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Scientific Research (A).

    研究機関:Tohoku University

    1999年 ~ 2000年

    詳細を見る 詳細を閉じる

    本研究はInAs/GaSb量子カスケード構造のサブバンド間光学遷移を利用した遠赤外〜テラヘルツ帯における高効率発光素子を実現することを目的として行われた。科学研究費補助金を請けて研究期間の初年度には遠赤外ステップスキャン方式フーリエ赤外分光器を、最終年度には光学測定用無振動冷凍機を新しく購入し、それを用いて以下の項目について研究を行った。 1.開発した計算機シュミレーターを用いてInAs/GaSb量子カスケード構造のレーザー閾値電流密度の理論的検討を行った結果、従来のタイプI量子カスケードレーザーの閾値電流密度の理論値と比較して、室温における閾値電流密度がおよそ1/5程度になることがわかった[大谷、大野、固体物理、Vol.34、699(1999)]。 2.InAs/GaSb量子カスケード構造だけでなく、非常に大きな波長可変性ををもつInAs/AlSb量子カスケード構造にも注目し、新しく購入した高感度ステップスキャンフーリエ変換赤外分光器を用いて世界で初めて電流注入サブバンド間発光を観測した[K.Ohtani et al., Electron Lett., Vol.35, 935(1999)]。 3.新しく購入した高感度ステップスキャンフーリエ変換赤外分光器を用いて、InAs/GaSb量子カスケード構造におけるエレクトロルミネッセンスの構造依存性及び温度依存性を調べ、サブバンド間発光とバンド構造の関係を明らかにした[K.Ohtani et al., Physica E, Vol.7, 80(2000)]。 4.InAs/AlSb量子井戸構造における光学特性が界面に形成されるボンドとバッファー層の種類に大きく依存することを明らかにした[K.Ohtani et al., Appl.Surf.Sci., Vol.159-160, 313(2000)]。 5.InAs/GaSb量子カスケード構造における周期数と発光強度の関係を調べ、発光強度が周期数に比例することを明らかにした[K.Ohtani et al., Proceedings of the 25^<th> International Conference on the Physics of Semiconductor, World Scientific, Singapore, 2001]。 6.InAs/GaSb量子カスケード構造における新しい発光素子構造を提案し、その構造を用いれば高効率に1THz近傍まで長波長化できることを理論的に示した[K.Ohtani et al., 論文投稿中]。

  11. 分子線エピタキシンにおける化合物半導体の成長過程と成長層の特性

    大野 英男, 大野 裕三, 松倉 文礼

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Scientific Research (B)

    研究機関:TOHOKU UNIVERSITY

    1998年 ~ 1999年

    詳細を見る 詳細を閉じる

    低温成長分子線エピタキシ(LT-MBE)法により、(LT-)GaAsやIII-V族磁性半導体およびそのナノ構造を形成し、反射高エネルギ電子線回折(RHEED)、原子間力(AFM)・磁気力(MFM)顕微鏡や磁気特性測定システム(SQUID)などを用いてそれらの成長過程及び構造、光・磁気・輸送特性について調べた。本研究で得られた主たる成果を以下に記す。 1.LT-MBEによるGaAs成長時にRHEEDの強度振動が低温で復活し、その大きさは基板温度とV/III比に依存することを見出した。また、過剰供給されたAs原子を自己表面活性剤としたモデルでシミュレーション計算を行った結果、実験結果を再現した。 2.数パーセントの濃度のMnを導入した(Ga,Mn)SbをMBEにより形成し、その物性と成長温度との関係を調べた。高温(560℃)成長の試料ではMnSbと思われる矩形のクラスターがAFM、MFMで観測され、室温で強磁性を示した。一方、LT-MBE(300℃)では、室温で強磁性を示すものの、20K以下で別の秩序相が現れることを確認した。これは低温で強磁性を示す(Ga,Mn)Sbが形成されていることを示している。 3.LT-MBEによりGaAs(211)B面上に形成した(In,Mn)Asナノ構造のAFM観察より、Mnがサイズを均一化するサーファクタント効果を有することを明らかにした。 4.すべて半導体から成る強磁性体(Ga,Mn)As/非磁性体(Al,Ga)As/強磁性体(Ga,Mn)As3層構造を作製し、層間の結合を磁化曲線から調べることより、非磁性層の厚さ・障壁高さでそれらの磁気的結合を制御できるこを示し、スピン依存散乱による巨大磁気抵抗効果をこの系で初めて確認した。

  12. スピン制御された半導体超構造の電子物性と応用

    大野 英男, 樽茶 清悟, 鈴木 直, 勝本 信吾

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Scientific Research on Priority Areas

    研究機関:Tohoku University

    1997年 ~ 1999年

    詳細を見る 詳細を閉じる

    電子物性制御班は、スピン制御された半導体超構造の電子物性、特に磁性・スピン物性と輸送特性を実験的・理論的に解明し、その制御と応用の可能性を明らかにすることを目的とした。以下に研究成果の概略を示す。 (1)(Ga,Mn)As,(In,Mn)As,(Ga,Mn)Sbなどの強磁性半導体とへテロ構造を低温成長分子線エピタキシで成長しその磁性と輸送特性を調べた。強磁性・非磁性半導体三層構造では、スピン依存散乱、層間結合、トンネル磁気抵抗が観測され、(Ga,Mn)Asエミッタの共鳴トンネルダイオードにおいて磁場なしの状態で強磁性転移に伴う電流のピークを観測した。また(Ga,Mn)Asを用いて強磁性半導体から非磁性半導体へのスピン偏極電流注入を実現した。(大野) (2)III-V族希薄磁性半導体(Ga,Mn)As、(In,Mn)Asの低温における磁性、電気伝導、磁場応答を詳細に調べ、巨大磁気抵抗効果を見出し、この2種類の半導体のMn濃度に対する相図が極めて似通っていることを見出した。また結晶成長後低温でアニールすることで、AsとMnの複合欠陥が消失し試料の性質が劇的に改善することがわかった。(勝本) (3)III-V族希薄磁性半導体(Ga,Mn)Asにおける強磁性探索とその発現機構を解明することを目的に(Ga,Mn)Asの電子状態を第一原理計算を行い、最近接遷移金属間の磁気相互作用は価電子バンドに正孔を供給するV,Cr,Mnにおいて強磁性的になることを明らかにした。(鈴木) (4)半導体人工原子及び人工分子を作製し、人工原子に関しては原子と同様な量子力学的な基本則が成り立つこと、磁場を印加することでスピンに関して様々な状態遷移が起こること、また人工分子に関してはスピンブロッケード、擬スピンブロッケード、スピン選択トンネルなど新しいスピン効果が現れることを示した。(樽茶)

  13. III-V族希薄磁性半導体におけるキャリア誘起磁性とその制御

    大野 英男, 大野 裕三, 松倉 文礼

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Scientific Research (B)

    研究機関:TOHOKU UNIVERSITY

    1996年 ~ 1997年

    詳細を見る 詳細を閉じる

    これまでにIII-V族半導体をベースにした希薄磁性半導体(In,Mn)As、(Ga,Mn)Asの成長が分子線エピタキシの低温成長で可能であって、さらにp形の試料では低温で正孔誘起の強磁性が現れることを確認した。 しかし、これらの正孔誘起磁性の起源をはじめとしてIII-V族希薄磁性半導体の磁性とキャリア濃度・Mn濃度との関係、またそれらと結晶成長条件との関連は解明されておらず、またド-ピングや電界効果などによるIII-V族希薄磁性半導体の磁性の制御の可能性も追求されていなかった。 本研究は、以上の背景の下に、我々が開発した強磁性III-V族希薄半導体(Ga,Mn)Asを用いて、磁性とキャリア濃度・Mn濃度の関係、量子構造の作製、更にキャリア濃度で磁性を制御する可能性を探求することを目的として行われた。 本研究の成果概要は以下の通りである。 1.Mn組成を変えた(Ga,Mn)Asの磁気輸送特性・磁気特性を調べ強磁性転移温度と生孔濃度のMn組成依存性を明らかにした。強磁性転移温度はMn濃度0.05以下では組成に比例して増加し、これまでに得られている最高の強磁性転移温度は110Kである。 2.(Ga,Mn)As/(Al,Ga)Asの強磁性半導体/非磁性半導体超格子構造・量子構造の作製が可能であり、これらの構造においても強磁性的性質が保たれる。 3.常磁性領域での抵抗率の磁場依存性と強磁性転移温度から、(Ga,Mn)Asの強磁性秩序の起源がRKKY相互作用であることを明らかにし、キャリア濃度と強磁性転移温度の関係に対する知見を得た。 これらのことは、キャリア濃度を制御することにより、磁性を制御できること、またヘテロ接合及び量子構造を利用した電界効果トランジスタ等のデバイスの可能性が開けたことを示すものである。

  14. スピン制御による半導体超構造の新展開

    大野 英男, 宗方 比呂夫, 獄山 正二郎, 家 泰弘, 吉田 博, 吉野 淳二

    1996年 ~ 1996年

    詳細を見る 詳細を閉じる

    半導体中のキャリアや磁性イオンのスピン間の交換相互作用に基づくさまざまな物性は、これまで応用の表舞台にでることはなかった。これは、材料技術、超構造作製技術が未発達であったので、電子のもつスピンという自由度を積極的に制御し利用することが出来なかったためである。しかしここ数年で状況は大きく変化した。II-VI族・III-V族希薄磁性半導体とその超構造が作製可能となり、磁性不純物添加半導体構造や磁性体/半導体ヘテロ構造も実現された。この結果半導体超構造のスピンを理解して積極的に制御し、応用を考えることが可能となりつつある。 本研究では、半導体超構造におけるスピンに関する材料、超構造作製、測定、理論の研究を総合的有機的に結びつけることによって、(1)スピン物性の顕著に発現する半導体超構造の作製法の確立し、(2)半導体超構造におけるスピン物性を解明して、(3)スピンという新しい自由度を利用した半導体超構造の応用の可能性を明らかにする、ことを目的とする重点領域研究のための企画調査を行った。 第1回目の研究会を平成8年9月26-27に仙台で行い、予定されている計画研究の内容を発表すると共に有機的に研究を推進するための協力関係について話し合った。さらに、一般に公開された第2回の研究会を平成9年1月27-28日仙台国際センターにて開催し、予定されている計画研究メンバのみならず広く国内・国外の研究者の参加を得て、III-V族化合物半導体、II-VI族化合物半導体、磁性不純物添加半導体、新しい磁性半導体の開発、メゾスコピック領域も含めた超構造のスピン物性についての研究発表と研究討論を行った。第3回の研究会は平成9年3月13日に行われ、重点領域の公募研究について討論を行った。

  15. 化合物半導体結合量子井戸構造における量子電子輸送現象とジョセフソン効果

    大野 英男, 大野 裕三, 松倉 文礼, 澤田 安樹, 江澤 潤一

    1996年 ~ 1996年

    詳細を見る 詳細を閉じる

    本研究は、結合量子井戸の量子電子輸送現象にとりあげ、高移動度を有する結合2重量子井戸構造の結晶成長と、2層の電子系それぞれに独立にコンタクトを有する素子の製作を行い、それを用いて低温・強磁場中での2層の2次元電子系の輸送現象を明らかにすることを目的としている。平成6-8年度の研究により次の成果を得た。(1) 2層の電子層それぞれにオーミックコンタクトを取るためにフロントゲートとバックゲートを使って上と下のチャネルをそれぞれ切るデバイス構造を作製するプロセスを開発し確立した。基板研磨と部分的エッチングを併用して100V以下のしきい値を実現した。(2)分子線エピタキシで成長した選択ドープAlGaAs/GaAs構造より作製したフロント、バックゲートつきのデバイスを用いて、希釈冷凍器つき超伝導磁石で8mK、14.5Tまでの測定を行い、2重量子井戸構造に特異な分数量子ホール効果のゲート電圧依存性が見られることを確認した。これは低キャリア濃度でかつ共鳴状態になるようにフロント・バック両ゲートによりキャリア濃度を調整したために観測可能となったものである。さらにこの特異な振る舞いが2層系の分数量子ホール状態がゲージ理論より導かれるコンポジットボゾンでよく説明できることを見出した。

  16. 希薄磁性半導体メモリデバイスの研究

    大野 英男, 横山 直樹, 大野 裕三, 松倉 文礼

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Scientific Research (A)

    研究機関:TOHOKU UNIVERSITY

    1995年 ~ 1996年

    詳細を見る 詳細を閉じる

    本研究は、申請者らの開発した強磁性III-V族希薄磁性半導体を用いたメモリを実現するための、結晶成長、プロセス技術、メモリデバイス、メモリ構成法を研究し、その性能・限界を明らかにすることを目的として行われた。 本研究の成果概要は以下の通り。 (1)強磁性III-V族希薄磁性半導体メモリ材料として新しく低温成長分子線エピタキシによりIII-V族化合物半導体でもっとも多く用いられているGaAsをベースにした(Ga,Mn)Asを創成した。最大のMn組成で0.071を得ている。さらに(Ga,Mn)Asの組成と格子定数との関係をX線回折により定めた。それによると組成と格子定数は線形な関係にある(ベガード則)。 (2)磁気輸送特性・磁化特性を調べ、(Ga,Mn)Asが強磁性体であることを確認した。これまでに得られているキュリー温度は110Kである。また0.05以下の組成の領域ではキュリー温度と組成が比例する。 (3)(In,Ga)Asバッファ層を挿入して(Ga,Mn)Asにかかる歪みを圧縮から引っ張りにかえることにより磁化容易軸の向きを面内から面に垂直にかえることが可能であることを明らかにした。これは異常ホール効果を利用したメモリの読み出しに必要不可欠なものである。 (4)臨界散乱とキュリー温度から強磁性の起源がRKKY相互作用であることを明らかにし、よりキュリー温度を上げるために必要な知見を得た。 (5)磁化容易軸を面に垂直に制御した(Ga,Mn)Asを用いてメモリエレメントを製作し、異常ホール効果により良好な読み出しができることを確認した。

  17. スピン制御による半導体超構造の新展開

    大野 英男, 宗方 比呂夫, 嶽山 正二郎, 家 泰弘, 吉田 博, 吉野 淳二

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Scientific Research (B)

    研究機関:TOHOKU UNIVERSITY

    1995年 ~ 1996年

    詳細を見る 詳細を閉じる

    研究目的:これまで個別に進められてきた半導体超構造におけるスピンに関する材料、超構造作製、測定、理論の研究を総合的有機的に結びつけることによって、(1)スピン物性の顕著に発現する半導体超構造の作製法の確立し、(2)半導体超構造におけるスピン物性を解明して、(3)スピンという新しい自由度を利用した半導体超構造の応用の可能性を明らかにする。 研究経過:III-V族化合物半導体、II-VI族化合物半導体、磁性不純物添加半導体をとりあげ、新しい磁性半導体の開発や、メゾスコピック領域も含めた超構造のスピン物性を明らかにする理論並びに実験を進めた。研究成果は平成9年1月27-28日に開催された公開の研究会にて発表した。 平成7-8年度の研究成果としては、次のものが特に重要である。 1.シリコン上への磁性体のエピタキシャル成長 半導体LSIの中心材料であるSi(001)上に、室温で強磁性を示す金属間化合物(MnAsなど)をエピタキシャル成長することに初めて成功した。 2.GaAsベースの新しい希薄磁性半導体:(Ga,Mn)As 世界に先駆けてGaASベースの(Ga,Mn)AsをGaAs上に成長することに成功し、(Ga,Mn)Asがキュリー温度110K以下で強磁性体であることを明らかにした。また(Ga,Mn)Asベースの超構造の成長にも成功した。 3.半導体超構造による磁性原子の交換相互作用の制御 磁性原子中の電子スピン間の交換相互作用が、半導体超構造における量子サイズ効果によって制御可能であることを理論的に示した。 4.自由磁気ポーラロンの確認 これまで無いとされてきた自由磁気ポーラロンの存在を実験的に明らかにした。

  18. エピタキシャル成長の量子論と構造のダイナミクス

    西永 頌, 白石 賢二, 伊藤 智徳, 大野 英男, 中山 弘, 一宮 彪彦

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Scientific Research (A)

    研究機関:The University of Tokyo

    1995年 ~ 1996年

    詳細を見る 詳細を閉じる

    本研究は平成7年度と8年度の2年間にわたって行われ、最終報告会も含め6回の研究会を行った。本研究では、エピタキシャル成長時、原子スケールでの原子の動きを明らかにする目的で理論家と実験家が協力して研究を進めた。先ず結晶表面の構造を原子スケールで明らかにし、そこに原子が飛来したときどのように振舞うかを明らかにする目的で第一原理量子論計算を行った。その結果、原子配置の決定に際し、エレクトロンカウンティングモデルが良く合うことを明らかにした。次にこのような表面において原子がどのように拡散し結晶にとり込まれて行くかを明らかにするためモンテカルロシミュレーションを行った。これにより、GaAs(001)面において、A-stepとB-stepがどのように振舞うかを明らかにした。さらに、従来行われて来なかった二元結晶の分子線エピタキシの様子をモンテカルロシミュレーションにより調べ、単元素子とどのように違うかについて議論した。原子ステップはエピタキシャル成長時、条件により集合したり分解したりし、成長を強く左右する。そこで、成長時の原子ステップの振舞を統計力学的現象論により解析した。この結果を実験結果と比較することによりステップのスティフネスを計算することができた。又、半導体の融液の振舞を理解するため分子動力学法によりシミュレーションを行った。 実験についてはシリコン表面における成長原子の振舞を走査型トンネル顕微鏡を用いて調べ、表面再構成構造と二次元アイランドの形状、原子の付着、離脱のしやすさの関係等を明らかにした。また、GaAsを例にとり、成長表面で原子が結晶にとり込まれるまでどの程度移動できるかをmicroprobe-RHEED/SEM MBEを用いて調べた。それによると、As圧によりその距離が大きく変わること、二つの面間での拡散の方がAs圧によって反転すること等が明らかになった。 まだ、理論と実験の間には差があるが、お互いの討論により、ある程度このギャップはうめられたものと考えられる。

  19. 化合物半導体結合量子井戸構造における量子電子輸送現象とジョセフソン効果

    大野 英男, 松倉 文礼, 澤田 安樹, 江澤 潤一

    1995年 ~ 1996年

    詳細を見る 詳細を閉じる

    本研究は、結合量子井戸の量子電子輸送現象をとりあげ、高移動度を有する結合2重量子井戸構造の結晶成長と、2層の電子系それぞれに独立にコンタクトを有する素子の製作を行い、それを用いて低温・強磁場中での2層の2次元電子系の輸送現象を明らかにすることを目的としている。本年度の研究では、分子線エピタキシによる結晶成長と測定用デバイス作製装置の製作、さらにデバイスの試作を行い、低温・高磁場下のヘテロ構造の測定準備を進めた。具体的には、2層の電子層それぞれにオーミックコンタクトを取るためにフロントゲートとバックゲートを使って上と下のチャネルをそれぞれ切るデバイス構造を作製するプロセスを開発し、実際にフロント、バックゲートの動作を確認した。また低温で高移動度(50万cm^2/Vs)を有する試料について、希釈冷凍器つき超伝導磁石で8mK、14.5Tまでの測定を行い2重量子井戸構造でで分数量子ホール効果の観測されることを確認した。

  20. 化合物半導体総合量子井戸構造における量子電子輸送現象とジョセフソン効果

    大野 英男, 松倉 文ひろ, 澤田 安樹, 江澤 潤一

    1994年 ~ 1994年

    詳細を見る 詳細を閉じる

    本研究は、結合量子井戸の量子電子輸送現象をとりあげ、高移動度を有する結合2重量子井戸構造の結晶成長と、2層の電子系それぞれに独立にコンタクトを有する素子の製作を行い、それを用いて低温・強磁場中での2層の2次元電子系の輸送現象を明らかにすることを目的としている。本年度の研究では、理論面で横磁場下での系の基底状態の相転移に関し新しい知見を得た。具体的には、2層の分数量子ホール状態にある電子層の間の量子位相の存在を明らかにするために横磁場B_<11>の効果を解析した。その結果、(1)B_<11>が小さいときには外部磁場は2層間で不完全にスクリーンされ、臨界磁場を越えると外部磁場は自由に2層間に侵入すること、(2)Murphyら(Phys.Rev.Lett.,72,728(1994))の報告した2層分数量子ホール系におけるp_<xx>の活性化エネルギの印加磁場角度依存性がこの2つの相で良く説明できること、が明らかになった。実験面では分子線エピタキシによる結晶成長と測定用デバイス作製装置の製作、さらにデバイスの試作を行い、低温・高磁場下のヘテロ構造の測定準備を進めた。具体的には、2層の電子層それぞれにオーミックコンタクトを取るためにフロントゲートとバックゲートを使って上と下のチャネルをそれぞれ切るデバイス構造を作製するプロセスを開発した。そのために必要な表面と裏面の構造をアラインさせるマスクアライナを製作した。測定では、希釈冷凍器つき超伝導磁石で8mK、14.5Tまでの予備測定を行い、選択ドープヘテロ接合で分数量子ホール効果の観測されることを確認した。

  21. ヘテロ接合エネルギフィルタを用いた量子構造長波長発光素子

    大野 英男, 水田 正志, 松倉 文礼, 中原 純一郎

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Developmental Scientific Research (B)

    1993年 ~ 1994年

    詳細を見る 詳細を閉じる

    本研究では、化合物半導体量子井戸構造中に形成される同一のバンドに属する量子準位間の光学遷移(サブバンド間遷移)を利用した長波長発光素子のための基礎的研究を行った。 本研究では、(1)通過する電子がすべてサブバンド間遷移に関与することを可能とする全く新しいInAs/AlSb/GaSbヘテロ構造エネルギフィルタを有する構造、および(2)エピタキシャル成長プロセス技術が成熟しているAlGaAs/GaAsヘテロ構造のエネルギフィルタを有する構造の2種類をとりあげ検討した。理論的には(1),(2)の両構造において発光素子が構成可能であり、報告されているフォノン散乱時間を考慮しても十分低い電流密度で反転分布の形成が可能であることを明らかにした。実験的には、AlGaAs/GaAs系の分子線エピタキシャル成長を行いプロセスを施して電界印加可能な構造とし、それによって室温における電界下でのサブバンド間遷移の挙動を調べた。低キャリア濃度の時にはシュタルク効果によるブルーシフトが観測され、高キャリア濃度の時にはレッドシフトが観測された。現在の所、実験的に発光を観測するに到ってないが、今後、素子の冷却およびInAs/GaSb系の実験的検討を行い、サブバンド間遷移を利用した発光素子を実現する。

  22. III-V族希薄磁性半導体ヘテロ接合における磁気秩序と電気伝導

    大野 英男, 中原 純一郎

    1993年 ~ 1993年

    詳細を見る 詳細を閉じる

    本研究では、申請者等が新しく合成に成功したIII-〓族をベースとする希薄磁性半導体を用いたヘテロ接合に見られる磁気秩序と電気伝導の関係を明らかにし、この新希薄磁性半導体ヘテロ接合の物性を解明し、応用の可能性を探ることを目的として研究を進めた。具体的には、(1)分子線エピタキシによる(In,Mn)As/(Al,Ga)Sbヘテロ構造の成長と加工、(2)1.4〜300K、最大8Tまでの磁場中での、磁気輸送特性(磁気抵抗効果、ホール効果)の測定を行った。 本研究で得られた新しい知見は、以下の点に要約される。試料としては、20nmの(In,Mn)As(MnAs組成0.18)を(Al,Ga)Sb(AlSb組成0.3)上に成長させたものを取り上げた。 (1)200K以下では、ホール抵抗は通常のホール効果と異常ホール効果よりなる。また、異常ホール効果の部分は磁化と抵抗の積に比例する。 (2)40K以上では、磁化は磁場に比例しキュリーワイス型の温度変化を示す。フィッティングよりキュリー温度として35Kを得る。このことは、Mn間の相互作用が強磁性的であることを示している。 (3)40K以下では、磁化曲線は急峻になり単純な常磁性と異なるふるまいを示す。10K以下で初めてヒステリシスが顕著になる。しかし、厚い試料で見られていた常磁性と強磁性の共存を示す特性は見られていない。 (4)平均場近似では40K以下の磁化のふるまいを理解することはできない。磁気ポーラロンなどの大きさを統計的に取り入れる、または超常磁性的ふるまいであると考えることで説明ができる可能性がある。

  23. 化合物半導体清浄表面と有機金属との相互作用

    大野 英男, 福井 孝志, 中原 純一郎

    1993年 ~ 1993年

    詳細を見る 詳細を閉じる

    本研究は、化合物半導体の種々の清浄表面と有機金属との相互作用を実験的に明らかにしていくことを目的とした。具体的には、超高真空中でMBE成長したGaAsなどの清浄表面に、有機金属を照射し、その相互作用の様子を電子分光法、反射高エネルギ電子線回折等を用いて明らかにすることを試み、さらに水素、水素ラジカル照射で、成長の様式や不純物(特に炭素)の取り込みがどのように変わるかを明らかにすることを試みた。本年度の成果は以下の通り。 オージェ電子分光、二次イオン質量分析法、透過電子顕微鏡を用いて、真空中においてGaAs清浄表面に照射されたトリメチルガリウム(TMGa)のカイネティクスと成長速度、炭素不純物の濃度との関係を統一的に明らかにした。GaAs上でTMGaはまず解離吸着し、メチル基が速い時定数(<1s)で脱離してメチルガリウム(ジメチル又はモノメチルガリウム)となる。その後100s(〜500℃)程度の時定数で、メチル基が脱離する。このメチル基が、原子層エピタキシにおける自己停止機構を実現している。さらに長い時定数(>600s)をもつ表面炭素も測定されているが、これがGaAs中の残留炭素濃度を決定するものと考えられる。高純度GaAsの結晶成長にはこの最後の炭素を除去することが必要となるが、これには、水素ラジカルを照射することが有効であり、残留炭素濃度を10^<20>cm^<-3>から10^<18>cm^<-3>以下に低減することが可能であることを明らかにした。ラジカルビームの強度、照射時間をあげることでよりいっそうの低減が可能である。また、TMGaパージサイクル中に水素ラジカルを照射することによって原子層エピタキシの成長速度が1ML以上に増加する、すなわち吸着したTMGaの量が1MLを越えていることを示す興味深い結果も得られた。

  24. 低周波プラズマCVD(TEOS+O_2)によるシリコン酸化膜の低温形成プロセス開発

    伊達 広行, 下妻 光夫, 下妻 光夫, 大野 英男, 田頭 博昭, 伊達 広行

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Developmental Scientific Research (B)

    研究機関:Hokkaido University

    1992年 ~ 1993年

    詳細を見る 詳細を閉じる

    最近の集積回路は、線幅サブミクロンスケールまで微細化が進んでおり、この技術を支えているのは、プラズマCVDやプラズマエッチング等のドライプロセスである。この集積回路における多層配線層間絶縁や表面保護膜としてシリコン酸化膜が使われ、段被覆性の良好なTEOS(Tetraethoxysilane)が材料として高周波プラズマCVDなどによって成膜されることが一般的である。しかし、これは加熱プロセスであるため微細な回路への温度の影響が大きく、低温プロセスの開発が望まれている。本研究は、この低温プロセスを低周波(50Hz)プラズマCVD法で達成しようと試みたものである。 平成4年度では、(1)Si基板上に堆積された薄膜の膜質は、加熱なしでは良好なものが得られない事が明らかとなった。(2)基板加熱200℃に上げると良質な膜が得られた。(3)堆積速度が60→30nm/minと減少し緻密な膜となっていくことがわかった。(4)IR吸収スペクトルから基板温度の上昇でSi-O結合が支配的になり、オージェ電子分光スペクトルからCが含まれていないことが明らかとなった。 平成5年度は、(1)Cの混入がない原因を実験的に明らかにするため種々の成膜材料を使い膜堆積を行い原料TEOS内のCが、プラズマ中および薄膜表面でCO,CO_2の気体分子となり脱離してしまうのではないかと言う結果を発光スペクトル測定より得た。(2)サブミクロントレンチを切ったシリコンウエハ-上にTEOS+O_2混合ガスでシリコン酸化膜を堆積し、ステップカバレージをSEM写真で観測し、段被覆性が非常によいことを確認した。従って、本方法は、200℃程度の低温プロセスで、炭素等の不純物が非常に少ないシリコン酸化膜を成膜でき、更にトレンチのカバレージ性が良いため、半導体集積回路素子薄膜生成プロセス低温化の一方法であることが明らかとなった。

  25. 3-5族希薄磁性半導体の強磁性秩序と電気伝導・光物性

    大野 英男, 中原 純一郎

    1992年 ~ 1992年

    詳細を見る 詳細を閉じる

    本研究は、申請者らが新しく合成に成功したIII-V族希薄磁性半導体に見られる強磁性秩序と電気伝導・光物性との関係を明らかにし、この新希薄磁性半導体の応用の可能性を探ることを目的として行われた。 本年度は、III-V族化合物半導体をベースにした希薄磁性半導体、InMnAsを対象に、その電気伝導・光物性と磁気的性質との関係を明らかにすることを試みた。特に、高正孔濃度のp形試料にのみ低温で(〜10K)見られる強磁性秩序の発現機構とその影響を明らかにすることを目標とした。 高正孔濃度のp形試料(MnAs組成〜0.013)は、中高温領域で常磁性であり、ある臨界温度以下で自発磁化が生じる。磁気輸送現象を調べると、半導体が磁化を持つことで現われる異常ホール効果が通常のホール効果より大きく、これに注目することで磁化を決定することができることが明らかになった。それによると膜厚1μm前後の試料では10K以下で自発磁化が観測される。自発磁化はn形試料には見られないことから正孔とMnのスピンとの相互作用が強磁性的相互作用の発現に重要な役割を果たしていることがわかった。また、強磁性秩序の発現とともに負の磁気抵抗効果が観測されはじめる。これは磁気秩序がキャリアの局在を促進していることを示している。これらのことは、以前から提案している傾いたスピンを内包する大きな磁気ポーラロンの存在により説明できる。さらに、p形ヘテロ接合試料でも強磁性秩序が観測された。薄膜・ヘテロ接合試料共にMnの内殼遷移を検出することを試みている。

  26. 化合物半導体清浄表面と有機金属との相互作用

    大野 英男, 福井 孝志, 中原 純一郎

    1992年 ~ 1992年

    詳細を見る 詳細を閉じる

    本研究では、化合物半導体の種々の清浄表面と有機金属との相互作用を実験的に明らかにしていくことを目的に、超高真空中で分子線エピタキシ成長したGaAsなどの清浄表面に有機金属を照射し、その相互作用の様子を反射電子線回折、電子分光などの手法で観測・解析した。 本年度は特に様々な面方位・表面最構成を有する清浄なGaAsに有機金属を照射し、その表面をオージェ電子分光、反射電子線回折、光反射により観測して表面状態や反応の時定数を明らかにし、相互作用に関する知見を得ることを試みた。 具体的には、反射電子線回折を装備した分子線エピタキシ装置と、それに接続したオージェ電子分光装置を用いて、GaAsのAsおよびGa安定化(100)、(111)B、(111)A、(110)各表面とトリメチルガリウム(TMGa)との相互作用を観測した。また原料の交互供給によるGaAs成長を行いその成長速度を調ベた。その結果、As・Ga安定化(100)面、(111)B面上には、約2MLのメチル基の起因するCがTMGa供給停止直後に存在し、その後ある時定数で減少して1MLの定常値に達するのに対し、(111)A面、(110)面ではC信号はほとんど見られないことが明らかになった。また交互供給成長の成長速度は後者が極めて遅く、Cのふるまいとあわせて表面に有機金属が安定に存在しないことが示された。(100)面では成長速度が0.7ML/サイクルに飽和する原子層エピタキシを確認した。また(111)Bでは成長速度の飽和が見られず、表面に有機金属を分解するサイトが存在する可能性が高いことが示された。

  27. 化合物半導体清浄表面と有機金属との相互作用

    大野 英男, 中原 純一郎

    1991年 ~ 1991年

    詳細を見る 詳細を閉じる

    本研究では、化合物半導体の種々の清浄表面と有機金属との相互作用を実験的に明らかにしていくことを目的に、超高真空人で分子線エピタキシ(MBE)により成長したGAASの清浄表面に有機金属(トリメチルガリウム、TMGa)を照射し、その相互作用の様子をオ-ジェ電子分光でin Situに観測した。 特に、TMGaのメチル基の振る舞いを明らかにするために、オ-ジェ電子分光の炭素信号の時間変化に注目して実験を進めた。基板には、GaAs(001)面を用い、GaAsをMBE装置でエピタキシャル成長した後、オ-ジェ電子分光室に移送し、そこで加熱しながらTMGaを導入した。測定は、TMGaを停止後直ちに開始した。 その結果、(a)TMGaに100L程度GaAs表面を曝すことにより表面に炭素が観測される、(b)TMGaを停止後、炭素は指数関数的に減衰し、定常値に達する、(c)減衰の時定数は活性化エネルギ1.3ev、pre‐exponential factor 6.6x10 ^<-7>Sであらわされ、(d)炭素信号の初期値と定常値の比はほぼ2であって、(e)定常値は、装置付属の感度表を用いると約1モノレ-ヤ(ML、GaAs(001)表面のGaサイトの密度を基準にしている)と見積もられる、ことが判明した。 この炭素信号の振る舞いは、TMGaが分解してジメチルガリウムとなって表面に吸着し、その後、TMGaの供給を停止すると、メチル基が一つ脱離し、約1MLのモノメチルガリウム(MMGa)が表面に残ると考えるとよく説明できる。本研究の成果は、有機金属と化合物半導体表面の相互作用のダイナミクスを、in situに、かつ直接表面をスペクトロスコピックに観測して明らかにした、初めてのものである。

  28. 低周波50HzプラズマCVD法によるカ-ボン薄膜の低温形成プロセスの開発

    下妻 光夫, 伊達 広行, 大野 英男, 田頭 博昭

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Developmental Scientific Research (B)

    研究機関:College of Medical Technology, Hokkaido University

    1990年 ~ 1991年

    詳細を見る 詳細を閉じる

    本研究は、商用低周波数50HzプラズマCVD法をハ-ドカ-ボン薄膜の低温形成プロセスとして確立させ、熱的ダメ-ジ等を回避し電子素子の微細化・高集積化、また各種材料の表面硬質化の促進に貢献することを目的としている。 平成3年度の研究成果は、次の様であった。:1)低周波プラズマCVD法において、ハ-ドカ-ボン薄膜堆積の最適周波数の探索を行ない、基板非加熱状態での堆積は、数kHz以下が最適である事を見出した。これ以上の周波数では徐々に薄膜の透明度が失われ、黄褐色に着色していき、光学ギャップが狭くなり組成が化学量論的なものから離れて行くようである。2)1)の結果から周波数の変化でプラズマの構造が変化していくものと考え、H^2+CH混合ガスプラズマ中の各発光(H^2 ^3Σ_g→ ^3Σ_u)、Hα)の位置分布を周波数50Hz、100kHzで測定した。結果は、発光の位置的な相違が見られず、むしろ発光の半周期ごとの放電初期過程に違いが見られた。この領域でのイオンの挙動やエネルギ-に影響し堆積物の再配列等に大きく関与するものと考えられる。・最終年度として平成2、3年度のまとめを次に述べると:1)低周波プラズマの平均電子温度(16000k)が、高周波の2倍程の高さを持ち、H^2+CH_4ガスプラズマ中で100kHz近辺がその境界になることがわかった。2)低周波50HzプラズマCVD法により基板非加熱状態で堆積したハ-ドカ-ボン薄膜の膜質は、抵抗率〉10^<14>Ωcm、破壊電界強度〉10^6V/cm、光学ギャップ〉4ev、屈折率2.4、高透明度、境面でCがsp^3結合の多いダイヤモンドに近いものであることが確認された。3)以上の結果から、低周波プラズマCVD法によって良質なハ-ドカ-ボン薄膜堆積ができ、この方法が低温プロセスとして十分使用できるものと考えられる。

  29. IIIーV族希薄磁性半導体の成長と評価

    大野 英男, 赤沢 正道, 飯塚 浩一, 長谷川 英機

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for General Scientific Research (B)

    研究機関:Hokkaido University

    1990年 ~ 1991年

    詳細を見る 詳細を閉じる

    本研究では、新しいIIIーV族希薄磁性半導体、(In,Mn)Asの分子線エピタキシ成長とその成長層の評価を行った。研究実験は、以下の通りである。 分子線エピタキシ 基板温度(200〜300℃)によって、相分離を起こさずに得られるMnの最大濃度が異なり、伝導型も異なる。300℃では相分離しない組成範囲はx〈0.03であり成長層はp形であるが、200℃ではx〈0.25n形である。その組成範囲を越えると、第2相としてMnAsが出現する。 エピタキシャル層の評価 (1)磁性n形試料はすべての温度にわたって、常磁性であり、Mn間の相互作用は、反強磁性的でその強さは、最近接Mn間でー1.6Kである。p形試料は、中高温領域で常磁性であり、ある温度以下では、自発磁化が生じる。そのふるまいは、やや複雑で、自発磁化と同時に、磁化には高い磁場に至るまで常磁性的応答する成分も含まれている。(2)電気的性質n形試料は、低温で負の磁気低抗効果を示した。p形試料は、室温から1.4Kの低温までホ-ル係数は正の値(p形)を示し、200K以下では、ホ-ル係数が異常ホ-ル効果に支配されていることが明らかとなった。7.5K以下では、ホ-ル係数のB依存性にヒステリシスがみられ、自発磁化が異常ホ-ル効果を通して観測された。同時に、高磁場まで負の磁気低抗効果が観測された。このp形特有の結果は、正孔とMn間の強磁性的相互作用の結果、互いに平行になろうとする多くの傾いたスピンを内包する大きな磁気ポ-ラロンが試料内に存在すると考えることで説明される。小さな磁場によって大きな磁気ポ-ラロンが回転する。これが自発磁化、ホ-ル効果のヒステリシスとなる。強い磁場ではポ-ラロン内の傾いていたスピンが徐々に揃えられ、試料内の磁気的不均一性が減じ、低抗が減少するため、負の磁気低抗効果としてあらわれる。希薄磁性半導体内で局在キャリア-磁性イオンの交換相互作用に基づく強磁性秩序を観測した初めての例である。

  30. 低周波放電のプロセスプラズマとしての適用とその制御法の開発

    下妻 光夫, 大森 義行, 伊達 広行, 大野 英男, 本間 利久

    1990年 ~ 1990年

    詳細を見る 詳細を閉じる

    平成2年度の研究結果は、次ぎのようである。 高・低周波CVDにおけるプラズマの相違について、昨年度今年度と、50Hz〜13.56MHzの広範囲において電子・イオンのプラズマ中での挙動を、プラズマ発光分光分析などからプラズマの周波数特性を明らかにし、低周波プラズマCVD法の特徴を把握しようとして研究を進めてきた。50Hz〜13.56MHzの範囲でのプラズマ中の電子温度と放電維持電圧をH_2+CH_4、H_2のガスについて測定し、どちらの傾向も低周波領域で一定値を取り、数百kHz以上で急激に減少している。これは、低周波プラズマが高エネルギ-電子の密度が高いことを意味し、これまでの常識を覆す結果が明らかにされた。更に、H_2+CH_4プラズマの電極間発光位置分布測定で、50Hz、13.56MHzプラズマで大きな違いが見られHα、Hβの発光強度が13.56MHzプラズマで50Hzより著しく小さいことも明らかになった。更に、電極間の位置に対するプラズマ発光の時間変化について50Hzと100kHzの条件で測定を行なった。実験装置は、微弱発光の高速測定が要求されるため、観測発光波長を固定し(H_2^*( ^3Σ_o→ ^3Σ_u):220nm、Hα:650nm)、光電子増倍管を冷却器(ー15℃)に入れS/N比を上げ、広帯域アンプとボックスカ-インテグレ-タによりデ-タを得るように改良した。低周波条件では、電圧の正負極性に対する2回の発光が見られ、プラズマの発生に急俊な立上がりを見せ、電圧波形も急激に崩壊する。また、消滅時は印加電圧の減少に従い緩やかに消滅していくのが見られる。 また、低周波プラズマCVD法による薄膜堆積実験の進行状況は、シリコン酸化膜堆積を行なっている。TEOSを材料とした酸化膜堆積は、200℃程度の加熱が必要であったが、N_2O+SiH_4の材料ガスでは基板非加熱で良質膜堆積が可能であることがわかった。

  31. 半導体キャリアの分布定数効果を利用した新しいマイクロ波モノリシック集積回路の製作

    長谷川 英機, 赤澤 正道, 飯塚 浩一, 深井 一郎, 大野 英男

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for General Scientific Research (B)

    研究機関:Hokkaido University

    1988年 ~ 1989年

    詳細を見る 詳細を閉じる

    マイクロ波・ミリ波を用いる高度情報通信システムの構築を目指し、半絶縁性GaAsを基板としたマイクロ波モノリシック集積回路(MMIC)の研究開発が活発に行われている。しかし、現状ではMMICの基板面積当たりの機能の集積度は、著しく低い。これは半導体能動素子は集中定数素子とみなせるよう小面積に作る一方、高価な基板の面積の大部分は寸法の大きい受動素子を作るのに、絶縁体として使用されるからである。本研究の目的は、半導体のキャリアがもたらす分布定数的効果を積極的に利用し線路波長を短縮するMIS形およびショットキ形のコプレ-ナ伝送線路の基礎的研究を行なうことにある。さらに、これら線路は、その伝送特性が電気的に変化できるので、そのユニ-クな性質を利用して、高性能・高機能化した新しいMMICを実現できる。 本研究の成果の概要は以下の通りである。(1)半導体基板上に形成されたMIS形およびショットキ形コプレ-ナ伝送線路構造の理論的検討を行い、伝送モ-ドおよび伝送特性量の幾何学的構造依存性、半導体表面層のパラメ-タ依存性、周波数依存性、バイアス依存性を明らかにした。(2)コプレ-ナ伝送線路試料の作製法を検討した。ことに、GaAsおよびInGaAsエピタキシャル表面半導体層を分子線エピタキシャル法で成長する方法および条件を明らかにした。(3)半絶縁性GaAs基板上に形成されたショットキ形コプレ-ナ線路の伝送特性の測定法を検討し、かつ、実際に測定を行い、その結果が、理論解析結果でよく説明できることを示した。(4)MIS形コプレ-ナ線路におけるフェルミ準位ピンニングの除去の重要性を認識し、シリコン超薄膜による界面制御により、ピンニングのないInGaAs MIS構造の製作に成功した。

  32. 低周波放電のプロセスプラズマとしての適用とその制御法の開発

    下妻 光夫, 大森 義行, 伊達 広行, 大野 英男, 本間 利久

    1988年 ~ 1988年

    詳細を見る 詳細を閉じる

    集積回路などにおけるプラズマを利用したドライプロセス技術は、ほとんどRFなど高周波電界を使って行なわれる。しかし、高周波では行なうことができない、低周波放電プラズマの特徴を生かした独自のプロセスと、それの制御法の開発がほとんど行なわれておらず、本研究の目的はこの点に付いて実験的に研究を行なうことにある。現在までに、窒化シリコン薄膜を50Hz低周波プラズマCVDで基板非加熱で良質な膜が大面積に均一に堆積できることを見出してきた。このメカニズムの究明を行なうことで低周波プラズマのプロセスへの応用が可能となる。この点に関して63年度の研究成果から、低周波プラズマの特徴であるイオンの可動性とプラズマの断続性が重要な役割をしていることが明らかになってきた。結果の要約として、1)プラズマ中の原子・分子イオンの堆積膜への射突による埋め込みで高密度薄膜形成がなされ、更にイオンの持つ運動エネルギーの射突後の原子再配列エネルギーへの変換による化学量論的な組成への薄膜生成、2)またプラズマ中の生成物(イオン、励起・解離・ラジカル種)の低周波プラズマの断続による発生消滅の結果として、プラズマ発生電圧とプラズマ維持電圧の上昇に伴うプラズマ内の電子エネルギー上昇によるガス分子の効率的な解離が、生成薄膜の物性的評価とプラズマ内電子エネルギー測定などから得られた。これらの事実から低周波プラズマCVDによる基板非加熱条件による良質薄膜堆積が可能ではないかと考えられる。これらをふまえ、高温での堆積が条件と考えられているダイヤモンドライクカーボン薄膜の堆積を低周波非加熱プラズマCVDでH_2+CH_4混合ガスを材料として薄膜堆積した結果、この薄膜が天然ダイヤの物性(電気的・工学的・物理的)に近い物であり、上記の考えが間違いではないことが認められた。今後の研究課題として、このプラズマの制御法について研究を進める予定である。

  33. 低周波プラズマCVDによるシリコン窒化膜の室温形成プロセスの開発

    下妻 光夫, 大森 義行, 大野 英男, 田頭 博昭, 沢田 孝幸

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Developmental Scientific Research

    研究機関:College of Medical Technology, Hokkaido University

    1986年 ~ 1987年

    詳細を見る 詳細を閉じる

    61年度では, シリコン窒化膜を室温・低周波(50Hz)プラズマCVD法で作製し, 良質な薄膜を得ることに成功した. 62年度は, この膜をデバイスに応用する事を目的として, 次のような研究結果を得た. 1.5インチφSiウェハー上に堆積した結果, 屈折率2.0±0.05, 膜厚 1000±30〓の面内分布をもつ均一なピンホールのない電気的性質のよい薄膜が得られた. この事から, 室温低周波50HzプラズマCVD法によっても大面積均一堆積が可能であることが明らかとなった. 2.Siウェハー上に均一な膜厚分布を持ったSi熱酸化膜上にシリコン窒化膜を堆積し, 高周波C-V, 準静的C-V測定を行ない, 固定電荷密度NFB1界面準位密度NSSを求め, それぞれ1.5×10^<11>cm^<-2>,8×10^<10>eV^<-1>cm^<-2>であった. これは, 非常に低い値であり低周波プラズマCVDにもかかわらず, イオンのダメージが少ない事を示している. 3.低周波プラズマCVDにおける基板加熱の影響について実験を行い基板温度が高いほど, 緻密な膜が形成され, わずかにSi過剰な膜となり, また電気的特性は, 基板温度に大きく依存しないことがわかった. 4.これらの事から室温低周波プラズマCVD法堆積によるシリコン窒化膜は, 低温プロセスが必要な化合物半導体, アモルファスシリコン上の絶縁膜や, 表面保護膜として十分な特性を持っているものと考えられる. 5.この室温低周波プラズマCVD法は, シリコン窒化膜以外の薄膜作製にも有効であるかについて, アモルファスシリコンとカーボン膜の堆積によって確認実験を行った結果, 良質な薄膜が得られた. この事から, この方法は, 広い使用範囲を持っていることが明らかとなった.

  34. 化合物半導体-絶縁体界面の物性と応用に関する研究

    長谷川 英機, 高橋 平七郎, 芳賀 哲也, 阿部 寛, 大野 英男

    1985年 ~ 1987年

    詳細を見る 詳細を閉じる

    化合物反半導体集積回路においては, 集積回路の基本構成要素てある絶縁体-半導体界面の理解, 制御, 最適化がなされていない. これは, 回路の微細化・高密度集積化・高速化に向けて, 集積回路技術を今後さらに発展させる上での重大な障害となっている. 本研究は, 化合物半導体-絶縁体界面における基礎的な物性を解明し, それによって得られる学問的理解にもとづき界面物性を原子的な尺度で制御する新しい界面制御技術を確立し, 化合物半導体集積回路技術の今後の発展に寄与することを目的としている. 昭和62年度は, 前年度までに確立した界面物性とその制御に関する基礎的理解にもとづき, 大規模集積回路製作に適用可能な実用界面制御技術を確立する目的で研究を進め, 次の成果を得た. (1)化学エッチ, イオンエッチング, プラズマや種々の気体雰囲気への露出, 熱アニール等のプロセス工程中に, GaAs InPの表面・界面にひき起こされる組成・構造・結合状態の変化を解明し, 界面の電気的特性との相関を明らかにするとともに, 「DIGSモデル」の妥当性と「界面制御」の有効性を示した. (2)RBS/PIXE法および極微小領域分析観察装置を用いた分析法において, 原子的な尺度における格子乱れを定量化する手法を発展させ, 極微細集積化構造に対するプロセス評価技術として確立した. (3)表面・界面におけるキャリアの捕獲・放出, 再結合, フォトルミネセンスを, 理論的および実験的に解明した. (4)種々の界面制御層をもつ絶縁膜を用いIPMISFETを製作し, 界面制御の有効性を実証するとともに, 耐熱セルフアラインゲート化により, 大規模集積化への見通しを得た. (5)GaAs MESFETのサイドゲート現象を検討し, その構造を解明し, かつ, 界面制御の有効性を示した. (6)「統一DIGSモデル」が化合物半導体の半導体-半導体界面や非晶質シリコンの界面にも適用可能であるこはを示した.

  35. 化合物半導体超格子構造を用いた進行波増幅素子の試作に関する研究

    深井 一郎, 下妻 光夫, 大野 英男, 長谷川 英機

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Developmental Scientific Research

    研究機関:Hokkaido University

    1985年 ~ 1986年

    詳細を見る 詳細を閉じる

    本研究は化合物半導体薄膜超格子構造における高移動度電子を用いた固体進行波増幅素子を実現するための基礎的研究を行なうことを目的としている。本研究で得られた成果は以下の通りである。[1]固体進行波相互作用の理論解析 理想的非分散性遅波導波路を有する固体進行波相互作用系およびインタディジタル遅波導波路を有する固体進行波相互作用系の理論解析を行ない、はじめて有限厚動作層を取り扱い厚さの重要性を指適した。その結果以下の点が明らかとなった。(【i】)相互作用により高い増幅利得および負性コンダクタンスが得られる。(【ii】)最大利得を得るには動作層厚をデバイ長程度とする。最大の負性コンダクタンスを得るには実効的誘電緩和周波数が動作周波数と同程度の半導体を選ぶ。(【iii】)最適動作層を層状に装荷することにより電力変換効率を向上させることができ、大電力増幅が可能である。[2]固体進行波素子用高耐圧誘電体スペーサ層の形成プロセスの確立…固体進行波素子用誘電体スペーサ層は高耐圧性が要求され、かつ形成プロセスは半導体に損傷を与えてはならない。このプロセスとしてプラズマCVD法により室温でシリコン窒化膜を形成する方法を検討した。形成されたシリコン窒化膜は抵抗率6×【10^(15)】Ωcm、破壊電界1.2×【10^7】V/cm屈折率20であり低温のため半導体の損傷の度合が小さい。[3]固体進行波相互作用の観測とその計算機解析 n-GaAsMOVPE層n-AlGaAs1GaAsMBEヘテロ接合構造層、n-InPVPE層を用いてインタディジタル型固体進行波素子を製作し実験的検討を加えた結果次の結論を得た。(【i】)すべての素子においてマイクロ波で進行波相互作用が認められた。(【ii】)さらにInP素子について固体進行波相互作用を実効誘電率で記述した理論を用いて二端子アドミタンスの計算機シミュレーションを行なった。その結果、実験結果とシミュレーション結果が良く一致することが示された。

︎全件表示 ︎最初の5件までを表示

社会貢献活動 14

  1. IEEE Magnetics Society Distinguished Lecturer

    2009年1月 ~ 2009年12月

    詳細を見る 詳細を閉じる

    世界各国の支部で講演

  2. 日本学術会議公開シンポジウム

    2012年11月26日 ~

    詳細を見る 詳細を閉じる

    「日本の復興・再生に向けた産学官連携の新しいありかた」パネル討論「イノベーションを支える産学官連携の課題」パネラー

  3. 三井業際研究所

    2012年10月24日 ~

    詳細を見る 詳細を閉じる

    「三井グループにおいて、異種業種間の業際分野における知識集団としての役割を果たすこと」を目的として活動している三井業際研究所において講演活動を行なった。

  4. 東北大学サイエンスカフェ

    2012年5月25日 ~

    詳細を見る 詳細を閉じる

    一般を対象に科学について気軽に話し合い、科学の楽しさと社会貢献の姿を知ってもらう。

  5. 東北大学艮陵同窓会140周年 東日本大震災復興プロジェクト

    2012年5月19日 ~

    詳細を見る 詳細を閉じる

    「鼎談塩野七生さんを囲んで 瓦礫と大理石:廃墟と繁栄」(鼎談者)

  6. スイス大使館・Guardian Angelsプロジェクト

    2012年2月15日 ~

    詳細を見る 詳細を閉じる

    セミナー&レセプションにおいて講演を行なう

  7. 東北大学北海道交流会

    2011年11月12日 ~

    詳細を見る 詳細を閉じる

    「半導体の復興にむけて -スピントロニクスの集積システム応用ー」と題する講演

  8. 第4回東北大学国際シンポジウム

    2011年10月27日 ~

    詳細を見る 詳細を閉じる

    「スピントロニクス集積回路:待機電力ゼロの社会に向けて」講演

  9. SEMI Forum Japan 2011

    2011年5月31日 ~

    詳細を見る 詳細を閉じる

    先端CMOSデバイス・プロセスセミナー -グラフェン・スピンエレクトロニクス、次世代に向けたデバイスプロセス」において「スピントロニクスによる不揮発性VLSI」と題する招待講演を行なった。

  10. FIRSTサイエンスフォーラム

    2011年2月13日 ~

    詳細を見る 詳細を閉じる

    トップ科学者と若者で切り拓く未来「ワンダー:科学は自分の周りの驚きからはじまる!」

  11. 科学技術交流財団 わかしゃち奨励賞優秀提案発表会最優秀賞選考会基調講演

    2010年2月 ~

  12. 長野県テクノ財団浅間テクノポリス地域センター

    2008年2月 ~

  13. 日本真空協会

    2007年11月 ~

    詳細を見る 詳細を閉じる

    真空に関する連合講演会

  14. 北陸先端科学技術大学院大学

    2007年7月 ~

    詳細を見る 詳細を閉じる

    マテリアルサイエンス研究科セミナー講師

︎全件表示 ︎最初の5件までを表示

メディア報道 2

  1. 報道ステーション

    テレビ朝日

    2011年6月17日

    メディア報道種別: テレビ・ラジオ番組

  2. 東北大学の新世紀

    東日本放送

    2011年1月17日

    メディア報道種別: テレビ・ラジオ番組

その他 11

  1. 卓越した大学院拠点形成支援補助金

    詳細を見る 詳細を閉じる

    本学は情報通信技術分野とエレクトロニクス材料・デバイス開発に関わるナノテクノロジー分野の研究において長い歴史と実績を有する。これらを継承しながら独創的かつ国際性豊かな研究を行うことのできる人材育成をめざして、世界最高水準の研究開発のための体制を強化し、海外拠点を活用した国際的な教育環境を整備して若手研究者を養成している。

  2. 耐災害性に優れた安心・安全社会のためのスピントロニクス材料・デバイス基盤技術の研究開発

    詳細を見る 詳細を閉じる

    不揮発性ワーキングメモリを有する耐災害性に優れたコンピュータシステムを実現するために、20nm以下の寸法を有する微細な高速、大容量、耐環境性に優れ、かつ低消費電力を実現する不揮発性スピントロニクスメモリの材料・デバイス技術を開発するとともに、そのコンピュータシステムへの適用法をシミュレーションで明らかにし、耐災害性に優れた安心・安全社会のためにスピントロニクス材料・デバイス基盤技術を確立する。

  3. 省エネルギー・スピントロニクス論理集積回路の研究開発

    詳細を見る 詳細を閉じる

    電子の持つスピンを利用することで、エネルギーを使わずに情報を記憶することができるスピントロニクス素子を用いた半導体論理集積回路を世界に先駆けて開発する。これにより、従来に比べてエネルギー消費量が極めて少ない電子機器の開発につなげ、省エネルギー社会の実現に貢献する。

  4. 次世代高機能・低消費電力スピンデバイス基盤技術の開発

    詳細を見る 詳細を閉じる

    次世代高機能・低消費電力スピンデバイス基盤技術の開発

  5. スピンダイナミックスとその機能デバイス応用

    詳細を見る 詳細を閉じる

    スピンダイナミックスとその機能デバイス応用

  6. テラヘルツ帯量子カスケードレーザーの研究

    詳細を見る 詳細を閉じる

    テラヘルツ帯量子カスケードレーザーの研究

  7. 非磁性半導体中の電子スピンに関する研究

    詳細を見る 詳細を閉じる

    非磁性半導体中の電子スピンに関する研究

  8. 高機能・超低消費電力メモリの開発

    詳細を見る 詳細を閉じる

    高機能・超低消費電力メモリの開発

  9. 酸化亜鉛薄膜ショットキーダイオード

    詳細を見る 詳細を閉じる

    酸化亜鉛薄膜ショットキーダイオード

  10. 非平衡表面層の原子スケールダイナミクスと新物質の創生

    詳細を見る 詳細を閉じる

    非平衡表面層の原子スケールダイナミクスと新物質の創生

  11. III-V族をベースとする希薄磁性半導体とその量子構造

    詳細を見る 詳細を閉じる

    III-V族をベースとする希薄磁性半導体とその量子構造

︎全件表示 ︎最初の5件までを表示