顔写真

アンドウ ヤスオ
安藤 康夫
Yasuo Ando
所属
大学院工学研究科 応用物理学専攻 先端スピントロニクス医療応用工学共同研究講座
職名
教授
学位
  • 博士(工学)(東北大学)

経歴 1

  • 1986年4月 ~ 1992年11月
    コニカ株式会社 研究員

学歴 2

  • 東北大学 工学研究科 応用物理学

    ~ 1986年3月25日

  • 東北大学 工学部 応用物理学科

    ~ 1984年3月25日

委員歴 50

  • 日本学術振興会 産学協力研究委員会147委員会委員

    2018年12月 ~ 継続中

  • 公益財団法人コニカミノルタ科学技術振興財団 奨励賞審査委員

    2014年1月 ~ 継続中

  • 応用物理学会 東北支部幹事

    2014年1月 ~ 継続中

  • 応用物理学会 スピンエレクトロニクス研究会幹事

    2012年1月 ~ 継続中

  • 応用物理学会 評議委員

    2011年3月 ~ 継続中

  • 応用物理学会スピントロニクス研究会 委員長

    2011年1月 ~ 継続中

  • スピントロニクス不揮発性機能技術調査委員会 委員

    2008年5月 ~ 継続中

  • スピントロニクス不揮発性機能技術調査委員会 委員

    2008年5月 ~ 継続中

  • 高機能・超低消費電力スピンデバイス・ストレージ基盤技術の開発プロジェクト 推進委員

    2007年10月 ~ 継続中

  • 高機能・超低消費電力スピンデバイス・ストレージ基盤技術の開発プロジェクト 推進委員

    2007年10月 ~ 継続中

  • ISAMMA 2007 Program Committee

    2007年6月 ~ 継続中

  • ISAMMA 2007 プログラム委員会

    2007年6月 ~ 継続中

  • 応用物理学会東北支部 幹事

    2007年4月 ~ 継続中

  • 応用物理学会東北支部 幹事

    2007年4月 ~ 継続中

  • 応用物理学会スピンエレクトロニクス研究会 幹事

    2006年1月 ~ 継続中

  • 応用物理学会 論文賞審査委員

    2017年 ~ 2018年

  • 日本学術振興会 学術システム研究センター研究員

    2013年4月 ~ 2016年3月

  • 応用物理学会 業績賞委員会委員

    2015年 ~ 2016年

  • 応用物理学会 東北支部長

    2012年1月 ~ 2013年12月

  • 応用物理学会 評議委員

    2011年3月 ~ 2013年3月

  • 応用物理学会スピントロニクス研究会 委員長

    2011年1月 ~ 2012年12月

  • 応用物理学会 2011年秋季学術講演会現地実行委員

    2010年8月 ~ 2011年8月

  • 応用物理学会 2011年秋季学術講演会現地実行委員

    2010年8月 ~ 2011年8月

  • ISAMMA 2010 Executive Committee

    2009年4月 ~ 2011年3月

  • ISAMMA 2010 Executive Committee

    2009年4月 ~ 2011年3月

  • 応用物理学会 理事

    2009年3月 ~ 2011年3月

  • 応用物理学会 理事

    2009年3月 ~ 2011年3月

  • 応用物理学会スピンエレクトロニクス研究会 幹事

    2006年1月 ~ 2010年12月

  • 日本磁気学会論文賞,学術奨励賞選考委員会 委員

    2008年4月 ~ 2010年3月

  • 日本磁気学会論文賞,学術奨励賞選考委員会 委員

    2008年4月 ~ 2010年3月

  • 新機能トランジスタ調査委員会 副委員長

    2007年6月 ~ 2010年3月

  • 新機能トランジスタ調査委員会 副委員長

    2007年6月 ~ 2010年3月

  • 特別研究員等審査会 審査委員

    2006年8月 ~ 2007年7月

  • 特別研究員等審査会 審査委員

    2006年8月 ~ 2007年7月

  • 応用物理学会 代議員

    2002年2月 ~ 2006年1月

  • 応用物理学会 代議員

    2002年2月 ~ 2006年1月

  • 応用物理学会スピンエレクトロニクス研究会 庶務幹事

    2003年1月 ~ 2004年12月

  • 応用物理学会スピンエレクトロニクス研究会 庶務幹事

    2003年1月 ~ 2004年12月

  • 応用物理学会東北支部 庶務幹事

    2000年1月 ~ 2001年12月

  • 応用物理学会東北支部 庶務幹事

    2000年1月 ~ 2001年12月

  • International Symposium on Nanoscale Magnetism and Transport 現地実行委員

    2000年3月 ~ 2000年3月

  • 19th International Colloquium on Magnetic Films and Surfaces Local Committee

    2006年8月 ~

  • International Conference on Magnetism 2006 Program Committee

    2006年8月 ~

  • 19th International Colloquium on Magnetic Films and Surfaces 現地委員会

    2006年8月 ~

  • International Conference on Magnetism 2006 プログラム委員会

    2006年8月 ~

  • INTERMAG 2005 Program Committee

    2005年4月 ~

  • INTERMAG 2005 プログラム委員会

    2005年4月 ~

  • 2004年秋季応用物理学会学術講演会 現地実行委員

    2004年9月 ~

  • 2004年秋季応用物理学会学術講演会 現地実行委員

    2004年9月 ~

  • International Symposium on Nanoscale Magnetism and Transport Local Committee

    2000年3月 ~

︎全件表示 ︎最初の5件までを表示

所属学協会 4

  • 日本物理学会

  • 電子情報通信学会

  • 日本磁気学会

  • 応用物理学会

研究キーワード 3

  • 界面構造

  • スピン注入

  • 強磁性トンネル接合

研究分野 4

  • 自然科学一般 / 磁性、超伝導、強相関系 /

  • ナノテク・材料 / 薄膜、表面界面物性 /

  • ナノテク・材料 / 結晶工学 / 磁気物性

  • ナノテク・材料 / 応用物性 / 磁気物性

受賞 11

  1. 支部貢献賞

    2020年12月 応用物理学会東北支部 応用物理学会東北支部における顕著な貢献

  2. フェロー

    2018年9月 日本磁気学会 日本磁気学会フェロー

  3. 第23回業績賞

    2018年9月 日本磁気学会 強磁性トンネル接合の高性能化とスピントロニクスデバイスへの応用

  4. 第9回(2015年度)応用物理学会フェロー表彰

    2015年9月13日 応用物理学会 スピンダイナミクスの先導的研究とスピンデバイス高性能化の研究

  5. The 74th JSAP Autumn Meeting, 2013, Poster Award

    2013年10月1日 応用物理学会 Magnetization dynamics in Mn-Ga/Fe exchange coupled bilayer thin films

  6. 第34回(2012年度)応用物理学会論文賞

    2012年9月 応用物理学会 Large Magnetoresistance Effect in Epitaxial Co2Fe0.4Mn0.6Si/Ag/Co2Fe0.4Mn0.6Si Devices

  7. 日本磁気学会平成20年度論文賞

    2008年9月 日本磁気学会 Co2MnSiを用いた強磁性トンネル接合における極高スピン分極率の実現

  8. 第39回原田研究奨励賞

    1999年11月4日 財団法人金属研究助成会 トンネル顕微鏡を用いた強磁性トンネル接合用超薄Al酸化膜の局所伝導特性解析

  9. 日本応用磁気学会平成9年度論文賞

    1997年7月1日 日本応用磁気学会 強磁性トンネル接合における絶縁障壁と磁気抵抗

  10. 日本化学会第71秋季年会シンポジウム賞

    1996年12月17日 日本化学会 高分子フェロセン誘導体薄膜における超構造と磁気特性

  11. トーキン科学技術振興財団研究奨励賞

    1995年3月6日 トーキン科学技術振興財団 LB法による有機人工格子薄膜の作製とその電磁気的性質に関する基礎的研究

︎全件表示 ︎最初の5件までを表示

論文 429

  1. TaFeB spacer for soft magnetic composite free layer in CoFeB/MgO/CoFeB-based magnetic tunnel junction 査読有り

    Takafumi Nakano, Kosuke Fujiwara, Seiji Kumagai, Yasuo Ando, Mikihiko Oogane

    Applied Physics Letters 122 (7) 072405 2023年2月13日

    DOI: 10.1063/5.0132866  

  2. Tunnel anisotropic magnetoresistance in magnetic tunnel junctions using FeAlSi 査読有り

    S. Akamatsu, T. Nakano, Muftah Al-Mahdawi, W. Yupeng, M. Tsunoda, Y. Ando, M. Oogane

    AIP Advances 13 (2) 025005 2023年2月1日

    DOI: 10.1063/9.0000440  

  3. Development of Magnetocardiograph without Magnetically Shielded Room Using High-Detectivity TMR Sensors

    Koshi Kurashima, Makoto Kataoka, Takafumi Nakano, Kosuke Fujiwara, Seiichi Kato, Takenobu Nakamura, Masaki Yuzawa, Masanori Masuda, Kakeru Ichimura, Shigeki Okatake, Yoshitaka Moriyasu, Kazuhiro Sugiyama, Mikihiko Oogane, Yasuo Ando, Seiji Kumagai, Hitoshi Matsuzaki, Hidenori Mochizuki

    Sensors 23 (2) 646-646 2023年1月6日

    出版者・発行元:MDPI AG

    DOI: 10.3390/s23020646  

    eISSN:1424-8220

    詳細を見る 詳細を閉じる

    A magnetocardiograph that enables the clear observation of heart magnetic field mappings without magnetically shielded rooms at room temperatures has been successfully manufactured. Compared to widespread electrocardiographs, magnetocardiographs commonly have a higher spatial resolution, which is expected to lead to early diagnoses of ischemic heart disease and high diagnostic accuracy of ventricular arrhythmia, which involves the risk of sudden death. However, as the conventional superconducting quantum interference device (SQUID) magnetocardiographs require large magnetically shielded rooms and huge running costs to cool the SQUID sensors, magnetocardiography is still unfamiliar technology. Here, in order to achieve the heart field detectivity of 1.0 pT without magnetically shielded rooms and enough magnetocardiography accuracy, we aimed to improve the detectivity of tunneling magnetoresistance (TMR) sensors and to decrease the environmental and sensor noises with a mathematical algorithm. The magnetic detectivity of the TMR sensors was confirmed to be 14.1 pTrms on average in the frequency band between 0.2 and 100 Hz in uncooled states, thanks to the original multilayer structure and the innovative pattern of free layers. By constructing a sensor array using 288 TMR sensors and applying the mathematical magnetic shield technology of signal space separation (SSS), we confirmed that SSS reduces the environmental magnetic noise by −73 dB, which overtakes the general triple magnetically shielded rooms. Moreover, applying digital processing that combined the signal average of heart magnetic fields for one minute and the projection operation, we succeeded in reducing the sensor noise by about −23 dB. The heart magnetic field resolution measured on a subject in a laboratory in an office building was 0.99 pTrms and obtained magnetocardiograms and current arrow maps as clear as the SQUID magnetocardiograph does in the QRS and ST segments. Upon utilizing its superior spatial resolution, this magnetocardiograph has the potential to be an important tool for the early diagnosis of ischemic heart disease and the risk management of sudden death triggered by ventricular arrhythmia.

  4. Scalp attached tangential magnetoencephalography using tunnel magneto-resistive sensors

    Akitake Kanno, Nobukazu Nakasato, Mikihiko Oogane, Kosuke Fujiwara, Takafumi Nakano, Tadashi Arimoto, Hitoshi Matsuzaki, Yasuo Ando

    Scientific Reports 12 (1) 2022年12月

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

    DOI: 10.1038/s41598-022-10155-6  

    eISSN:2045-2322

    詳細を見る 詳細を閉じる

    Abstract Non-invasive human brain functional imaging with millisecond resolution can be achieved only with magnetoencephalography (MEG) and electroencephalography (EEG). MEG has better spatial resolution than EEG because signal distortion due to inhomogeneous head conductivity is negligible in MEG but serious in EEG. However, this advantage has been practically limited by the necessary setback distances between the sensors and scalp, because the Dewar vessel containing liquid helium for superconducting quantum interference devices (SQUIDs) requires a thick vacuum wall. Latest developments of high critical temperature (high-T<sub>c</sub>) SQUIDs or optically pumped magnetometers have allowed closer placement of MEG sensors to the scalp. Here we introduce the use of tunnel magneto-resistive (TMR) sensors for scalp-attached MEG. Improvement of TMR sensitivity with magnetic flux concentrators enabled scalp-tangential MEG at 2.6 mm above the scalp, to target the largest signal component produced by the neural current below. In a healthy subject, our single-channel TMR-MEG system clearly demonstrated the N20m, the initial cortical component of the somatosensory evoked response after median nerve stimulation. Multisite measurement confirmed a spatially and temporally steep peak of N20m, immediately above the source at a latency around 20 ms, indicating a new approach to non-invasive functional brain imaging with millimeter and millisecond resolutions.

  5. てんかん診療の近未来〜デバイスと医薬品開発の最前線〜 トンネル磁気抵抗効果を用いた頭皮密着型脳磁計の開発

    菅野 彰剛, 神 一敬, 柿坂 庸介, 石田 誠, 中里 信和, 大兼 幹夫, 安藤 康夫

    てんかん研究 40 (2) 308-308 2022年8月

    出版者・発行元:(一社)日本てんかん学会

    ISSN:0912-0890

    eISSN:1347-5509

  6. Magnetic tunnel junctions using epitaxially grown FeAlSi electrode with soft magnetic property

    Shoma Akamatsu, Mikihiko Oogane, Masakiyo Tsunoda, Yasuo Ando

    AIP Advances 12 (7) 075021-075021 2022年7月1日

    出版者・発行元:AIP Publishing

    DOI: 10.1063/5.0094619  

    eISSN:2158-3226

    詳細を見る 詳細を閉じる

    Magnetic tunnel junctions (MTJs) with (001)-oriented D0<sub>3</sub>-FeAlSi epitaxial films, which have both soft magnetic properties and surface flatness, were fabricated and characterized. A tunnel magnetoresistance (TMR) ratio of 121% was observed, and a relatively low switching field was also confirmed, reflecting the soft magnetic property of FeAlSi. However, the results of the cross-sectional TEM image of the MTJ and the bias dependence of the TMR ratio indicate that the FeAlSi/MgO interface is probably oxidized. Therefore, since an insertion layer at the interface can suppress oxidation and further improve the TMR ratio, MTJs using FeAlSi epitaxial films are promising structures suitable for applications such as MTJ-based magnetic sensors and worthy of further investigation.

  7. Guidelines for attaining optimal soft magnetic properties in FeAlSi films

    Shoma Akamatsu, Mikihiko Oogane, Masakiyo Tsunoda, Yasuo Ando

    Applied Physics Letters 120 (24) 242406-242406 2022年6月13日

    出版者・発行元:AIP Publishing

    DOI: 10.1063/5.0086322  

    ISSN:0003-6951

    eISSN:1077-3118

    詳細を見る 詳細を閉じる

    Nm-order FeAlSi epitaxial films with a partially D0<sub>3</sub>-ordered structure were grown on MgO substrates, and ideal soft magnetic properties were obtained. We found that the sign of the magnetocrystalline anisotropy constant K<sub>1</sub> changes with increasing annealing temperature for certain FeAlSi compositions. This is caused by a change in the volume balance of the ordered phases with the annealing process and the point at which K<sub>1</sub> ∼ 0 shifts to the Al-rich concentration as the degree of D0<sub>3</sub>-ordering decreases. K<sub>1</sub> was precisely measured by ferromagnetic resonance under the optimal condition, and the value of 1.6 × 10<sup>2</sup> (erg/cc) was obtained, which is comparable to that of bulk. The uniaxial component of the magnetic anisotropy due to magnetostriction was small, and a fourfold symmetric component due to magnetocrystalline anisotropy was dominant.

  8. Control of sensitivity in vortex-type magnetic tunnel junction magnetometer sensors by the pinned layer geometry

    Motoki Endo, Muftah Al-Mahdawi, Mikihiko Oogane, Yasuo Ando

    Journal of Physics D: Applied Physics 55 (19) 195001-195001 2022年5月12日

    出版者・発行元:IOP Publishing

    DOI: 10.1088/1361-6463/ac5080  

    ISSN:0022-3727

    eISSN:1361-6463

    詳細を見る 詳細を閉じる

    Abstract The tuning of sensitivity and dynamic range in linear magnetic sensors is required in various applications. We demonstrate the control and design of the sensitivity in magnetic tunnel junction (MTJ) sensors with a vortex-type sensing layer. In this work, we develop sensor MTJs with NiFe sensing layers having a vortex magnetic configuration. We demonstrate that by varying the pinned layer size, the sensitivity to magnetic field is tuned linearly. We obtain a high magnetoresistance ratio of 140%, and we demonstrate a controllable sensitivity from 0.85% Oe<sup>−1</sup> to 4.43% Oe<sup>−1</sup>, while keeping the vortex layer fixed in size. We compare our experimental results with micromagnetic simulations. We find that the linear displacement of vortex core by an applied field makes the design of vortex sensors simple. The control of the pinned layer geometry is an effective method to increase the sensitivity, without affecting the vortex state of the sensing layer. Furthermore, we propose that the location of the pinned layer can be used to realize more sensing functionalities from a single sensor.

  9. Observation of unconventional spin-polarization induced spin–orbit torque in L1<sub>2</sub>-ordered antiferromagnetic Mn<sub>3</sub>Pt thin films

    Longjie Yu, Shutaro Karube, Min Liu, Masakiyo Tsunoda, Mikihiko Oogane, Yasuo Ando

    Applied Physics Express 15 (3) 033002-033002 2022年3月1日

    出版者・発行元:IOP Publishing

    DOI: 10.35848/1882-0786/ac52d7  

    ISSN:1882-0778

    eISSN:1882-0786

    詳細を見る 詳細を閉じる

    Abstract Non-collinear antiferromagnets exhibit richer magneto-transport properties compared to nonmagnetic materials due to the topological spin structure they possess, which allows us to manipulate the charge-spin conversion more freely by taking advantage of the chirality. In this work, we explore the unconventional spin–orbit torque of L1<sub>2</sub>-ordered Mn<sub>3</sub>Pt with a triangular spin structure. We observed an unconventional spin–orbit torque along the x-direction for the (001)-oriented L1<sub>2</sub> Mn<sub>3</sub>Pt and found that it has a sign reversal behavior relative to the crystalline orientation. This generation of unconventional spin–orbit torque can be interpreted as stemming from the magnetic spin Hall effect.

  10. 最新のセンサー系から見た心臓磁場計測技術と脳磁場計測に向けた展望 室温動作TMRセンサーを用いたリアルタイム心磁場および体性感覚誘発脳磁場の計測

    藤原 耕輔, 菅野 彰剛, 中野 貴文, 熊谷 静似, 松崎 斉, 有本 直, 大兼 幹彦, 中里 信和, 安藤 康夫

    日本生体磁気学会誌 35 (1) 76-77 2022年

    出版者・発行元:日本生体磁気学会

    ISSN:0915-0374

  11. Deep Learning Models for Magnetic Cardiography Edge Sensors Implementing Noise Processing and Diagnostics

    Sadman Sakib, Mostafa M. Fouda, Muftah Al-Mahdawi, Attayeb Mohsen, Mikihiko Oogane, Yasuo Ando, Zubair Md. Fadlullah

    IEEE Access 10 2656-2668 2022年

    出版者・発行元:Institute of Electrical and Electronics Engineers (IEEE)

    DOI: 10.1109/access.2021.3138976  

    eISSN:2169-3536

  12. Sub-pT magnetic field detection by tunnel magneto-resistive sensors

    Mikihiko Oogane, Kosuke Fujiwara, Akitake Kanno, Takafumi Nakano, Hiroshi Wagatsuma, Tadashi Arimoto, Shigemi Mizukami, Seiji Kumagai, Hitoshi Matsuzaki, Nobukazu Nakasato, Yasuo Ando

    Applied Physics Express 14 (12) 123002-123002 2021年12月1日

    出版者・発行元:IOP Publishing

    DOI: 10.35848/1882-0786/ac3809  

    ISSN:1882-0778

    eISSN:1882-0786

    詳細を見る 詳細を閉じる

    <title>Abstract</title> We developed tunnel magneto-resistive (TMR) sensors based on magnetic tunnel junctions (MTJs) that are able to detect a weak, sub-pT, magnetic field at a low frequency. Small detectivities of 0.94 pT/Hz<sup>1/2</sup> at 1 Hz and 0.05 pT/Hz<sup>1/2</sup> at 1 kHz were achieved by lowering the resistance of MTJs and enhancement of the signal using a thick CoFeSiB layer and magnetic flux concentrators. We demonstrated real-time measurement of magnetocardiography (MCG) and nuclear magnetic resonance (NMR) of protons using developed sensors. This result shows that both MCG and NMR can be measured by the same measurement system with ultra-sensitive TMR sensors.

  13. 室温生体磁気計測の進歩:SQUIDを超えて TMRセンサの原理と心磁図計測

    大兼 幹彦, 菅野 彰剛, 藤原 耕輔, 中野 貴文, 熊谷 静似, 松崎 斉, 中里 信和, 安藤 康夫

    臨床神経生理学 49 (5) 299-299 2021年10月

    出版者・発行元:(一社)日本臨床神経生理学会

    ISSN:1345-7101

    eISSN:2188-031X

  14. 室温生体磁気計測の進歩:SQUIDを超えて 頭皮上に密着可能なトンネル磁気抵抗素子を用いた室温脳磁計の開発

    菅野 彰剛, 大兼 幹彦, 藤原 耕輔, 柿坂 庸介, 松崎 斉, 安藤 康夫, 中里 信和

    臨床神経生理学 49 (5) 300-300 2021年10月

    出版者・発行元:(一社)日本臨床神経生理学会

    ISSN:1345-7101

    eISSN:2188-031X

  15. 第32回小児脳機能研究会:臨床神経生理からみた小児の機能評価-中枢から末梢まで- 頭皮上に密着可能なトンネル磁気抵抗素子を用いた室温脳磁計の開発

    菅野 彰剛, 大兼 幹彦, 藤原 耕輔, 柿坂 庸介, 松崎 斉, 安藤 康夫, 中里 信和

    臨床神経生理学 49 (5) 371-371 2021年10月

    出版者・発行元:(一社)日本臨床神経生理学会

    ISSN:1345-7101

    eISSN:2188-031X

  16. 室温生体磁気計測の進歩:SQUIDを超えて TMRセンサの原理と心磁図計測

    大兼 幹彦, 菅野 彰剛, 藤原 耕輔, 中野 貴文, 熊谷 静似, 松崎 斉, 中里 信和, 安藤 康夫

    臨床神経生理学 49 (5) 299-299 2021年10月

    出版者・発行元:(一社)日本臨床神経生理学会

    ISSN:1345-7101

    eISSN:2188-031X

  17. 室温生体磁気計測の進歩:SQUIDを超えて 頭皮上に密着可能なトンネル磁気抵抗素子を用いた室温脳磁計の開発

    菅野 彰剛, 大兼 幹彦, 藤原 耕輔, 柿坂 庸介, 松崎 斉, 安藤 康夫, 中里 信和

    臨床神経生理学 49 (5) 300-300 2021年10月

    出版者・発行元:(一社)日本臨床神経生理学会

    ISSN:1345-7101

    eISSN:2188-031X

  18. 第32回小児脳機能研究会:臨床神経生理からみた小児の機能評価-中枢から末梢まで- 頭皮上に密着可能なトンネル磁気抵抗素子を用いた室温脳磁計の開発

    菅野 彰剛, 大兼 幹彦, 藤原 耕輔, 柿坂 庸介, 松崎 斉, 安藤 康夫, 中里 信和

    臨床神経生理学 49 (5) 371-371 2021年10月

    出版者・発行元:(一社)日本臨床神経生理学会

    ISSN:1345-7101

    eISSN:2188-031X

  19. Quadratic magnetoelectric effect during field cooling in sputter grown Cr2O3 films

    Muftah Al-Mahdawi, Tomohiro Nozaki, Mikihiko Oogane, Hiroshi Imamura, Yasuo Ando, Masashi Sahashi

    Physical Review Materials 5 (9) 2021年9月14日

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

    DOI: 10.1103/physrevmaterials.5.094406  

    eISSN:2475-9953

  20. Noise-Removal from Spectrally-Similar Signals Using Reservoir Computing for MCG Monitoring

    Sadman Sakib, Mostafa M. Fouda, Muftah Al-Mahdawi, Attayeb Mohsen, Mikihiko Oogane, Yasuo Ando, Zubair Md Fadlullah

    ICC 2021 - IEEE International Conference on Communications 2021年6月

    出版者・発行元:IEEE

    DOI: 10.1109/icc42927.2021.9500993  

  21. Serial MTJ-Based TMR Sensors in Bridge Configuration for Detection of Fractured Steel Bar in Magnetic Flux Leakage Testing

    Zhenhu Jin, Muhamad Arif Ihsan Mohd Noor Sam, Mikihiko Oogane, Yasuo Ando

    Sensors 21 (2) 668-668 2021年1月19日

    出版者・発行元:MDPI AG

    DOI: 10.3390/s21020668  

    eISSN:1424-8220

    詳細を見る 詳細を閉じる

    Thanks to high sensitivity, excellent scalability, and low power consumption, magnetic tunnel junction (MTJ)-based tunnel magnetoresistance (TMR) sensors have been widely implemented in various industrial fields. In nondestructive magnetic flux leakage testing, the magnetic sensor plays a significant role in the detection results. As highly sensitive sensors, integrated MTJs can suppress frequency-dependent noise and thereby decrease detectivity; therefore, serial MTJ-based sensors allow for the design of high-performance sensors to measure variations in magnetic fields. In the present work, we fabricated serial MTJ-based TMR sensors and connected them to a full Wheatstone bridge circuit. Because noise power can be suppressed by using bridge configuration, the TMR sensor with Wheatstone bridge configuration showed low noise spectral density (0.19 μV/Hz0.5) and excellent detectivity (5.29 × 10−8 Oe/Hz0.5) at a frequency of 1 Hz. Furthermore, in magnetic flux leakage testing, compared with one TMR sensor, the Wheatstone bridge TMR sensors provided a higher signal-to-noise ratio for inspection of a steel bar. The one TMR sensor system could provide a high defect signal due to its high sensitivity at low lift-off (4 cm). However, as a result of its excellent detectivity, the full Wheatstone bridge-based TMR sensor detected the defect even at high lift-off (20 cm). This suggests that the developed TMR sensor provides excellent detectivity, detecting weak field changes in magnetic flux leakage testing.

  22. トンネル磁気抵抗素子を用いた室温脳磁計による体性感覚誘発磁界の測定

    菅野 彰剛, 大兼 幹彦, 藤原 耕輔, 松﨑 斉, 安藤 康夫, 中里 信和

    生体医工学 59 752-753 2021年

    出版者・発行元:公益社団法人 日本生体医工学会

    DOI: 10.11239/jsmbe.Annual59.752  

    ISSN:1347-443X

    詳細を見る 詳細を閉じる

    <p>"【背景】従来の脳磁計は超伝導量子干渉素子(SQUID)を液体ヘリウム容器に格納する必要があり、センサと頭皮との距離が離れる欠点があった。我々は室温で体表に接した生体磁気計測を可能とすべく、トンネル磁気抵抗(TMR)素子を用いたセンサを開発し、すでに健常被験者における心磁図や脳磁図アルファ波の計測に成功している。今回、正中神経刺激による体性感覚誘発磁界の第1波N20mを再現性よく計測できたので報告する。【方法】健常被験者の左手首の正中神経刺激を、通常の臨床検査と同様に、持続時間は0.3 ms、刺激頻度は2.9 Hz、刺激強度は母指外転筋運動閾値の1.5倍で刺激した。磁気シールド室内で、1チャンネルのTMR素子(JST S-イノベプロジェクトで製作)と磁束集束構造を組み合わせた磁気センサを、被験者の右頭頂部に固定し、頭皮に水平な磁界成分を計測した。得られた信号は16ビットでサンプル周波数2,000HzにてA/D変換し、帯域フィルタ5-250Hzで処理後に、波形が明瞭になるまで合計1,000から5,000回の平均加算を行った。【結果】刺激から潜時約20msに頂点をもつ第1波と、その後の第2、第3波が明瞭に記録され、同一被験者でSQUID脳磁計にて測定した波形と同一成分と確認できた。【結語】今回の結果は、TMR脳磁計の実用化に大きく寄与するものと期待される。"</p>

  23. トンネル磁気抵抗素子を用いた室温脳磁計による体性感覚誘発磁界の測定

    菅野 彰剛, 大兼 幹彦, 藤原 耕輔, 松﨑 斉, 安藤 康夫, 中里 信和

    生体医工学 59 243-243 2021年

    出版者・発行元:公益社団法人 日本生体医工学会

    DOI: 10.11239/jsmbe.Annual59.243  

    ISSN:1347-443X

    詳細を見る 詳細を閉じる

    <p>【背景】従来の脳磁計は超伝導量子干渉素子(SQUID)を液体ヘリウム容器に格納する必要があり、センサと頭皮との距離が離れる欠点があった。我々は室温で体表に接した生体磁気計測を可能とすべく、トンネル磁気抵抗(TMR)素子を用いたセンサを開発し、すでに健常被験者における心磁図や脳磁図アルファ波の計測に成功している。今回、正中神経刺激による体性感覚誘発磁界の第1波N20mを再現性よく計測できたので報告する。【方法】健常被験者の左手首の正中神経刺激を、通常の臨床検査と同様に、持続時間は0.3 ms、刺激頻度は2.9 Hz、刺激強度は母指外転筋運動閾値の1.5倍で刺激した。磁気シールド室内で、1チャンネルのTMR素子(JST S-イノベプロジェクトで製作)と磁束集束構造を組み合わせた磁気センサを、被験者の右頭頂部に固定し、頭皮に水平な磁界成分を計測した。得られた信号は16ビットでサンプル周波数2,000HzにてA/D変換し、帯域フィルタ5-250Hzで処理後に、波形が明瞭になるまで合計1,000から5,000回の平均加算を行った。【結果】刺激から潜時約20msに頂点をもつ第1波と、その後の第2、第3波が明瞭に記録され、同一被験者でSQUID脳磁計にて測定した波形と同一成分と確認できた。【結語】今回の結果は、TMR脳磁計の実用化に大きく寄与するものと期待される。</p>

  24. トンネル磁気抵抗素子を用いた室温脳磁計による体性感覚誘発磁界の測定

    菅野 彰剛, 大兼 幹彦, 藤原 耕輔, 松崎 斉, 安藤 康夫, 中里 信和

    日本生体磁気学会誌 34 (1) 112-113 2021年

    出版者・発行元:日本生体磁気学会

    ISSN:0915-0374

  25. Highly-sensitive magnetic sensor for detecting magnetic nanoparticles based on magnetic tunnel junctions at a low static field

    Z. Jin, Thomas Myeongseok Koo, Myeong Soo Kim, M. Al-Mahdawi, M. Oogane, Y. Ando, Young Keun Kim

    AIP Advances 11 (1) 015046-015046 2021年1月1日

    出版者・発行元:AIP Publishing

    DOI: 10.1063/9.0000189  

    eISSN:2158-3226

  26. Detection of Small Magnetic Fields Using Serial Magnetic Tunnel Junctions with Various Geometrical Characteristics

    Zhenhu Jin, Yupeng Wang, Kosuke Fujiwara, Mikihiko Oogane, Yasuo Ando

    Sensors 20 (19) 5704-5704 2020年10月7日

    出版者・発行元:MDPI AG

    DOI: 10.3390/s20195704  

    eISSN:1424-8220

    詳細を見る 詳細を閉じる

    Thanks to their high magnetoresistance and integration capability, magnetic tunnel junction-based magnetoresistive sensors are widely utilized to detect weak, low-frequency magnetic fields in a variety of applications. The low detectivity of MTJs is necessary to obtain a high signal-to-noise ratio when detecting small variations in magnetic fields. We fabricated serial MTJ-based sensors with various junction area and free-layer electrode aspect ratios. Our investigation showed that their sensitivity and noise power are affected by the MTJ geometry due to the variation in the magnetic shape anisotropy. Their MR curves demonstrated a decrease in sensitivity with an increase in the aspect ratio of the free-layer electrode, and their noise properties showed that MTJs with larger junction areas exhibit lower noise spectral density in the low-frequency region. All of the sensors were able detect a small AC magnetic field (Hrms = 0.3 Oe at 23 Hz). Among the MTJ sensors we examined, the sensor with a square-free layer and large junction area exhibited a high signal-to-noise ratio (4792 ± 646). These results suggest that MTJ geometrical characteristics play a critical role in enhancing the detectivity of MTJ-based sensors.

  27. Scaling of quadratic and linear magneto-optic Kerr effect spectra with L2(1) ordering of Co2MnSi Heusler compound

    Robin Silber, Daniel Kral, Ondrej Stejskal, Takahide Kubota, Yasuo Ando, Jaromir Pistora, Martin Veis, Jaroslav Hamrle, Timo Kuschel

    APPLIED PHYSICS LETTERS 116 (26) 2020年6月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/5.0008427  

    ISSN:0003-6951

    eISSN:1077-3118

    詳細を見る 詳細を閉じる

    Spectral ellipsometry is a useful technique allowing fast, nondestructive, and contactless characterization of thin films and constituent materials. In this Letter, we show that both the linear magneto-optic Kerr effect (LinMOKE, proportional to the magnetization M) and the quadratic MOKE (QMOKE, proportional toM 2) can be a useful extension of spectral ellipsometry and are able to sense the crystallographic ordering of Heusler compounds. This is demonstrated for the Heusler compound Co2MnSi, which has a crystallographic transition from a B2 to an L2(1) structure with increasing annealing temperature T-a. We investigated a set of Co2MnSi thin films deposited on MgO(001) substrates and annealed from 300 to 500 degrees C. The amplitude of LinMOKE and QMOKE spectra, detected in the extended visible spectral range of 0.8-5.5eV, scales linearly with T-a, and this effect is pronounced at the resonant peaks of the QMOKE spectra below 2.0eV. Furthermore, the spectra of the magneto-optic (MO) parameters, which fully describe the MO response of Co2MnSi up to the second order in M, are obtained depending on T-a. Finally, the spectra are compared with ab initio calculations of a purely L2(1)-ordered Co2MnSi Heusler compound.

  28. AI Aided Noise Processing of Spintronic Based IoT Sensor for Magnetocardiography Application

    Attayeb Mohsen, Muftah Al-Mahdawi, Mostafa M. Fouda, Mikihiko Oogane, Yasuo Ando, Zubair Md Fadlullah

    ICC 2020 - 2020 IEEE International Conference on Communications (ICC) 2020年6月

    出版者・発行元:IEEE

    DOI: 10.1109/icc40277.2020.9148617  

  29. High-Temperature Magnetic Tunnel Junction Magnetometers Based on L1$_0$-PtMn Pinned Layer

    Sina Ranjbar, Muftah Al-Mahdawi, Mikihiko Oogane, Yasuo Ando

    IEEE Sensors Letters 4 (5) 1-4 2020年5月

    出版者・発行元:Institute of Electrical and Electronics Engineers (IEEE)

    DOI: 10.1109/lsens.2020.2991654  

    eISSN:2475-1472

  30. Controlling domain configuration of the sensing layer for magnetic tunneling junctions by using exchange bias

    Sina Ranjbar, Muftah Al-Mahdawi, Mikihiko Oogane, Yasuo Ando

    AIP Advances 10 (2) 025119-025119 2020年2月1日

    出版者・発行元:AIP Publishing

    DOI: 10.1063/1.5130486  

    eISSN:2158-3226

  31. Large spin signals in n+ -Si/MgO/ Co2Fe0.4Mn0.6Si lateral spin-valve devices 査読有り

    T. Koike, M. Oogane, M. Tsunoda, Y. Ando

    127 (8) 085306-1-085306-8 2020年2月

  32. Fabrication and evaluation of highly c-plane oriented Mn3Sn thin films 査読有り

    T. Ikeda, M. Tsunoda, M. Oogane, S. Oh, T. Morita, Y. Ando

    AIP Advances 10 015310-1-015310-5 2020年1月

  33. Fabrication of soft-magnetic FeAlSi thin films with nm-order thickness for the free layer of magnetic tunnel junction based sensors 査読有り

    S. Akamatsu, M. Oogane, M. Tsunoda, Y. Ando

    AIP Advances 10 015302-1-015302-4 2020年1月

  34. Composition dependence of the secondorder interfacial magnetic anisotropy for MgO/CoFeB/Ta films 査読有り

    T. Ogasawara, M. Oogane, M. Al-Mahdawi, M. Tsunoda, Y. Ando

    AIP Advances 9 125053-1-125053-5 2019年12月

  35. Polycrystalline Co2Fe0.4Mn0.6Si Heusler alloy thin films with high B2 ordering and small magnetic anisotropy for magnetic tunnel junction based sensors 査読有り

    N. Kudo, M. Oogane, M. Tsunoda, Y. Ando

    AIP Advances 9 125036-1-125036-4 2019年12月

  36. Effect of second-order magnetic anisotropy on nonlinearity of conductance in CoFeB/MgO/CoFeB magnetic tunnel junction for magnetic sensor devices 査読有り

    T. Ogasawara, M. Oogane, M. Al-Mahdawi, M. Tsunoda, Y. Ando

    Scientific Reports 9 17018-1-17018-9 2019年11月

  37. Investigation of a Magnetic Tunnel Junction Based Sensor for the Detection of Defects in Reinforced Concrete at High Lift-Off

    Muhamad Arif Ihsan Mohd Noor Sam, Zhenhu Jin, Mikihiko Oogane, Yasuo Ando

    Sensors 19 (21) 4718-4718 2019年10月30日

    出版者・発行元:MDPI AG

    DOI: 10.3390/s19214718  

    eISSN:1424-8220

    詳細を見る 詳細を閉じる

    Magnetic flux leakage (MFL) testing is a method of non-destructive testing (NDT), whereby the material is magnetized, and when a defect is present, the magnetic flux lines break out of the material. The magnitude of the leaked magnetic flux decreases as the lift-off (distance from the material) increases. Therefore, for detection at high lift-off, a sensitive magnetic sensor is required. To increase the output sensitivity, this paper proposes the application of magnetic tunnel junction (MTJ) sensors in a bridge circuit for the NDT of reinforced concrete at high lift-off. MTJ sensors were connected to a full-bridge circuit, where one side of the arm has two MTJ sensors connected in series, and the other contains a resistor and a variable resistor. Their responses towards a bias magnetic field were measured, and, based on the results, the sensor circuit sensitivity was 0.135 mV/mT. Finally, a reinforced concrete specimen with a 1 cm gap in the center was detected. The sensor module (with an amplifier and low pass filter circuits) could determine the gap even at 50 cm, suggesting that MTJ sensors have the potential to detect defects at high lift-off values and have a promising future in the field of NDT.

  38. Composition dependence of exchange anisotropy in PtxMn100−x/CoyFe100-y films 査読有り

    S. Ranjbar, M. Tsunoda, M. Al-Mahdawi, M. Oogane, Y. Ando

    IEEE Magnetics Letters 10 4505905-1-4505905-5 2019年10月

  39. In-plane and perpendicular exchange bias effect induced by an antiferromagnetic D0(19) Mn2FeGa thin film 査読有り

    Ogasawara Takahiro, Jackson Edward, Tsunoda Masakiyo, Ando Yasuo, Hirohata Atsufumi

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 484 307-312 2019年8月

    出版者・発行元:None

    DOI: 10.1016/j.jmmm.2019.04.024  

    ISSN:0304-8853

    eISSN:1873-4766

  40. Improvement of Large Anomalous Hall Effect in Polycrystalline Antiferromagnetic Mn3+xSn Thin Films 査読有り

    Ikeda Tomoki, Tsunoda Masakiyo, Oogane Mikihiko, Oh Seungjun, Morita Tadashi, Ando Yasuo

    IEEE TRANSACTIONS ON MAGNETICS 55 (7) 2019年7月

    DOI: 10.1109/TMAG.2019.2899223  

    ISSN:0018-9464

  41. Controlled growth and magnetic property of a-plane-oriented Mn3Sn thin films 査読有り

    Oh Seungjun, Morita Tadashi, Ikeda Tomoki, Tsunoda Masakiyo, Oogane Mikihiko, Ando Yasuo

    AIP ADVANCES 9 (3) 2019年3月

    DOI: 10.1063/1.5079688  

    ISSN:2158-3226

  42. Serial magnetic tunnel junction based sensors for detecting far-side pitsin metallic specimens 査読有り

    Zhenhu Jin, Muhamad Arif Ihsan, Mikihiko Oogane, Kousuke Fujiwara, Yasuo Ando

    Japanese Journal of Applied Physics 58 043003-1-043003-6 2019年3月

    DOI: 10.7567/1347-4065/aafe71  

  43. Composition dependence of exchange anisotropy in PtxMn1−x/Co70Fe30 films 査読有り

    Sina Ranjbar, Masakiyo Tsunoda, Mikihiko Oogane, Yasuo Ando

    Japanese Journal of Applied Physics 58 043001-1-043001-5 2019年3月

    DOI: 10.7567/1347-4065/ab03e3  

  44. Structural and antiferromagnetic characterization of noncollinear D019 Mn3Ge polycrystalline film 査読有り

    Takahiro Ogasawara, Jun-young Kim, Yasuo Ando, Atsufumi Hirohata

    Journal of Magnetism and Magnetic Materials 473 7-11 2019年

    出版者・発行元:None

    DOI: 10.1016/j.jmmm.2018.10.035  

    ISSN:0304-8853

    eISSN:1873-4766

  45. Anomalous Hall effect in polycrystalline Mn3Sn thin films 査読有り

    Tomoki Ikeda, Masakiyo Tsunoda, Mikihiko Oogane, Seungjun Oh, Tadashi Morita, Yasuo Ando

    APPLIED PHYSICS LETTERS 113 222405-1-222405-5 2018年11月

    DOI: 10.1063/1.5051495  

  46. Epitaxial L10-MnAl Thin Films With High Perpendicular Magnetic Anisotropy and Small Surface Roughness 査読有り

    Most Shahnaz Parvin, Mikihiko Oogane, Miho Kubota, Masakiyo Tsunoda, Yasuo Ando

    EEE TRANSACTIONS ON MAGNETICS 54 (11) 3401704-1-3401704-4 2018年11月

    DOI: 10.1109/TMAG.2018.2834553  

    ISSN:0018-9464

  47. Effects of annealing temperature on sensing properties of magnetic-tunnel-junction-based sensors with perpendicular syntheticantiferromagnetic Co/Pt pinned layer 査読有り

    Takahiro Ogasawara, Mikihiko Oogane, Masakiyo Tsunoda, Yasuo Ando

    Japanese Journal of AppliedPhysics 57 (11) 110308-1-110308-4 2018年10月

    DOI: 10.7567/JJAP.57.110308  

  48. Large exchange coupling field in perpendicular synthetic antiferromagnetic structures with CoPt alloy 査読有り

    Takahiro Ogasawara, Mikihiko Oogane, Masakiyo Tsunoda, Yasuo Ando

    JAPANESE JOURNAL OF APPLIED PHYSICS 57 (8) 088004-1-088004-3 2018年7月

    DOI: 10.7567/JJAP.57.088004  

  49. Fourfold symmetric anisotropic magnetoresistance in half-metallic Co2MnSi Heusler alloy thin films 査読有り

    Mikihiko Oogane, Anthony P. McFadden, Yohei Kota, Tobias L. Brown-Heft, Masakiyo Tsunoda, Yasuo Ando, Chris J. Palmstrøm

    Japanese Journal of Applied Physics 57 (6) 063001-1-063001-4 2018年6月1日

    出版者・発行元:Japan Society of Applied Physics

    DOI: 10.7567/JJAP.57.063001  

    ISSN:1347-4065 0021-4922

    詳細を見る 詳細を閉じる

    In this study, we systematically investigated the anisotropic magnetoresistance (AMR) effect in half-metallic Co2MnSi Heusler alloy films epitaxially grown by molecular beam epitaxy. The fourfold symmetric AMR was observed in the temperature range of 25-275 K. In addition, the films exhibited a marked change in twofold symmetric AMR below 100 K. This specific temperature dependence of the AMR effect in Co2MnSi films can be caused by the tetragonal crystal field because of the distortion of the lattice at low temperatures. The influence of tetragonal distortion on both the AMR effect and half-metallicity is also discussed by first-principles calculations.

  50. Low magnetic damping and large negative anisotropic magnetoresistance in half-metallic Co2-xMn1+xSi Heusler alloy films grown by molecular beam epitaxy 査読有り

    M.Oogane, AP.McFadden, K.Fukuda, M.Tsunoda, Y.Ando, CJ. Palmstrom

    APPLIED PHYSICS LETTERS 112 (26) 262407-1-262407-5 2018年6月

    DOI: 10.1063/1.5030341  

  51. Annealing effect on interlayer exchange coupling in perpendicularly magnetized synthetic antiferromagnetic structure based on Co/Pd multilayers with ultrathin Ru spacer 査読有り

    Takafumi Nakano, Mikihiko Oogane, Yasuo Ando

    JAPANESE JOURNAL OF APPLIED PHYSICS 57 (7) 073001-1-073001-4 2018年6月

    DOI: 10.7567/JJAP.57.073001  

  52. Magnetic-sensor performance evaluated from magneto-conductance curve in magnetic tunnel junctions using in-plane or perpendicularly magnetized synthetic antiferromagnetic reference layers 査読有り

    T. Nakano, M. Oogane, T. Furuichi, Y. Ando

    AIP Advances 8 (4) 045011-1-045011-6 2018年4月1日

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

    DOI: 10.1063/1.5027768  

    ISSN:2158-3226

    詳細を見る 詳細を閉じる

    The automotive industry requires magnetic sensors exhibiting highly linear output within a dynamic range as wide as ±1 kOe. A simple model predicts that the magneto-conductance (G-H) curve in a magnetic tunnel junction (MTJ) is perfectly linear, whereas the magneto-resistance (R-H) curve inevitably contains a finite nonlinearity. We prepared two kinds of MTJs using in-plane or perpendicularly magnetized synthetic antiferromagnetic (i-SAF or p-SAF) reference layers and investigated their sensor performance. In the MTJ with the i-SAF reference layer, the G-H curve did not necessarily show smaller nonlinearities than those of the R-H curve with different dynamic ranges. This is because the magnetizations of the i-SAF reference layer start to rotate at a magnetic field even smaller than the switching field (Hsw) measured by a magnetometer, which significantly affects the tunnel magnetoresistance (TMR) effect. In the MTJ with the p-SAF reference layer, the G-H curve showed much smaller nonlinearities than those of the R-H curve, thanks to a large Hsw value of the p-SAF reference layer. We achieved a nonlinearity of 0.08% FS (full scale) in the G-H curve with a dynamic range of ±1 kOe, satisfying our target for automotive applications. This demonstrated that a reference layer exhibiting a large Hsw value is indispensable in order to achieve a highly linear G-H curve.

  53. Realization of a Spin-Wave Switch Based on the Spin-Transfer-Torque Effect 査読有り

    Thomas Meyer, Thomas Bracher, Frank Heussner, Alexander A. Serga, Hiroshi Naganuma, Koki Mukaiyama, Mikihiko Oogane, Yasuo Ando, Burkard Hillebrands, Philipp Pirro

    IEEE Magnetics Letters 9 3102005-1-3102005-5 2018年2月7日

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

    DOI: 10.1109/LMAG.2018.2803737  

    ISSN:1949-307X

    詳細を見る 詳細を閉じる

    We investigate the amplification of externally excited spin-waves via the spin-transfer-torque (STT) effect in combination with the spin-Hall effect (SHE) resulting from short current pulses. In the case of overcompensation of the spin-wave damping, a strong nonlinear shift of the spin-wave frequency spectrum occurs. In particular, this shift limits spin-wave amplification from the SHE-STT effect. However, it allows for the realization of a spin-wave switch. At the corresponding working point, efficient spin-wave excitation is possible only in the presence of the SHE-STT effect with a spin-wave intensity that is a factor of 20 larger than in the absence of the SHE-STT effect.

  54. Magnetocardiography and magnetoencephalography measurements at room temperature using tunnel magneto-resistance sensors 査読有り

    Kosuke Fujiwara, Mikihiko Oogane, Akitake Kanno, Masahiro Imada, Junichi Jono, Takashi Terauchi, Tetsuo Okuno, Yuuji Aritomi, Masahiro Morikawa, Masaaki Tsuchida, Nobukazu Nakasato, Yasuo Ando

    Applied Physics Express 11 (2) 023001-1-023001-4 2018年2月

    DOI: 10.7567/APEX.11.023001  

    ISSN:1882-0778

    eISSN:1882-0786

    詳細を見る 詳細を閉じる

    © 2018 The Japan Society of Applied Physics. Magnetocardiography (MCG) and magnetoencephalography (MEG) signals were detected at room temperature using tunnel magneto-resistance (TMR) sensors. TMR sensors developed with low-noise amplifier circuits detected the MCG R wave without averaging, and the QRS complex was clearly observed with averaging at a high signal-to-noise ratio. Spatial mapping of the MCG was also achieved. Averaging of MEG signals triggered by electroencephalography (EEG) clearly observed the phase inversion of the alpha rhythm with a correlation coefficient as high as 0.7 between EEG and MEG.

  55. Characterization of spin-transfer-torque effect induced magnetization dynamics driven by short current pulses 査読有り

    T. Meyer, T. Brächer, F. Heussner, A. A. Serga, H. Naganuma, K. Mukaiyama, M. Oogane, Y. Ando, B. Hillebrands, P. Pirro

    Applied Physics Letters 112 (2) 022401-1-022401-5 2018年1月8日

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

    DOI: 10.1063/1.5011721  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    We present a time-resolved study of the magnetization dynamics in a microstructured Cr|Heusler|Pt waveguide driven by the spin-Hall-effect and the spin-transfer-torque effect via short current pulses. In particular, we focus on the determination of the threshold current at which the spin-wave damping is compensated. We have developed an alternative method based on the temporal evolution of the magnon density at the beginning of an applied current pulse at which the magnon density deviates from the thermal level. Since this method does not depend on the signal-to-noise ratio, it allows for a robust and reliable determination of the threshold current which is important for the characterization of any future application based on the spin-transfer-torque effect.

  56. Structural and Magnetic Properties in Mn2VAl Full-Heusler Epitaxial Thin Films 査読有り

    Kenji Fukuda, Mikihiko Oogane, Yasuo Ando

    IEEE TRANSACTIONS ON MAGNETICS 53 (11) 2017年11月

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

    DOI: 10.1109/TMAG.2017.2697078  

    ISSN:0018-9464

    eISSN:1941-0069

    詳細を見る 詳細を閉じる

    Epitaxially grown Mn2VAl full-Heusler thin films were fabricated on single crystalline MgO (001) substrates by using an ultrahigh-vacuum magnetron sputtering technique. X-ray diffraction revealed that epitaxial Mn2VAl films with a highly L2(1)-ordered structure were obtained by annealing around 600 degrees C. For the films deposited without a buffer layer and annealed at 500 degrees C-600 degrees C, the saturation magnetization was about 240 emu/cm(3) at 300 K, which was close to the theoretical value. The effective magnetic damping constant of Mn2VAl thin films was investigated using the ferromagnetic resonance technique. The effective damping constant was much larger than expected due to the inhomogeneity in the Mn2VAl films.

  57. Observation of Magnetoresistance Effect in n-Type Non-Degenerate Germanium With Co2Fe0.4Mn0.6Si Heusler Alloy Electrodes 査読有り

    Takeo Koike, Mikihiko Oogane, Tetsurou Takada, Hidekazu Saito, Yasuo Ando

    IEEE TRANSACTIONS ON MAGNETICS 53 (11) 2017年11月

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

    DOI: 10.1109/TMAG.2017.2704780  

    ISSN:0018-9464

    eISSN:1941-0069

    詳細を見る 詳細を閉じる

    The local 3-terminal magnetoresistance properties of n-Ge/MgO/Co2Fe0.4Mn0.6Si lateral spin-valve devices were systematically investigated. In the spin extraction condition, clear steep voltage changes were successfully observed. We measured the bias voltage and temperature dependences of the spin resistance-area product. At a high bias voltage, the spin signal increased with increasing voltage, reaching a maximum value of 7.0 Omega mu m(2) at V-bias = 663 mV. The signal decreased with increasing temperature but was still observed up to 160 K.

  58. Magnetic sensor based on serial magnetic tunnel junctions for highly sensitive detection of surface cracks 査読有り

    Zhenhu Jin, Mikihiko Oogane, Kosuke Fujiwara, Yasuo Ando

    JOURNAL OF APPLIED PHYSICS 122 (17) 113903 2017年11月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.5001098  

    ISSN:0021-8979

    eISSN:1089-7550

    詳細を見る 詳細を閉じる

    Magnetic tunnel junctions (MTJs) that consist of two ferromagnets separated by a thin insulator are among the core devices used in spintronic applications such as magnetic sensors. Since magnetic sensors require high sensitivity for nondestructive eddy current testing, we developed and demonstrated magnetic sensors based on various configurations of serial MTJs. We fabricated sensors with 4, 16, 28, 40, and 52 serial MTJs in various numbers of rows (1, 4, 7, 10, and 13) to detect surface cracks via eddy current testing. All of the sensors could detect and discriminate between surface cracks 0.1 mm in width and 0.1 to 1.0 mm in depth on an aluminum specimen. Systematic studies on the effect of the number of MTJs showed a signal to noise ratio as high as 115 dB when detecting 0.1 mm deep cracks with 28 serial MTJs in 7 rows. This suggests that suitably configured serial MTJ sensors can offer an excellent performance in the detection of tiny surface defects via eddy current testing. Published by AIP Publishing.

  59. Micro-Focused Pulse Laser-Induced Propagating Spin Waves in Permalloy Films With Different Thicknesses 査読有り

    Akira Kamimaki, Satoshi Iihama, Yuta Sasaki, Yasuo Ando, Shigemi Mizukami

    IEEE TRANSACTIONS ON MAGNETICS 53 (11) 4300604-1-4300604-1 2017年11月

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

    DOI: 10.1109/TMAG.2017.2707421  

    ISSN:0018-9464

    eISSN:1941-0069

    詳細を見る 詳細を閉じる

    Propagating spin waves excited by a micro-focused ultra-short pulse laser were investigated in Permalloy films with the thicknesses of 20, 50, and 100 nm by means of an all-optical space-and-time-resolved magneto-optical Kerr effect. Although various perpendicular standing spin-wave modes were excited, the propagating magneto-static surface spin wave was clearly detected in each film, where the group velocities of approximately 4, 8, and 12 km/s and the propagation lengths of 3.8, 6.6, and 13 mu m for the 20, 50, and 100 nm-thick films, respectively, were evaluated. The evaluated group velocities were consistent with the theoretical values, whereas the propagation lengths were smaller than the theoretical values with the Gilbert damping constant alpha of 0.008.

  60. DC Bias Reversal Behavior of Spin-Torque Ferromagnetic Resonance Spectra in CoFeB/MgO/CoFeB Perpendicular Magnetic Tunnel Junction 査読有り

    Tian Yu, Hiroshi Naganuma, Mikihiko Oogane, Yasuo Ando

    IEEE TRANSACTIONS ON MAGNETICS 53 (9) 1400205-1-1400205-5 2017年9月

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

    DOI: 10.1109/TMAG.2017.2707081  

    ISSN:0018-9464

    eISSN:1941-0069

    詳細を見る 詳細を閉じる

    Spin-torque ferromagnetic resonance (ST-FMR) spectra of nano-scaled CoFeB/MgO/CoFeB full perpendicular magnetic tunnel junctions (p-MTJs) were investigated, especially in detail at low dc-bias voltage region. Usually in in-plane magnetized MTJs (i-MTJs), the ST-FMR spectrum line shape reverses its symmetry as switching dc-bias voltage polarities; however, it is found that in the p-MTJs the line shape reversal behaves differently, that not only the spectrum shows anti-symmetric line shape at zero dc bias but also the dependence of reversal symmetry on dc bias is broken. Based on the framework of homodyne-detected ST-FMR, we extracted the parameters characterizing the spectra and discussed the possible factors resulting these differences.

  61. Wide-dynamic-range magnetic sensor based on magnetic tunnel junctions using perpendicularly magnetized synthetic antiferromagnetic reference layer 査読有り

    T. Nakano, M. Oogane, T. Furuichi, Y. Ando

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

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

    DOI: 10.1109/INTMAG.2017.8007558  

    詳細を見る 詳細を閉じる

    Magnetic tunnel junctions (MTJs) with an MgO barrier, which exhibit a giant tunnel magnetoresistance (TMR) effect [1]-[4], have been intensively studied for application to various magnetic sensors in the automotive industry.

  62. Magnetic properties of ferrimagnetic (Mn1-xCox)2VAl full-Heusler epitaxial thin films 査読有り

    K. Fukuda, M. Oogane, Y. Ando

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

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

    DOI: 10.1109/INTMAG.2017.8007971  

    詳細を見る 詳細を閉じる

    Half-metallic ferrimagnets have attracted many scientists as an ideal source of spin injection because of high spin polarization and low magnetization, which can realize small energy consumption in spintronic devices, such as magnetic random access memory (MRAM).

  63. CoFeAlB alloy with low damping and low magnetization as a candidate for spin transfer torque switching 査読有り

    A. Conca, T. Nakano, T. Meyer, Y. Ando, B. Hillebrands

    JOURNAL OF APPLIED PHYSICS 122 (7) 073902-1-073902-5 2017年8月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.4998813  

    ISSN:0021-8979

    eISSN:1089-7550

    詳細を見る 詳細を閉じる

    We investigate the effect of Al doping on the magnetic properties of the CoFeB alloy. Comparative measurements of the saturation magnetization, the Gilbert damping parameter a, and the exchange constant as a function of the annealing temperature for CoFeB and CoFeAlB thin films are presented. Our results reveal a strong reduction of the magnetization for CoFeAlB in comparison to CoFeB. If the prepared CoFeAlB films are amorphous, the damping parameter a is unaffected by the Al doping in comparison to the CoFeB alloy. In contrast, in the case of a crystalline CoFeAlB film, a is found to be reduced. Furthermore, the x-ray characterization and the evolution of the exchange constant with the annealing temperature indicate a similar crystallization process in both alloys. The data prove that CoFeAlB fulfills the requirements to be considered an attractive candidate for spin torque switching purposes and a reduction of the switching current in comparison with CoFeB is expected. Published by AIP Publishing.

  64. Reciprocal excitation of propagating spin waves by a laser pulse and their reciprocal mapping in magnetic metal films 査読有り

    A. Kamimaki, S. Iihama, Y. Sasaki, Y. Ando, S. Mizukami

    PHYSICAL REVIEW B 96 (1) 014438-1-014438-11 2017年7月

    出版者・発行元:AMER PHYSICAL SOC

    DOI: 10.1103/PhysRevB.96.014438  

    ISSN:2469-9950

    eISSN:2469-9969

    詳細を見る 詳細を閉じる

    Focused pulse-laser-induced propagating magnetostatic surface spin waves (MSSWs) were investigated using an all-optical space-time-resolved magneto-optical Kerr effect microscope in 20-nm-thick permalloy thin films to clarify reciprocity and symmetry of MSSW emission. The microscope setup was constructed with variable direction of the applied magnetic field, and the corresponding angular dependence was examined. MSSWs were reciprocally emitted from the laser spot, in contrast to the nonreciprocal emission obtained by the antenna method. Specifically, the observed excitation amplitude and phase were independent of the propagation and magnetization directions within experimental error. By transforming the data into wave number-frequency space, the MSSW dispersion relation was clearly identified within the wave number of 2-3rad/mu m and frequency of 10 GHz. These observations are consistent with the model of ultrafast modulation of out-of-plane shape magnetic anisotropy inside the focused laser spot. In addition to confirming the symmetric and reciprocal emission of laser-induced MSSWs, the study demonstrated that this technique can provide all-optical microscopic spectroscopy for MSSW in metals, such as Brillouin light-scattering technique.

  65. Thickness dependencies of structural and magnetic properties of cubic and tetragonal Heusler alloy bilayer films 査読有り

    R. Ranjbar, K. Z. Suzuki, A. Sugihara, Y. Ando, T. Miyazaki, S. Mizukami

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 433 195-201 2017年7月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/j.jmmm.2017.03.018  

    ISSN:0304-8853

    eISSN:1873-4766

    詳細を見る 詳細を閉じる

    The thickness dependencies of the structural and magnetic properties for bilayers of cubic Co-based Heusler alloys (CCHAs: Co2FeAl (CFA), Co2FeSi (CFS), Co2MnAl (CMA), and Co2MnSi (CMS)) and D0(22)-MnGa were investigated. Epitaxy of the B2 structure of CCHAs on a MnGa film was achieved; the smallest thickness with the B2 structure was found for 3-nm-thick CMS and CFS. The interfacial exchange coupling (J(ex)) was antiferromagnetic (AFM) for all of the CCHAs/MnGa bilayers except for unannealed CFA/MnGa samples. A critical thickness (t(crit)) at which perpendicular magnetization appears of approximately 4-10 nm for the CMA/MnGa and CMS/MnGa bilayers was observed, whereas this thickness was 1-3 nm for the CFA/MnGa and CFS/MnGa films. The critical thickness for different CCHAs materials is discussed in terms of saturation magnetization (Ms) and the J(ex). (C) 2017 Elsevier B.V. All rights reserved.

  66. Estimation of surface crack dimensional characteristics by an eddy current method using a single magnetic tunnel junction device 査読有り

    Zhenhu Jin, Masahiko Abe, Mikihiko Oogane, Kousuke Fujiwara, Yasuo Ando

    JAPANESE JOURNAL OF APPLIED PHYSICS 56 (7) 1-5 2017年7月

    出版者・発行元:IOP PUBLISHING LTD

    DOI: 10.7567/JJAP.56.073001  

    ISSN:0021-4922

    eISSN:1347-4065

    詳細を見る 詳細を閉じる

    Eddy current testing plays a significant role in detecting surface defects in a nondestructive testing field. The magnetoresistive sensors based on magnetic tunnel junction devices attracted considerable attention for their use in eddy current testing owing to their high sensitivity and capability of being miniaturized. We investigated the detection of surface cracks in eddy current testing using a single magnetic tunnel junction. A perpendicular component with a secondary magnetic field from an eddy current was measured by using an optimized rectangular magnetic tunnel junction device with an aspect ratio of 4 (20 x 80 mu m(2)). Furthermore, according to the extracted Delta X and Delta V from the sensor output signal, surface cracks with various widths (0.1, 0.3, and 0.5 mm) and depths (0.5, 1.0, 1.5, and 3.0mm) in aluminum specimens were successfully estimated using the magnetic tunnel junction device in eddy current testing when an excitation frequency of 1000 Hz was used. (C) 2017 The Japan Society of Applied Physics

  67. L1

    Oogane Mikihiko, Watanabe Kenta, Saruyama Haruaki, Hosoda Masaki, Shahnaz Parvin, Kurimoto Yuta, Kubota Miho, Ando Yasuo

    Jpn. J. Appl. Phys. 56 (8) 0802A2 2017年6月1日

    出版者・発行元:Institute of Physics

    DOI: 10.7567/JJAP.56.0802A2  

    ISSN:0021-4922

    詳細を見る 詳細を閉じる

    L1<inf>0</inf>-ordered MnAl thin films were epitaxially grown by sputtering. The film composition dependences of structural and magnetic properties were systematically investigated in the MnAl thin films. Both the L1<inf>0</inf>-ordered parameter and the perpendicular magnetic anisotropy energy strongly depended on the composition of the MnAl thin films. The MnAl thin films with a Mn composition of 53–54 at. % showed both the highest L1<inf>0</inf>-ordered parameter and the perpendicular magnetic anisotropy. The substrate and annealing temperatures were optimized to improve the magnetic properties and surface morphology. We have fabricated MnAl thin films with both a very high K<inf>u</inf>of 12 × 10<sup>6</sup>erg/cm<sup>3</sup>and a small surface roughness of ca. 0.2 nm by optimizing the film composition and substrate and annealing temperatures. These results are useful guidelines for the fabrication of highly L1<inf>0</inf>-ordered MnAl thin films with a large perpendicular magnetic anisotropy.

  68. Cobalt substituted L1

    Watanabe Kenta, Oogane Mikihiko, Ando Yasuo

    Jpn. J. Appl. Phys. 56 (8) 0802B1 2017年6月1日

    出版者・発行元:Institute of Physics

    DOI: 10.7567/JJAP.56.0802B1  

    ISSN:0021-4922

    詳細を見る 詳細を閉じる

    The Co composition dependences of the structural and magnetic properties of L1<inf>0</inf>-(MnAl)<inf>1−</inf><inf>x</inf>Co<inf>x</inf>alloy films were investigated. The lattice constants of (MnAl)<inf>1−</inf><inf>x</inf>Co<inf>x</inf>films gradually changed with increasing Co content while maintaining the L1<inf>0</inf>-ordered structure below x = 0.08. The saturation magnetization gradually decreased with increasing Co content, and perpendicular magnetic anisotropy was observed below x = 0.08. In addition, Co substitution markedly improved the surface roughness of the films by decreasing the substrate temperature of (MnAl)<inf>1−</inf><inf>x</inf>Co<inf>x</inf>films. We found that both a high magnetic anisotropy and a small surface roughness can be obtained by the substitution of Co atoms into MnAl films.

  69. Cobalt substituted L10-MnAl thin films with large perpendicular magnetic anisotropy 査読有り

    Kenta Watanabe, Mikihiko Oogane, Yasuo Ando

    Jpn. J. Appl. Phys. 2017年6月

  70. L10-ordered MnAl thin films with high perpendicular magnetic anisotropy 招待有り 査読有り

    Mikihiko Oogane, Kenta Watanabe, Haruaki Saruyama, Masaki Hosoda, Parvin Shahnaz, Yuta Kurimoto, Miho Kubota, Yasuo Ando

    Jpn. J. Appl. Phys. 2017年6月

  71. Grain-Size-Dependent Low-Temperature Electrical Resistivity of Polycrystalline Co2MnAl Heusler Alloy Thin Films 査読有り

    Resul Yilgin, Mikihiko Oogane, Yasuo Ando, Terunobu Miyazaki

    JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM 30 (6) 1577-1584 2017年6月

    出版者・発行元:SPRINGER

    DOI: 10.1007/s10948-016-3957-5  

    ISSN:1557-1939

    eISSN:1557-1947

    詳細を見る 詳細を閉じる

    Low-temperature electrical resistivity of Co2MnAl Heusler alloy thin films prepared by DC magnetron sputtering technique has been investigated. After deposition of Co2MnAl thin films, they were annealed at 200-400 C-ay to control the crystal structure and the atomic order between Co, Mn, and Al sites. The ratio of intensity of (200) and (220) XRD peaks increases with increasing annealing temperature. The low-temperature dependence of electrical resistivity demonstrated that the film structure and magnetic ordering effected to the resistivity of Co2MnAl. The temperature dependence of resistivity for all samples has demonstrated the exponential decrease when temperature increases. However, 1000 (au)(1 /T) dependence of the logarithmic resistivity variation has not demonstrated the linear characteristic for all samples, and also, the temperature dependency of the deposited and annealed films has not been agreed with logarithmic, , behaviors. The temperature dependence of conductivity of samples has a relation with the square root of temperature. These kinds of behaviors have been attributed to grains/clusters and disordering of samples.

  72. All-optical detection of magnetization precession in tunnel junctions under applied voltage 査読有り

    Yuta Sasaki, Kazuya Suzuki, Atsushi Sugihara, Akira Kamimaki, Satoshi Iihama, Yasuo Ando, Shigemi Mizukami

    APPLIED PHYSICS EXPRESS 10 (2) 023002 2017年2月

    出版者・発行元:IOP PUBLISHING LTD

    DOI: 10.7567/APEX.10.023002  

    ISSN:1882-0778

    eISSN:1882-0786

    詳細を見る 詳細を閉じる

    An all-optical time-resolved magneto-optical Kerr effect measurement of a micron-sized tunnel junction with a CoFeB electrode was performed. The femtosecond (fs) laser-induced magnetization precession was clearly observed at various magnetic field angles. The frequency f and relaxation time t of the magnetization precession varied with the voltage applied via a MgO barrier. The precession dynamics were in accordance with Kittel's ferromagnetic resonance mode, and the voltage- induced changes in f and t were well explained by the voltage- induced change in the perpendicular magnetic anisotropy of -36 fJ/Vm. (C) 2017 The Japan Society of Applied Physics

  73. Fabrication of orientation-controlled nanocomposite Nd2Fe14B/Mo/α–Fe multilayer films 査読有り

    K. Kobayashi, D. Ogawa, K. Koike, H. Kato, M. Oogane, T. Miyazaki, Y. Ando, M. Itakura

    Journal of Physics, Conference series 2017年

    出版者・発行元:IOP Institute of Physics

  74. Experimental Investigation of the Temperature-Dependent Magnon Density and Its Influence on Studies of Spin-Transfer-Torque-Driven Systems 査読有り

    Thomas Meyer, Thomas Braecher, Frank Heussner, Alexander A. Serga, Hiroshi Naganuma, Koki Mukaiyama, Mikihiko Oogane, Yasuo Ando, Burkard Hillebrands, Philipp Pirro

    IEEE MAGNETICS LETTERS 8 318005 2017年

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

    DOI: 10.1109/LMAG.2017.2734773  

    ISSN:1949-307X

    詳細を見る 詳細を閉じる

    We present the temperature dependence of the thermal magnon density in a thin ferromagnetic layer. By employing Brillouin light scattering and varying the temperature, an increase of the magnon density accompanied by a lowering of the spin-wave frequency is observed with increasing temperature. The magnon density follows the temperature according to the Bose-Einstein distribution function, which leads to an approximately linear dependency. In addition, the influence of this effect in spin-transfer-torque-driven systems is presented. In particular, the increase in the magnon density with temperature sets the limit for a suppression of magnons in charge current-driven systems. Hence, the maximum possible suppression of thermal magnons occurs at a finite current.

  75. Magnetic tunnel junctions using perpendicularly magnetized synthetic antiferromagnetic reference layer for wide-dynamic-range magnetic sensors 査読有り

    T. Nakano, M. Oogane, T. Furuichi, Y. Ando

    APPLIED PHYSICS LETTERS 110 (1) 012401 2017年1月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.4973462  

    ISSN:0003-6951

    eISSN:1077-3118

    詳細を見る 詳細を閉じる

    We developed CoFeB/MgO/CoFeB magnetic tunnel junctions (MTJs) with a perpendicularly magnetized synthetic antiferromagnetic (p-SAF) reference layer for magnetic sensor applications. The MTJs exhibited linear tunnel magnetoresistance curves to out-of-plane applied magnetic fields with dynamic ranges more than +/- 2.5 kOe, which are wider than those in CoFeB/MgO/CoFeB-MTJs reported to date. The performance metrics of MTJ sensors, i.e., sensitivity and nonlinearity, depend significantly on the anisotropy field of the free layer. We explained the dependences by a simple model based on the Stoner-Wohlfarth and Slonczewski models, which gives us a guideline to design the sensor performance metrics. These findings demonstrated that MTJs with a p-SAF reference layer are promising candidates for wide-dynamic-range magnetic sensors. Published by AIP Publishing.

  76. Investigation of magnetic sensor properties of magnetic tunnel junctions with superparamagnetic free layer at low frequencies for biomedical imaging applications 査読有り

    Kyohei Ishikawa, Mikihiko Oogane, Kousuke Fujiwara, Junichi Jono, Masaaki Tsuchida, Yasuo Ando

    JAPANESE JOURNAL OF APPLIED PHYSICS 55 (12) 123001 2016年12月

    出版者・発行元:IOP PUBLISHING LTD

    DOI: 10.7567/JJAP.55.123001  

    ISSN:0021-4922

    eISSN:1347-4065

    詳細を見る 詳細を閉じる

    The magnetic sensor properties of magnetic tunnel junctions (MTJs) with a superparamagnetic (SP) free layer were systematically investigated at low frequencies (&lt;10 Hz). We prepared four varieties of MTJs with various SP properties by changing the annealing temperature. The temperature dependence of magnetoresistance curves and the signal/noise property at 285K were evaluated. We found that the SP free layer has the advantage of detecting very small and low-frequency AC magnetic fields compared with a ferromagnetic free layer. The SP free layer strongly suppressed magnetic 1/f noise at low frequencies and expressed a very linear response to a small magnetic field. The obtained properties in MTJs with the SP free layer are suitable for detecting biomagnetic fields. The detectivity was 111 nT at low frequencies (from 0.1 to 10Hz), which is one of the highest values in single-MTJ sensors. (C) 2016 The Japan Society of Applied Physics

  77. ナノスケール構造制御による高性能磁石創製への指針獲得 招待有り

    加藤宏朗, 小川大介, 小池邦博, 安藤康夫, 宮崎孝道, 板倉 賢

    電気学会研究会資料〜マグネティックス研究会〜 MAG-16 (178-196) 73-76 2016年11月28日

    出版者・発行元:電気学会

  78. Influence of L1(0) order parameter on Gilbert damping constants for FePd thin films investigated by means of time-resolved magneto-optical Kerr effect 査読有り

    Satoshi Iihama, Akimasa Sakuma, Hiroshi Naganuma, Mikihiko Oogane, Shigemi Mizukami, Yasuo Ando

    PHYSICAL REVIEW B 94 (17) 174425 2016年11月

    出版者・発行元:AMER PHYSICAL SOC

    DOI: 10.1103/PhysRevB.94.174425  

    ISSN:2469-9950

    eISSN:2469-9969

    詳細を見る 詳細を閉じる

    We have systematically investigated the Gilbert damping constant a for L1(0)-FePd films using the time-resolved magneto-optical Kerr effect (TRMOKE). The field angle dependence of TRMOKE signals was measured and analyzed. The field angle dependence of the lifetime of magnetization precession was explained by evaluating extrinsic contributions such as the anisotropy distribution and two-magnon scattering. The crystalline uniaxial perpendicular magnetic anisotropy constant K-u and alpha values were evaluated for FePd films for various L1(0) order parameters S. K-u values of approximately 15 Merg/cm(3) were obtained for films with large-S values (i.e., over 0.8). In addition, alpha for the low-S film was found to be approximately 0.007 and decreased with increasing S. Smaller values of alpha (of 0.002-0.004) were obtained for films with S values of approximately 0.6-0.8. Results revealed that FePd films have both large-K-u and small-alpha values, which is a useful property for low-power magnetization switching while maintaining high thermal stability in spin-transfer-torque magnetoresistive random access memory applications.

  79. Fabrication of highly ordered Co2Fe0.4Mn0.6Si Heusler alloy films on Si substrates 査読有り

    Takeo Koike, Mikihiko Oogane, Atsuo Ono, Yasuo Ando

    JAPANESE JOURNAL OF APPLIED PHYSICS 55 (8) 088001 2016年8月

    出版者・発行元:IOP PUBLISHING LTD

    DOI: 10.7567/JJAP.55.088001  

    ISSN:0021-4922

    eISSN:1347-4065

    詳細を見る 詳細を閉じる

    The structural and magnetic properties of Si(100)/MgO/Co2Fe0.4Mn0.6Si (CFMS) Heusler alloy thin films were systematically investigated. Highly B2-ordered CFMS Heusler films with an ordering parameter of ca. 70-80% were obtained by both the insertion of a very thin Mg layer into the Si/MgO interfaces to prevent oxidation of the Si surface and the optimization of the annealing temperature for the CFMS films. The prepared CFMS films exhibited high magnetization close to that of the CFMS bulk. Such highly B2-ordered CFMS films are very useful for realizing high spin injection efficiency in Si because of the half-metallicity of the CFMS films. (C) 2016 The Japan Society of Applied Physics.

  80. Fermiology of possible topological insulator Tl0.5Bi2Te3 derived from hole-doped topological insulator 査読有り

    C. X. Trang, Z. Wang, D. Takane, K. Nakayama, S. Souma, T. Sato, T. Takahashi, A. A. Taskin, Y. Ando

    Phys. Rev. B 93 241103R 2016年7月1日

    DOI: 10.1103/PhysRevB.93.241103  

  81. Quantification of a propagating spin-wave packet created by an ultrashort laser pulse in a thin film of a magnetic metal 査読有り

    S. Iihama, Y. Sasaki, A. Sugihara, A. Kamimaki, Y. Ando, S. Mizukami

    PHYSICAL REVIEW B 94 (2) 020401 2016年7月

    出版者・発行元:AMER PHYSICAL SOC

    DOI: 10.1103/PhysRevB.94.020401  

    ISSN:2469-9950

    eISSN:2469-9969

    詳細を見る 詳細を閉じる

    Coherent spin-wave generation by focused ultrashort laser pulse irradiation was investigated for a permalloy thin film atmicrometer scale using an all-optical space-and time-resolved magneto-opticalKerr effect microscope. The spin-wave packet propagating perpendicular to the magnetization direction was clearly observed; however, that propagating parallel to the magnetization direction was not observed. The propagation length, group velocity, center frequency, and packet width of the observed spin-wave packet were evaluated and quantitatively explained in terms of the propagation of a magnetostatic spin wave driven by the ultrafast change of an out-of-plane demagnetization field induced by the focused-pulse laser.

  82. Magnetic Tunnel Junctions With [Co/Pd]-Based Reference Layer and CoFeB Sensing Layer for Magnetic Sensor 査読有り

    Takafumi Nakano, Mikihiko Oogane, Takamoto Furuichi, Kenichi Ao, Hiroshi Naganuma, Yasuo Ando

    IEEE TRANSACTIONS ON MAGNETICS 52 (7) 4001304 2016年7月

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

    DOI: 10.1109/TMAG.2016.2518188  

    ISSN:0018-9464

    eISSN:1941-0069

    詳細を見る 詳細を閉じる

    We investigated the tunneling magnetoresistance (TMR) properties for the magnetic sensor application in MgO-based magnetic tunnel junctions (MTJs) using a perpendicularly magnetized [Co/Pd]-based reference layer and an in-plane magnetized CoFeB sensing layer with various thicknesses (t(CoFeB)). Linear TMR curves to an out-of-plane magnetic field were successfully obtained with a dynamic range of more than 600 Oe, corresponding to the coercivity of the [Co/Pd]-based reference layer. The MTJs showed the highest sensitivity of 0.026%/Oe for t(CoFeB) = 1.8 nm and the smallest nonlinearity of 0.11% full scale for t(CoFeB) = 3 nm. We clarified that the sensitivity and the nonlinearity in the MTJs are significantly associated with tCoFeB, which is attributed to the change in the anisotropy field of the CoFeB sensing layer.

  83. Magnetic field-controlled hysteresis loop bias in orthogonal exchange-spring coupling composite magnetic films 査読有り

    Jun Jiang, Tian Yu, Rui Pan, Qin-Tong Zhang, Pan Liu, Hiroshi Naganuma, Mikihiko Oogane, Yasuo Ando, Xiufeng Han

    APPLIED PHYSICS EXPRESS 9 (6) 063003 2016年6月

    出版者・発行元:IOP PUBLISHING LTD

    DOI: 10.7567/APEX.9.063003  

    ISSN:1882-0778

    eISSN:1882-0786

    詳細を見る 詳細を閉じる

    The exchange bias (EB) is an effective fundamental and applicational method to realize magnetic hysteresis loop shifting. However, further manipulation of EB unidirectional anisotropy is difficult after setup using either field deposition or post-annealing. In this work, we experimentally show a new approach to control the magnetic hysteresis loop bias in a[ Co(0.2)/Pd(1)](5)/CoFeB orthogonal exchange-spring (ES) coupling system, where the direction and strength of unidirectional anisotropy can be easily manipulated by applying an external magnetic field. (C) 2016 The Japan Society of Applied Physics

  84. Effect of annealing on Curie temperature and phase transition in La0.55Sr0.08Mn0.37O3 epitaxial films grown on SrTiO3 (100) substrates by reactive radio frequency magnetron sputtering 査読有り

    T. Ichinose, H. Naganuma, T. Miyazaki, M. Oogane, Y. Ando, T. Ueno, N. Inami, K. Ono

    Materials Characterization 118 37-43 2016年5月

    DOI: 10.1016/j.matchar.2016.05.002  

  85. Structural and magnetic properties of cubic and tetragonal Heusler alloy bilayers 査読有り

    R. Ranjbar, K. Suzuki, A. Sugihara, Q. L. Ma, X. M. Zhang, Y. Ando, T. Miyazaki, S. Mizukami

    MATERIALS & DESIGN 96 490-498 2016年4月

    出版者・発行元:ELSEVIER SCI LTD

    DOI: 10.1016/j.matdes.2016.02.047  

    ISSN:0264-1275

    eISSN:1873-4197

    詳細を見る 詳細を閉じる

    Different cubic Co-based Heusler alloys - Co 2FeAl (CFA), Co 2FeSi (CFS), Co 2MnAl (CMA), and Co 2MnSi (CMS) - were grown epitaxially on tetragonal Heusler-like D0 (22)-MnGa at different annealing temperatures (T-a) in the form of Heusler (20 nm)/MnGa (30 nm) bilayers. The CMA/MnGa bilayer showed the largest critical temperature (450 degrees C), indicating good structural stability against interdiffusion. The experimental results showed an easier interdiffusion of the Fe and Si elements than of Mn and Al. An inverted hysteresis loop was observed in a polar magneto-optical Kerr effect (P-MOKE) measurement for the CFS/MnGa, CMA/MnGa, and CMS/MnGa bilayers. This is one piece of evidence for the existence of the antiferromagnetic (AFM) interfacial exchange coupling (J (ex)). We evaluated J (ex) for the Heusler/MnGa bilayers annealed at different temperatures. J (ex) changed from ferromagnetic (FM) to AFM after annealing at 300 degrees C for the CFA/MnGa bilayer. Other bilayers showed only AFM coupling. The strongest J (ex) value of approximately -3.2 erg/cm (2) was obtained for the CMS/MnGa bilayer annealed at 400 degrees C. It was found that the tendency of the Mn and Si elements to make AFM J (ex) in the Heusler/MnGa bilayers interfaces is larger than that of Fe and Al. (C) 2016 Elsevier Ltd. All rights reserved.

  86. Observation of single-spin transport in an island-shaped CoFeB double magnetic tunnel junction prepared by magnetron sputtering 査読有り

    Thamrongsin Siripongsakul, Hiroshi Naganuma, Andras Kovacs, Amit Kohn, Mikihiko Oogane, Yasuo Ando

    PHILOSOPHICAL MAGAZINE 96 (4) 310-319 2016年2月

    出版者・発行元:TAYLOR & FRANCIS LTD

    DOI: 10.1080/14786435.2015.1131343  

    ISSN:1478-6435

    eISSN:1478-6443

    詳細を見る 詳細を閉じる

    The Co40Fe40B20(CFB)/MgO/CFB/MgO/CFB-based multilayer was prepared by conventional magnetron sputtering and utilised in the fabrication of double magnetic tunnel junctions (DMTJs) for which the middle CFB layers were island-shaped. By analysing the magnetic property of the CFB islands with Langevin's equation, it was possible to identify their diameters of 7.6, 8.9 and 11.0nm; accordingly submicron-scaled DMTJs were fabricated to investigate single-spin transport phenomena. The coulomb staircase and the oscillatory tunnel magnetoresistive (TMR) were able to be observed at 6K, where the TMR ratio was enhanced up to 60%, which is the highest value ever achieved in this structure.

  87. 19pPSB-43 パーマロイ薄膜におけるレーザー励起スピン波伝播と膜厚依存性

    上牧 瑛, 飯浜 賢志, 佐々木 悠太, 安藤 康夫, 水上 成美

    日本物理学会講演概要集 71 1169-1169 2016年

    出版者・発行元:一般社団法人日本物理学会

    DOI: 10.11316/jpsgaiyo.71.1.0_1169  

    ISSN:2189-079X

  88. Controlling Magnetization Switching and DC Transport Properties of Magnetic Tunnel Junctions by Mircowave Injection 査読有り

    Cheng Xin, Yu Guo Liu, Lin Shi, Tian Yu, Hiroshi Naganuma, Mikihiko Oogane, Yasuo Ando

    7TH IEEE INTERNATIONAL NANOELECTRONICS CONFERENCE (INEC) 2016 2016年

    出版者・発行元:IEEE

    ISSN:2159-3523

    詳細を見る 詳細を閉じる

    Searching new approaches to combine spintronic devices and microwave applications is a fascinating topic. On one hand, the application of spintronic devices opens new roads to generate and detect microwave in wide frequency range, on the other hand, applying/injection microwave also modulates the spintronic devices properties. In this report, we present our recent work on effects of MW injection on the switching properties of magnetic tunneling junctions (MTJs). Magnetic tunneling junction is a promising device cell choice for spintronic applications, such as magnetic sensors, nonvolatile magnetic random access memories, and magnetic logical. As the MTJ cell size approaches to nanoscale, magnetic materials with large magnetic anisotropy are usually adopted as MTJ magnetic electrodes to keep the thermal stability. This usually inevitably increases magnetization switching field or spin transfer torque switching current density. Therefore, searching methods to assist MTJ magnetization switching becomes important for practical applications. Here, we show that directly injecting microwave current into MTJ and taking advantage of microwave current induced spin transfer torque (STT) effect can assist magnetization switching effectively. Since microwave current rather than MW magnetic field is utilized, it enables us to control the switching assistance electrically and eliminates cross-talking between neighboring cells.

  89. Ultrafast demagnetization of L1(0) FePt and FePd ordered alloys 査読有り

    Satoshi Iihama, Yuta Sasaki, Hiroshi Naganuma, Mikihiko Oogane, Shigemi Mizukami, Yasuo Ando

    JOURNAL OF PHYSICS D-APPLIED PHYSICS 49 (3) 035002 2016年1月

    出版者・発行元:IOP PUBLISHING LTD

    DOI: 10.1088/0022-3727/49/3/035002  

    ISSN:0022-3727

    eISSN:1361-6463

    詳細を見る 詳細を閉じる

    The cause of the time scale for ultrafast demagnetization induced by irradiation using a fs pulse laser remains an open issue. Spin-flip mediated by electron-phonon scattering due to spin-orbit interactions is one major theory proposed to explain ultrafast demagnetization. Ultrafast demagnetization in Ni, FePd, and FePt films was investigated in order to systematically study the influence of heavy elements on the demagnetization time. The ultrafast demagnetization in these systems was analyzed using the microscopic three temperature model, which is a theory based on spin-flip mediated by electron-phonon scattering. The spin-flip probability (a(sf)) values for the Ni, FePd, and FePt films were evaluated in the low pump fluence regime. It was found that the a(sf) value for the Ni film was larger than that for the FePd and FePt films. Thus, there is no correlation between the a(sf) value and the spin-orbit coupling strength. Fast demagnetization of the FePd film was also observed due to large electron-phonon scattering. In addition, it was found that the a(sf) values decreased with increasing magnetization quenching for all the films.

  90. Modification of the Interface Nanostructure and Magnetic Properties in Nd-Fe-B Thin Films 査読有り

    Kunihiro Koike, Takanao Kusano, Daisuke Ogawa, Keisuke Kobayashi, Hiroaki Kato, Mikihiko Oogane, Takamichi Miyazaki, Yasuo Ando, Masaru Itakura

    NANOSCALE RESEARCH LETTERS 11 33 2016年1月

    出版者・発行元:SPRINGER

    DOI: 10.1186/s11671-016-1227-x  

    ISSN:1556-276X

    詳細を見る 詳細を閉じる

    The effects of Nd2Fe14B grain size and Nd coating on the coercivity in sputter-deposited Nd-Fe-B/Nd thin films have been investigated in order to gain an insight into the coercivity mechanism of Nd-Fe-B magnets. Highly textured Nd2Fe14B particles were grown successfully on the MgO(100) single-crystal substrate with the Mo underlayer. As the Nd-Fe-B layer thickness t(NFB) was decreased from 70 to 5 nm, the coercivity H-c increased gradually from 6.5 to 16 kOe. By depositing the Nd overlayer onto these films and post-annealing at 500 degrees C, the H-c value further increased from 17.5 kOe (t(NFB) = 70 nm) to 26.2 kOe (t(NFB) = 5 nm). The amount of H-c increase by the combination of the Nd coating and post-annealing was about 10 kOe irrespective of the t(NFB) value. These results therefore suggest an independence of size and interface effects on the coercivity of Nd-Fe-B magnets.

  91. Low frequency noise in magnetic tunneling junctions with Co40Fe40B20/Co70.5Fe4.5Si15B10 composite free layer 査読有り

    Z. H. Yuan, J. F. Feng, Peng Guo, C. H. Wan, H. X. Wei, S. S. Ali, X. F. Han, T. Nakano, H. Naganuma, Y. Ando

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 398 215-219 2016年1月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/j.jmmm.2015.09.026  

    ISSN:0304-8853

    eISSN:1873-4766

    詳細を見る 詳細を閉じる

    Magnetic tunneling junctions with Co40Fe40B20/Co70.5Fe4.5Si15B10 composite free layer have been fabricated and annealed at different temperatures to obtain the highest tunneling magnetoresistance. The field and temperature dependences of the low frequency noise have been measured to understand the origin of noise. The random telegraph noise has been observed at low magnetic field, and the corresponding fluctuating moment is estimated to be 4.8 x 10(5) mu(B) with an effective area of 240 nm(2). The dependence of noise on temperature was coincident with the thermally activated kinetics model above 30 K while it deviated from this model below 30 K. Studying the origin of the low frequency noise is helpful to reduce the noise level in MTJs. (C) 2015 Elsevier B.V. All rights reserved.

  92. Antiferromagnetic coupling in perpendicularly magnetized cubic and tetragonal Heusler bilayers 査読有り

    R. Ranjbar, K. Suzuki, A. Sugihara, Q. L. Ma, X. M. Zhang, T. Miyazaki, Y. Ando, S. Mizukami

    Materials Letters 160 88-91 2015年12月

    DOI: 10.1016/j.matlet.2015.07.118  

    ISSN:0167-577X

  93. Systematic Investigation on Correlation Between Sensitivity and Nonlinearity in Magnetic Tunnel Junction for Magnetic Sensor 査読有り

    Takafumi Nakano, Mikihiko Oogane, Hiroshi Naganuma, Yasuo Ando

    IEEE TRANSACTIONS ON MAGNETICS 51 (11) 4005104 2015年11月

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

    DOI: 10.1109/TMAG.2015.2448723  

    ISSN:0018-9464

    eISSN:1941-0069

    詳細を見る 詳細を閉じる

    We fabricated magnetic tunnel junctions (MTJs) with a perpendicularly magnetized Co-Fe-B sensing layer for magnetic sensor applications exhibiting a linear tunneling magnetoresistance behavior, and systematically investigated correlation between sensitivity and nonlinearity in the MTJs. The experimental results in the MTJs annealed at different temperatures with various thicknesses and compositions of the Co-Fe-B sensing layer were compared with the simple calculation based on the Stoner-Wohlfarth model, which predicts the tradeoff relationship between the sensitivity and the nonlinearity. We found the clear tradeoff correlation between them regardless the annealing temperature and the composition of the Co-Fe-B sensing layer. These results show us a guideline for designing the sensing properties of magnetic sensors based on MTJs.

  94. Negative exchange coupling in Nd2Fe14B(100)/α-Fe interface 査読有り

    Daisuke Ogawa, Kunihiro Koike, Shigemi Mizukami, Takamichi Miyazaki, Mikihiko Oogane, Yasuo Ando, Hiroaki Kato

    Appl. Phys. Lett. 2015年9月

  95. Engineered Heusler Ferrimagnets with a Large Perpendicular Magnetic Anisotropy 査読有り

    Reza Ranjbar, Kazuya Suzuki, Atsushi Sugihara, Terunobu Miyazaki, Yasuo Ando, Shigemi Mizukami

    Materials 8 (9) 6531-6542 2015年9月

    DOI: 10.3390/ma8095320  

    ISSN:1996-1944

  96. Spintronics technology and device development 査読有り

    Yasuo Ando

    JAPANESE JOURNAL OF APPLIED PHYSICS 54 (7) 070101 2015年7月

    出版者・発行元:IOP PUBLISHING LTD

    DOI: 10.7567/JJAP.54.070101  

    ISSN:0021-4922

    eISSN:1347-4065

    詳細を見る 詳細を閉じる

    Spintronics is an emerging field of research that has made great advances in the last two decades. During this period, various new outstanding spintronics-related phenomena and devices using these phenomena have been proposed. In recent years, the period from the discovery of new spintronics-related materials and phenomena to the development and commercialization of devices using such materials and phenomena has markedly shortened. The importance of understanding the fundamental principles of spintronics has been increasing. In this review, I will first overview the features of spintronics technologies. Then, I will summarize the key technologies applied in the development of spintronic devices and describe their future prospects. (C) 2015 The Japan Society of Applied Physics

  97. Intrinsic Gilbert damping constant in epitaxial Co2Fe0.4Mn0.6Si Heusler alloys films 査読有り

    Augustin L. Kwilu, Mikihiko Oogane, Hiroshi Naganuma, Masashi Sahashi, Yasuo Ando

    JOURNAL OF APPLIED PHYSICS 117 (17) 17D140 2015年5月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.4917334  

    ISSN:0021-8979

    eISSN:1089-7550

    詳細を見る 詳細を閉じる

    The (001)-oriented and (110)-oriented epitaxial grown Co2Fe0.4Mn0.6Si films were fabricated by magnetron sputtering technique in order to investigate the annealing temperature dependence of the intrinsic Gilbert damping constant (alpha). The stuck films, deposited on MgO and Al2O3 a-plane substrates, respectively, were annealed at various temperatures ranging from 400 degrees C to 550 degrees C. The X-ray diffraction analysis was conducted to confirm that all the films were epitaxially grown. In addition, the ferromagnetic resonance measurements as well as the vibrating sample magnetometer were carried out to determine their magnetic properties. A small alpha of 0.004 was recorded for the sample with 001-oriented Co2Fe0.4Mn0.6Si (CFMS (001)) and 110-oriented CFMS (CFMS (110)) annealed at 450 degrees C. VC 2015 AIP Publishing LLC.

  98. Interfacial exchange coupling in cubic Heusler Co(2)FeZ (Z = Al and Si)/tetragonal Mn3Ga bilayers 査読有り

    R. Ranjbar, K. Suzuki, A. Sugihara, Q. L. Ma, X. M. Zhang, T. Miyazaki, Y. Ando, S. Mizukami

    JOURNAL OF APPLIED PHYSICS 117 (17) 17A332 2015年5月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.4918764  

    ISSN:0021-8979

    eISSN:1089-7550

    詳細を見る 詳細を閉じる

    We have fabricated bilayer films of tetragonal Heusler-like D0(22) Mn3Ga and cubic Heusler Co(2)FeZ (Z = Si and Al) on (100) single-crystalline MgO substrates and investigated their structural and interfacial exchange coupling. The coupling in the Mn3Ga/Co2FeAl bilayer was either ferromagnetic or antiferromagnetic, depending on annealing temperature, whereas only antiferromagnetic exchange coupling was observed in the Mn3Ga/Co2FeSi bilayers. The effects of annealing on the structure and coupling strength in the bilayers are discussed. (C) 2015 AIP Publishing LLC.

  99. Magnetic damping constant in Co-based full heusler alloy epitaxial films 査読有り

    M. Oogane, T. Kubota, H. Naganuma, Y. Ando

    JOURNAL OF PHYSICS D-APPLIED PHYSICS 48 (16) 164012-1-164012-7 2015年4月

    出版者・発行元:IOP PUBLISHING LTD

    DOI: 10.1088/0022-3727/48/16/164012  

    ISSN:0022-3727

    eISSN:1361-6463

    詳細を見る 詳細を閉じる

    Co-based full-Heusler alloys, such as Co2MnSi and Co2MnGe, are expected to be used as half-metallic ferromagnetic material, which has complete spin polarization. They are the most promising materials for realizing half-metallicity at room temperature due to their high Curie temperature. The optimization of the magnetic damping constant of ferromagnetic materials is extremely important for achieving high-speed magnetization switching and reducing critical current density for spin torque transfer switching. We have systematically investigated the magnetic damping constant in Co-based full Heusler alloy epitaxial films. We found that the Gilbert damping constant seems to be roughly proportional to the total density of states at the Fermi level (E-F) by first principle calculation. A very small magnetic damping constant of 0.003 in the Co2Fe0.4Mn0.6Si epitaxial film was demonstrated. The small magnetic damping constant in Co2FexMn1-xSi films with x &lt; 0.6 can be attributed to the half-metallicity of Heusler alloys. Co-based full Heusler alloys with both half-metallicity and small magnetic damping will be very useful for future applications based on spintronic devices.

  100. All-optical characterisation of the spintronic Heusler compound Co2Mn0.6Fe0.4Si 査読有り

    Thomas Sebastian, Yuki Kawada, Bjoern Obry, Thomas Braecher, Philipp Pirro, Dmytro A. Bozhko, Alexander A. Serga, Hiroshi Naganuma, Mikihiko Oogane, Yasuo Ando, Burkard Hillebrands

    JOURNAL OF PHYSICS D-APPLIED PHYSICS 48 (16) 164015-1-164015-7 2015年4月

    出版者・発行元:IOP PUBLISHING LTD

    DOI: 10.1088/0022-3727/48/16/164015  

    ISSN:0022-3727

    eISSN:1361-6463

    詳細を見る 詳細を閉じる

    This article is devoted to the evaluation of the material parameters of the Heusler compound Co2Mn0.6Fe0.Si-4 via Brillouin light scattering spectroscopy. Recently, cobalt-based Heusler compounds and, in particular, the compound Co2Mn0.6Fe0.4Si have attracted huge interest in the fields of spintronics and magnon spintronics. Thus, evaluation of the material parameters that govern spin dynamics in the gigahertz regime is essential to develop and understand advanced experimental scenarios as well as potential technical applications. We demonstrate the evaluation of these parameters based on wavevector as well as time-resolved Brillouin light scattering spectroscopy. The focus of our study is the determination of the spin-wave damping in an individual microstructure as wells as of the exchange constant of Co2Mn0.6Fe0.4Si-parameters, that are difficult to estimate with alternative techniques.

  101. Impact of local order and stoichiometry on the ultrafast magnetization dynamics of Heusler compounds 査読有り

    Daniel Steil, Oliver Schmitt, Roman Fetzer, Takahide Kubota, Hiroshi Naganuma, Mikihiko Oogane, Yasuo Ando, Steven Rodan, Christian G. F. Blum, Benjamin Balke, Sabine Wurmehl, Martin Aeschlimann, Mirko Cinchetti

    JOURNAL OF PHYSICS D-APPLIED PHYSICS 48 (16) 164016-1-164016-7 2015年4月

    出版者・発行元:IOP PUBLISHING LTD

    DOI: 10.1088/0022-3727/48/16/164016  

    ISSN:0022-3727

    eISSN:1361-6463

    詳細を見る 詳細を閉じる

    Nowadays, a wealth of information on ultrafast magnetization dynamics of thin ferromagnetic films exists in the literature. Information is, however, scarce on bulk single crystals, which may be especially important for the case of multi-sublattice systems. In Heusler compounds, representing prominent examples for such multi-sublattice systems, off-stoichiometry and degree of order can significantly change the magnetic properties of thin films, while bulk single crystals may be generally produced with a much more well-defined stoichiometry and a higher degree of ordering. A careful characterization of the local structure of thin films versus bulk single crystals combined with ultrafast demagnetization studies can, thus, help to understand the impact of stoichiometry and order on ultrafast spin dynamics. Here, we present a comparative study of the structural ordering and magnetization dynamics for thin films and bulk single crystals of the family of Heusler alloys with composition Co2Fe1-xMnxSi. The local ordering is studied by Co-59 nuclear magnetic resonance (NMR) spectroscopy, while the time-resolved magneto-optical Kerr effect gives access to the ultrafast magnetization dynamics. In the NMR studies we find significant differences between bulk single crystals and thin films, both regarding local ordering and stoichiometry. The ultrafast magnetization dynamics, on the other hand, turns out to be mostly unaffected by the observed structural differences, especially on the time scale of some hundreds of femtoseconds. These results confirm hole-mediated spin-flip processes as the main mechanism for ultrafast demagnetization and the robustness of this demagnetization channel against defect states in the minority band gap as well as against the energetic position of the band gap with respect to the Fermi energy. The very small differences observed in the magnetization dynamics on the picosecond time-scale, on the other hand, can be explained by considering the differences in the electronic structure at the Fermi energy and in the heat diffusion of thin films and bulk crystals.

  102. Probing the electronic and spintronic properties of buried interfaces by extremely low energy photoemission spectroscopy 査読有り

    Roman Fetzer, Benjamin Stadtmueller, Yusuke Ohdaira, Hiroshi Naganuma, Mikihiko Oogane, Yasuo Ando, Tomoyuki Taira, Tetsuya Uemura, Masafumi Yamamoto, Martin Aeschlimann, Mirko Cinchetti

    SCIENTIFIC REPORTS 5 8537-1-8537-6 2015年2月

    出版者・発行元:NATURE PUBLISHING GROUP

    DOI: 10.1038/srep08537  

    ISSN:2045-2322

    詳細を見る 詳細を閉じる

    Ultraviolet photoemission spectroscopy (UPS) is a powerful tool to study the electronic spin and symmetry features at both surfaces and interfaces to ultrathin top layers. However, the very low mean free path of the photoelectrons usually prevents a direct access to the properties of buried interfaces. The latter are of particular interest since they crucially influence the performance of spintronic devices like magnetic tunnel junctions (MTJs). Here, we introduce spin-resolved extremely low energy photoemission spectroscopy (ELEPS) to provide a powerful way for overcoming this limitation. We apply ELEPS to the interface formed between the half-metallic Heusler compound Co2MnSi and the insulator MgO, prepared as in state-of-the-art Co2MnSi/MgO-based MTJs. The high accordance between the spintronic fingerprint of the free Co2MnSi surface and the Co2MnSi/MgO interface buried below up to 4 nm MgO provides clear evidence for the high interface sensitivity of ELEPS to buried interfaces. Although the absolute values of the interface spin polarization are well below 100%, the now accessible spin-and symmetry-resolved wave functions are in line with the predicted existence of non-collinear spin moments at the Co2MnSi/MgO interface, one of the mechanisms evoked to explain the controversially discussed performance loss of Heusler-based MTJs at room temperature.

  103. 16pPSA-34 NiFe 薄膜における全光学的空間・時間分解磁気光学カー効果

    飯浜 賢志, 佐々木 悠太, 安藤 康夫, 水上 成美

    日本物理学会講演概要集 70 846-846 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_846  

    ISSN:2189-079X

  104. 生体磁場センサ応用に向けたホイスラー合金電極 強磁性トンネル接合の作製

    小野 敦央, 大兼 幹彦, 永沼 博, 安藤 康夫

    生体医工学 53 S187_01-S187_01 2015年

    出版者・発行元:一般社団法人 日本生体医工学会

    DOI: 10.11239/jsmbe.53.S187_01  

    詳細を見る 詳細を閉じる

    Magnetic tunnel junctions (MTJs) have great advantages for the magnetic field sensor applications. However, a significant improvement of tunnel magneto-resistance (TMR) ratio is needed to detect a small bio-magnetic field. In this study, we fabricated MTJs with half-metallic Co<sub>2</sub>Fe<sub>0.4</sub>Mn<sub>0.6</sub>Si(CFMS) Heusler alloy which are expected to increase TMR ratio. The fabricated MTJswere annealed twice to achieve sensor-type TMR curves. Figure shows the 2nd annealing temperature dependence of TMR curves. In MTJ annealed at 200℃, TMR curve showed a linear resistance response, which is required for sensor applications. This work was supported by the S-Innovation program, Japan Science and Technology Agency (JST).

  105. 生体磁場計測に向けた強磁性トンネル接合センサの作製とノイズ特性

    藤原 耕輔, 大兼 幹彦, 加藤 大樹, 城野 純一, 永沼 博, 桂田 弘之, 安藤 康夫

    生体医工学 53 S187_03-S187_03 2015年

    出版者・発行元:一般社団法人 日本生体医工学会

    DOI: 10.11239/jsmbe.53.S187_03  

    詳細を見る 詳細を閉じる

    MTJ is a small size device, working in room temperature with low power consumption, and is expected to enable detection of bio-magnetic field without liquid He. For the purpose of practical realization of MTJ bio-magnetic sensor, this study evaluated the signal and noise with various MgO barrier thicknesses in MTJ to reduce 1/f noise in frequency domain. Figures show MgO thickness dependence of signal voltage, noise voltage and S/N ratio measured from 18 Hz, 120 nT<sub>p-p</sub> input signal. Both signal and noise voltage increased with increasing MgO thickness. From this relation of signal and noise, maximum 154 S/N ratio was acquired by 2.2 nm MgO thickness.

  106. Optimization of Domain Wall Oscillations in Magnetic Nanowires 査読有り

    A. S. Demiray, H. Naganuma, M. Oogane, Y. Ando

    IEEE MAGNETICS LETTERS 6 3700104-1-3700104-4 2015年

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

    DOI: 10.1109/LMAG.2014.2379629  

    ISSN:1949-307X

    詳細を見る 詳細を閉じる

    By properly choosing material parameters and geometry of a magnetic nanowire, pinned domain wall oscillations at a local constriction can be obtained at low current densities. The thickness modulation of the wire gives an additional uniaxial magnetic anisotropy, which modifies the transverse anisotropy energy that defines the critical current density required for the onset of domain wall oscillations. Broadband microwave signals are obtained with these values of current density.

  107. Electrical Detection of Millimeter-Waves by Magnetic Tunnel Junctions Using Perpendicular Magnetized L1(0)-FePd Free Layer 査読有り

    Hiroshi Naganuma, G. Kirn, Yuki Kawada, Nobuhito Inami, Kenzo Hatakeyama, Satoshi Iihama, Khan Mohammed Nazrul Islam, Mikihiko Oogane, Shigemi Mizukami, Yasuo Ando

    NANO LETTERS 15 (1) 623-628 2015年1月

    出版者・発行元:AMER CHEMICAL SOC

    DOI: 10.1021/nl504114v  

    ISSN:1530-6984

    eISSN:1530-6992

    詳細を見る 詳細を閉じる

    Spin dynamics excited by spin-polarized current in magnetic tunnel junctions (MTJs) is potentially useful in nanoscale electrical oscillation sources and detection devices. A spin oscillator/detector should work at a high frequency, such as that of a millimeter-wave, where the quality of a semiconductor device is restricted by carrier mobility, the CR time constant, and so on. Developers of spin systems for practical use need to find out how to excite spin dynamics (i) in the millimeter-wave region, (ii) with low power consumption (ex: no external magnetic field, low damping material), and (iii) for broad frequency modulation. Here L1(0)-ordered FePd alloy with perpendicular magnetocrystalline anisotropy (PMA) and a low damping constant, 0.007, was used for the free layer in the MTJs, and a homodyne-detected ferromagnetic resonance (FMR) signal was obtained at around 30 GHz together with the possibility of one-octave frequency modulation. The FMR signal in out-of-plane magnetized L10-ordered FePd free layer could be excited without an external magnetic field by injecting in-plane spin polarized alternating current. This study shows the potential utility of L1(0)-ordered alloy materials such as FePt, CoPt, MnAl, and MnGa in a variety of millimeter-wave spin devices.

  108. Preparation of monoclinic 0.9(BiFeO3)-0.1(BiCoO3) epitaxial films on orthorhombic YAlO3 (100) substrates by r.f. magnetron sputtering 査読有り

    T. Ichinose, H. Naganuma, K. Mukaiyama, M. Oogane, Y. Ando

    JOURNAL OF CRYSTAL GROWTH 409 18-22 2015年1月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/j.jcrysgro.2014.09.044  

    ISSN:0022-0248

    eISSN:1873-5002

    詳細を見る 詳細を閉じる

    0.9BiFeO(3)-0.1BiCoO(3) (BFCO) films (t = 100 nm) were prepared on orthorhombic YAlO3 (YAO) (100) substrates by r.f. magnetron sputtering. Film flatness, crystallinity, crystal symmetry, and secondary phase formation are strongly affected by the pressure of the sputtering gasses. Ar and O-2. Phi-scan measurements showed that the films were epitaxially grown on the substrates, with the crystal relation [101](p)(101)(p) BFCOII[101](p)( 101)(p) YAO. X-ray reciprocal space mapping revealed that the crystal symmetry of the BECO films was a pseudo-cubic-like monoclinic structure, with M-C phase, rather than the Cm symmetry of the bulk BFCO. Cross-sectional transmission electron microscopy analysis revealed that the film had, as a result of a lattice misfit of 7%, strong compressive strain less than 10 nm from the interface, which relaxed monotonically with increasing distance from the interface. Magnetic measurements show that strained monoclinic BFCO has smaller magnetization compared to rhombohedral BFCO. (C) 2014 Elsevier B.V. All rights reserved

  109. Magnetization Dynamics and Damping for L10-FePd Thin Films with Perpendicular Magnetic Anisotropy 査読有り

    S. Iihama, M. Khan, H. Naganuma, M. Oogane, T. Miyazaki, S. Mizukami, Y. Ando

    J. Magn. Soc. Jpn. 39 (2) 57-61 2015年

    出版者・発行元:The Magnetics Society of Japan

    DOI: 10.3379/msjmag.1501R004  

    ISSN:1882-2924

    詳細を見る 詳細を閉じる

    Magnetization dynamics and damping for FePd films were investigated using the all-optical time-resolved magneto-optical Kerr effect. We deposited 16-nm-thick FePd thin films on a single crystal MgO(001) substrate. Both in-plane magnetic anisotropy and perpendicular magnetic anisotropy (PMA) FePd films were fabricated using the magnetron sputtering method at various substrate temperatures <i>T</i><sub>s</sub>. The dependencies of magnetization dynamics on the external magnetic field angle at fixed external magnetic field strengths were analyzed. The effective damping constant, <i>α</i><sub>eff</sub>, for FePd films with PMA exhibited anisotropy, whereas the <i>α</i><sub>eff</sub> for FePd with in-plane magnetic anisotropy did not depend significantly on the field angle. A uniaxial crystalline magnetic anisotropy constant, <i>K</i><sub>u1</sub>, of 11 Merg/cm<sup>3</sup> and a minimum for <i>α</i><sub>eff</sub> of 0.007 were observed for film prepared at <i>T</i><sub>s</sub> = 200°C. This <i>α</i><sub>eff</sub> value was much smaller than that for other Fe- and Co-based materials with large PMA such as <i>L</i>1<sub>0</sub>-FePt alloy, Co/Pt(Pd) multilayers.

  110. Penetration depth of transverse spin current in (001)-oriented epitaxial ferromagnetic films 査読有り

    Augustin L. Kwilu, Hiroshi Naganuma, Mikihiko Oogane, Yasuo Ando

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 368 333-337 2014年11月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/j.jmmm.2014.05.043  

    ISSN:0304-8853

    eISSN:1873-4766

    詳細を見る 詳細を閉じる

    We fabricated (001)-oriented epitaxial four-layered thin films of Cr/Co2MnSi/Cu/Co50Fe50 by dc magnetron sputtering in order to investigate the physical characteristics of the transverse spin current. The penetration depth lambda(T) characterizes the transverse spin current generated by the spin pumping effect that takes place in a film subjected to an external magnetic field. By analyzing the dependence on the Co50Fe50 thickness of the peak-to-peak line widths of ferromagnetic resonance, we determined AT within the Co50Fe50 layer and found it to be lambda(T) = 0.9 nm. (C) 2014 Elsevier B.V. All rights reserved.

  111. Non-Gilbert-damping Mechanism in a Ferromagnetic Heusler Compound Probed by Nonlinear Spin Dynamics 査読有り

    P. Pirro, T. Sebastian, T. Braecher, A. A. Serga, T. Kubota, H. Naganuma, M. Oogane, Y. Ando, B. Hillebrands

    PHYSICAL REVIEW LETTERS 113 (22) 227601-1-227601-5 2014年11月

    出版者・発行元:AMER PHYSICAL SOC

    DOI: 10.1103/PhysRevLett.113.227601  

    ISSN:0031-9007

    eISSN:1079-7114

    詳細を見る 詳細を閉じる

    The nonlinear decay of propagating spin waves in the low-Gilbert-damping Heusler film Co2Mn0.6Fe0.4Si is reported. Here, two initial magnons with frequency f(0) scatter into two secondary magnons with frequencies f(1) and f(2). The most remarkable observation is that f(1) stays fixed if f(0) is changed. This indicates, that the f(1) magnon mode has the lowest instability threshold, which, however, cannot be understood if only Gilbert damping is present. We show that the observed behavior is caused by interaction of the magnon modes f(1) and f(2) with the thermal magnon bath. This evidences a significant contribution of the intrinsic magnon-magnon scattering mechanisms to the magnetic damping in high-quality Heusler compounds.

  112. Low precessional damping observed for L1(0)-ordered FePd epitaxial thin films with large perpendicular magnetic anisotropy 査読有り

    S. Iihama, A. Sakuma, H. Naganuma, M. Oogane, T. Miyazaki, S. Mizukami, Y. Ando

    APPLIED PHYSICS LETTERS 105 (14) 142403 2014年10月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.4897547  

    ISSN:0003-6951

    eISSN:1077-3118

    詳細を見る 詳細を閉じる

    High-quality L1(0) ordered 20 nm-thick FePd epitaxial thin films with a large perpendicular magnetic anisotropy were fabricated using a SrTiO3 substrate. The uniaxial crystalline magnetic anisotropy constant Ku evaluated for the films annealed above 500 degrees C was 14 Merg/cm(3). A very low effective damping constant, alpha(eff) = 0.007, was observed for FePd thin films annealed at 500 degrees C. This value is smaller than that of other Fe-based ordered alloys with a large perpendicular magnetic anisotropy. (C) 2014 AIP Publishing LLC.

  113. Present and perspective of bio-magnetic measurement using ferromagnetic tunnel junctions 査読有り

    Y. Ando, T. Nishikawa, K. Fujiwara, M. Oogane, D. Kato, H. Naganuma

    Transactions of Japanese Society for Medical and Biological Engineering 52 33-OS-34 2014年8月17日

    出版者・発行元:Japan Soc. of Med. Electronics and Biol. Engineering

    DOI: 10.11239/jsmbe.52.OS-33  

    ISSN:1347-443X 1881-4379

    詳細を見る 詳細を閉じる

    Currently, SQUID is the most sensitive of the magnetic sensor and is used for the measurement of biological fields. However, dissemination of the device to the medical field realistically is very strict due to the big size of the device, in terms of introduction and maintenance costs. In particular, a dewar for holding a low temperature is required in order to immersion in liquid helium for operating the SQUID element. The distance of the dewar from the head surface, and also the dewar surface from the SQUID element, act as restraint for accurate measurement. This paper proposes a sensor for the biomagnetic field measurementwith magnetic tunnel junction (MTJ) devices. It can be operated at room temperature and is brought it into close contact with the head. We describe the necessary technical challenges toward its realizationand the feasibility in the future.

  114. Fabrication of integrated magnetic tunnel junctions for detection of bio-magnetic field 査読有り

    Kosuke Fujiwara, Mikihiko Oogane, Daiki Kato, Takuo Nishikawa, Hiroshi Naganuma, Yasuo Ando

    Transactions of Japanese Society for Medical and Biological Engineering 52 O-505-0-506 2014年8月17日

    出版者・発行元:Japan Soc. of Med. Electronics and Biol. Engineering

    DOI: 10.11239/jsmbe.52.O-505  

    ISSN:1347-443X 1881-4379

    詳細を見る 詳細を閉じる

    Since MTJ sensor is an element of room temperature operation, low power consumption, low cost and small device size, thus it is expectable to spread widely the medical diagnostics and basic research using bio-magnetic fields. In this study, in order to reduce 1/f noise, 100×100 MTJ sensor arrays were fabricated. Figure shows the system of imperceptible magnetic filed detection. The magnetic field was generated with the one turn coil, using the sine wave of 123 Hz. The result is shown in figure. In this study, the detection of a magnetic field of 0.29 nT was demonstrated with fabricated 100×100 MTJ sensor array.

  115. Correlations between atomic structure and giant magnetoresistance ratio in Co-2(Fe, Mn) Si spin valves 査読有り

    L. Lari, K. Yoshida, P. L. Galindo, J. Sato, J. Sizeland, D. Gilks, G. M. Uddin, Z. Nedelkoski, P. J. Hasnip, A. Hirohata, M. Oogane, Y. Ando, V. K. Lazarov

    JOURNAL OF PHYSICS D-APPLIED PHYSICS 47 (32) 322003-1-322003-5 2014年8月

    出版者・発行元:IOP PUBLISHING LTD

    DOI: 10.1088/0022-3727/47/32/322003  

    ISSN:0022-3727

    eISSN:1361-6463

    詳細を見る 詳細を閉じる

    We show that the magnetoresistance of Co2FexMn1-x Si-based spin valves, over 70% at low temperature, is directly related to the structural ordering in the electrodes and at the electrodes/spacer (Co2FexMn1-x Si/Ag) interfaces. Aberration-corrected atomic resolution Z-contrast scanning transmission electron microscopy of device structures reveals that annealing at 350 degrees C and 500 degrees C creates partial B-2/L(2)1 and fully L2(1) ordering of electrodes, respectively. Interface structural studies show that the Ag/Co2FexMn1-x Si interface is more ordered compared to the Co2FexMn1-x Si/Ag interface. The release of interface strain is mediated by misfit dislocations that localize the strain around the dislocation cores, and the effect of this strain is assessed by first principles electronic structure calculations. This study suggests that by improving the atomic ordering and strain at the interfaces, further enhancement of the magnetoresistance of CFMS-based current-perpendicular-to-plane spin valves is possible.

  116. Mode change of vortex core oscillation induced by large direct current in 120 nm sized current perpendicular-to-plane giant magnetoresistance devices with a perpendicular polarizer 査読有り

    Yuki Kawada, Hiroshi Naganuma, Ahmet Serdar Demiray, Mikihiko Oogane, Yasuo Ando

    APPLIED PHYSICS LETTERS 105 (5) 052407 2014年8月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.4892077  

    ISSN:0003-6951

    eISSN:1077-3118

    詳細を見る 詳細を閉じる

    Current-induced microwave spectra were measured in small-sized giant magnetoresistance devices composed of a NiFe vortex free layer and an out-of-plane magnetized Co/Pd multilayer polarizer. The influence of a large direct current (DC) and a bias field on the excited mode of the free layer is systematically investigated. For small current values, microwave spectra due to the vortex core oscillation were observed around 1 GHz, while the frequency abruptly changed to 4-4.5 GHz at certain DC values. The experimental data were reproduced by micromagnetic simulation, which indicates that the mode change of the vortex core oscillation in the free layer is dominated by the Oersted field from the large DC. (C) 2014 AIP Publishing LLC.

  117. Preparation of a heteroepitaxial LaxSryMnzO3/BiFeO3 bilayer by r.f. magnetron sputtering with various oxygen gas flow ratios 査読有り

    H. Naganuma, T. Ichinose, H. A. Begum, S. Sato, X. F. Han, T. Miyazaki, In-T. Bae, M. Oogane, Y. Ando

    AIP ADVANCES 4 (8) 087133 2014年8月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.4893998  

    ISSN:2158-3226

    詳細を見る 詳細を閉じる

    BiFeO3 (BFO) and La(x)Sr(y)MnzO(3) (LSMO) films were epitaxially grown on SrTiO3 (100) substrates by r.f. magnetron sputtering with various oxygen gas flow ratios (F-O2). Compositional ratios of each atom in both of BFO and LSMO could be controlled kept to around 10 at.% by changing F-O2. Adjusting the compositional ratio to La0.35Sr0.15Mn0.5O3 not only increase T-c of LSMO but also produces sufficient oxygen to form a perovskite lattice. For an LSMO/BFO heterostructure, detailed observation by cross sectional transmission electron microscopy (TEM) revealed that the lattice of rhombohedral (SG: R-3c) LSMO was shrank by a clamping effect from the SrTiO3 substrates, and then the BFO was grown in two layers: (i) an interfacial BFO layer (7 nm thick) with evenly shrunk a-axis and c-axis, and (ii) an upper BFO layer (25 nm thick) expanded along the c-axis. Neither misfit strain nor dislocations appeared at the interface between the shrunken BFO and LSMO layers, and these heterostructures did not show exchange bias. These results suggest that BFO is suitable for a tunneling barrier combine with LSMO electrode. (C) 2014 Author(s).

  118. Ultrafast magnetization dynamics in Co-based Heusler compounds with tuned chemical ordering 査読有り

    D. Steil, O. Schmitt, R. Fetzer, T. Kubota, H. Naganuma, M. Oogane, Y. Ando, A. K. Suszka, O. Idigoras, G. Wolf, B. Hillebrands, A. Berger, M. Aeschlimann, M. Cinchetti

    NEW JOURNAL OF PHYSICS 16 (6) 63068-1-63068-17 2014年6月

    出版者・発行元:IOP PUBLISHING LTD

    DOI: 10.1088/1367-2630/16/6/063068  

    ISSN:1367-2630

    詳細を見る 詳細を閉じる

    We have studied thin film samples of Co2FeSi and Co2MnSi with different degrees of chemical ordering using the time-resolved magneto-optical Kerr effect to elucidate the influence of defects in the crystal structure on magnetization dynamics. Surprisingly, we find that the presence of defects does not influence the optically induced magnetization dynamics on the ultrashort timescale (some 100 fs). However, we observe a second demagnetization stage with a timescale of tens of picoseconds in Co2MnSi for low chemical ordering; that is, a large number of defects. We interpret this second demagnetization step as originating from scattering of mostly thermalized majority electrons into unoccupied minority defect states.

  119. Magnetization dynamics for L1(0) MnGa/Fe exchange coupled bilayers 査読有り

    S. Mizukami, T. Kubota, S. Iihama, R. Ranjbar, Q. Ma, X. Zhang, Y. Ando, T. Miyazaki

    JOURNAL OF APPLIED PHYSICS 115 (17) 17C119-1-17C119-3 2014年5月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.4868087  

    ISSN:0021-8979

    eISSN:1089-7550

    詳細を見る 詳細を閉じる

    The precessional magnetization dynamics of L1(0) MnGa/Fe bilayers with a large perpendicular magnetic anisotropy are investigated using vector network analyzer ferromagnetic resonance (VNA-FMR) and time-resolved magneto-optical Kerr effect (TRMOKE). The MnGa/Fe(1 nm) bilayer exhibited perpendicular magnetization and MnGa/Fe(2 and 5 nm) bilayers showed in-plane magnetizations. The VNA-FMR and TRMOKE data for these bilayers are well explained from calculations, based on the coupled Landau-Lifshitz equations, taking into account the interfacial exchange coupling of 2.4 erg/cm(2). (C) 2014 AIP Publishing LLC.

  120. Spin-dependent transport behavior in C-60 and Alq(3) based spin valves with a magnetite electrode (invited) 招待有り 査読有り

    Xianmin Zhang, Shigemi Mizukami, Qinli Ma, Takahide Kubota, Mikihiko Oogane, Hiroshi Naganuma, Yasuo Ando, Terunobu Miyazaki

    JOURNAL OF APPLIED PHYSICS 115 (17) 172608-1-172608-6 2014年5月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.4870154  

    ISSN:0021-8979

    eISSN:1089-7550

    詳細を見る 詳細を閉じる

    The spin-dependent transport behavior in organic semiconductors (OSs) is generally observed at low temperatures, which likely results from poor spin injection efficiency at room temperature from the ferromagnetic metal electrodes to the OS layer. Possible reasons for this are the low Curie temperature and/or the small spin polarization efficiency for the ferromagnetic electrodes used in these devices. Magnetite has potential as an advanced candidate for use as the electrode in spintronic devices, because it can achieve 100% spin polarization efficiency in theory, and has a high Curie temperature (850 K). Here, we fabricated two types of organic spin valves using magnetite as a high efficiency electrode. C-60 and 8-hydroxyquinoline aluminum (Alq(3)) were employed as the OS layers. Magnetoresistance ratios of around 8% and over 6% were obtained in C-60 and Alq(3)-based spin valves at room temperature, respectively, which are two of the highest magnetoresistance ratios in organic spin valves reported thus far. The magnetoresistance effect was systemically investigated by varying the thickness of the Alq(3) layer. Moreover, the temperature dependence of the magnetoresistance ratios for C-60 and Alq(3)-based spin valves were evaluated to gain insight into the spin-dependent transport behavior. This study provides a useful method in designing organic spin devices operated at room temperature. (C) 2014 AIP Publishing LLC.

  121. Tunnel magnetoresistance effect using perpendicularly magnetized tetragonal and cubic Mn-Co-Ga Heusler alloy electrode 査読有り

    T. Kubota, S. Mizukami, Q. L. Ma, H. Naganuma, M. Oogane, Y. Ando, T. Miyazaki

    JOURNAL OF APPLIED PHYSICS 115 (17) 17C704-1-17C704-3 2014年5月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.4855016  

    ISSN:0021-8979

    eISSN:1089-7550

    詳細を見る 詳細を閉じる

    Epitaxially grown tetragonal and cubic Mn-Co-Ga thin films were fabricated onto single crystalline Cr (001) under a layer. High perpendicular magnetic anisotropy is achieved in the tetragonal Mn2.3Co0.4Ga1.3 film, and a small, unexpected perpendicular magnetic anisotropy was induced in the cubic Mn1.8Co1.2Ga1.0 film as well. The tunnel magnetoresistance (TMR) effect of the Mn-Co-Ga/MgO/CoFeB magnetic tunnel junctions (MTJs) were investigated. TMR ratios of 5% and 11% were observed at room temperature for the MTJs using tetragonal Mn2.3Co0.4Ga1.3 and cubic Mn1.8Co1.2Ga1.0 electrodes, respectively. The composition dependence is discussed briefly. (C) 2014 AIP Publishing LLC.

  122. Static and dynamic magnetic properties of cubic Mn-Co-Ga Heusler films 査読有り

    A. S. Demiray, T. Kubota, S. Iihama, S. Mizukami, T. Miyazaki, H. Naganuma, M. Oogane, Y. Ando

    JOURNAL OF APPLIED PHYSICS 115 (17) 17D133-1-17D133-3 2014年5月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.4864250  

    ISSN:0021-8979

    eISSN:1089-7550

    詳細を見る 詳細を閉じる

    We investigated the static and dynamic magnetic properties of thin films of Mn-Co-Ga Heusler compound. Gilbert damping and exchange stiffness constants of the films were evaluated by using the ferromagnetic resonance technique in the X-band regime (f = 9.4 GHz). By analyzing the experimental spectra, magnetic parameters of the films such as the line width and the Gilbert damping were deduced, and the exchange stiffness constant was estimated from the perpendicular standing spin-wave resonance. The Gilbert damping constant was estimated to be 0.017 in a specific film composition. The exchange stiffness constant showed a linear dependence on the film composition. (C) 2014 AIP Publishing LLC.

  123. Gilbert damping constants of Ta/CoFeB/MgO(Ta) thin films measured by optical detection of precessional magnetization dynamics 査読有り

    Satoshi Iihama, Shigemi Mizukami, Hiroshi Naganuma, Mikihiko Oogane, Yasuo Ando, Terunobu Miyazaki

    PHYSICAL REVIEW B 89 (17) 174416-1-174416-6 2014年5月

    出版者・発行元:AMER PHYSICAL SOC

    DOI: 10.1103/PhysRevB.89.174416  

    ISSN:1098-0121

    eISSN:1550-235X

    詳細を見る 詳細を閉じる

    The magnetization dynamics of both Ta/CoFeB/MgO and Ta/CoFeB/Ta films were investigated using an all-optical pump-probe method. The magnetic field strength and the applied field direction dependencies of the precession frequency and the relaxation time were explained well by the Landau-Lifshitz-Gilbert equation when taking the magnetic anisotropy distribution in the film into account. The thickness dependence of the a values obtained for both stacked films was also discussed. The a values increased linearly with increasing inverse CoFeB thickness (t(CoFeB)). The slope of the a vs 1/t(CoFeB) characteristic for Ta/CoFeB/MgO films was smaller than that for Ta/CoFeB/Ta films, implying that the enhancement of a was caused by the CoFeB/Ta interface. Comparison of the annealing temperature dependence of a and the perpendicular magnetic anisotropy constant Ku revealed no correlation between a and Ku.

  124. Effect of Dy/Nd double layer on coercivity in Nd-Fe-B thin films 査読有り

    K. Koike, J. Umezawa, H. Ishikawa, D. Ogawa, Y. Mizuno, H. Kato, T. Miyazaki, Y. Ando

    JOURNAL OF APPLIED PHYSICS 115 (17) 17A735 2014年5月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.4866893  

    ISSN:0021-8979

    eISSN:1089-7550

    詳細を見る 詳細を閉じる

    The Nd-Fe-B (t(NFB) = 30 nm)/[Dy (t(Dy) nm)/Nd (t(Nd) nm)] (t(Dy/Nd) = 20 nm) (thickness t(Dy) = 0-10 nm) thin films were deposited on Al2O3(0001) substrate and subsequently in-situ annealed at 470 degrees C. As-deposited Nd-Fe-B thin films with a highly perpendicular orientation of c-axis were deposited by introducing bcc-Mo(111) single crystal buffer layer. After post-annealing, the grain size of the Nd-Fe-B/Dy/Nd thin films with the t(Dy) = 10 nm and t(Nd) = 10 nm becomes large due to the Dy and the Nd atoms thermal diffusion, while DyFe2 and Dy oxide compounds are formed in Nd-Fe-B layers, which is confirmed by means of a combination of atomic force microscopy observation and X-ray diffraction measurement. The H-c of Nd-Fe-B/Dy/Nd thin films with the t(Dy) = 10 nm and t(Nd) = 10 nm was approximately the same value of the Nd-Fe-B thin films without Dy/Nd double layer annealed at 470 degrees C. On the other hand, H-c is enhanced to be about 22.1 kOe in the annealed Nd-Fe-B/Dy/Nd films with the t(Dy) 0.8 nm and t(Nd) 19.2 nm. (C) 2014 AIP Publishing LLC.

  125. Half-metal CPP GMR sensor for magnetic recording 査読有り

    Z. Diao, M. Chapline, Y. Zheng, C. Kaiser, A. Ghosh Roy, C. J. Chien, C. Shang, Y. Ding, C. Yang, D. Mauri, Q. Leng, M. Pakala, M. Oogane, Y. Ando

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 356 73-81 2014年4月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/j.jmmm.2013.12.050  

    ISSN:0304-8853

    eISSN:1873-4766

    詳細を見る 詳細を閉じる

    Current-perpendicular-to-plane (CPP) giant magnetoresistance in magnetic CoFeMnSi Heusler alloy based spin valves and its potential application for high areal density recording are investigated, given that film stack design and crystalline structure matching during film growth are considered. Modeling of electron transport in spin valves predicts the CPP GMR of up to 130% and 25% in pseudo and antiferromagnet pinned spin valves at large bulk diffusive scattering asymmetry in Heusler alloy layers. Experimentally, the testing structures of pseudo spin valves, which have the L2(1) ordered Huesler alloy layers grown on single crystal MgO substrates, were built and demonstrate the CPP GMR of 55% or larger with Delta RA &gt;= 27.5 m Omega mu m(2). CPP GMR reader sensors were fabricated based on antiferromagnet pinned spin valves using the same Huesler alloy materials albeit on AlTiC wafers, with narrow track widths of down to 35 nm. The CPP GMR obtained is up to 13% (18%, Delta RA=9.0 m Omega mu m(2) after correction of current distribution in device). Reader test results show that the low frequency track averaged output amplitude is 3.14 mV with the electrical SNR=28 dB. These read heads have the transition width of readback waveform T50 of similar to 22 am and the magnetic read track width of 35.6 nm. The obtained on-track bit error rate is close to 10(-3) decade at a linear density of 1800 KFCI, potentially realizing a magnetic recording with an areal density of up to 800 Gb/in(2). (C) 2013 Elsevier B.V. All rights reserved.

  126. Abrupt Transition from Ferromagnetic to Antiferromagnetic of Interfacial Exchange in Perpendicularly Magnetized L1(0)- MnGa/FeCo Tuned by Fermi Level Position 査読有り

    Q. L. Ma, S. Mizukami, T. Kubota, X. M. Zhang, Y. Ando, T. Miyazaki

    PHYSICAL REVIEW LETTERS 112 (15) 157202-1-157202-5 2014年4月

    出版者・発行元:AMER PHYSICAL SOC

    DOI: 10.1103/PhysRevLett.112.157202  

    ISSN:0031-9007

    eISSN:1079-7114

    詳細を見る 詳細を閉じる

    An abrupt transition of the interfacial exchange coupling from ferromagnetic to antiferromagnetic was observed in the interface of perpendicularly magnetized L1(0)-MnGa/Fe1-xCox epitaxial bilayers when x was around 25%. By considering the special band structure of the MnGa alloy, we present a model explaining this transition by the spin-polarization reversal of Fe1-xCox alloys due to the rise of the Fermi level as the Co content increases. The effect of interfacial exchange coupling on the coercive force (H-c) and the spin-dependent tunneling effect in perpendicular magnetic tunnel junctions (pMTJs) based on the coupled composite were also studied. Changes from the normal spin valve to inverted magnetoresistance loops corresponding to the coupling transition were observed in pMTJs with MnGa/Fe1-xCox as an electrode.

  127. Development of Integrated Magnetic Tunnel Junctions for Detection of Bio-magnetic Field

    Nishikawa Takuo, Oogane Mikihiko, Fujiwara Kousuke, Kato Daiki, Naganuma Hiroshi, Ando Yasuo

    生体医工学 52 O-503-O-503 2014年

    出版者・発行元:Japanese Society for Medical and Biological Engineering

    DOI: 10.11239/jsmbe.52.O-503  

    ISSN:1347-443X

    詳細を見る 詳細を閉じる

    Although the biomagnetic field is useful to observe an organic activity and the superconducting quantum interference device (SQUID) is used to detect at the moment, there is a problem of needing a liquid helium in order to operate this SQUID. This research focuses attention on the ferromagnetic tunnel junction (MTJ) device which is operable in a room temperature, and aims at the reduction of the elements for using this MTJ device as a biomagnetic field sensor and the reduction of the circuit system noise.

  128. Fabrication of Magnetic Tunnel Junctions with Amorphous CoFeSiB for the Bio-magnetic Field Sensor Devices

    Kato Daiki, Oogane Mikihiko, Fujiwara Kosuke, Nishikawa Takuo, Naganuma Hiroshi, Ando Yasuo

    生体医工学 52 O-504-O-504 2014年

    出版者・発行元:Japanese Society for Medical and Biological Engineering

    DOI: 10.11239/jsmbe.52.O-504  

    ISSN:1347-443X

    詳細を見る 詳細を閉じる

    In magnetic tunnel junctions (MTJs), the resistance changes by external magnetic field through tunnel magnetoresistance (TMR) effect and MTJs can be applied to magnetic field sensors. To detect a small bio-magnetic field, we have to develop MTJs with high sensitivity (=TMR/2<I>H</I><SUB>k</SUB>, <I>H</I><SUB>k</SUB>: magnetic anisotropy field) of more than 100%/Oe, which is two digit larger than that of actual devices. In this work, MTJs with a low <I>H</I><SUB>k</SUB> CoFeSiB amorphous electrode was fabricated to realize such a highly sensitive magnetic sensor. After optimizing the preparation condition of CoFeSiB, a very high sensitivity of 40%/Oe was obtained. The result came much closer to our goal.

  129. Spin and symmetry properties of the buried Co2MnSi/MgO interface 査読有り

    R. Fetzer, Y. Ohdaira, H. Naganuma, M. Oogane, Y. Ando, T. Taira, T. Uemura, M. Yamamoto, M. Aeschlimann, M. Cinchetti

    58th Annual Conf. on Magnetism and Magnetic Materials, Abstracts 624 (GB-14) 2013年11月

  130. Magnetic properties of L1(0)-Mn57Ga43/Co bilayer films with different Co thicknesses 査読有り

    R. Ranjbar, S. Mizukami, Y. Ando, T. Kubota, Q. L. Ma, X. M. Zhang, T. Miyazaki

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 346 53-57 2013年11月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/j.jmmm.2013.07.008  

    ISSN:0304-8853

    詳細を見る 詳細を閉じる

    In order to investigate the interlayer exchange coupling between L1(0)-MnGa and Co bilayer films, we carried out Magneto Optical Kerr Effect (MOKE) measurement and magnetization measurement by VSM for L1(0)-Mn57Ga43 (30 nm)/Co (0-20 nm) bilayer films without annealing and with annealing at 350 degrees C. The Co thickness dependence of the MOKE signal is explained simply by adding Mn-Ga and Co MOKE signals for the unannealed samples, but not for the annealed samples. We found an inverted Kerr hysteresis curve for the annealed bilayer film with 20 nm Co thickness. This result indicates the antiferromagnetic interlayer exchange coupling between the Mn-Ga and Co layers. (C) 2013 Elsevier B.V. All rights reserved.

  131. スピントロニクスを用いた集積回路と省エネ社会への貢献(<特別小特集>東北から明るい未来を創るICT技術) 査読有り

    大野 英男, 遠藤 哲郎, 羽生 貴弘, 安藤 康夫, 笠井 直記, 池田 正二

    電子情報通信学会誌 96 (10) 771-775 2013年10月1日

  132. Fabrication of Magnetic Tunnel Junctions with Amorphous CoFeSiB Ferromagnetic Electrode for Magnetic Field Sensor Devices 査読有り

    Daiki Kato, Mikihiko Oogane, Kosuke Fujiwara, Takuo Nishikawa, Hiroshi Naganuma, Yasuo Ando

    APPLIED PHYSICS EXPRESS 6 (10) 103004-1-103004-3 2013年10月

    出版者・発行元:IOP PUBLISHING LTD

    DOI: 10.7567/APEX.6.103004  

    ISSN:1882-0778

    eISSN:1882-0786

    詳細を見る 詳細を閉じる

    The magnetic tunnel junctions (MTJs) with a soft magnetic CoFeSiB amorphous electrode and a MgO barrier layer were fabricated. A double annealing process was carried out to obtain the linear resistance response to the external magnetic field. The effect of the annealing temperature on the sensitivity of magnetic sensors was systematically investigated. We achieved a high sensitivity of 40%/Oe, where the sensitivity is defined as TMR/(2H(k)), where TMR is the tunnel magnetoresistance ratio and H-k is the magnetic anisotropy field of the free layer of MTJs. (C) 2013 The Japan Society of Applied Physics

  133. Tunneling magnetoresistance effect in MnGa based perpendicular magnetic tunnel junction with Fe/Co interlayer 査読有り

    Qinli Ma, Shigemi Mizukami, Takahide Kubota, Xianmin Zhang, Atsushi Sugihara, Hiroshi Naganuma, Mikihiko Oogane, Yasuo Ando, Terunobu Miyazaki

    JOURNAL OF APPLIED PHYSICS 114 (16) 163913-1-163913-3 2013年10月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.4828483  

    ISSN:0021-8979

    eISSN:1089-7550

    詳細を見る 詳細を閉じる

    In order to enhance the magnetoresistance (MR) of perpendicular magnetic tunnel junctions (pMTJs) based on MnGa alloys, a single ferromagnetic layer such as Fe and Co was previously inserted between MnGa and MgO barrier. In this study, to further enhance the spin-filter effect, we introduced a Fe/Co bilayer as an interlayer in the MnGa/MgO interface. Compared to the single Co interlayer, an apparent MR ratio enhancement was obtained when Fe layer thickness was around 0.3 nm for pMTJs with MnGa compositions of Mn57Ga43, Mn62Ga38, and Mn70Ga30, and the maximum MR ratio reaches 50% at room temperature. In addition, inverted magnetoresistance loops were observed due to the antiparallel alignment of the magnetic moments of Co and MnGa layers separated by the thin Fe layer. (C) 2013 AIP Publishing LLC.

  134. The role of structure on magneto-transport properties of Heusler Co2MnSi films deposited on MgO(001) 査読有り

    N. Tal, D. Mogilyanski, A. Kovacs, H. Naganuma, S. Tsunegi, M. Oogane, Y. Ando, A. Kohn

    JOURNAL OF APPLIED PHYSICS 114 (16) 163904-1-163904-10 2013年10月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.4826908  

    ISSN:0021-8979

    eISSN:1089-7550

    詳細を見る 詳細を閉じる

    We present an experimental study identifying structural reasons that degrade spin-polarization of Co2MnSi thin films deposited on MgO(001) substrates. Through the fabrication of magnetic tunnel junctions, we measure a range of values for tunneling magneto-resistance (TMR) ratios following post-deposition annealing and epitaxial crystallization of the Heusler film. These TMR ratios reflect qualitatively the change in spin polarization of the Co2MnSi thin films. Low-temperature annealing results in low spin-polarization due to a high fraction of an amorphous phase. As annealing temperatures increase, the fraction of L2(1) and B2 chemically ordered phases increases, thus improving significantly the spin-polarization. However, for samples annealed at higher temperatures, significant degradation in the cubic magneto-crystalline anisotropy is observed, which we attribute to the detection of manganese diffusion into the MgO substrate. This Mn diffusion is manifested in a reduction of the value of the TMR ratio, namely, the spin polarization. Additionally, the maximum TMR ratio measured here, approximately 65% at room-temperature, is limited because the semi-coherent interface of Co2MnSi with the MgO substrate terminates with a Mn-Si layer. (C) 2013 AIP Publishing LLC.

  135. Interface state and coercivity in Nd-Fe-B/Dy films 査読有り

    Jin Umezawa, Yoshiki Sakai, Kunihiro Koike, Daisuke Ogawa, Yoshiyuki Mizuno, Hiroaki Kato, Takamichi Miyazaki, Yasuo Ando

    JOURNAL OF THE KOREAN PHYSICAL SOCIETY 63 (3) 616-619 2013年8月

    出版者・発行元:KOREAN PHYSICAL SOC

    DOI: 10.3938/jkps.63.616  

    ISSN:0374-4884

    eISSN:1976-8524

    詳細を見る 詳細を閉じる

    We fabricated a model interface system, which consised of a Nd2Fe14B layer with Dy overlayers, in order to study the relationship between the microstructure near the interface and the coercivity. The coercivity H (c) of the 1-A mu m-thick Nd-Fe-B films with a Dy overlayer was enhanced by thermal diffusion of Dy atoms from the film's surface into the Nd-Fe-B layer. The Nd-Fe-B/Dy films annealed at 700 A degrees C showed a significant increase in the H (c) of up to about 17 kOe. The maximum increase in the value of the coercivity Delta H (c) of the annealed films with a Dy overlayer was approximately 13 kOe. The XRD measurement suggested the existence of rare-earth oxides (NdO and Dy2O3) in the Dy-coated films with high value of the Delta H (c) .

  136. Evaluation of interlayer exchange coupling in alpha-Fe(100)/Nd2Fe14B(001) films 査読有り

    Daisuke Ogawa, Kunihiro Koike, Hiroaki Kato, Shigemi Mizukami, Takamichi Miyazaki, Mikihiko Oogane, Yasuo Ando

    JOURNAL OF THE KOREAN PHYSICAL SOCIETY 63 (3) 489-492 2013年8月

    出版者・発行元:KOREAN PHYSICAL SOC

    DOI: 10.3938/jkps.63.489  

    ISSN:0374-4884

    eISSN:1976-8524

    詳細を見る 詳細を閉じる

    We fabricated alpha-Fe(100)/Nd2Fe14B(001) bilayer films with different thicknesses values of the alpha-Fe layer on MgO(100) substrates by using an ultra-high-vacuum (UHV) magnetron sputtering system. The exchange coupling constant at the heterointerfaces of alpha-Fe(100)/Nd2Fe14B(001) was evaluated by analyzing the magnetization curves and the ferromagnetic resonance (FMR) spectra. We observed a significant lower shift of the alpha-Fe resonance field compared to that of the alpha-Fe single layer irrespective of the Fe-layer thickness, which suggests the existence of an internal field owing to a positive exchange coupling between the alpha-Fe(100) and the Nd2Fe14B(001) layers.

  137. Evaluation of interlayer exchange coupling in α-Fe(100)/Nd2Fe14B(001) Films 査読有り

    D. Ogawa, K. Koike, S. Mizukami, T. Miyazaki, M. Oogane, Y. Ando, H. Kato

    J. Korean Phys. Soc. 63 (2) 0-0 2013年7月

  138. Effect of Annealing Temperature on Structure and Magnetic Properties of L1(0)-FePd/CoFeB Bilayer 査読有り

    M. N. I. Khan, H. Naganuma, N. Inami, M. Oogane, Y. Ando

    IEEE TRANSACTIONS ON MAGNETICS 49 (7) 4409-4412 2013年7月

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

    DOI: 10.1109/TMAG.2013.2251612  

    ISSN:0018-9464

    eISSN:1941-0069

    詳細を見る 詳細を閉じる

    The effects of annealing temperature on the structural and magnetic properties of CoFeB/FePd bilayer were systematically investigated. A thin (0.5 nm) CoFeB layer was inserted between the FePd and MgO layers and then annealed at different temperatures. The magnetic anisotropy field increased with an increase in the annealing temperature owing to the enhancement of the interfacial perpendicular magnetic anisotropy (PMA) by crystallizing the thin CoFeB layer. The thermal annealing of the deposited layers promoted L1(0) ordering and reduced the surface roughness. It was found that a thinner FePd layer requires a higher annealing temperature in order to achieve PMA. After annealing at 350 degrees C, a PMA of 7.1 Merg/cc was obtained even for a thin FePd film with a thickness of 2.0 nm.

  139. Observation of Precessional Magnetization Dynamics in L1(0)-FePt Thin Films with Different L1(0) Order Parameter Values 査読有り

    Satoshi Iihama, Shigemi Mizukami, Nobuhito Inami, Takashi Hiratsuka, Gukcheon Kim, Hiroshi Naganuma, Mikihiko Oogane, Terunobu Miyazaki, Yasuo Ando

    JAPANESE JOURNAL OF APPLIED PHYSICS 52 (7) 073002-1-073002-4 2013年7月

    出版者・発行元:IOP PUBLISHING LTD

    DOI: 10.7567/JJAP.52.073002  

    ISSN:0021-4922

    eISSN:1347-4065

    詳細を見る 詳細を閉じる

    Fast magnetization precession was observed in L1(0)-FePt thin films with different L1(0) order parameter values by all optical pump-probe technique. Precession frequency was varied widely for the films with different order parameter, which is due to large difference in perpendicular magnetic anisotropy. Gilbert damping constant (alpha) was estimated from relaxation time as apparent damping. Clear difference in alpha was not observed with different perpendicular magnetic anisotropy. (C) 2013 The Japan Society of Applied Physics

  140. Fabrication of L1(0)-Ordered MnAl Films for Observation of Tunnel Magnetoresistance Effect 査読有り

    Haruaki Saruyama, Mikihiko Oogane, Yuta Kurimoto, Hiroshi Naganuma, Yasuo Ando

    JAPANESE JOURNAL OF APPLIED PHYSICS 52 (6) 063003-1-063003-4 2013年6月

    出版者・発行元:IOP PUBLISHING LTD

    DOI: 10.7567/JJAP.52.063003  

    ISSN:0021-4922

    eISSN:1347-4065

    詳細を見る 詳細を閉じる

    We succeeded in fabricating L1(0)-ordered MnAl films with a high perpendicular magnetic anisotropy energy of 10(7) erg/cm(3) and a small average film roughness of 0.4nm by using a molten Mn-Al sputtering alloyed target and optimizing the substrate temperature. In addition, we investigated the tunnel magnetoresistance (TMR) effect in magnetic tunnel junctions (MTJs) with the prepared L1(0)-ordered MnAl electrode. The TMR effect was observed at RT in an MTJ with a very thin Co50Fe50 layer inserted into the MnAl electrode and MgO tunneling barrier interface. This is the first observation of the TMR effect in MTJs with an L1(0)-ordered MnAl electrode. (C) 2013 The Japan Society of Applied Physics

  141. Magnetic and transport properties of tetragonal- or cubic-Heusler-type Co-substituted Mn-Ga epitaxial thin films 査読有り

    T. Kubota, S. Ouardi, S. Mizukami, G. H. Fecher, C. Felser, Y. Ando, T. Miyazaki

    JOURNAL OF APPLIED PHYSICS 113 (17) 17C723 2013年5月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.4799143  

    ISSN:0021-8979

    eISSN:1089-7550

    詳細を見る 詳細を閉じる

    The composition dependence of the structural, magnetic, and transport properties of epitaxially grown Mn-Co-Ga films were investigated. The crystal structure was observed to change from tetragonal to cubic as the Co content was increased. In terms of the dependence of saturation magnetization on the Co content, relatively small value was obtained for the Mn2.3Co0.4Ga1.3 film at a large K-u value of 9.2 Merg/cm(3). Electrical resistivity of Mn-Co-Ga films was larger than that of pure Mn-Ga film. The maximum value of the resistivity was 490 mu Omega cm for Mn2.2Co0.6Ga1.2 film. The high resistivity of Mn-Co-Ga might be due to the presence of localized electron states in the films due to chemical disordering caused by the Co substitution. (C) 2013 American Institute of Physics.

  142. Interface tailoring effect on magnetic properties and their utilization in MnGa-based perpendicular magnetic tunnel junctions 査読有り

    Q. L. Ma, T. Kubota, S. Mizukami, X. M. Zhang, H. Naganuma, M. Oogane, Y. Ando, T. Miyazaki

    PHYSICAL REVIEW B 87 (18) 184426-1-184426-18 2013年5月

    出版者・発行元:AMER PHYSICAL SOC

    DOI: 10.1103/PhysRevB.87.184426  

    ISSN:1098-0121

    詳細を見る 詳細を閉じる

    Insertion of a thin 3d ferromagnetic metal/alloy layer between the barrier layer and the perpendicularly magnetized ferromagnetic electrode is an effective method to enhance the magnetoresistance (MR) ratio in perpendicular magnetic tunnel junctions (p-MTJs). In the present paper we systematically studied the structural and magnetic properties as well as the spin-dependent transport in p-MTJs with a core structure MnGa/FM/MgO/CoFeB (FM = Fe, Co), with the MnGa being the L1(0) MnGa alloy (Mn57Ga43, Mn62Ga38) and the D0(22) MnGa alloy (Mn70Ga30). The insertion of the Fe and Co layers enhances the MR ratio significantly as well as the MnGa composition dependence of the MR ratio. In addition, opposite magnetic properties and MR(H) curves of MTJs with Fe and Co interlayers are observed, naturally suggesting the ferromagnetic and antiferromagnetic exchange coupling for MnGa/Fe(bcc) and MnGa/Co(bcc), respectively. By considering the exchange coupling between the FMand MnGa, we successfully simulated the MR(H) curves of the samples with Fe and Co interlayers based on a simple model. Furthermore, the interlayer effect on the transport properties are discussed based on the temperature dependence of the MR ratio by using the magnon excitation model modified with impurity-induced hopping. It shows that the FM interlayer restrains the impurity induced hopping and the magnon excitation; and furthermore, the Co is more effective in restraining the impurity diffusion and magnon excitation as compared to Fe.

  143. Detection of sub-nano-tesla magnetic field by integrated magnetic tunnel junctions with bottom synthetic antiferro-coupled free layer 査読有り

    Kosuke Fujiwara, Mikihiko Oogane, Takuo Nishikawa, Hiroshi Naganuma, Yasuo Ando

    Japanese Journal of Applied Physics 52 (4) 04CM07-1-04CM07-4 2013年4月

    DOI: 10.7567/JJAP.52.04CM07  

    ISSN:0021-4922 1347-4065

    詳細を見る 詳細を閉じる

    Arrays of 100 × 100 magnetic tunnel junctions (MTJs) connected in parallel and series were fabricated. A synthetic antiferro-coupled bottom free layer with a NiFe/Ru/CoFeB structure and MgO tunneling barrier were used to realize a high sensitivity, which is defined as TMR/2Hk, where, TMR is the tunneling magnetoresistance ratio and Hkis the magnetic anisotropy field of the free layer. To obtain a linear response of tunneling resistance against an applied external magnetic field, a double annealing process was carried out. From R-H curve measurements, the sensitivity of the 100 × 100 integrated MTJs was lower (8%/Oe) than that of a single MTJ (25%/Oe). However, a 1/30 decrease in noise power density was realized in the integrated MTJs. Consequently, a very small magnetic field of 0.29 nT was detected with the integrated MTJs. © 2013 The Japan Society of Applied Physics.

  144. Magnetic tunnel junctions of perpendicularly magnetized L1(0)-MnGa/Fe/MgO/CoFe structures: Fe-layer-thickness dependences of magnetoresistance effect and tunnelling conductance spectra 査読有り

    T. Kubota, Q. L. Ma, S. Mizukami, X. M. Zhang, H. Naganuma, M. Oogane, Y. Ando, T. Miyazaki

    JOURNAL OF PHYSICS D-APPLIED PHYSICS 46 (15) 155001 2013年4月

    出版者・発行元:IOP PUBLISHING LTD

    DOI: 10.1088/0022-3727/46/15/155001  

    ISSN:0022-3727

    eISSN:1361-6463

    詳細を見る 詳細を閉じる

    The tunnel magnetoresistance (TMR) effect and the bias voltage dependence of tunnelling conductance spectra were measured in L1(0) Mn-Ga/Fe/MgO/CoFe magnetic tunnel junctions (MTJs). The TMR ratio and bias-voltage dependences on annealing conditions and Fe-layer thickness were investigated. The TMR ratio showed an increase subsequent to Fe-layer deposition under the optimum annealing condition, and a maximum value of 24% was achieved in an MTJ with a perpendicularly magnetized Fe layer of thickness of 1.1 nm at room temperature; this corresponded to a 57% TMR ratio in the case of completely antiparallel magnetization configuration. In the tunnelling conductance spectra, an anomalous dip, the so-called zero-bias anomaly, was observed for all the samples. The zero-bias anomaly is speculated to have appeared because of an increase in magnon excitation at the magnetic layer/barrier interfaces according to the model by Zhang et al (1997 Phys. Rev. Lett. 79 3744). In our experiments magnitude of the zero-bias anomaly depended on both the annealing condition and the Fe-layer thickness. We discuss our observation of the variation in the Curie temperature of the magnetic layer at the barrier layer interface depending on the the preparation conditions of the Fe insertion layer, which caused the change in the magnitude of the zero-bias anomaly.

  145. Structural and magnetic properties of L10-FePd/MgO films on GaAs and InP lattice mismatched substrates 査読有り

    M. Kohda, S. Iimori, R. Ohsugi, H. Naganuma, T. Miyazaki, Y. Ando, J. Nitta

    Applied Physics Letters 102 (10) 102411 2013年3月11日

    DOI: 10.1063/1.4795443  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    Structural and magnetic properties of epitaxial L10-FePd/MgO films on GaAs and InP lattice mismatched substrates are investigated at different MgO and FePd growth temperatures. While c-axis lattice constants of MgO and FePd show similar values on both substrates, the remanent magnetization becomes larger on GaAs than that on InP. Since the ratio of FePd (002) tetragonal ordered phase and FePd (200) cubic disordered phase follows similar growth temperature dependence to the remanent magnetization and the long range chemical order parameter, the perpendicular magnetic anisotropy grown on the lattice-mismatched semiconductors is strongly affected by formation of the disordered phase. © 2013 American Institute of Physics.

  146. Nonlinear Emission of Spin-Wave Caustics from an Edge Mode of a Microstructured Co2Mn0.6Fe0.4Si Waveguide 査読有り

    T. Sebastian, T. Braecher, P. Pirro, A. A. Serga, B. Hillebrands, T. Kubota, H. Naganuma, M. Oogane, Y. Ando

    PHYSICAL REVIEW LETTERS 110 (6) 067201-1-067201-5 2013年2月

    出版者・発行元:AMER PHYSICAL SOC

    DOI: 10.1103/PhysRevLett.110.067201  

    ISSN:0031-9007

    詳細を見る 詳細を閉じる

    Magnetic Heusler materials with very low Gilbert damping are expected to show novel magnonic transport phenomena. We report nonlinear generation of higher harmonics leading to the emission of caustic spin-wave beams in a low-damping microstructured Co2Mn0.6Fe0.4Si Heusler waveguide. The source for the higher harmonic generation is a localized edge mode formed by the strongly inhomogeneous field distribution at the edges of the spin-wave waveguide. The radiation characteristics of the propagating caustic waves observed at twice and three times the excitation frequency are described by an analytical calculation based on the anisotropic dispersion of spin waves in a magnetic thin film. DOI: 10.1103/PhysRevLett.110.067201

  147. Tunnel magnetoresistance effect in tunnel junctions with Co2MnSi heusler alloy electrode and MgO barrier 査読有り

    Yasuo Ando, Sumito Tsunegi, Mikihiko Oogane, Hiroshi Naganuma, Koki Takanashi

    Spintronics: From Materials to Devices 355-366 2013年1月1日

    出版者・発行元:Springer Netherlands

    DOI: 10.1007/978-90-481-3832-6_17  

    詳細を見る 詳細を閉じる

    We demonstrated that a large TMR ratio of 753 % has been observed at 2 K in a MTJ using a Co2MnSi Heusler alloy electrode and a crystalline MgO tunnel barrier. At room temperature (RT), we also have observed a large TMR ratio of 217 %, which value at RT is much larger than that of MTJs using an amorphous Al-oxide tunnel barrier. However, the temperature dependence of the TMR ratio was still large. In order to improve the interface, we investigated the TMR effect in Co2MnSi/CoFeB(0-2 nm)/MgO/CoFe MTJs. TMR ratio was enhanced by inserting a thin CoFeB layer at the Co2MnSi/MgO interface. The MTJ with CoFeB thickness of 0.5 nm exhibited the highest TMR ratio. From the conductance-voltage measurements for the fabricated MTJs, we inferred that the highly spin polarized electron created in Co2MnSi can conserve the polarization through the 0.5 nm thick FeB layer.

  148. Magnetoresistance enhancement in MnxGa 100 - X/MgO/CoFeB perpendicular magnetic tunnel junctions by using CoFeB interlayer 査読有り

    Q. L. Ma, T. Kubota, S. Mizukami, X. M. Zhang, M. Oogane, H. Naganuma, Y. Ando, T. Miyazaki

    IEEE Transactions on Magnetics 49 (7) 4339-4342 2013年

    DOI: 10.1109/TMAG.2013.2242861  

    ISSN:0018-9464

    詳細を見る 詳細を閉じる

    The magnetoresistance effects of the perpendicular magnetic tunnel junctions (p-MTJs) based on Mn-Ga ordered alloys are reported. By tuning the Mn-Ga composition, the MTJs based on L10 and D022 structured Mn-Ga alloys were achieved in the MTJ stack structure of Cr(40)/MnxGa100 - x(30)/Mg(0.4)/MgO(2.2)/CoFeB(1.2)/Ta(5)/ Ru(7) (nm). The values of magnetoresistance (MR) ratio at room temperature for different Mn-Ga composition are around 5%. In order to enhance the MR ratio, a thin CoFeB layer was introduced between the Mn-Ga and the MgO barrier. The MR effect shows a strong Mn-Ga composition dependent as CoFeB interlayer thickness increases. An MR ratio of 50% was obtained at room temperature when the CoFeB thickness is 1.5 nm for Mn62 Ga38 based MTJs. © 2013 IEEE.

  149. Observation of a large spin-dependent transport length in organic Spin valves at room temperature 査読有り

    Xianmin Zhang, Shigemi Mizukami, Takahide Kubota, Qinli Ma, Mikihiko Oogane, Hiroshi Naganuma, Yasuo Ando, Terunobu Miyazaki

    Nature Communications 4 1392 2013年

    DOI: 10.1038/ncomms2423  

    ISSN:2041-1723

    詳細を見る 詳細を閉じる

    The integration of organic semiconductors and magnetism has been a fascinating topic for fundamental scientific research and future applications in electronics, because organic semiconductors are expected to possess a large spin-dependent transport length based on weak spin-orbit coupling and weak hyperfine interaction. However, to date, this length has typically been limited to several nanometres at room temperature, and a large length has only been observed at low temperatures. Here we report on a novel organic spin valve device using C 60 as the spacer layer. A magnetoresistance ratio of over 5% was observed at room temperature, which is one of the highest magnetoresistance ratios ever reported. Most importantly, a large spin-dependent transport length of approximately 110 nm was experimentally observed for the C 60 layer at room temperature. These results provide insights for further understanding spin transport in organic semiconductors and may strongly advance the development of spin-based organic devices. © 2013 Macmillan Publishers Limited. All rights reserved.

  150. Magnetic Properties of Single Crystalline Co2MnAl Heusler Alloy Thin Films 査読有り

    Yilgin Resul, Sakuraba Yuya, Oogane Mikihiko, Ando Yasuo, Miyazaki Terunobu

    JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM 25 (8) 2659-2663 2012年12月

    DOI: 10.1007/s10948-011-1238-x  

    ISSN:1557-1939

  151. Magnetic Properties andMagnetic Domain Structures Evolution Modulated by CoFeB Layer in [Pd/Co]/CoFeB/MgO/CoFeB/[Co/Pd] Perpendicular MTJ Films 査読有り

    Tian Yu, Hiroshi Naganuma, D. W. Shi, Yasuo Ando, X. F. Han

    IEEE Transactions on Magnetics 48 2812-2815 2012年10月19日

    DOI: 10.1109/TMAG.2012.2198795  

  152. EVALUATION OF EXCHANGE COUPLING IN Nd2Fe14B/α-Fe INTERFACES

    D. Ogawa, K. Koike, S. Mizukami, T. Miyazaki, M. Oogane, Y. Ando, H. Kato

    Proceedings on 21st Workshop on Rare-Earth Permanent Magnets and their Applications (REPM'12) 2012年9月2日

  153. COERCIVITY ENHANCEMENT PHENOMENA OBSERVED IN VARIOUS SERIES OF Nd2Fe14B/Nd FILMS

    K. Koike, T. Kusano, D. Ogawa, Y. Mizuno, T. Miyazaki, Y. Ando, H. Kato

    Proceedings on 21st Workshop on Rare-Earth Permanent Magnets and their Applications (REPM'12) 2012年9月2日

  154. Effect of Mg interlayer on perpendicular magnetic anisotropy of CoFeB films in MgO/Mg/CoFeB/Ta structure 査読有り

    Q. L. Ma, S. Iihama, T. Kubota, X. M. Zhang, S. Mizukami, Y. Ando, T. Miyazaki

    APPLIED PHYSICS LETTERS 101 (12) 122414 2012年9月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.4754118  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    The effects of Mg metallic interlayer on the magnetic properties of thin CoFeB films in MgO/Mg (t(Mg))/CoFeB (1.2nm)/Ta structures were studied in this letter. Our experimental result shows that the CoFeB film exhibits perpendicular magnetic anisotropy (PMA) when the CoFeB and MgO layers are separated by a metallic Mg layer with a maximum thickness of 0.8 nm. The origin of PMA was discussed by considering the preferential transmission of the Delta(1) symmetry preserved by the Mg interlayer in crystallized MgO/Mg/CoFeB/Ta. In addition, the thin Mg interlayer also contributes to enhancing the thermal stability and reducing the effective damping constant and coercivity of the CoFeB film. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4754118]

  155. Enhancement of magnetoresistance using CoFe/Ru/CoFe synthetic ferrimagnetic pinned layer in BiFeO3 based spin-valves 査読有り

    Hiroshi Naganuma, In-Tae Bae, Takamichi Miyazaki, Miho Kubota, Nobuhito Inami, Yuki Kawada, Mikihiko Oogane, Shigemi Mizukami, X. F. Han, Yasuo Ando

    APPLIED PHYSICS LETTERS 101 (7) 072901-1-072901-3 2012年8月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.4745504  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    SrTiO3 (100) sub/BiFeO3/CoFe/Ru/CoFe/Cu/CoFe/Ta structure was prepared by a combination of chemical solution deposition and sputtering method, and followed by a systematical investigation for the structural, magnetic and magnetoresistance properties at room temperature (RT) as a function of CoFe and Ru thicknesses. It was revealed that introduction of synthetic CoFe/Ru/CoFe as a pinning layer increased the giant magentoresistance (MR) ratio to 8.3% at RT. This enhancement of MR ratio might be attributed to (i) the increase of pinning field, and (ii) suppression of the influence of the surface roughness of BiFeO3 by inserting the synthetic CoFe/Ru/CoFe layer. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4745504]

  156. Damping of Magnetization Precession in Perpendicularly Magnetized CoFeB Alloy Thin Films 査読有り

    Satoshi Iihama, Qinli Ma, Takahide Kubota, Shigemi Mizukami, Yasuo Ando, Terunobu Miyazaki

    APPLIED PHYSICS EXPRESS 5 (8) 083001 2012年8月

    出版者・発行元:JAPAN SOC APPLIED PHYSICS

    DOI: 10.1143/APEX.5.083001  

    ISSN:1882-0778

    詳細を見る 詳細を閉じる

    Gilbert damping is investigated in perpendicularly magnetized CoFeB thin films using ferromagnetic resonance and time-resolved magneto-optical Kerr effect. The CoFeB films were deposited on a MgO layer and annealed at different temperatures. The lowest effective damping constant alpha(eff) values were 0.017, 0.013, and 0.009 for the films annealed at 250, 300, and 350 degrees C, respectively; these values were smaller than the values reported previously. (C) 2012 The Japan Society of Applied Physics

  157. Magnetoresistance effect in L1(0)-MnGa/MgO/CoFeB perpendicular magnetic tunnel junctions with Co interlayer 査読有り

    Q. L. Ma, T. Kubota, S. Mizukami, X. M. Zhang, H. Naganuma, M. Oogane, Y. Ando, T. Miyazaki

    APPLIED PHYSICS LETTERS 101 (3) 032402-1-032402-3 2012年7月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.4737000  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    The fully perpendicular magnetic tunnel junctions (p-MTJs) based on L1(0)-MnGa and thin CoFeB electrodes with MgO barrier were reported in this letter. A thin Co layer was introduced between the MnGa layer and the MgO barrier layer to investigate interfacial effect on the device's magnetic and transport properties. The magnetoresistance ratio improved significantly due to the Co insertion, and reached 40% at room temperature (80% at 5 K) when the Co thickness was 1.5 nm. Moreover, the junctions with Co interlayer exhibited four low-resistance states in one full cycle rather than two in normal MTJs. The physical origin was discussed by considering the coupling between MnGa and Co layers. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4737000]

  158. Nd2Fe14B/α-Fe界面における交換結合の評価

    小川大介, 小池邦博, 水上成美, 大兼幹彦, 安藤康夫, 宮崎孝道, 加藤宏朗

    信学技報 2012年6月14日

  159. Observation of magnetic moments at the interface region in magnetic tunnel junctions using depth-resolved x-ray magnetic circular dichroism 査読有り

    S. Tsunegi, Y. Sakuraba, K. Amemiya, M. Sakamaki, E. Ozawa, A. Sakuma, K. Takanashi, Y. Ando

    Phys. Rev. B 85 180408-1-180408-4 2012年5月

    DOI: 10.1103/PhysRevB.85.180408  

  160. Annealing Temperature and Co Layer Thickness Dependence of Magnetoresistance Effect for -MnGa/Co/MgO/CoFeB Perpendicular Magnetic Tunnel Junctions 査読有り

    Q. L. Ma, Takahide Kubota, Shigemi Mizukami, X. M. Zhang, Mikihiko Oogane, Hiroshi Naganuma, Yasuo Ando, Terunobu Miyazaki

    IEEE Transactions on Magnetics 48 2808-2811 2012年4月16日

    DOI: 10.1109/TMAG.2012.2196420  

  161. Electrical manipulation of spin polarization and generation of giant spin current using multi terminal spin injectors 査読有り

    S. Nonoguchi, T. Nomura, Y. Ando, T. Kimura

    JOURNAL OF APPLIED PHYSICS 111 (7) 2012年4月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.3672245  

    ISSN:0021-8979

    eISSN:1089-7550

    詳細を見る 詳細を閉じる

    Two advantages of the lateral spin valve using multi-terminal spin injections have been demonstrated. First, the effective spin polarization for the pure spin current can be controlled by the two anti-parallely aligned spin injectors. We show that the magnitude and the sign of the spin polarization are electrically manipulated by adjusting the current ratio between two injectors. Secondly, we show that the giant pure spin current can be generated by the nonlolcal spin injections from the quadruple spin injectors. (C) 2012 American Institute of Physics. [doi:10.1063/1.3672245]

  162. Fabrication of L1(0)-MnAl perpendicularly magnetized thin films for perpendicular magnetic tunnel junctions 査読有り

    Masaki Hosoda, Mikihiko Oogane, Miho Kubota, Takahide Kubota, Haruaki Saruyama, Satoshi Iihama, Hiroshi Naganuma, Yasuo Ando

    JOURNAL OF APPLIED PHYSICS 111 (7) 07A324-1-07A324-3 2012年4月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.3676428  

    ISSN:0021-8979

    eISSN:1089-7550

    詳細を見る 詳細を閉じる

    Structural and magnetic properties of MnAl thin films with different composition, growth temperature, and post-annealing temperature were investigated. The optimum condition for fabrication of L1(0)-MnAl perpendicularly magnetized thin film deposited on Cr-buffered MgO single crystal substrate was revealed. The results of x ray diffraction indicated that the MnAl films annealed at proper temperature had a (001)-orientation and L1(0)-ordered structure. The L1(0)-ordered films were perpendicularly magnetized and had a large perpendicular anisotropy. In addition, low surface roughness was achieved. For the optimized fabrication condition, the saturation magnetization M-s of 600 emu/cm(3) and perpendicular magnetic anisotropy K-u of 1.0 x 10(7) erg/cm(3) was obtained using the Mn48Al52 target at deposition temperature of 200 degrees C and post-annealing temperature of 450 degrees C. (C) 2012 American Institute of Physics. [doi:10.1063/1.3676428]

  163. Promotion of L1(0) ordering of FePd films with amorphous CoFeB thin interlayer 査読有り

    M. N. I. Khan, N. Inami, H. Naganuma, Y. Ohdaira, M. Oogane, Y. Ando

    JOURNAL OF APPLIED PHYSICS 111 (7) 07C112-1-07C112-3 2012年4月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.3673409  

    ISSN:0021-8979

    eISSN:1089-7550

    詳細を見る 詳細を閉じる

    The L1(0)-ordered FePd thin films were prepared using an ultrahigh vacuum magnetron sputtering system on MgO(001) substrates at 300 degrees C. The crystallographic and magnetic properties and the surface morphology of films with and without a very thin amorphous CoFeB intermediate layer inserted between the FePd and the MgO layers were systematically investigated as a function of the thickness of the FePd layer. The perpendicular anisotropy of the samples was increased by inserting the thin CoFeB as an intermediate layer below the FePd with a thickness of 4.0 nm. The reason for the enhancement by inserting the amorphous CoFeB layer is attributed to: (i) the promotion of the L1(0) ordering of the FePd due to the reduction of the lattice mismatch between the MgO and FePd, and (ii) the fact that thin CoFeB has a perpendicular anisotropy at the interface of the MgO, which superposed the perpendicular anisotropy of the L1(0)-FePd. (C) 2012 American Institute of Physics. [doi:10.1063/1.3673409]

  164. Dependence of Tunnel Magnetoresistance Effect on Fe Thickness of Perpendicularly Magnetized L1(0)-Mn62Ga38/Fe/MgO/CoFe Junctions 査読有り

    Takahide Kubota, Qinli Ma, Shigemi Mizukami, Xianmin Zhang, Hiroshi Naganuma, Mikihiko Oogane, Yasuo Ando, Terunobu Miyazaki

    APPLIED PHYSICS EXPRESS 5 (4) 043003-1-043003-3 2012年4月

    出版者・発行元:IOP PUBLISHING LTD

    DOI: 10.1143/APEX.5.043003  

    ISSN:1882-0778

    eISSN:1882-0786

    詳細を見る 詳細を閉じる

    The tunnel magnetoresistance (TMR) ratio in a magnetic tunnel junction (MTJ) with an L1(0)-Mn62Ga38/Fe/MgO/CoFe structure was considerably improved by Fe layer insertion. A maximum TMR ratio of 24% was observed in an MTJ with a Fe thickness of 1.1nm at room temperature, which corresponded to a 57% TMR ratio in the case of a complete antiparallel magnetization configuration. Fe layer thickness dependences of the magnetization curve and TMR effect were also investigated. It was revealed that the magnetization of Fe on 30-nm-thick MnGa could be fixed in a perpendicular direction when the thickness of the Fe was below 2.0 nm. (C) 2012 The Japan Society of Applied Physics

  165. Fabrication of magnetic tunnel junctions with a bottom synthetic antiferro-coupled free layers for high sensitive magnetic field sensor devices 査読有り

    Kosuke Fujiwara, Mikihiko Oogane, Saeko Yokota, Takuo Nishikawa, Hiroshi Naganuma, Yasuo Ando

    JOURNAL OF APPLIED PHYSICS 111 (7) 07C710-1-07C710-3 2012年4月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.3677266  

    ISSN:0021-8979

    eISSN:1089-7550

    詳細を見る 詳細を閉じる

    Magnetic tunnel junctions with a Ni80Fe20/Ru/Co40Fe40B20 synthetic antiferro-coupled bottom free layer and an MgO barrier layer have been fabricated. Double annealing process was carried out in order to obtain linearity against magnetic field with hysteresis-free resistance response. The effect of the annealing temperature and NiFe thickness in the free layer on the magnetic field sensor performance was investigated. We have observed a very high sensitivity of 25.3%/Oe while keeping linearity. (C) 2012 American Institute of Physics. [doi: 10.1063/1.3677266]

  166. Dependence of spin-transfer switching characteristics in magnetic tunnel junctions with synthetic free layers on coupling strength 査読有り

    Masayuki Nishimura, Mikihiko Oogane, Hiroshi Naganuma, Nobuhito Inami, Tadashi Morita, Yasuo Ando

    JOURNAL OF APPLIED PHYSICS 111 (7) 07C905-1-07C905-3 2012年4月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.3672240  

    ISSN:0021-8979

    eISSN:1089-7550

    詳細を見る 詳細を閉じる

    Dependence of spin-transfer switching characteristics on the interlayer exchange coupling strength in the MTJs with synthetic free layers of Co90Fe10/Ru/Co40Fe40B20 with strong coupling strength was investigated. In the MTJ with the relatively weakly coupled synthetic ferrimagnetic free layer, larger thermal stability (Delta(0)) and lower intrinsic critical current density (J(c0)) than those of the MTJ with the single free layer were observed. Meanwhile, in the MTJs with the strongly coupled synthetic ferri- or ferromagnetic free layers, very large Delta(0) and high J(c0) were observed probably due to high effective magnetic energy barrier. It was found that the MTJ with the relatively weakly coupled synthetic ferrimagnetic free layer is suitable for the STTRAM application. (C) 2012 American Institute of Physics. [doi:10.1063/1.3672240]

  167. Large change of perpendicular magnetic anisotropy in Cobalt ultrathin film induced by varying capping layers 査読有り

    Xianmin Zhang, Shigemi Mizukami, Takahide Kubota, Qinli Ma, Hiroshi Naganuma, Mikihiko Oogane, Yasuo Ando, Terunobu Miyazaki

    JOURNAL OF APPLIED PHYSICS 111 (7) 07B320-1-07B320-3 2012年4月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.3676240  

    ISSN:0021-8979

    eISSN:1089-7550

    詳細を見る 詳細を閉じる

    The magnetic films of Co with Si/SiO2/Pt/Co/molecule structure were fabricated and their structural properties and magnetic anisotropy were investigated by varying both Co (0.5-1.8 nm) thickness and molecular capping layers of 5,6,11,12-tetraphenylnaphthacene (rubrene) and copper phthalocyanine (CuPc), respectively. The crystal structures were characterized using x-ray diffraction (XRD) and the magnetization curves were measured using vibrating sample magnetometer with an applied field both in parallel and perpendicular to a film plane. It was found that the thickness of Co for the maximum perpendicular magnetic anisotropy (PMA) is around 0.7 nm for both group films. However, the estimated effective magnetic anisotropy energy for Co was 2.9 +/- 0.3 x 10(6) erg/cc for rubrene-capped sample, which was smaller than the value of 4.9 +/- 0.4 x 10(6) erg/cc for CuPc-capped sample. The XRD patterns showed the crystal structure of rubrene layer was of amorphous structure and CuPc layer was polycrystalline. The different interface effects of Co/CuPc and Co/rubrene were discussed to analyze the change of PMA. (C) 2012 American Institute of Physics. [doi:10.1063/1.3676240]

  168. Annealing temperature dependence of exchange bias in BiFeO3/CoFe bilayers 査読有り

    T. Yu, H. Naganuma, W. X. Wang, Y. Ando, X. F. Han

    JOURNAL OF APPLIED PHYSICS 111 (7) 07D908-1-07D908-3 2012年4月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.3673435  

    ISSN:0021-8979

    eISSN:1089-7550

    詳細を見る 詳細を閉じる

    BiFeO3/CoFe bilayers with different BiFeO3 (BFO) crystalities were fabricated by chemical solution deposition and sputtering method. Exchange bias has been successfully induced in these bilayers by post-annealing. The annealing temperature dependence of exchange bias as well as coercivity was investigated. Two kinds of annealing temperature dependence behaviors were observed. It is found that, similar to the conventional antiferromagnet/ferromagnet system, the temperature dependence of exchange bias is dominated by direct interface coupling, and the crystality of BFO has no profound effect on exchange bias. (C) 2012 American Institute of Physics. [doi:10.1063/1.3673435]

  169. Low-damping spin-wave propagation in a micro-structured Co2Mn0.6Fe0.4Si Heusler waveguide 査読有り

    T. Sebastian, Y. Ohdaira, T. Kubota, P. Pirro, T. Braecher, K. Vogt, A. A. Serga, H. Naganuma, M. Oogane, Y. Ando, B. Hillebrands

    APPLIED PHYSICS LETTERS 100 (11) 112402-1-112402-3 2012年3月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.3693391  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    We report on the investigation of spin-wave propagation in a micro-structured Co2Mn0.6Fe0.4Si (CMFS) Heusler waveguide. The reduced magnetic losses of this compound compared to the commonly used Ni81Fe19, allow for the observation of spin-wave propagation over distances as high as 75 mu m via Brillouin light scattering (BLS) microscopy. In the linear regime, a maximum decay length of 16.7 mu m of the spin-wave amplitude was found. The coherence length of the observed spin-wave modes was estimated to be at least 16 mu m via phase-resolved BLS techniques. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3693391]

  170. Evaluation of Exchange Coupling in α-Fe(100)/Nd2Fe14B(001) Interface 査読有り

    D. Ogawa, K. Koike, N. Mizukami, K. Oogane, Y. Ando, T. Miyazaki, H. Kato

    Journal of magnetics society of Japan 36 (1) 5-12 2012年1月

  171. Composition dependence of magnetic properties in perpendicularly magnetized epitaxial thin films of Mn-Ga alloys 査読有り

    S. Mizukami, T. Kubota, F. Wu, X. Zhang, T. Miyazaki, H. Naganuma, M. Oogane, A. Sakuma, Y. Ando

    PHYSICAL REVIEW B 85 (1) 014416-1-014416-6 2012年1月

    出版者・発行元:AMER PHYSICAL SOC

    DOI: 10.1103/PhysRevB.85.014416  

    ISSN:1098-0121

    詳細を見る 詳細を閉じる

    Mn-Ga binary alloys show strong magnetism and large uniaxial magnetic anisotropy even though these alloys do not contain any noble, rare-earth metals or magnetic elements. We investigate the composition dependence of saturation magnetization M(S) and uniaxial magnetic anisotropy K(u) in epitaxial films of M(n-x)Ga(1-x) alloys (x similar to 0.5-0.75) grown by magnetron sputtering. The M(S) values decrease linearly from approximately 600 to 200 emu/cm(3) with increasing x, whereas the K(u) values decrease slightly from approximately 15 to 10 Merg/cm(3) with increasing x. These trends are distinct from those for known tetragonal hard magnets obtained in a limited composition range in Mn-Al and Fe-Pt binary alloys. These data are analyzed using a localized magnetic moment model.

  172. The magnetic and structural properties of Co2MnSi Heusler alloy thin films on the orientation of Ge substrate 査読有り

    M. A. I. Nahid, Mikihiko Oogane, Hiroshi Naganuma, Yasuo Ando

    Phys. Status Solidi A 208 675-378 2011年12月6日

    DOI: 10.1002/pssa.201026569  

  173. Composition dependence of magnetoresistance effect and its annealing endurance in tunnel junctions having Mn-Ga electrode with high perpendicular magnetic anisotropy 査読有り

    Takahide Kubota, Masaaki Araidai, Shigemi Mizukami, Xianmin Zhang, Qinli Ma, Hiroshi Naganuma, Mikihiko Oogane, Yasuo Ando, Masaru Tsukada, Terunobu Miyazaki

    APPLIED PHYSICS LETTERS 99 (19) 192509-1-192509-3 2011年11月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.3659484  

    ISSN:0003-6951

    eISSN:1077-3118

    詳細を見る 詳細を閉じる

    The composition dependence of the tunnel magnetoresistance (TMR) effect in Mn-Ga/MgO/CoFe magnetic tunnel junctions (MTJs) for Mn54Ga46, Mn62Ga38, and Mn71Ga29 (at. %) electrodes was investigated. An MTJ with a Mn62Ga38 electrode showed a maximum TMR ratio of 23% at 10 K and high annealing endurance up to 375 degrees C. The bias voltage dependence of the TMR ratio was distinct among MTJs with different Mn-Ga compositions. Here, we discuss this dependence on the basis of the difference in the Delta(1) band dispersions for Mn-Ga alloys calculated by first principles. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3659484]

  174. Large Magnetoresistance Effect in Epitaxial Co2Fe0.4Mn0.6Si/Ag/Co2Fe0.4Mn0.6Si Devices 査読有り

    Jo Sato, Mikihiko Oogane, Hiroshi Naganuma, Yasuo Ando

    APPLIED PHYSICS EXPRESS 4 (11) 113005-1-113005-3 2011年11月

    出版者・発行元:IOP PUBLISHING LTD

    DOI: 10.1143/APEX.4.113005  

    ISSN:1882-0778

    eISSN:1882-0786

    詳細を見る 詳細を閉じる

    Fully epitaxial current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) devices with a Co2Fe0.4Mn0.6Si/Ag/Co2Fe0.4Mn0.6Si structure were fabricated. The bottom and top Co2Fe0.4Mn0.6Si layers had good crystallinity and an L2(1)-ordered structure. In addition, we found from scanning transmission electron microscopy (STEM) measurements that both Co2Fe0.4Mn0.6Si/Ag and Ag/Co2Fe0.4Mn0.6Si interfaces were very flat and sharp. The magnetoresistance (MR) ratio at room temperature was 74.8%, the largest to date for CPP-GMR devices. CPP-GMR devices with Co2Fe0.4Mn0.6Si electrodes would be very useful for the next generation of hard disk drive (HDD) read heads. (C) 2011 The Japan Society of Applied Physics

  175. Transport Properties of Pure Spin Currents in a Polycrystalline Gd Wire 査読有り

    S. Nonoguchi, Y. Ando, S. Yakata, T. Kimura

    IEEE TRANSACTIONS ON MAGNETICS 47 (10) 2750-2752 2011年10月

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

    DOI: 10.1109/TMAG.2011.2158407  

    ISSN:0018-9464

    詳細を見る 詳細を閉じる

    We have investigated the magneto- and spin-current-transport properties in patterned Gd wires in order to understand the interplay between the spin current and the spin entropy. From the magneto-transport measurements, the electrical resistance was found to decrease with decreasing the spin entropy because of the suppression of the spin fluctuation. We also found that the Gd acts as a strong absorber both for the ac and dc pure spin currents from the ferromagnetic resonance and nonlocal spin injection experiments.

  176. Interface effects on perpendicular magnetic anisotropy for molecular-capped cobalt ultrathin films 査読有り

    Xianmin Zhang, Shigemi Mizukami, Takahide Kubota, Mikihiko Oogane, Hiroshi Naganuma, Yasuo Ando, Terunobu Miyazaki

    APPLIED PHYSICS LETTERS 99 (16) 162509-1-162509-3 2011年10月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.3651766  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    The perpendicular magnetic anisotropy (PMA) of cobalt (0.5-1.8 nm) films capped separately by pentacene (Pc), fullerene (C(60)), and 8-hydroxyquinoline-aluminum (Alq(3)) are investigated. For all three series, the thickness of Co is around 0.7 nm for maximum out-of-plane coercivity. It is found that the coercivity of C(60)-capped films is nearly equal to that for Alq(3)-capped samples, although both are smaller than for Pc-capped films. The different interface effects of Co/molecules are discussed to explain this observation. This work highlights the PMA of ferromagnetic metal, which can be markedly infected depending on the nature of organic molecule. (C) 2011 American Institute of Physics. [doi:10.1063/1.3651766]

  177. Time-Resolved Kerr Effect in Very Thin Films of CoCrPt Alloys 査読有り

    Shigemi Mizukami, Daisuke Watanabe, Takahide Kubota, X. Zhang, Hiroshi Naganuma, Mikihiko Oogane, Yasuo Ando, T. Miyazaki

    IEEE Transaction on Magnetics 47 (10) 3897-38900 2011年9月23日

    DOI: 10.1109/TMAG.2011.2154357  

  178. Spin Transport in Co/Al2O3 Alq3 Co Organic Spin Valve 査読有り

    Xianmin Zhang, Shigemi Mizukami, Takahide Kubota???, Mikihiko Oogane, Hiroshi Naganuma, Yasuo Ando, Terunobu Miyazaki

    IEEE TRANSACTIONS ON MAGNETICS 47 (10) 2649-2651 2011年9月

  179. Spin transistor using magnetic tunnel junctions with half-metallic Co2MnSi Heusler alloy electrodes 査読有り

    Y. Ohdaira, M. Oogane, H. Naganuma, Y. Ando

    APPLIED PHYSICS LETTERS 99 (13) 132513-1-132513-3 2011年9月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.3645637  

    ISSN:0003-6951

    eISSN:1077-3118

    詳細を見る 詳細を閉じる

    We fabricated a spin transistor structure that consisted of two magnetic tunnel junctions with half-metallic Co2MnSi electrodes. Transient responses were observed by applying pulsing gate voltage. Output currents were controlled by both the source-drain and gate voltage and magnetic configuration of the Co2MnSi. The drain current increased around 3000 times at a source-drain voltage of 0.01 V and anti-parallel magnetic configuration, when a gate voltage of 1 V peak-to-peak was applied. In addition, the maximum magnetocurrent ratios were 215% at 6 K. Expected operation properties are observed in our proposed spin transistor. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3645637]

  180. Quadratic magneto-optical Kerr effect in Co2MnSi 査読有り

    Georg Wolf, Jaroslav Hamrle, Simon Trudel, Takahide Kubota, Yasuo Ando, Burkard Hillebrands

    JOURNAL OF APPLIED PHYSICS 110 (4) 043904-1-043904-5 2011年8月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.3622512  

    ISSN:0021-8979

    詳細を見る 詳細を閉じる

    Quadratic magneto-optical Kerr effects (QMOKE) are investigated in epitaxial Co2MnSi thin films as a function of the post-deposition annealing temperature. We determine the amplitude of the QMOKE signal for different annealing temperatures, which provide various degrees of L2(1) crystal ordering, as manifested by X-ray diffraction. We observe that QMOKE is significantly present only when the L2(1) ordering phase is also present, and that the QMOKE signal increases with the higher degree of L2(1) ordering. Additionally, we notice that the linear magneto-optical Kerr effect (LMOKE) decreases with higher annealing temperature. A comparison of the linear and quadratic MOKE contributions shows the amplitudes are of similar magnitude. From these results, we conclude that the presence of QMOKE is linked to the higher degree of L2(1) ordering in Co2MnSi. (C) 2011 American Institute of Physics. [doi:10.1063/1.3622512]

  181. Fabrication of MgO-based magnetic tunnel junctions for subnanosecond spin transfer switching 査読有り

    Tatsuya Aoki, Yasuo Ando, Mikihiko Oogane, Hiroshi Naganuma

    Journal of Physics: conference serise 266 012086 2011年7月

    DOI: 10.1088/1742-6596/266/1/012086  

  182. The perpendicular anisotropy of Co40Fe40B20 sandwiched between Ta and MgO layers and its application in CoFeB/MgO/CoFeB tunnel junction 査読有り

    W. X. Wang, Y. Yang, H. Naganuma, Y. Ando, R. C. Yu, X. F. Han

    APPLIED PHYSICS LETTERS 99 (1) 012502-1-012502-3 2011年7月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.3605564  

    ISSN:0003-6951

    eISSN:1077-3118

    詳細を見る 詳細を閉じる

    Magnetic anisotropy of Co40Fe40B20 thin films sandwiched between Ta and MgO layers was investigated. Magnetic properties of CoFeB layers deposited on top and bottom of MgO layer are different. The thickness of the CoFeB layer and annealing temperature are the critical parameters to achieve and keep the perpendicular magnetic anisotropy. The phase diagram of perpendicular anisotropic strength of CoFeB layers on annealing temperatures and thicknesses of CoFeB layers is observed. According to phase diagrams, perpendicular CoFeB/MgO/CoFeB tunnel junctions were fabricated, and tunneling magnetoresistance (TMR) ratio was higher than 30% at low temperatures. (C) 2011 American Institute of Physics. [doi:10.1063/1.3605564]

  183. Effect of metallic Mg insertion on the magnetoresistance effect in MgO-based tunnel junctions using D0(22)-Mn3-delta Ga perpendicularly magnetized spin polarizer 査読有り

    Takahide Kubota, Shigemi Mizukami, Daisuke Watanabe, Feng Wu, Xianmin Zhang, Hiroshi Naganuma, Mikihiko Oogane, Yasuo Ando, Terunobu Miyazaki

    JOURNAL OF APPLIED PHYSICS 110 (1) 013915-1-013915-5 2011年7月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.3603034  

    ISSN:0021-8979

    詳細を見る 詳細を閉じる

    Effects of metallic Mg insertion on tunnel magnetoresistance (TMR) effect were investigated in D0(22)-Mn2.4Ga/Mg/MgO/CoFe magnetic tunnel junctions (MTJs). The thickness of Mg (d(Mg)) was varied from 0 to 1.4 nm. TMR ratio exhibited maximum value of 22% with the d(Mg) = 0.4 nm and a negative value of 14% with the d(Mg) = 1.4 nm at 10 K. The dependence of resistance area products (R x A) on the d(Mg) showed similar trend compared with those of what reported in conventional CoFeB-MgO based MTJs. Bias voltage dependences of differential conductance (dI/dV) and TMR ratio exhibited asymmetry with respect to the zero-bias. The difference of the zero-bias anomaly in the dI/dV spectra was also discussed, and an indication of reducing the inelastic tunneling process was found, implying the improvement of barrier/magnetic-layer interfaces by the Mg insertion. Considering a theoretical work done by Wang et al. [Phys. Rev. B 82, 054405 (2010)], the inversion of the sign and the asymmetric bias voltage dependence of TMR ratio were inferred to be attributed to the minority spin tunneling via a quantum well state in the thin metallic Mg layer between Mn2.4Ga and MgO. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3603034]

  184. Fabrication of Multiferroic Co-Substituted BiFeO3 Epitaxial Films on SrTiO3 (100) Substrates by Radio Frequency Magnetron Sputtering 査読有り

    Husne Ara Begum, Hiroshi Naganuma, Mikihiko Oogane, Yasuo Ando

    Materials 4 1087-1095 2011年6月9日

    DOI: 10.3390/ma4061087  

  185. The effect of film and interface structure on the transport properties of Heusler based current-perpendicular-to-plane spin valves 査読有り

    V. K. Lazarov, K. Yoshida, J. Sato, P. J. Hasnip, M. Oogane, A. Hirohata, Y. Ando

    APPLIED PHYSICS LETTERS 98 (24) 242508-1-242508-3 2011年6月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.3600792  

    ISSN:0003-6951

    eISSN:1077-3118

    詳細を見る 詳細を閉じる

    We present direct link between the transport properties of Co2MnSi and Co2FeMnSi Heusler based current-perpendicular-to-plane spin valves (CPP-SVs) and interface atomic structures resolved by aberration-corrected electron microscopy. The structure of the Co2FeMnSi electrodes is L2(1) but their interface with the CoSi spacer is disordered. In contrast to the Co2FeMnSi-electrodes, the Co2MnSi-electrodes have abrupt interfaces with the Ag spacer though their ordering is not fully L2(1). The magnetoresistance of the Co2MnSi-SV is over two orders of magnitude better than those of Co2FeMnSi-SV, demonstrating that the atomic interface ordering is crucial for the enhancement of the magnetoresistance in the Heusler CPP-SVs. (C) 2011 American Institute of Physics. [doi:10.1063/1.3600792]

  186. Magnetoresistance Effect in Tunnel Junctions with Perpendicularly Magnetized D0<SUB>22</SUB>-Mn<SUB>3-δ</SUB>Ga Electrode and MgO Barrier 査読有り

    Yoshio Miura, Daisuke Watanabe, Shigemi Mizukami, Feng Wu, Hiroshi Naganuma, Xianmin Zhang, Mikihiko Oogane, Masafumi Shirai, Yasuo Ando, Terunobu Miyazaki

    Appl. Phys. Exp 4 (4) 043002-1-043002-3 2011年4月

    出版者・発行元:None

    DOI: 10.1143/APEX.4.043002  

    ISSN:1882-0778

  187. Exchange biases of Co, Py, Co40Fe40B20, Co75Fe25, and Co50Fe50 on epitaxial BiFeO3 films prepared by chemical solution deposition 査読有り

    Hiroshi Naganuma, Mikihiko Oogane, Yasuo Ando

    JOURNAL OF APPLIED PHYSICS 109 (7) 07D736-1-07D736-3 2011年4月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.3563061  

    ISSN:0021-8979

    詳細を見る 詳細を閉じる

    Multiferroic BiFeO3 epitaxial films were fabricated on SrTiO3 (100) substrates by a chemical solution deposition method. Magnetic layers of Co, Py, Co40Fe40B20, Co75Fe25, and Co50Fe50 were then deposited by sputtering under a magnetic field. Despite employing a chemical process, a clear exchange bias was observed for all the magnetic materials. The temperature dependence of Hex was evaluated for a Co50Fe50/BiFeO3 bilayer having a relatively large Hex and high squareness. The Hex of Co50Fe50/BiFeO3 bilayer increased between 10 to 250 K. (c) 2011 American Institute of Physics. [doi: 10.1063/1.3563061]

  188. Long-Lived Ultrafast Spin Precession in Manganese Alloys Films with a Large Perpendicular Magnetic Anisotropy 査読有り

    S. Mizukami, F. Wu, A. Sakuma, J. Walowski, D. Watanabe, T. Kubota, X. Zhang, H. Naganuma, M. Oogane, Y. Ando, T. Miyazaki

    PHYSICAL REVIEW LETTERS 106 (11) 117201-1-117201-4 2011年3月

    出版者・発行元:AMER PHYSICAL SOC

    DOI: 10.1103/PhysRevLett.106.117201  

    ISSN:0031-9007

    詳細を見る 詳細を閉じる

    Spin precession with frequencies up to 280 GHz is observed in Mn(3-delta)Ga alloy films with a perpendicular magnetic anisotropy constant K(u) similar to 15 Merg/cm(3). The damping constant alpha, characterizing macroscopic spin relaxation and being a key factor in spin-transfer-torque systems, is not larger than 0.008 (0.015) for the delta = 1.46 (0.88) film. Those are about one-tenth of alpha values for known materials with large K(u). First-principles calculations well describe both low alpha and large K(u) for these alloys.

  189. Pressure-induced half-metallic gap transformation in Co2MnSi observed by tunneling conductance spectroscopy 査読有り

    M. Nobori, T. Nakano, J. Hasegawa, G. Oomi, Y. Sakuraba, K. Takanashi, Y. Miura, Y. Ohdaira, Y. Ando

    PHYSICAL REVIEW B 83 (10) 104410-1-104410-6 2011年3月

    出版者・発行元:AMER PHYSICAL SOC

    DOI: 10.1103/PhysRevB.83.104410  

    ISSN:2469-9950

    eISSN:2469-9969

    詳細を見る 詳細を閉じる

    Applied hydrostatic pressure dependence of tunneling magnetoresistance (TMR) properties was investigated in magnetic tunnel junctions using the half-metallic Heusler alloy Co2MnSi (CMS). The half-metallic electronic structure in CMS was observed by measuring tunneling-conductance spectroscopy under different applied pressure. The effect of tetragonal distortion in CMS on the electronic structure was also calculated on the basis of the first-principle density-functional method. The TMR ratio showed no remarkable variation with increasing pressure from ambient to 1.5 GPa. It was clearly found that the valence-band edge of the half-metallic gap moved toward the Fermi level with increasing pressure up to 1.8 GPa. These experimental results showed good qualitative agreement with the theoretical calculation of density of states of CMS at high pressure.

  190. The effect of inserting thin Co2MnAl layer into the Co2MnSi/MgO interface on tunnel magnetoresistance effect 査読有り

    E. Ozawa, S. Tsunegi, M. Oogane, H. Naganuma, Y. Ando

    Journal ofPhysics:ConferenceSeries 266 012104-1-012104-4 2011年1月28日

    DOI: 10.1088/1742-6596/266/1/012104  

  191. Magnetoresistance Effect in Co2MnSi/semimetallic-Fe2VAl/CoFe Junctions 査読有り

    T Kubota, M Oogane, S Mizukami, H Naganuma, Y Ando, T Miyazaki

    Journal ofPhysics:ConferenceSeries 266 012096-1-012096-5 2011年1月28日

    DOI: 10.1088/1742-6596/266/1/012096  

  192. Influence of composition on structure and magnetic properties of epitaxial Mn-Ga films 査読有り

    F Wu, S Mizukami, D Watanabe, H Naganuma, M Oogane, Y Ando, T Miyazaki

    Journal of Physics: Conference Series 266 012112-1-012112-5 2011年1月28日

    DOI: 10.1088/1742-6596/266/1/012112  

  193. Laser-induced fast magnetization precession and Gilbert damping for CoCrPt alloy thin films with perpendicular magnetic anisotropy 査読有り

    Shigemi Mizukami, Daisuke Watanabe, Takahide Kubota, Xianmin Zhang, Hiroshi Naganuma, Mikihiko Oogane, Yasuo Ando, Terunobu Miyazaki

    Applied physics express 3 123001-1-123001-3 2011年

  194. Gilbert Damping in Ni/Co Multilayer Films Exhibiting Large Perpendicular Anisotropy 査読有り

    Shigemi Mizukami, Xianmin Zhang, Takahide Kubota, Hiroshi Naganuma, Mikihiko Oogane, Yasuo Ando, Terunobu Miyazaki

    Applied Physics Express 4 (2011) 013005 4 (1) 13005-013005-3 2011年

    出版者・発行元:Japan Society of Applied Physics

    DOI: 10.1143/APEX.4.013005  

    ISSN:1882-0778

    詳細を見る 詳細を閉じる

    Gilbert damping is reported in perpendicularly magnetized Ni/Co multilayer films with Pt buffer and capping layers, and investigated through the time-resolved magneto-optical Kerr effect under various applied magnetic field strengths and directions. Both damping constant $\alpha$ and perpendicular magnetic anisotropy energy $K_{\text{u } }$ depend strongly on layer thickness and bilayer periodicity, and rise to approximately 0.08 and 8 Merg/cm3, respectively. The Gilbert damping rate depends linearly on inverse multilayer thickness, indicating that large damping in the Ni/Co multilayers stems from its interfaces in contact with the Pt layers.

  195. Influence of Pt Doping on Gilbert Damping in Permalloy Films and Comparison with the Perpendicularly Magnetized Alloy Films 査読有り

    Shigemi Mizukami, Takahide Kubota, Xianmin Zhang, Hiroshi Naganuma, Mikihiko Oogane, Yasuo Ando, Terunobu Miyazaki

    Japanese Journal of Applied Physics 50 (2011) 103003 50 (10) 103003-103003-5 2011年

    出版者・発行元:Published by the Japan Society of Applied Physics through the Institute of Pure and Applied Physics

    DOI: 10.1143/JJAP.50.103003  

    ISSN:0021-4922

    詳細を見る 詳細を閉じる

    Effects of Pt doping on magnetic properties and Gilbert damping are investigated for Ni80Fe20 permalloy films to compare with damping in alloy films containing Pt with a large perpendicular anisotropy. Gilbert damping constant \alpha and g-factor g for (Ni80Fe20)100-xPtx (x = 0{\mbox{-- } }34 at. %) are evaluated from out-of-plane angular variations of ferromagnetic resonance (FMR) linewidth and resonance field with an analysis based on the Landau--Lifshitz--Gilbert equation. Data of angular dependence of the FMR linewidth are fitted reasonably well by a theoretical model without having to take into account any extrinsic influences on linewidth, thereby allowing us to determine precise values of \alpha. The \alpha values show variation with increasing Pt concentration rising by {\sim}0.06 at a Pt concentration of 34 at. %, which is very close to those in perpendicularly magnetized CoCrPt and FePt film reported recently. Nevertheless, Gilbert damping rate G for the Pt doped permalloy films is smaller than those in CoCrPt and FePt films. These experimental results are discussed with a spin--orbit torque theory.

  196. Fast magnetization precession observed in L1(0)-FePt epitaxial thin film 査読有り

    S. Mizukami, S. Iihama, N. Inami, T. Hiratsuka, G. Kim, H. Naganuma, M. Oogane, Y. Ando

    APPLIED PHYSICS LETTERS 98 (5) 052501-1-052501-3 2011年1月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.3549704  

    ISSN:0003-6951

    eISSN:1077-3118

    詳細を見る 詳細を閉じる

    Fast magnetization precession is observed in L1(0)-FePt alloy epitaxial thin films excited and detected by all-optical means. The precession frequency varies from 45 to 65 GHz depending on the applied magnetic field strength and direction, which can be explained by a uniform precession model taking account of first- and second-order uniaxial magnetic anisotropy. The lowest effective Gilbert damping constant has a minimum value of 0.055, which is about half that in Co/Pt multilayers and is comparable to Ni/Co multilayers with perpendicular magnetic anisotropy. (C) 2011 American Institute of Physics. [doi:10.1063/1.3549704]

  197. Fabrication of Magnetic Tunnel Junctions with a Synthetic Ferrimagnetic Free Layer for Magnetic Field Sensor Applications 査読有り

    Kousuke Fujiwara, Mikihiko Oogane, Futoyoshi Kou, Daisuke Watanabe, Hiroshi Naganuma, Yasuo Ando

    JAPANESE JOURNAL OF APPLIED PHYSICS 50 (1) 013001-1-013001-3 2011年1月

    出版者・発行元:JAPAN SOC APPLIED PHYSICS

    DOI: 10.1143/JJAP.50.013001  

    ISSN:0021-4922

    詳細を見る 詳細を閉じる

    Magnetic tunnel junctions (MTJs) with a CoFeB/Ru/Ni80Fe20 synthetic ferrimagnetic free layer and an MgO barrier layer were fabricated. The effect of the shape and thickness of the free layer on the magnetic field sensor characteristics was systematically investigated. We achieved a high sensitivity of 4.8%/Oe in the MTJ with a 70-nm-thick Ni80Fe20 layer and an aspect ratio of 1.0. Here, sensitivity is defined as TMR/(2H(k)), where TMR is tunnel magnetoresistance ratio in the MTJ and H-k is a magnetic anisotropy field of the free layer. Furthermore, we successfully increased the detection field range up to 230 Oe while keeping high sensitivity and linearity. (c) 2011 The Japan Society of Applied Physics

  198. Retraction: ‘‘Large Tunnel Magnetoresistance of 1056% at Room Temperature in MgO Based Double Barrier Magnetic Tunnel Junction’’ [Appl. Phys. Express 2 (2009) 083002] 査読有り

    Hiroshi Naganuma, Lixian Jiang, Mikihiko Oogane, Yasuo Ando

    Applied Physics Express 4 (1) 019201-019201 2010年12月16日

    出版者・発行元:The Japan Society of Applied Physics

    DOI: 10.1143/APEX.4.019201  

    ISSN:1882-0778

  199. Band-Structure-Dependent Demagnetization in the Heusler Alloy Co2Mn1-xFexSi 査読有り

    Daniel Steil, Sabine Alebrand, Tobias Roth, Michael Krauss, Takahide Kubota, Mikihiko Oogane, Yasuo Ando, Hans Christian Schneider, Martin Aeschlimann, Mirko Cinchetti

    PHYSICAL REVIEW LETTERS 105 (21) 217202-1-217202-4 2010年11月

    出版者・発行元:AMER PHYSICAL SOC

    DOI: 10.1103/PhysRevLett.105.217202  

    ISSN:0031-9007

    詳細を見る 詳細を閉じる

    We investigate the ultrafast demagnetization for two Heusler alloys (Co2Mn1-xFexSi) with a different lineup of the minority band gap and the Fermi level. Even though electronic spin-flip transitions are partially blocked by the band gap in one compound, the respective magnetization dynamics, as measured by the time-resolved Kerr effect, are remarkably similar. Based on a dynamical model that includes momentum and spin-dependent carrier scattering, we show that the magnetization dynamics are dominated by hole spin-flip processes, which are not influenced by the gap.

  200. Ferromagnetic resonance investigation of exchange coupling in Nd2Fe14B/α-Fe interfaces

    D. Ogawa, K. Koike, T. Miyazaki, S. Mizukami, T. Akiya, M. Oogane, Y. Ando, H. Kato

    Proc. on the 21th International Workshop on Rare-earth Permanent Magnets and their Applications 2010年8月28日

  201. Structural characterization of epitaxial multiferroic BiFeO3 films grown on SrTiO3 (100) substrates by crystallizing amorphous Bi-Fe-O-x 査読有り

    Hiroshi Naganuma, Takamichi Miyazaki, Akihiko Ukachi, Mikihiko Oogane, Shigemi Mizukami, Yasuo Ando

    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 118 (1380) 648-651 2010年8月

    出版者・発行元:CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI

    DOI: 10.2109/jcersj2.118.648  

    ISSN:1882-0743

    eISSN:1348-6535

    詳細を見る 詳細を閉じる

    Amorphous Bi-Fe-O-x films prepared on SrTiO3 (100) substrates using a conventional r.f. magnetron sputtering system were crystallized by post-annealing at 873 K in an atmosphere. Microstructural observations by X-ray diffraction and cross-sectional transmission electron microscopy revealed that the crystallized Bi-Fe-O-x films were well-epitaxially BiFeO3 fabricated without interfacial layer although as-prepared film was amorphous structure with excess Bi. The crystallized BiFeO3 films have fairly epitaxial compatibly ([001](001)BiFeO3 // [001](001)SrTiO3). These results indicate that (1) BiFeO3 has good epitaxial compatibility with SrTiO3 and (2) crystallizing amorphous Bi-Fe-O-x is one possible method that can be used to fabricate high-quality multiferroic barriers for tunnel junctions. (C) 2010 The Ceramic Society of Japan. All rights reserved.

  202. Gilbert magnetic damping constant of epitaxially grown Co-based Heusler alloy thin films 査読有り

    M. Oogane, T. Kubota, Y. Kota, S. Mizukami, H. Naganuma, A. Sakuma, Y. Ando

    APPLIED PHYSICS LETTERS 96 (25) 252501-1-252501-3 2010年6月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.3456378  

    ISSN:0003-6951

    eISSN:1077-3118

    詳細を見る 詳細を閉じる

    The magnetic damping constant in a series of Co2MnAlxSi1-x and Co2FexMn1-xSi Heusler alloy epitaxial films were systematically investigated by using ferromagnetic resonance technique. The determined magnetic damping constant is roughly proportional to the density of states at the Fermi energy of the first principle calculation. The result is consistent with the theoretical prediction when taking spin-orbit interaction into account. The small Gilbert damping constant for the fabricated films other than the Co2FexMn1-xSi film with x&gt;0.6 can be originated in the half-metallic electronic structure of Heusler alloys. (C) 2010 American Institute of Physics. [doi:10.1063/1.3456378]

  203. Structural and Magnetic Properties of Perpendicular Magnetized Mn2.5Ga Epitaxial Films 査読有り

    F. Wu, S. Mizukami, D. Watanabe, E. P. Sajitha, H. Naganuma, M. Oogane, Y. Ando, T. Miyazaki

    IEEE TRANSACTIONS ON MAGNETICS 46 (6) 1863-1865 2010年6月

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

    DOI: 10.1109/TMAG.2010.2045108  

    ISSN:0018-9464

    詳細を見る 詳細を閉じる

    The influence of annealing temperature and film thickness on structural and magnetic properties of Mn2.5Ga films were investigated in this work. The annealing temperature of 400 degrees C was found to be the optimum condition to obtain the films with high perpendicular magnetic anisotropy (PMA) (K-u(eff) = 7.8 x 10(6) erg/cm(3)) and smooth surface (R-a approximate to 0.15 nm). The PMA property was maintained in the 5 nm thick film, and deterioration of the PMA properties with decreasing film thickness can be ascribed to the tensile strain existed in the thin Mn2.5Ga films.

  204. Fabrication of perpendicularly magnetized magnetic tunnel junctions with [formula omitted] hybrid electrode 査読有り

    T. Hiratsuka, G. Kim, Y. Sakuraba, T. Kubota, K. Kodama, N. Inami, H. Naganuma, M. Oogane, T. Nakamura, K. Takanashi, Y. Ando

    Journal of Applied Physics 107 (9) 2010年5月1日

    DOI: 10.1063/1.3358239  

    ISSN:1089-7550 0021-8979

    eISSN:1089-7550

    詳細を見る 詳細を閉じる

    Magnetic tunnel junctions (MTJs) of perpendicularly magnetized [formula omitted] structure were fabricated. In-plane x-ray diffraction measurements and element specific evaluation of magnetic properties using soft x-ray magnetic circular dichroism were carried out to examine quite thin [formula omitted] (CMS) inserted layer between CoPt and MgO interface. Ordered [formula omitted] was successfully fabricated onto [formula omitted] as thin as 1 nm thick, and CMS layer shows perpendicular magnetic anisotropy below 3 nm thick via exchange coupling with CoPt layer. In the MTJ-stacking, epitaxial growth was confirmed except for partial misalignment in the upper FePt layer, and coercive field difference clearly appeared between the bottom and the top ferromagnetic electrodes. © 2010, American Institute of Physics. All rights reserved.

  205. Fabrication of perpendicularly magnetized magnetic tunnel junctions with L1(0)-CoPt/Co2MnSi hybrid electrode 査読有り

    T. Hiratsuka, G. Kim, Y. Sakuraba, T. Kubota, K. Kodama, N. Inami, H. Naganuma, M. Oogane, T. Nakamura, K. Takanashi, Y. Ando

    JOURNAL OF APPLIED PHYSICS 107 (9) 09C714-1-09C714-3 2010年5月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.3358239  

    ISSN:0021-8979

    eISSN:1089-7550

    詳細を見る 詳細を閉じる

    Magnetic tunnel junctions (MTJs) of perpendicularly magnetized L1(0)-CoPt/Co2MnSi/MgO/FePt structure were fabricated. In-plane x-ray diffraction measurements and element specific evaluation of magnetic properties using soft x-ray magnetic circular dichroism were carried out to examine quite thin Co2MnSi (CMS) inserted layer between CoPt and MgO interface. Ordered B2-CMS was successfully fabricated onto L1(0)-CoPt as thin as 1 nm thick, and CMS layer shows perpendicular magnetic anisotropy below 3 nm thick via exchange coupling with CoPt layer. In the MTJ-stacking, epitaxial growth was confirmed except for partial misalignment in the upper FePt layer, and coercive field difference clearly appeared between the bottom and the top ferromagnetic electrodes. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3358239]

  206. Reproducible trajectory on subnanosecond spin-torque magnetization switching under a zero-bias field for MgO-based ferromagnetic tunnel junctions 査読有り

    Tatsuya Aoki, Yasuo Ando, Mikihiko Oogane, Hiroshi Naganuma

    APPLIED PHYSICS LETTERS 96 (14) 142502-1-142502-3 2010年4月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.3380595  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    One of the features of spin-transfer torque (STT)-based magnetic random access memories (spin-RAMs) is a fast write cycle; however, switching properties in the subnanosecond regime for MgO-based magnetic tunnel junctions (MTJs) are still unclear. In this work, we demonstrated subnanosecond magnetization switching by STT for MgO-based MTJs. We also discuss the thermal effect on subnanosecond STT switching, as well as the subnanosecond pulse width that is dependent on the remarkable plateau that switching probability has under a zero-bias field.

  207. Gilbert damping in perpendicularly magnetized Pt/Co/Pt films investigated by all-optical pump-probe technique 査読有り

    S. Mizukami, E. P. Sajitha, D. Watanabe, F. Wu, T. Miyazaki, H. Naganuma, M. Oogane, Y. Ando

    APPLIED PHYSICS LETTERS 96 (15) 152502-1-152502-3 2010年4月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.3396983  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    To investigate the correlation between perpendicular magnetic anisotropy and intrinsic Gilbert damping, time-resolved magneto-optical Kerr effect was measured in Pt/Co(d(Co))/Pt films. These films showed perpendicular magnetization at d(Co)=1.0 nm and a perpendicular magnetic anisotropy energy K(u)(eff) that was inversely proportional to d(Co). With an analysis based on the Landau-Lifshitz-Gilbert equation, the intrinsic Gilbert damping constant alpha was evaluated by parameter-fitting of frequency and lifetime expressions to experimental data of angular variations in spin precession frequency and life-times. The alpha values increased significantly with decreasing d(Co) but not inversely proportional to d(Co).

  208. Evidence of Fermi level control in a half-metallic Heusler compound Co2MnSi by Al-doping: Comparison of measurements with first-principles calculations 査読有り

    Y. Sakuraba, K. Takanashi, Y. Kota, T. Kubota, M. Oogane, A. Sakuma, Y. Ando

    PHYSICAL REVIEW B 81 (14) 144422-1-144422-5 2010年4月

    出版者・発行元:AMER PHYSICAL SOC

    DOI: 10.1103/PhysRevB.81.144422  

    ISSN:2469-9950

    eISSN:2469-9969

    詳細を見る 詳細を閉じる

    The Fermi level (E-F) control of half-metallic Heusler alloy Co2MnSi by Al-doping was challenged in magnetic tunnel junctions with a Co2MnAlxSi1-x (CMAS) electrode. The observed bias voltage dependence on tunneling conductance (G-V curves) clearly shows a shift in E-F toward the center of the half-metallic gap with x, which showed excellent agreement with our first-principles calculations. However, the ratio of tunnel magnetoresistance (TMR) at 10 K to that at room temperature does not exhibit a remarkable change with x. The weak exchange energy at the CMAS interface may be the origin for the large temperature dependence of the TMR ratio.

  209. Epitaxial growth of Co2MnSi thin films at the vicinal surface of n-Ge(111) substrate 査読有り

    M. A. I. Nahid, M. Oogane, H. Naganuma, Y. Ando

    APPLIED PHYSICS LETTERS 96 (14) 142501-1-142501-3 2010年4月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.3378986  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    The structure and magnetic properties of Co2MnSi films on n-Ge(111) substrate were investigated for the motivation of spin injection. The 50-nm-thick Co2MnSi films were fabricated on n-Ge(111) substrates by dc sputtering and postannealed about 1 h at the various temperatures ranging from 200-500 degrees C. In the annealing temperature range of 300-400 degrees C, the Co2MnSi were grown epitaxially at the vicinal surface of n-Ge(111) substrates. The epitaxial layer of Co2MnSi films was about 18 nm thick at 350 degrees C and exhibited ferromagnetic behavior. Interestingly, there was no diffusion of Ge inside the epitaxial layer and atomically flat interface was obtained.

  210. フェリ磁性ホイスラー合金Mn<SUB>2</SUB>VAlエピタキシャル薄膜の元素選択的磁気特性評価 査読有り

    児玉兼司, 中村哲也, 桜庭裕弥, 大兼幹彦, 永沼博, 高梨弘毅, 安藤康夫

    日本磁気学会誌 34 (2) 100-106 2010年4月

    出版者・発行元:The Magnetics Society of Japan

    DOI: 10.3379/msjmag.1002R0004  

    ISSN:1882-2924

    詳細を見る 詳細を閉じる

    We successfully fabricated <i>L</i>2<sub>1</sub>-ordered Mn<sub>2</sub>VAl Heusler thin films and evaluated their ferrimagnetic properties by soft x-ray magnetic circular dichroism (XMCD). The buffer layers and annealing temperatures were varied to prepare the Mn<sub>2</sub>VAl films. We discovered that Mn<sub>2</sub>VAl could be ordered in an <i>L</i>2<sub>1</sub> phase well when it was deposited directly onto an MgO (001) single crystalline substrate. The maximum values of <i>L</i>2<sub>1</sub> and <i>B</i>2 long-range order parameters we obtained were about 0.5 for both phases for samples without a buffer layer, when substrates were heated at 500°C or 600°C. The saturation magnetization (<i>M</i><sub>s</sub>) for these samples was roughly 150 emu/cc. This is rather small compared to that expected from the ideal Slater-Pauling behavior, which might be due to the suppressed degree of <i>L</i>2<sub>1</sub> or <i>B</i>2 ordering. Ferrimagnetism in the Mn<sub>2</sub>VAl, ferrimagnetic coupling between Mn and V moments was clearly observed by using the XMCD technique in well-ordered <i>L</i>2<sub>1</sub>-Mn<sub>2</sub>VAl film as has been predicted in theoretical investigations.

  211. MgO障壁を用いたFePt垂直磁化トンネル磁気抵抗素子の磁気抵抗特性および極微構造 査読有り

    永沼博, 平塚喬士, 金国天, 宮﨑孝道, 佐藤和久, 今野豊彦, 大兼幹彦, 安藤康夫

    日本磁気学会誌 34 (3) 293-296 2010年4月

    出版者・発行元:The Magnetics Society of Japan

    DOI: 10.3379/msjmag.1003R047  

    ISSN:1882-2924

    詳細を見る 詳細を閉じる

    Perpendicularly magnetized magnetic tunnel junctions (MTJs) were fabricated by depositing thin L1<sub>0</sub>-ordered FePt films on MgO(001) substrates using a UHV sputtering system, and the dependence of structural, magnetic, and magnetotransport properties of the junctions on the thickness of the FePt layers was investigated. A full epitaxial structure of MgO(001) sub./Cr/Pt/FePt/MgO/CoPt/Ta was observed. The tunnel magnetoresistance (TMR) ratio was measured to be 6% at room temperature, and magnetization switching was clearly observed in the thin FePt layer. Transmission electron microscopy (TEM) observations revealed that the interface between FePt, MgO, and CoPt layer has strain due to lattice mismatch, which might be a reason for the low TMR ratio.

  212. Investigation of spin-dependent transport properties and spin-spin interactions in a CuPc-Co nano-composite system 査読有り

    Z.Tang, S.Tanabe, D.Hatanaka, T.Nozaki, T.Shinjo, S.Mizukami, Y.Ando, Y.Suzuki, M.Shiraishi

    Japanese Journal of Applied Physics Vol.49, 133002-1-4 2010年3月

    DOI: 10.1143/JJAP.49.033002  

  213. Optically induced magnetization dynamics and variation of damping parameter in epitaxial Co2MnSi Heusler alloy films 査読有り

    Y. Liu, L. R. Shelford, V. V. Kruglyak, R. J. Hicken, Y. Sakuraba, M. Oogane, Y. Ando

    PHYSICAL REVIEW B 81 (9) 094402-1-094402-12 2010年3月

    出版者・発行元:AMER PHYSICAL SOC

    DOI: 10.1103/PhysRevB.81.094402  

    ISSN:2469-9950

    eISSN:2469-9969

    詳細を見る 詳細を閉じる

    All-optical pump-probe measurements of magnetization dynamics have been performed upon epitaxial Co2MnSi(001) Heusler alloy thin films annealed at temperatures of 300, 400, and 450 degrees C. An ultrafast laser-induced modification of the magnetocrystalline anisotropy triggers precession which is detected by time-resolved magneto-optical Kerr effect measurements. From the damped oscillatory Kerr rotation, the frequency and relaxation rate of the precession is determined. Using a macrospin solution of the Landau-Lifshitz-Gilbert equation the effective fields acting upon the sample magnetization are deduced. This reveals that the magnetization is virtually independent of the annealing temperature while the fourfold magnetocrystalline anisotropy decreases dramatically with increasing annealing temperature as the film structure changes between the B2 and L2(1) phases. From the measured relaxation rates, the value of the apparent Gilbert damping parameter is found to depend strongly upon the static field strength and in-plane static field orientation. The variation of the apparent damping parameter is generally well reproduced by an inhomogeneous broadening model in which the presence of B2 and L2(1) phases leads to a large dispersion of the magnetocrystalline anisotropy. However, for the sample annealed at a temperature of 300 degrees C, the lack of a detailed fit to the data suggests that the apparent anisotropy of the apparent damping parameter might alternatively arise due to a network of dislocations with fourfold symmetry.

  214. Co-concentration dependence of half-metallic properties in Co–Mn–Si epitaxial films 査読有り

    Y. Sakuraba, N. Hirose, M. Oogane, T. Nakamura, Y. Ando, K. Takanashi

    Appl. Phys. Lett 96 (9) 092511-1-092511-3 2010年3月

    出版者・発行元:None

    DOI: 10.1063/1.3330942  

    ISSN:0003-6951

    eISSN:1077-3118

  215. Note: Probing quadratic magneto-optical Kerr effects with a dual-beam system 査読有り

    Simon Trudel, Georg Wolf, Helmut Schultheiss, Jaroslav Hamrle, Burkard Hillebrands, Takahide Kubota, Yasuo Ando

    REVIEW OF SCIENTIFIC INSTRUMENTS 81 (2) 026105-1-026105-3 2010年2月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.3276715  

    ISSN:0034-6748

    詳細を見る 詳細を閉じる

    In this Note, we present a dual-beam magneto-optical Kerr effect (MOKE) magnetometer for the study of quadratic MOKE in magnetic thin films. The two beams simultaneously probe the sample, located in the middle of a quadrupole magnet, at two angles of incidence (0 degrees and 45 degrees). This combination of two systems allows one to automatically and routinely perform measurements that are sensitive to the combined longitudinal and quadratic MOKE signals (45 degrees), or the quadratic effect alone (0 degrees). Orientation-dependent and automated quantitative analyses of the quadratic effect&apos;s amplitude are also implemented. We present representative measurements on Heusler compound thin films to illustrate the newly combined capabilities of this instrument.

  216. Optimization of interface condition for efficient spin injection in Permalloy/Cu lateral spin valve 査読有り

    S. Yakata, Y. Ando, T. Kimura

    TENCON 2010: 2010 IEEE REGION 10 CONFERENCE 126-128 2010年

    出版者・発行元:IEEE

    DOI: 10.1109/TENCON.2010.5685852  

    ISSN:0886-1420

    詳細を見る 詳細を閉じる

    We have investigated the cleaning condition of the Permalloy (Py) surface optimized for the efficient pure spin current injection in Py/Cu lateral spin valve structure. The efficiency of the spin injection is found to depend on the beam voltage and milling time strongly. The post annealing is also found to improve the spin injection efficiency.

  217. Synthetic CoFeB/Ru/NiFe free layer on MgO barrier layer for spin transfer switching 査読有り

    Takuya Ono, Hiroshi Naganuma, Mikihiko Oogane, Yasuo Ando

    J. Phys.: Conf. Ser. 2010年

    DOI: 10.1088/1742-6596/200/6/062019  

  218. Spin transistor based on double tunnel junctions using half-metallic Co2MnSi electrodes 査読有り

    Yusuke Ohdaira, Mikihiko Oogane, Hiroshi Naganuma, Yasuo Ando

    J. Phys.: Conf. Ser. 2010年

    DOI: 10.1088/1742-6596/200/5/052019  

  219. Dynamic Magnetic Intermediate State during Nanosecond Spin Transfer Switching for MgO-Based Magnetic Tunnel Junctions 査読有り

    Tatsuya Aoki, Yasuo Ando, Mikihiko Oogane, Hiroshi Naganuma

    Applied Physics Express 3 (5) 53002-053002-3 2010年

    出版者・発行元:Japan Society of Applied Physics

    DOI: 10.1143/APEX.3.053002  

    ISSN:1882-0778

    詳細を見る 詳細を閉じる

    We report for the first time that the dynamic magnetic intermediate state (DMI) was observed at a speed of several ns during spin transfer switching for MgO-based magnetic tunnel junctions (MTJs). The DMI was observed as slow resistance oscillation at the center of the parallel to anti-parallel state by single shot time domain measurements. The DMI is observable at certain current amplitudes. The outbreak probability decreases with further current increase. We concluded that the DMI originates from inhomogeneous magnetization behavior. On the other hand, previous single shot time domain measurements have shown only for single-domain-like magnetization behavior.

  220. Magnetization Dynamics in CoFeB Buffered Perpendicularly Magnetized Co/Pd Multilayer 査読有り

    Sajitha, E.P, Walowski, J, Watanabe, D, Mizukami, S, Feng Wu, Naganuma, H, Oogane, M, Ando, Y, Miyazaki, T

    IEEE Transactions on Magnetics 2010年

    DOI: 10.1109/TMAG.2009.2038929  

  221. The Effect of Doping Concentration of Si on the Nature of Barrier of CoMnSi/MgO/n-Si Junctions 査読有り

    Nahid, M.A.I, Oogane, M, Naganuma, H, Ando, Y

    IEEE Transactions on Magnetics 2010年

    DOI: 10.1109/TMAG.2010.2043223  

  222. 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.

  223. High efficient spin transfer torque writing on perpendicular magnetic tunnel junctions for high density MRAMs 査読有り

    Hiroaki Yoda, Tatsuya Kishi, Toshihiko Nagase, Masatoshi Yoshikawa, Katsuya Nishiyama, Eiji Kitagawa, Tadaomi Daibou, Minoru Amano, Naoharu Shimomura, Shigeki Takahashi, Tadashi Kai, Masahiko Nakayama, Hisanori Aikawa, Sumio Ikegawa, Makoto Nagamine, Junichi Ozeki, Shigemi Mizukami, Mikihiko Oogane, Yasuo Ando, Shinji Yuasa, Kei Yakushiji, Hitoshi Kubota, Yoshishige Suzuki, Yoshinobu Nakatani, Terunobu Miyazaki, Koji Ando

    CURRENT APPLIED PHYSICS 10 (1) E87-E89 2010年1月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/j.cap.2009.12.021  

    ISSN:1567-1739

    eISSN:1878-1675

    詳細を見る 詳細を閉じる

    An Fe-based perpendicular alloy with small damping constant was applied to an MTJ storage layer and small switching current of 9 mu A was obtained for a write current width of 5 ms. The efficiency of spin transfer torque writing was proved to be higher than those for in-plane MTJs. The estimated Ic for the MTJ with 50 nsec pulse width is lower than 20 mu A and smaller than the drive currents of CMOS transistor at Gbits density. (C) 2010 Elsevier B.V. All rights reserved.

  224. Electrical transport properties of perpendicular magnetized Mn-Ga epitaxial films 査読有り

    Feng Wu, E. P. Sajitha, Shigemi Mizukami, Daisuke Watanabe, Terunobu Miyazaki, Hiroshi Naganuma, Mikihiko Oogane, Yasuo Ando

    APPLIED PHYSICS LETTERS 96 (4) 042505-1-042505-3 2010年1月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.3298363  

    ISSN:0003-6951

    eISSN:1077-3118

    詳細を見る 詳細を閉じる

    We report electrical transport properties of perpendicular magnetized Mn-Ga epitaxial films with various thicknesses. The maximum extraordinary Hall resistivity and Hall angle is 11.5 mu cm and 5.7%, respectively, which is comparable to the highest value reported in amorphous Fe0.79Gd0.21 alloy. In the low temperature region, resistivity was proportional to T-2.9 owing to the unconventional one-magnon scattering processes, indicating high spin polarization of this material.

  225. Ultrafast Demagnetization for Ni80Fe20 and Half-metallic Co2MnSi Heusler Alloy Films 査読有り

    S. Mizukami, S. Tunegi, T. Kubota, M. Oogane, D. Watanabe, H. Naganuma, Y. Ando, T. Miyazaki

    INTERNATIONAL CONFERENCE ON MAGNETISM (ICM 2009) 200 042017-1-042017-4 2010年

    出版者・発行元:IOP PUBLISHING LTD

    DOI: 10.1088/1742-6596/200/4/042017  

    ISSN:1742-6588

    詳細を見る 詳細を閉じる

    We investigated ultrafast demagnetization for NM/Ni80Fe20 (Py)/NM (NM=Ta,Pt) and epitaxial half-metallic Co2MnSi (CMS) films using an all-optical pump-probe technique to clarify the correlation between demagnetization time tau(M) and magnetic damping constant alpha or spin polarization. The signal from the all-optical time-resolved magneto-optical Kerr effect exhibited rapid decrease in the sub-ps time regime and damped oscillations for these films. Values of tau(M) and alpha were evaluated using the three-temperature model and the Landau-Lifshitz-Gilbert equation. The alpha values for the NM/Py/NM films depended on both the Py thickness and NM materials while tau M was almost constant. The tau(M) values for the epitaxial CMS films were almost independent of L2(1)-ordering and a little shorter than those for NM/Py/NM films.

  226. Structural, Magnetic, and Magnetotransport Properties of FePt/MgO/CoPt Perpendicularly Magnetized Tunnel Junctions 査読有り

    N. Inami, G. Kim, T. Hiratsuka, H. Naganuma, M. Oogane, Y. Ando

    INTERNATIONAL CONFERENCE ON MAGNETISM (ICM 2009) 200 052008-1-052008-4 2010年

    出版者・発行元:IOP PUBLISHING LTD

    DOI: 10.1088/1742-6596/200/5/052008  

    ISSN:1742-6588

    詳細を見る 詳細を閉じる

    Perpendicularly magnetized magnetic tunnel junctions (MTJs) were fabricated by depositing thin L1(0)-ordered FePt films on MgO(001) substrates using a UHV sputtering system, and the dependence of structural, magnetic, magnetotransport properties of the junctions on the thickness of the FePt layers was investigated. A full epitaxial structure was observed when the thickness of the L1(0)-ordered FePt film was 4 nm. The tunnel magnetoresistance (TMR) ratio was measured to be 6% at room temperature, and magnetization switching was clearly observed in the thin FePt layer.

  227. Magnetotransport properties of CoFeB/MgO/CoFe/MgO/CoFeB double barrier magnetic tunnel junctions with large negative magnetoresistance at room temperature 査読有り

    L. X. Jiang, H. Naganuma, M. Oogane, K. Fujiwara, T. Miyazaki, K. Sato, T. J. Konno, S. Mizukami, Y. Ando

    INTERNATIONAL CONFERENCE ON MAGNETISM (ICM 2009) 200 052009-1-052009-4 2010年

    出版者・発行元:IOP PUBLISHING LTD

    DOI: 10.1088/1742-6596/200/5/052009  

    ISSN:1742-6588

    詳細を見る 詳細を閉じる

    CoFeB/MgO/CoFe/MgO/CoFeB double-barrier magnetic-tunnel junctions were fabricated using an ultrahigh vacuum magnetron sputtering system, and their magnetotransport properties were characterized at room temperature. After post-deposition annealing, the polarity of TMR changed from negative to positive with increasing bias voltage. A relatively high negative TMR ratio of 30% was obtained at a negative bias voltage. Furthermore, a unique bias voltage dependence of conductance was observed at room temperature. This behavior may be attributable to the large minority density of states caused by the interfacial oxidation of the middle CoFe layer.

  228. Magnetoresistance of Perpendicularly Magnetized Tunnel Junction Using L1(0)-CoNiPt with Low Saturation Magnetization 査読有り

    G. Kim, T. Hiratsuka, H. Naganuma, M. Oogane, Y. Ando

    INTERNATIONAL CONFERENCE ON MAGNETISM (ICM 2009) 200 052011-1-052011-4 2010年

    出版者・発行元:IOP PUBLISHING LTD

    DOI: 10.1088/1742-6596/200/5/052011  

    ISSN:1742-6588

    詳細を見る 詳細を閉じる

    Investigations of the structural and magnetic properties of thin Co(50-x)Ni(x)Pt(50) (x = 0, 10, 15, 37.5) films and fabrication of magnetic tunnel junctions (MTJs) using Co(50)Pt(50) and Co(35)Ni(15)Pt(50) electrodes were performed. X-ray diffraction analyses revealed that 20-nm-thick CoPt and CoNiPt films were epitaxially grown with (001)-orientation with an L1(0)-chemical order parameter of 0.66-0.82. CoNiPt with various Ni contents magnetized perpendicularly; the saturation magnetization reduced to 157 emu/cm(3) when the Ni content was increased to 37.5%. Magnetotransport measurements under a magnetic field applied perpendicular to the film plane revealed a tunnel magnetoresistance ratio of 10% and 1% at 10 K and 300 K, respectively, for MTJ using Co(35)Ni(15)Pt(50) electrodes.

  229. Structural and magnetic properties of Mn(2.5)Ga films 査読有り

    F. Wu, S. Mizukami, D. Watanabe, H. Naganuma, M. Oogane, Y. Ando, T. Miyazaki

    INTERNATIONAL CONFERENCE ON MAGNETISM (ICM 2009) 200 062037-1-062037-4 2010年

    出版者・発行元:IOP PUBLISHING LTD

    DOI: 10.1088/1742-6596/200/6/062037  

    ISSN:1742-6588

    詳細を見る 詳細を閉じる

    In this work polycrystalline and epitaxial Mn(2.5)Ga films were prepared by dc magnetron sputtering technique. The lower sputtering power and higher annealing temperature are found to be beneficial for increasing ratio of DO(22) phase in the polycrystalline Mn2.5Ga films, leading to the improved magnetic properties although perpendicular magnetic anisotropy (PMA) properties cannot be observed. On the contrary, (001)-oriented epitaxial Mn(2.5)Ga films grown on Cr buffered MgO substrates possess low saturation magnetization and giant PMA properties simultaneously.

  230. Interlayer exchange coupling in perpendicularly magnetized synthetic ferrimagnet structure using CoCrPt and CoFeB 査読有り

    D. Watanabe, S. Mizukami, F. Wu, M. Oogane, H. Naganuma, Y. Ando, T. Miyazaki

    INTERNATIONAL CONFERENCE ON MAGNETISM (ICM 2009) 200 072104-1-072104-4 2010年

    出版者・発行元:IOP PUBLISHING LTD

    DOI: 10.1088/1742-6596/200/7/072104  

    ISSN:1742-6588

    詳細を見る 詳細を閉じる

    Interlayer exchange coupling in synthetic ferrimagnet structures consisting of perpendicularly magnetized CoCrPt and in-plane magnetized CoFeB layers, which are coupled by a Ru thin spacer, were investigated. The magnetization of the CoFeB layer turned perpendicular to the film plane after annealing at 300 degrees C because of the appearance of interlayer coupling from the CoCrPt layer. The coupling varied between antiferromagnetic and ferromagnetic depending on the Ru spacer thickness. The sign and strength of the coupling were also observed through analyses of magnetization curves and ferromagnetic resonance spectra.

  231. Structure, exchange stiffness, and magnetic anisotropy of Co<SUB>2</SUB>MnAl<SUB>x</SUB>Si<SUB>1−x</SUB> Heusler compounds 査読有り

    Takahide Kubota, Jaroslav Hamrle, Yuya Sakuraba, Oksana Gaier, Mikihiko Oogane, Akimasa Sakuma, Burkard Hillebrands, Koki Takanashi, Yasuo Ando

    J. Appl. Phys. 106 (11) 113907-1-113907-4 2009年12月

    出版者・発行元:None

    DOI: 10.1063/1.3265428  

    ISSN:0021-8979

    eISSN:1089-7550

  232. Ferrimagnetism in epitaxially grown Mn<SUB>2</SUB>VAl Heusler alloy investigatedby means of soft x-ray magnetic circular dichroism 査読有り

    T.Kubota, K. Kodama, T. Nakamura, Y. Sakuraba, M. Oogane, K. Takanashi, Y. Ando

    Appl. Phys. Lett. 95 (22) 222503-1-222503-3 2009年11月30日

    DOI: 10.1063/1.3269609  

    ISSN:0003-6951

  233. Tunnel magnetoresistance in epitaxially grown magnetic tunnel junctions using Heusler alloy electrode and MgO barrier 査読有り

    S. Tsunegi, Y. Sakuraba, M. Oogane, N. D. Telling, L. R. Shelford, E. Arenholz, G. van der Laan, R. J. Hicken, K. Takanashi, Y. Ando

    JOURNAL OF PHYSICS D-APPLIED PHYSICS 42 (19) 195004-1-195004-6 2009年10月

    出版者・発行元:IOP PUBLISHING LTD

    DOI: 10.1088/0022-3727/42/19/195004  

    ISSN:0022-3727

    eISSN:1361-6463

    詳細を見る 詳細を閉じる

    Epitaxially grown magnetic tunnel junctions (MTJs) with a stacking structure of Co2MnSi/MgO/CoFe were fabricated. Their tunnel magnetoresistance (TMR) effects were investigated. The TMR ratio and tunnelling conductance characteristics of MTJs were considerably different between those with an MgO barrier prepared using sputtering (SP-MTJ) and those prepared using EB evaporation (EB-MTJ). The EB-MTJ exhibited a very large TMR ratio of 217% at room temperature and 753% at 2K. The bias voltage dependence of the tunnelling conductance in the parallel magnetic configuration for the EB-MTJ suggests that the observed large TMR ratio at RT results from the coherent tunnelling process through the crystalline MgO barrier. The tunnelling conductance in the anti-parallel magnetic configuration suggests that the large temperature dependence of the TMR ratio results from the inelastic spin-flip tunnelling process.

  234. Study of Structure, Magnetic and Electrical Properties of Co2MnSi Heusler Alloy Thin Films Onto n-Si Substrates 査読有り

    M. A. I. Nahid, Mikihiko Oogane, Hiroshi Naganuma, Yasuo Ando

    IEEE TRANSACTIONS ON MAGNETICS 45 (10) 4030-4032 2009年10月

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

    DOI: 10.1109/TMAG.2009.2024320  

    ISSN:0018-9464

    eISSN:1941-0069

    詳細を見る 詳細を閉じる

    The structural, magnetic and electrical properties of Co2MnSi thin films grown onto n-doped Si(110) and n-Si(100) substrates were studied. The structure and magnetic properties of Co2MnSi thin films were found to depend strongly on the annealing temperature (T-A). At T-A = 275-350 degrees C, the Co2MnSi films were of B2 phase with &lt; 100 &gt; texture and possessed magnetic moment on both substrates. The saturation magnetization (M-S) of Co2MnSi thin films was found maximum at T-A = 300 degrees C. Chemical reaction might occur between Co2MnSi and Si above T-A = 350 degrees C which caused nearly zero M-S value. The current-voltage (I-V) characteristic of the Co2MnSi thin films onto n-Si substrates was obtained linear suggesting the contacts were ohmic nature.

  235. Silica coating of Co–Pt alloy nanoparticles prepared in the presence of poly(vinylpyrrolidone) 査読有り

    Yoshio Kobayashi, Hidekazu Kakinuma, Daisuke Nagao, Yasuo Ando, Terunobu Miyazaki, Mikio Konno

    J Nanopart Res. 11 (7) 1787-1794 2009年10月

    出版者・発行元:None

    DOI: 10.1007/s11051-009-9617-y  

    ISSN:1388-0764

  236. Direct Observation of Atomic Ordering and Interface Structure in Co2MnSi/MgO/Co2MnSi Magnetic Tunnel Junctions by High-Angle Annular Dark-Field Scanning Transmission Electron Microscopy 査読有り

    Toyoo Miyajima, Mikihiko Oogane, Yasutoshi Kotaka, Takashi Yamazaki, Mineharu Tsukada, Yuji Kataoka, Hiroshi Naganuma, Yasuo Ando

    APPLIED PHYSICS EXPRESS 2 (9) 093001-1-093001-3 2009年9月

    出版者・発行元:IOP PUBLISHING LTD

    DOI: 10.1143/APEX.2.093001  

    ISSN:1882-0778

    eISSN:1882-0786

    詳細を見る 詳細を閉じる

    The atomic ordering of Co2MnSi (CMS) full-Heusler film and the interface structure of CMS/MgO/CMS magnetic tunnel junctions (MTJs) were investigated by high-angle annular dark-field scanning transmission electron microscopy (HAADF STEM). We observed the atomic ordering of L2(1) and B2 structures of CMS from the atomic number (Z) contrast STEM images. We also confirmed that the interface structure consists of the layer next to the Co layer terminating in the CMS to MgO layer from the layer periodicity along the [001] direction, however, site-disorder exists between two atomic layers at the termination of CMS, including locally L2(1)-ordered MnSi terminated structure. (C) 2009 The Japan Society of Applied Physics

  237. Large Tunnel Magnetoresistance of 1056% at Room Temperature in MgO Based Double Barrier Magnetic Tunnel Junction (Retracted article. See vol. 4, artn no. 019201, 2011) 査読有り

    Lixian Jiang, Hiroshi Naganuma, Mikihiko Oogane, Yasuo Ando

    APPLIED PHYSICS EXPRESS 2 (8) 083002-1-083002-3 2009年8月

    出版者・発行元:IOP PUBLISHING LTD

    DOI: 10.1143/APEX.2.083002  

    ISSN:1882-0778

    eISSN:1882-0786

    詳細を見る 詳細を閉じる

    CoFeB/MgO/CoFeB/MgO/CoFeB double barrier magnetic tunnel junctions (DBMTJs) with thin middle layers were fabricated on SiO2/Si(001) substrates by r.f. magnetron sputtering. We successfully obtained a large tunnel magnetoresistance of 1056% at room temperature in a DBMTJ with a middle CoFeB layer thickness of 1.2 nm that was fabricated at a relatively low post-deposition annealing temperature of 350 degrees C. This DBMTJ also realized sharp magnetization switching in the free middle CoFeB layer, which is attributed to strong antiferromagnetic coupling between the exterior CoFeB and PtMn layers. These favorable magnetoresistive properties offer interesting possibilities for developing practical spintronics applications and noble magnetotransport physics. (C) 2009 The Japan Society of Applied Physics

  238. Enhancement in tunnel magnetoresistance effect by inserting CoFeB to the tunneling barrier interface in Co2MnSi/MgO/CoFe magnetic tunnel junctions 査読有り

    S. Tsunegi, Y. Sakuraba, M. Oogane, Hiroshi Naganuma, K. Takanashi, Y. Ando

    APPLIED PHYSICS LETTERS 94 (25) 252503-1-252503-3 2009年6月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.3156858  

    ISSN:0003-6951

    eISSN:1077-3118

    詳細を見る 詳細を閉じる

    Tunnel magnetoresistance (TMR) effect was investigated in Co2MnSi/CoFeB(0-2 nm)/MgO/CoFe magnetic tunnel junctions (MTJs). TMR ratio was enhanced by inserting a thin CoFeB layer at the Co2MnSi/MgO interface. The MTJ with CoFeB thickness of 0.5 nm exhibited the highest TMR ratio. From the conductance-voltage measurements for the fabricated MTJs, we infer that the highly spin polarized electron created in Co2MnSi can conserve the polarization through the 0.5-nm-thick CoFeB layer. Furthermore, by insertion of the thin CoFeB layer, the temperature dependence of the TMR ratio was improved because of the suppression of the fluctuation of the magnetic moment at the Co2MnSi/MgO interface.

  239. Structural, magnetic, and ferroelectric properties of multiferroic BiFeO3-based composite films with exchange bias 査読有り

    Hiroshi Naganuma, Tomosato Okubo, Sho Sekiguchi, Yasuo Ando, Soichiro Okamura

    JOURNAL OF APPLIED PHYSICS 105 (7) 07D903-1-07D903-3 2009年4月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.3055284  

    ISSN:0021-8979

    詳細を見る 詳細を閉じる

    BiFeO3-based composite films with excess iron content were fabricated, and the dependence of their magnetic and ferroelectric properties on the excess iron content was systematically investigated. Structural and magnetic analyses indicated that the specimens might be composed of large antiferromagnetic BiFeO3 grains and small ferromagnetic component. When the iron content was increased, saturation magnetization (M-s) increased and remanent polarization decreased. Antiferromagnetic coupling (H-ex) between the antiferromagnetic BiFeO3 grains and the ferromagnetic grains was observed at 10 K. It was revealed that grain growth is the key to increasing M-s and P-r and observing H-ex at room temperature in BiFeO3-based composite films. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3055284]

  240. Tunnel magnetoresistance effect in magnetic tunnel junctions using epitaxial Co2FeSi Heusler alloy electrode 査読有り

    Mikihiko Oogane, Masatsugu Shinano, Yuya Sakuraba, Yasuo Ando

    JOURNAL OF APPLIED PHYSICS 105 (7) 07C903-1-07C903-3 2009年4月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.3062814  

    ISSN:0021-8979

    eISSN:1089-7550

    詳細を見る 詳細を閉じる

    Magnetic tunnel junctions (MTJs) using epitaxially grown (100)-oriented and (110)-oriented Co2FeSi Heusler alloy bottom electrodes and amorphous Al-oxide barriers were fabricated. The tunnel magnetoresistance (TMR) ratios were 80% at 2 K and 48% at room temperature for the MTJ with the (100)-Co2FeSi bottom electrode. The MTJ with the (100)-Co2FeSi bottom electrode had a smaller TMR ratio than the MTJ with (100)-Co2FeSi electrode. The TMR ratio in MTJs with Co2FeSi electrode is smaller than that of a MTJ with Co2MnSi electrode. Tunnel conductance characteristics were investigated, revealing no half-metallic character in MTJs with Co2FeSi electrode in the conductance-voltage curves. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3062814]

  241. Fabrication of MgO-based magnetic tunnel junctions with CoCrPt perpendicularly magnetized electrodes 査読有り

    Daisuke Watanabe, Shigemi Mizukami, Mikihiko Oogane, Hiroshi Naganuma, Yasuo Ando, Terunobu Miyazaki

    JOURNAL OF APPLIED PHYSICS 105 (7) 07C911-1-07C911-3 2009年4月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.3062816  

    ISSN:0021-8979

    詳細を見る 詳細を閉じる

    The applicability of perpendicularly magnetized CoCrPt films to the MgO-based magnetic tunnel junctions (MTJs) was investigated. For this study, CoCrPt films deposited on the Ru buffer exhibited hcp(0002)-oriented growth by sputtering method using the low substrate temperature of 250 degrees C, low saturation magnetization of around 360 emu/cm(3), and high magnetic anisotropy field of 6 kOe, which is sufficient to retain the thermal stability of the magnetization direction. The MgO-based MTJs with a synthetic ferrimagnetlike structure were fabricated: CoFe was coupled magnetically with CoCrPt through the thin Ru layer. Transport properties with a magnetic field applied perpendicular to the film plane revealed a tunnel magnetoresistance ratio of about 6% at room temperature. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3062816]

  242. Tunnel magnetoresistance effect in double magnetic tunnel junctions using half-metallic Heusler alloy electrodes 査読有り

    Yusuke Ohdaira, Mikihiko Oogane, Yasuo Ando

    JOURNAL OF APPLIED PHYSICS 105 (7) 07C920-1-07C920-3 2009年4月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.3072023  

    ISSN:0021-8979

    eISSN:1089-7550

    詳細を見る 詳細を閉じる

    Double magnetic tunnel junctions (DMTJs) using half-metallic Co2MnSi Heusler alloy electrodes were fabricated. Their tunnel magnetoresistance (TMR) effects were then investigated. Large TMR ratios were observed as 25% at room temperature and as 320% at 6 K. The bias voltage dependence of tunnel conductance suggests a half-metallic nature of the Co2MnSi electrode. These results show that high-quality DMTJ with half-metallic Heusler alloy electrodes was fabricated and that the DMTJ exhibited the expected performance. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3072023]

  243. Reduction in switching current using a low-saturation magnetization Co-Fe-(Cr, V)-B free layer in MgO-based magnetic tunnel junctions 査読有り

    Hitoshi Kubota, Akio Fukushima, Kay Yakushiji, Satoshi Yakata, Shinji Yuasa, Koji Ando, Mikihiko Ogane, Yasuo Ando, Terunobu Miyazaki

    JOURNAL OF APPLIED PHYSICS 105 (7) 07D117-1-07D117-3 2009年4月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.3068484  

    ISSN:0021-8979

    eISSN:1089-7550

    詳細を見る 詳細を閉じる

    Magnetic properties, magnetoresistance (MR), and spin-transfer switching of magnetic tunnel junctions having a structure of Co60Fe20B20 3 nm/MgO 1 nm/(Co75Fe25)(80-X)Cr(V)(X)B-20 2 nm (X=0-25) were investigated. Magnetization of the (Co-Fe)-(Cr, V)-B free layer decreased from 1.2 T before substitution to 0.6 T at Cr of 10% (0.8 T at V of 10%). The MR ratio and a resistance-area product (RA) before substitution were, respectively, about 130% and about 2 Omega mu m(2). The MR ratio decreased to 80% at Cr of 10% and 40% at V of 10%. The RA values were almost independent of the composition. The intrinsic switching current density (J(c0)) decreased from 15 to 8 MA/cm(2) at Cr of 10% and 12 MA/cm(2) for V of 10%. Upon the further increase in Cr and V, stable switching was difficult to observe. In summary, J(c0) decreased to half in the case of Cr, but the effect was small for V. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3068484]

  244. Low damping constant for Co2FeAl Heusler alloy films and its correlation with density of states 査読有り

    S. Mizukami, D. Watanabe, M. Oogane, Y. Ando, Y. Miura, M. Shirai, T. Miyazaki

    JOURNAL OF APPLIED PHYSICS 105 (7) 07D306-1-07D306-3 2009年4月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.3067607  

    ISSN:0021-8979

    詳細を見る 詳細を閉じる

    Gilbert damping for the epitaxial Co2FeAl Heusler alloy films was investigated. Gilbert damping constant for the films was evaluated by analyzing the data of ferromagnetic resonance measured at the frequency of 2-20 GHz. Gilbert damping constant for the film without annealing was rather large, while it decreased remarkably with postannealing. Gilbert damping constant for the film annealed at 600 degrees C was similar or equal to 0.001. These behavior of Gilbert damping constant can be well explained by the fact that the density of states calculated from first principles decreases with increasing the degree of B2 order. (c) 2009 American Institute of Physics. [DOI: 10.1063/1.3067607]

  245. Electronic properties of Co2MnSi thin films studied by hard x-ray photoelectron spectroscopy 査読有り

    Siham Ouardi, Andrei Gloskovskii, Benjamin Balke, Catherine A. Jenkins, Joachim Barth, Gerhard H. Fecher, Claudia Felser, Mihaela Gorgoi, Marcel Mertin, Franz Schaefers, Eiji Ikenaga, Ke Yang, Keisuke Kobayashi, Takahide Kubota, Mikihiko Oogane, Yasuo Ando

    JOURNAL OF PHYSICS D-APPLIED PHYSICS 42 (8) 084011-1-084011-8 2009年4月

    出版者・発行元:IOP PUBLISHING LTD

    DOI: 10.1088/0022-3727/42/8/084011  

    ISSN:0022-3727

    詳細を見る 詳細を閉じる

    This work reports on the electronic properties of thin films of the Heusler compound Co2MnSi studied by means of hard x-ray photoelectron spectroscopy (HAXPES). The results of photoelectron spectroscopy from multilayered thin films excited by photons of 2-8 keV are presented. The measurements were performed on (substrate/buffer layer/Co2MnSi(z)/capping layer) multilayers with a thickness z ranging from 0 to 50 nm. It is shown that high energy spectroscopy is a valuable tool for non-destructive depth profiling. The experimentally determined values of the inelastic electron mean free path in Co2MnSi increase from about 19.5 to 67 angstrom on increasing the kinetic energy from about 1.9 to 6.8 keV. The influence of the thermal treatment of Co2MnSi thin films on the electronic properties was also explored. The structure of the thin films is significantly improved by heat treatment as revealed by x-ray diffraction. It was found that the electronic structure of annealed samples as measured by photoelectron spectroscopy is similar to that of a well-ordered bulk reference sample. The samples without heat treatment show strong deviations from the electronic structure of bulk material. The differences between the disordered and the ordered films are also observed in core level spectra. Chemical shifts of about 100 meV are observed at the Mn 2p states. The stronger localization of the Mn d states in the ordered samples is obvious from the multiplet satellite of the Mn 2p(3/2) state.

  246. Determination of exchange constants of Heusler compounds by Brillouin light scattering spectroscopy: application to Co2MnSi 査読有り

    J. Hamrle, O. Gaier, Seong-Gi Min, B. Hillebrands, Y. Sakuraba, Y. Ando

    JOURNAL OF PHYSICS D-APPLIED PHYSICS 42 (8) 084005-1-084005-6 2009年4月

    出版者・発行元:IOP PUBLISHING LTD

    DOI: 10.1088/0022-3727/42/8/084005  

    ISSN:0022-3727

    詳細を見る 詳細を閉じる

    Brillouin light scattering spectroscopy from so-called standing spin waves in thin magnetic films is often used to determine the magnetic exchange constant. The data analysis of the experimentally determined spin-wave modes requires an unambiguous assignment to the correct spin-wave mode orders. Often additional investigations are needed to guarantee correct assignment. This is particularly important in the case of Heusler compounds where values of the exchange constant vary substantially between different compounds. As a showcase, we report on the determination of the exchange constant (exchange stiffness constant) in Co2MnSi, which is found to be A = 2.35 +/- 0.1 mu erg cm(-1) (D = 575 +/- 20 meV angstrom(2)), a value comparable to the value of the exchange constant of Co.

  247. Improvement of structural, electronic, and magnetic properties of Co2MnSi thin films by He+ irradiation 査読有り

    O. Gaier, J. Hamrle, B. Hillebrands, M. Kallmayer, P. Poersch, G. Schoenhense, H. J. Elmers, J. Fassbender, A. Gloskovskii, C. A. Jenkins, C. Felser, E. Ikenaga, Y. Sakuraba, S. Tsunegi, M. Oogane, Y. Ando

    APPLIED PHYSICS LETTERS 94 (15) 152508-1-152508-3 2009年4月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.3119188  

    ISSN:0003-6951

    eISSN:1077-3118

    詳細を見る 詳細を閉じる

    The influence of 30 keV He+ ion irradiation on structural, electronic, and magnetic properties of Co2MnSi thin films with a partial B2 order was investigated. It was found that room temperature irradiation with light ions can improve the local chemical order. This provokes changes of the electronic structure and element-specific magnetization toward the bulk properties of a well-ordered Co2MnSi Heusler compound.

  248. Half-metallicity and Gilbert damping constant in Co<SUB>2</SUB>Fe<SUB>x</SUB>Mn<SUB>1−x</SUB>Si Heusler alloys depending on the film composition 査読有り

    Takahide Kubota, Sumito Tsunegi, Mikihiko Oogane, Shigemi Mizukami, Terunobu Miyazaki, Hiroshi Naganuma, Yasuo Ando

    Appl. Phys. Lett., 94 (12) 122504-1-122504-3 2009年3月

    出版者・発行元:None

    DOI: 10.1063/1.3105982  

    ISSN:0003-6951

    eISSN:1077-3118

  249. Large voltage-induced magnetic anisotropy change in a few atomic layers of iron 査読有り

    T. Maruyama, Y. Shiota, T. Nozaki, K. Ohta, N. Toda, M. Mizuguchi, A. A. Tulapurkar, T. Shinjo, M. Shiraishi, S. Mizukami, Y. Ando, Y. Suzuki

    NATURE NANOTECHNOLOGY 4 (3) 158-161 2009年3月

    出版者・発行元:NATURE PUBLISHING GROUP

    DOI: 10.1038/NNANO.2008.406  

    ISSN:1748-3387

    詳細を見る 詳細を閉じる

    In the field of spintronics, researchers have manipulated magnetization using spin-polarized currents(1-3). Another option is to use a voltage-induced symmetry change in a ferromagnetic material to cause changes in magnetization or in magnetic anisotropy(4-14). However, a significant improvement in efficiency is needed before this approach can be used in memory devices with ultralow power consumption. Here, we show that a relatively small electric field (less than 100 mV nm(-1)) can cause a large change (similar to 40%) in the magnetic anisotropy of a bcc Fe(001)/MgO(001) junction. The effect is tentatively attributed to the change in the relative occupation of 3d orbitals of Fe atoms adjacent to the MgO barrier. Simulations confirm that voltage-controlled magnetization switching in magnetic tunnel junctions is possible using the anisotropy change demonstrated here, which could be of use in the development of low-power logic devices and non-volatile memory cells.

  250. Epitaxial Mn2.5Ga thin films with giant perpendicular magnetic anisotropy for spintronic devices 査読有り

    Feng Wu, Shigemi Mizukami, Daisuke Watanabe, Hiroshi Naganuma, Mikihiko Oogane, Yasuo Ando, Terunobu Miyazaki

    APPLIED PHYSICS LETTERS 94 (12) 122503-1-122503-3 2009年3月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.3108085  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    We report on epitaxial growth and magnetic properties of Mn2.5Ga thin films, which were deposited on Cr/MgO single crystal substrates by magnetron sputtering. X-ray diffraction results revealed the epitaxial relationships as Mn2.5Ga(001)[100]parallel to Cr(001)[110]parallel to MgO(001)[100]. The presence of (002) and (011) superlattice peaks indicates that the films were crystallized into DO22 ordered structures. The perpendicular magnetic anisotropy (PMA) properties were found to be related to the extent of DO22 chemical ordering. A giant PMA (K-u(eff)=1.2x10(7) erg/cm(3)) and low saturation magnetization (M-s=250 emu/cm(3)) can be obtained for the film with highest chemical ordering parameter (S=0.8).

  251. Structural and Magnetic Properties of Co2MnSi Heusler Alloy Thin Films on Si 査読有り

    M. Ariful Nahid, M. Oogane, H. Naganuma, Y. Ando

    Jpn. J. Appl. Phys. 48 (8) 83002-083002-3 2009年

    出版者・発行元:Published by the Japan Society of Applied Physics through the Institute of Pure and Applied Physics

    DOI: 10.1143/JJAP.48.083002  

    ISSN:0021-4922

    詳細を見る 詳細を閉じる

    The structural and magnetic properties of Co2MnSi thin films grown on n-doped Si(110) and Si(100) substrates were studied and observed to have a strong dependence on annealing temperature ($T_{\text{A } }$). At $T_{\text{A } }=275--350$ °C, the Co2MnSi films exhibited the B2 phase with a $\langle 100\rangle$ orientation and a magnetic moment on both substrates. The saturation magnetization ($M_{\text{S } }$) of Co2MnSi thin films was observed to reach a maximum at $T_{\text{A } }=300$ °C, above which it was found to decrease. We consider that at $T_{\text{A } }\simeq 300$ °C, the Co2MnSi thin films on Si substrates exhibited the $\langle 100\rangle$ orientation, a high $M_{\text{S } }$ and a low roughness which might promote spin injection.

  252. The effect of MgO barrier on the structure and magnetic properties of Co2MnSi films on n-Si(100) substrates 査読有り

    M. A. I. Nahid, M. Oogane, H. Naganuma, Y. Ando

    J. Appl. Phys. 2009年

    DOI: 10.1063/1.3260253  

  253. Boron Composition Dependence of Spin-Transfer Switching in Magnetic Tunnel Junctions with CoFeB Free Layers 査読有り

    Daisuke Watanabe, Mikihiko Oogane, Shigemi Mizukami, Yasuo Ando, Terunobu Miyazaki

    JAPANESE JOURNAL OF APPLIED PHYSICS 48 (1) 013001-1-013001-4 2009年1月

    出版者・発行元:IOP PUBLISHING LTD

    DOI: 10.1143/JJAP.48.013001  

    ISSN:0021-4922

    eISSN:1347-4065

    詳細を見る 詳細を閉じる

    We investigated tunnel magnetoresistance (TMR) and magnetization switching due to spin-transfer torque in CoFeB/MgO/CoFeB junctions having three different free layer compositions, (Co50Fe50)(100-x)B-x (x = 20, 25, 30), and measured their magnetic properties, including magnetization (M-s) and Gilbert damping constant (alpha), which are theoretically predicted to contribute to the critical current density (J(c0)) for spin-transfer switching. We found that the J(c0) in the magnetic tunnel junctions (MTJs) with x = 30 became smaller than that in the MTJs with x = 20 despite having a lower TMR ratio and a larger alpha. We showed that the J(c0) for each composition tends to follow the theoretical relationship for the magnetic factor of the tree layer. (c) 2009 The Japan Society of Applied Physics

  254. Co置換Biフェライト薄膜の室温での強誘電性および磁気特性 査読有り

    永沼 博, 三浦 淳, 神島 謙二, 柿崎 浩一, 平塚 信之, 安藤 康夫, 岡村 総一郎

    日本磁気学会誌 33 (3) 237-241 2009年

    出版者・発行元:The Magnetics Society of Japan

    DOI: 10.3379/msjmag.0903RC8081  

    ISSN:1882-2924

    詳細を見る 詳細を閉じる

    Co substituted BiFeO<sub>3</sub> polycrystalline films were fabricated on Pt/Ti/SiO<sub>2</sub>/Si(100) substrates by a chemical solution deposition method that was followed by post-deposition annealing between 673 and 1073 K. The substitution of cobalt at <i>B</i>-sites for iron in BiFeO<sub>3</sub> was promoted at relatively high temperatures, and saturated at around 923 K. The leakage current density was suppressed by substituting Co; therefore, ferroelectricity could be observed at room temperature. The remanent polarization increased by substituting Co due to the reduced electric coercive field. The saturation magnetization increased by promoting Co substitution, and a magnetic coercive field of 1.5 kOe and remanent magnetization of 3 emu/cm<sup>3</sup> were obtained by annealing at 923 K. This indicated that Co substituted BiFeO<sub>3</sub> films are candidate materials that enable ferromagnetism and ferroelectricity to coexist above room temperature.

  255. Co<SUB>2</SUB>MnSiを電極とする微小二重トンネル接合の作製と評価 査読有り

    大平 祐介, 大兼 幹彦, 安藤 康夫

    日本磁気学会誌 33 (3) 262-265 2009年

    出版者・発行元:The Magnetics Society of Japan

    DOI: 10.3379/msjmag.0903RE8052  

    ISSN:1882-2924

    詳細を見る 詳細を閉じる

    Double magnetic tunnel junctions (DMTJs) using half-metallic Heusler alloy Co<sub>2</sub>MnSi electrodes were fabricated. A tunnel magneto-resistance ratio as large as 25% (at RT) and 320% (at 6 K) was observed in the DMTJs with various junction areas. The dependence of the tunnel magneto-resistance on bias voltage was a typical characteristic of DMTJs. These results indicate that high-quality DMTJs were stably fabricated.

  256. 高アニール耐性・高反平行結合強度を有する積層フェリ構造の開発 査読有り

    西村 真之, 渡邉 大輔, 大兼 幹彦, 安藤 康夫

    日本磁気学会誌 33 (3) 266-269 2009年

    出版者・発行元:The Magnetics Society of Japan

    DOI: 10.3379/msjmag.0903RE8054  

    ISSN:1882-2924

    詳細を見る 詳細を閉じる

    We investigated the dependencies of the saturation field, <i>H</i><sub>s</sub>, for synthetic ferrimagnetic (SyF) structures with various stacking structures on annealing temperature and Ru middle layer thickness. The buffer layer was optimized using Co<sub>75</sub>Fe<sub>25</sub>/Ru/Co<sub>75</sub>Fe<sub>25</sub>-SyF. The SyF on the Ta/Ru buffer layer demonstrated high annealing stability and large <i>H</i><sub>s</sub>. Moreover, we investigated the dependence on annealing temperature of <i>H</i><sub>s</sub> for Ta(5 nm)/Ru(5 nm)/ ferromagnetic-layer/Ru(0.8 nm)/Co<sub>40</sub>Fe<sub>40</sub>B<sub>20</sub>(2 nm) SyFs with various ferromagnetic layers. The SyFs using Co<sub>75</sub> Fe<sub>25</sub> and Ni<sub>80</sub>Fe<sub>20</sub> ferromagnetic layers exhibited high annealing stability and large <i>H</i><sub>s</sub>. The dependence on Ru middle layer thickness of <i>H</i><sub>s</sub> for the SyFs consisting of Ta(5 nm)/Ru(5 nm)/Co<sub>75</sub> Fe<sub>25</sub>(2 nm)/Ru(0.2-1.2 nm)/Co<sub>40</sub>Fe<sub>40</sub>B<sub>20</sub>(2 nm)/ MgO(2.5 nm)/Ta(10 nm) was investigated. As a result, we demonstrated the possibility of fabricating CoFeB/MgO/ CoFeB MTJs with SyF having both high annealing stability and strong interlayer exchange coupling.

  257. Co<SUB>2</SUB>FeMnSiホイスラー合金の磁気緩和定数 査読有り

    大兼 幹彦, 窪田 崇秀, 廣瀬 直紀, 安藤 康夫

    日本磁気学会誌 33 (3) 270-273 2009年

    出版者・発行元:The Magnetics Society of Japan

    DOI: 10.3379/msjmag.0903RE8063  

    ISSN:1882-2924

    詳細を見る 詳細を閉じる

    Magnetic damping constants of Co<sub>2</sub>Fe<sub>x</sub>Mn<sub>1-x</sub>Si (x = 0.0 - 1.0) Heusler alloy thin films have been investigated. Co<sub>2</sub>Fe<sub>x</sub>Mn<sub>1-x</sub>Si thin films were epitaxitially grown on the single crystal MgO(100) substrate using magnetron sputtering technique. Damping constants were estimated by analyzing the line width of ferromagnetic resonance (FMR) spectra. Damping constant of Co<sub>2</sub>Fe<sub>x</sub>Mn<sub>1-x</sub>Si films showed a minimum value of 0.003 at x = 0.4. This damping constant is very small compared with other ferromagnetic metals. Additionally, damping constants significantly increased above x = 0.6. In this article, the relationship between the damping constant and the half-metallicity of Co<sub>2</sub>Fe<sub>x</sub>Mn<sub>1-x</sub>Si films is discussed.

  258. Gilbert Damping for Various Ni80Fe20 Thin Films Investigated Using All-Optical Pump-Probe Detection and Ferromagnetic Resonance 査読有り

    Shigemi Mizukami, Hiroyuki Abe, Daisuke Watanabe, Mikihiko Oogane, Yasuo Ando, Terunobu Miyazaki

    APPLIED PHYSICS EXPRESS 1 (12) 121301-1-121301-3 2008年12月

    出版者・発行元:JAPAN SOC APPLIED PHYSICS

    DOI: 10.1143/APEX.1.121301  

    ISSN:1882-0778

    詳細を見る 詳細を閉じる

    All-optical pump-probe detection of magnetization precession has been performed to investigate Gilbert damping in several types of Ni80Fe20 films. The frequency and decay time of magnetization precession depended on pump fluence. At low pump fluence, Gilbert damping constants, derived from the magnetic field dependence on frequency and decay time of magnetization precession, were identical to values obtained from X-band ferromagnetic resonance within the experimental errors. (C) 2008 The Japan Society of Applied Physics

  259. Evidence of local moment formation in Co-based Heusler alloys 査読有り

    N. D. Telling, P. S. Keatley, G. van der Laan, R. J. Hicken, E. Arenholz, Y. Sakuraba, M. Oogane, Y. Ando, K. Takanashi, A. Sakuma, T. Miyazaki

    PHYSICAL REVIEW B 78 (18) 184438-1-184438-7 2008年11月

    出版者・発行元:AMER PHYSICAL SOC

    DOI: 10.1103/PhysRevB.78.184438  

    ISSN:2469-9950

    eISSN:2469-9969

    詳細を見る 詳細を閉じる

    We examine the formation of local moments in Heusler alloys of the composition Co(2)MnZ (where Z=Si or Al) using the combined techniques of x-ray magnetic circular and linear dichroism. The existence of local moments in half-metallic Heusler alloys is reliant upon the band gap in the minority-spin states. By utilizing the element-specific nature of x-ray absorption techniques we are able to explore the degree of localization of moments on Co and Mn atoms. We observe a crucial difference in the localization of the Co moment when comparing Co2MnSi (CMS) and Co2MnAl films that is consistent with the predicted larger minority-spin gap in the Co partial density of states for CMS. These results provide important evidence for the dominant role of the Co minority-spin states in realizing half-metallic ferromagnetism in this system.

  260. Electrical conductance properties for magnetic tunnel junctions with MgO barriers 査読有り

    K. Tamanoi, M. Sato, M. Oogane, Y. Ando, T. Tanaka, Y. Uehara, T. Uzumaki

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 320 (22) 2959-2962 2008年11月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/j.jmmm.2008.08.004  

    ISSN:0304-8853

    詳細を見る 詳細を閉じる

    We measured inelastic electron tunneling (IET) spectra and conductance for MgO tunneling magnetoresistance (TMR) films to obtain information on the ferromagnetic/barrier layer interface. The IET spectra showed the difference between amorphous and crystalline structures in the barrier. In the magnetic tunnel junction (MTJ) with a crystalline barrier the IET spectra indicated an Mg-O phonon peak at a low bias voltage by measurement with a parallel magnetization configuration. On the other hand, no peak was observed in the MTJ with an amorphous barrier. (C) 2008 Elsevier B. V. All rights reserved.

  261. Penetration Depth of Transverse Spin Current in Ferromagnetic Metals 査読有り

    Tomohiro Taniguchi, Satoshi Yakata, Hiroshi Imamura, Yasuo Ando

    IEEE TRANSACTIONS ON MAGNETICS 44 (11) 2636-2639 2008年11月

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

    DOI: 10.1109/TMAG.2008.2003036  

    ISSN:0018-9464

    詳細を見る 詳細を閉じる

    The line width of the ferromagnetic resonance (FMR) spectrum of Cu/CoFeB/Cu/Co/Cu is studied. Analyzing the FMR spectrum by the theory of spin pumping, we determined the penetration depth of the transverse spin current in the Co layer. The obtained penetration depth of Co is 1.7 nm.

  262. Large tunnel magnetoresistance in magnetic tunnel junctions using a Co2MnSi Heusler alloy electrode and a MgO barrier 査読有り

    Sumito Tsunegi, Yuya Sakuraba, Mikihiko Oogane, Koki Takanashi, Yasuo Ando

    APPLIED PHYSICS LETTERS 93 (11) 112506-1-112506-3 2008年9月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.2987516  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    A large tunnel magnetoresistance (TMR) ratio of 753% has been observed at 2 K in a magnetic tunnel junction (MTJ) using a Co2MnSi Heusler alloy electrode and a crystalline MgO tunnel barrier. This TMR ratio is the largest reported to date in MTJs using a Heusler alloy electrode. Moreover, we have observed a large TMR ratio of 217% at room temperature (RT). This TMR at RT is much larger than that of MTJs using an amorphous Al-oxide tunnel barrier. However, the temperature dependence of the TMR ratio is still large because of inelastic tunneling in the antiparallel magnetic configuration. (C) 2008 American Institute of Physics.

  263. Annealing temperature dependences of ferroelectric and magnetic properties in polycrystalline Co-substituted BiFeO3 films 査読有り

    Hiroshi Naganuma, Jun Miura, Mitsumasa Nakajima, Hiromi Shima, Soichiro Okamura, Shintaro Yasui, Hiroshi Funakubo, Ken Nishida, Takashi Iijima, Masaki Azuma, Yasuo Ando, Kenji Kamishima, Koichi Kakizaki, Nobuyuki Hiratsuka

    JAPANESE JOURNAL OF APPLIED PHYSICS 47 (9) 7574-7578 2008年9月

    出版者・発行元:JAPAN SOC APPLIED PHYSICS

    DOI: 10.1143/JJAP.47.7574  

    ISSN:0021-4922

    eISSN:1347-4065

    詳細を見る 詳細を閉じる

    Multiferroic Co-substituted BiFeO3 films were fabricated by chemical solution deposition method followed by post deposition annealing at various temperatures. The substitution of Cobalt of B-sites for iron in BiFeO3 was promoted at relatively high temperatures. The B-site substitution by cobalt promoted increases in saturation magnetization and spontaneous magnetization By substitution. leakage Current density Was suppressed ill a high-electric-field region and ferroelectric hysteresis (P-E) loops became measurable even at room temperature. The optimal annealing temperature for the coexistence of a high remanent polarization and a high remanent magnetization was 923 K having a high B-site substitution ratio of cobalt.

  264. Temperature dependence of the interface moments in Co2MnSi thin films 査読有り

    N. D. Telling, P. S. Keatley, L. R. Shelford, E. Arenholz, G. van der Laan, R. J. Hicken, Y. Sakuraba, S. Tsunegi, M. Oogane, Y. Ando, K. Takanashi, T. Miyazaki

    APPLIED PHYSICS LETTERS 92 (19) 192503-1-192503-3 2008年5月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.2927482  

    ISSN:0003-6951

    eISSN:1077-3118

    詳細を見る 詳細を閉じる

    X-ray magnetic circular dichroism (XMCD) is utilized to explore the temperature dependence of the interface moments in Co2MnSi (CMS) thin films capped with aluminum. By increasing the thickness of the capping layer, we demonstrate enhanced interface sensitivity of the measurements. L2(1)-ordered CMS films show no significant temperature dependence of either the Co or Mn interface moments. However, disordered CMS films show a decreased moment at low temperature possibly caused by increased Mn-Mn antiferromagnetic coupling. It is suggested that for ordered L2(1) CMS films the temperature dependence of the tunneling magnetoresistance is not related to changes in the interface moments. (c) 2008 American Institute of Physics.

  265. Spin transfer switching in the nanosecond regime for CoFeB/MgO/CoFeB ferromagnetic tunnel junctions 査読有り

    Tatsuya Aoki, Yasuo Ando, Daisuke Watanabe, Mikihiko Oogane, Terunobu Miyazaki

    JOURNAL OF APPLIED PHYSICS 103 (10) 103911-1-103911-4 2008年5月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.2930873  

    ISSN:0021-8979

    詳細を見る 詳細を閉じる

    Detailed spin transfer switching properties in the nanosecond region for CoFeB/MgO(001)/CoFeB magnetic tunnel junctions are reported. The switching current (I(C)) was greatly increased in the &lt; 10 ns region. This characteristic resembles that of current-perpendicular-to-plane giant magnetoresistance (CPP-GMR), although both the junction geometry and resistance differ from those of a CPP-GMR device. We discussed the switching properties considering the contribution of high frequency loss and the theoretical limitation of the analytical model. Furthermore, we observed real-time switching in the nanosecond region. Using these results, we discuss the spin transfer switching mechanism in the nanosecond region with both adiabatic and thermally activated models. (C) 2008 American Institute of Physics.

  266. Influence of the L2(1) ordering degree on the magnetic properties of Co2MnSi Heusler films 査読有り

    O. Gaier, J. Hamrle, S. J. Hermsdoerfer, H. Schultheiss, B. Hillebrands, Y. Sakuraba, M. Oogane, Y. Ando

    JOURNAL OF APPLIED PHYSICS 103 (10) 103910-1-103910-3 2008年5月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.2931023  

    ISSN:0021-8979

    eISSN:1089-7550

    詳細を見る 詳細を閉じる

    We report on the influence of the improved L2(1) ordering degree on the magnetic properties of Co2MnSi Heusler films. Different fractions of the L2(1) phase are obtained by different postgrowth annealing temperatures ranging from 350 degrees C to 500 degrees C. Room temperature magneto-optical Kerr effect measurements reveal an increase of the coercivity at an intermediate annealing temperature of 425 degrees C. This is probably a result of an increasing number of pinning centers on the one hand and a drop of the cubic anisotropy constant K-1 by a factor of 10 on the other for an increasing amount of the L2(1) phase. Furthermore, Brillouin light scattering studies show that the improvement of the L2(1) order in the Co2MnSi films is correlated with a decrease of the saturation magnetization by about 7%. The exchange stiffness constant of Co2MnSi, however, increases by about 8% when the L2(1) order is improved. (C) 2008 American Institute of Physics.

  267. Tunneling magnetoresistance of magnetic tunnel junctions using perpendicular magnetization L1(0)-CoPt electrodes 査読有り

    Gukcheon Kim, Yuya Sakuraba, Mikihiko Oogane, Yasuo Ando, Terunobu Miyazaki

    APPLIED PHYSICS LETTERS 92 (17) 172502-1-172502-3 2008年4月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.2913163  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    Magnetic tunnel junctions (MTJs) using L1(0)-ordered CoPt electrodes with perpendicular magnetic anisotropy were fabricated. Full-epitaxial CoPt/MgO/CoPt-MTJs were prepared onto single crystal MgO-(001) substrate by sputtering method. X-ray diffraction analyses revealed that both bottom and top CoPt electrodes were epitaxially grown with (001)-orientation. The L1(0)-chemical order parameter of 0.82 was obtained for the bottom CoPt electrode deposited at substrate temperature of 600 degrees C. The transport measurements with applying magnetic field perpendicular to the film plane showed a tunnel magnetoresistance ratio of 6% at room temperature and 13% at 10 K. (C) 2008 American Institute of Physics.

  268. Magnetic second harmonic generation at the Co2MnSi/AlOx interface 査読有り

    L. R. Shelford, Y. Liu, R. J. Hicken, Y. Sakuraba, M. Oogane, Y. Ando

    JOURNAL OF APPLIED PHYSICS 103 (7) 07D720-1-07D720-3 2008年4月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.2841174  

    ISSN:0021-8979

    eISSN:1089-7550

    詳細を見る 詳細を閉じる

    We have studied magnetic second harmonic generation (MSHG) at the Co2MnSi/AlOx interface. The variation of the MSHG intensity was consistent with the nonvanishing components of the nonlinear susceptibility tensor expected for the (001) cubic surface. The difference in the MSHG asymmetry, the MSHG anisotropy, is found to have maximum value at an annealing temperature of 450 degrees C, for which similar samples have previously been found to show optimum L2(1) site ordering and maximum tunnel magnetoresistance. (C) 2008 American Institute of Physics.

  269. Determination of penetration depth of transverse spin current in ferromagnetic metals by spin pumping 査読有り

    Tomohiro Taniguchi, Satoshi Yakata, Hiroshi Imamura, Yasuo Ando

    APPLIED PHYSICS EXPRESS 1 (3) 031301-1-031301-3 2008年3月

    出版者・発行元:JAPAN SOC APPLIED PHYSICS

    DOI: 10.1143/APEX.1.031302  

    ISSN:1882-0778

    詳細を見る 詳細を閉じる

    Spin pumping in nonmagnetic/ferromagnetic metal multilayers is studied both theoretically and experimentally. We show that the line widths of the ferromagnetic resonance (FMR) spectrum depend on the thickness of the ferromagnetic metal layers, which must not be in resonance with the oscillating magnetic field. We also show that the penetration depths of the transverse spin current in ferromagnetic metals can be determined by analyzing the line widths of their FMR spectra. The obtained penetration depths in NiFe, CoFe, and CoFeB were 3.7, 2.5, and 12.0 nm, respectively. (C) 2008 The Japan Society of Applied Physics.

  270. Tunnel magnetoresistance effect in magnetic tunnel junctions using a Co2MnSi(110) electrode 査読有り

    Masashi Hattori, Yuya Sakuraba, Mikihiko Oogane, Yasuo Ando, Terunobu Miyazaki

    APPLIED PHYSICS EXPRESS 1 (2) 021301-1-021301-3 2008年2月

    出版者・発行元:IOP PUBLISHING LTD

    DOI: 10.1143/APEX.1.021301  

    ISSN:1882-0778

    eISSN:1882-0786

    詳細を見る 詳細を閉じる

    Magnetic tunnel junctions (MTJs) with half-metallic electrodes are expected to show a large tunnel magnetoresistance (TMR) ratio, according to Julliere's model. A Co2MnSi Heusler alloy is theoretically expected to possess a half-metallic electronic state. Experimentally, at low temperature, Co2MnSi(100)/Al-oxide/CoFe junctions exhibited a large TMR ratio. We fabricated MTJs with high-quality (110)oriented Co2MnSi electrodes and investigated the TMR effects. We obtained a TMR ratio of about 40% at room temperature and 120% at 2 K, respectively. However, we observed degradation of the energy gap Of Co2MnSi in the minority spin band from the conductance-voltage characteristics. We infer that the interface of Co2MnSi(110) possesses no half-metallic property. (c) 2008 The Japan Society of Applied Physics.

  271. Nonquasiparticle states in Co2MnSi evidenced through magnetic tunnel junction spectroscopy measurements 査読有り

    L. Chioncel, Y. Sakuraba, E. Arrigoni, M. I. Katsnelson, M. Oogane, Y. Ando, T. Miyazaki, E. Burzo, A. I. Lichtenstein

    PHYSICAL REVIEW LETTERS 100 (8) 086402-1-086402-4 2008年2月

    出版者・発行元:AMER PHYSICAL SOC

    DOI: 10.1103/PhysRevLett.100.086402  

    ISSN:0031-9007

    eISSN:1079-7114

    詳細を見る 詳細を閉じる

    We investigate the effects of electronic correlations in the full-Heusler Co2MnSi, by combining a theoretical analysis of the spin-resolved density of states with tunneling-conductance spectroscopy measurements using Co2MnSi as electrode. Both experimental and theoretical results confirm the existence of so-called nonquasiparticle states and their crucial contribution to the finite-temperature spin polarization in this material.

  272. スピントロニクスの形成と発展 招待有り 査読有り

    宮﨑照宣, 大兼幹彦, 桜庭裕弥, 渡邉大輔, R. Yilgin, 佐久間昭正, 安藤康夫, 久保田均

    粉体および粉末治金 55 (2) 109-115 2008年

    出版者・発行元:Japan Society of Powder and Powder Metallurgy

    DOI: 10.2497/jjspm.55.109  

    ISSN:0532-8799

    詳細を見る 詳細を閉じる

    History about the research of magnetoresistance effect was reviewed. Also, we looked back on the research trends in the past when both giant magnetoresistance of Fe/Cr multi layered films and large tunnel magnetoresistance at room temperature were found.<BR>Special emphasis was placed on the recent developments of huge TMR ratio for both MgO barrier tunnel junctions and Heusler alloy electrode tunnel junctions which contribute further to the development of spinelectronic research fields. Principle and importance of spin-transfer torque were also explained.

  273. CoFeB/MgO/CoFeB トンネル接合のナノ秒領域におけるスピン注入磁化反転と実時間観測 査読有り

    青木達也, 大兼幹彦, 宮崎照宣, 安藤康夫

    日本磁気学会誌 32 (3) 355-360 2008年

    出版者・発行元:公益社団法人日本磁気学会

    DOI: 10.3379/msjmag.32.355  

    ISSN:1882-2924

    詳細を見る 詳細を閉じる

    Detailed spin-transfer switching (STS) properties in the nanosecond regime were investigated. We prepared a CoFeB/MgO/CoFeB magnetic tunnel junction that exhibits a 115 % magnetoresistance ratio. The STS property in the ≥ 2 ns region was obtained by static measurement. We then examined this property from several points of view. In addition, we outlined a new method of real-time switching observation. That is expected to clarify the STS mechanism directly. Using this method, the contribution of the thermal activation effect in a switching current below <i>I</i><sub>C0</sub> was successfully detected. This indicates that the real-time method has the advantage that it clarifies the STS mechanism.

  274. TMR素子を用いた高感度地磁気センサーの開発 査読有り

    高太好, 大兼幹彦, 安藤康夫

    日本磁気学会誌 32 (3) 361-365 2008年

    出版者・発行元:公益社団法人日本磁気学会

    DOI: 10.3379/msjmag.32.361  

    ISSN:1882-2924

    詳細を見る 詳細を閉じる

    The TMR (<u>T</u>unneling <u>M</u>agneto-<u>r</u>esistive) junctions of SiO<sub>2</sub>-sub./bottom-electrode/IrMn/CoFe/Al-oxide/NiFe/ top-electrode were fabricated. We have succeeded to observe both high sensitivity and linearity in a low magnetic field for the optimized TMR junctions. The circuit of magnetic sensor using developed TMR junctions exhibited high output signal enough to resolve over 36 directions at terrestrial magnetism. The terrestrial sensor using TMR junctions is very small size and low energy consumption, so will be key "tools" for some solutions, for example, a navigation sensor with Global Positioning System(GPS) in cell phones.

  275. 高配向Nd<SUB>2</SUB>Fe<SUB>14</SUB>B薄膜のX線回折と磁気特性 査読有り

    小川大介, 秋屋貴博, 大兼幹彦, 安藤康夫, 加藤宏朗

    日本磁気学会誌 32 (6) 548-553 2008年

    出版者・発行元:公益社団法人日本磁気学会

    DOI: 10.3379/msjmag.32.548  

    ISSN:1882-2924

    詳細を見る 詳細を閉じる

    Nd<sub>2</sub>Fe<sub>14</sub>B thin films were fabricated with a DC magnetron sputtering system. X-ray diffraction experiments and the Rietveld analysis showd that the crystallites of the Nd<sub>2</sub>Fe<sub>14</sub>B phase were highly oriented perpendicular to the film plane. In addition to the diffraction peaks originated from the Nd<sub>2</sub>Fe<sub>14</sub>B phase, we observed extra reflections that can be assigned as a NdO phase. The relative intensity, hence the volume fraction of the NdO phase varied depending on the sputtering conditions such as the substrate temperature, Ar gas pressure, and Ta buffer layer thickness. It was found that the magnetization value depends strongly on the Ar gas pressure and reaches a maximum at 0.7 Pa of Ar gas pressure. The maximum magnetization value is 15 kG, which is comparable with the bulk value. The optimized values of the maximum energy product, saturation magnetization, and coercivity are (<i>BH</i>)<sub>max</sub> = 36 MGOe, 4π<i>M</i><sub>s</sub> = 14.7 kG, and <i>H</i><sub>c</sub> = 6.7 kOe, respectively.

  276. Development of high-sensitive magnetoresistance devices using half-metallic Heusler alloy Co<SUB>2</SUB>MnSi, 査読有り

    Yuya SAKURABA, Taku IWASE, Sumito TSUNEGI, Kesami SAITO, Mikihiko OGANE, Yasuo ANDO, Akimasa SAKUMA, Koki TAKANASHI

    IEICE Technical Report, 103 13-18 2008年

  277. Ultrafast optical modification of magnetic anisotropy and stimulated precession in an epitaxial Co2MnAl thin film 査読有り

    Y. Liu, L. R. Shelford, V. V. Kruglyak, R. J. Hicken, Y. Sakuraba, M. Oogane, Y. Ando, T. Miyazaki

    JOURNAL OF APPLIED PHYSICS 101 (9) 09C106-1-09C106-3 2007年5月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.2711702  

    ISSN:0021-8979

    eISSN:1089-7550

    詳細を見る 詳細を閉じる

    An all-optical pump-probe method was used to study magnetization precession in an epitaxial Co2MnAl Heusler alloy thin film. The frequency and amplitude of precession showed a clear fourfold variation as the orientation of the static field was applied in different directions within the plane of the film, revealing that the precession is induced by an ultrafast modification of the magnetocrystalline anisotropy field. The effective fields acting upon the magnetization have been determined and the damping parameter is found to decrease rapidly as the strength of the applied field is increased.

  278. Magnetic damping constant of Co2FeSi Heusler alloy thin film 査読有り

    Mikihiko Oogane, Resul Yilgin, Masatsugu Shinano, Satoshi Yakata, Yuya Sakuraba, Yasuo Ando, Terunobu Miyazaki

    JOURNAL OF APPLIED PHYSICS 101 (9) 09J501-1-09J501-3 2007年5月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.2709751  

    ISSN:0021-8979

    eISSN:1089-7550

    詳細を見る 詳細を閉じる

    Co2FeSi films were prepared using magnetron sputtering technique on Cr buffer layers and MgO(001) substrates at various annealing temperatures. We investigated the crystal structures, magnetic properties (M-s and H-c), surface roughness, and magnetic damping constants (alpha) of the prepared Co2FeSi films. Out-of-plane angular dependences of the resonance field and the linewidth of the ferromagnetic resonance spectra were measured and fitted using the Landau-Lifshitz-Gilbert equation to determine the damping constant. The as-deposited Co2FeSi film exhibited an amorphous and disordered structure; the alpha value was 0.008. In contrast, the Co2FeSi films annealed over 300 degrees C showed epitaxial growth and had a (001)-oriented and L2(1) ordered structure. Both disordered and L2(1) ordered Co2FeSi films showed similar alpha values. (C) 2007 American Institute of Physics.

  279. Tunneling spin polarization and magnetic properties of Co-Fe-B alloys and their dependence on boron content 査読有り

    Takahide Kubota, Tadaomi Daibou, Mikihiko Oogane, Yasuo Ando, Terunobu Miyazaki

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS & EXPRESS LETTERS 46 (8-11) L250-L252 2007年3月

    出版者・発行元:INST PURE APPLIED PHYSICS

    DOI: 10.1143/JJAP.46.L250  

    ISSN:0021-4922

    詳細を見る 詳細を閉じる

    Tunneling spin polarization (TSP) of (Co50Fe50)(100-x)B-x alloys with various boron contents is measured by superconducting tunneling spectroscopy (STS). Because magnetic tunnel junctions (MTJs) using Co-Fe-B alloys exhibit a large tunnel magnetoresistance (TMR) effect, they are highly valued materials; in addition, the TSP of Co-Fe-13 alloys is expected to be high. The maximum observed TSP value is 49% for (Co50Fe50)(80)B-20, which is higher than that of pure Co5oFe5o (37%). An ;X-ray diffraction pattern showed that the structure of (Co50Fe50)(80)B-20 is amorphous. We infer that the structure is changed to the amorphous state by increasing the boron content, which enhances the TSP of Co-Fe-B alloys.

  280. Thermally excited spin wave modes in synthetic antiferromagnetic stripes 査読有り

    Yasuo Ando, Young Min Lee, Tatsuya Aoki, Terunobu Miyazaki, Helmut Schultheiss, Burkard Hillebrands

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 310 (2) 1949-1951 2007年3月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/j.jmmm.2006.10.828  

    ISSN:0304-8853

    詳細を見る 詳細を閉じる

    Brillouin light scattering ( BLS) microscopy studies were performed on patterned synthetic antiferromagnetic ( SAF). films. SAF films with the stacking structure of SiO2/ Ta( 5 nm)/ FeNi( 6.8 nm)/ Ru( 0.4 nm)/ FeNi( 3.6 nm)/ Ru( 3 nm) were prepared using magnetron sputtering and were patterned into a stripe shape with a width of 2 mm. We measured the micro- BLS spectra at the center and the edge positions of the SAF stripe in a static magnetic field of 950 Oe applied perpendicular to the long axis. The spin wave frequencies of the SAF stripe decrease in comparison with those of the single FeNi film stripe. The difference between the spin wave frequencies at the center and at the edge is relatively small in the SAF samples, which is indicative for SAF films with small stray fields. Micromagnetic simulations provide a good account for the experimental observations. (c) 2006 Elsevier B. V. All rights reserved.

  281. Enhancement of DC voltage generated in ferromagnetic resonance for magnetic thin film 査読有り

    S. Mizukami, S. Nagashima, S. Yakata, Y. Ando, T. Miyazaki

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 310 (2) 2248-2249 2007年3月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/j.jmmm.2006.10.827  

    ISSN:0304-8853

    詳細を見る 詳細を閉じる

    DC voltage generated in ferromagnetic resonance was investigated for Cu/F(20 nm)/Cu (F = Ni80Fe20,Co)films. Microwave frequency was varied from 6 to 18 GHz and DC voltage depended significantly on the film shape and frequency. DC voltage for the circular patch films was enhanced remarkably at around 9 GHz. (c) 2006 Elsevier B.V. All rights reserved.

  282. Gilbert damping constant in polycrystalline CO2MnSi Heusler alloy films 査読有り

    R. Yilgin, M. Oogane, Y. Ando, T. Miyazaki

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 310 (2) 2322-2323 2007年3月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/j.jmmm.2006.11.032  

    ISSN:0304-8853

    詳細を見る 詳細を閉じる

    The Gilbert damping constant was investigated in polycrystalline Co2MnSi Heusler alloy thin films by ferromagnetic resonance ( FMR) technique. Samples were prepared using the magnetron sputtering technique on SiO2 substrate and annealed at various temperatures to control the structure. The intrinsic Gilbert damping constant was obtained from angular dependences of peak- to- peak line widths fitting from FMR spectra using Landau - Lifshitz - Gilbert equation. Intrinsic damping constants of the polycrystalline Co2MnSi films were almost independent of the annealing temperature. (c) 2006 Elsevier B. V. All rights reserved.

  283. Bias voltage dependence of tunnel magnetoresistance effect in CoFeB/MgO/Co2X(X = Fe, Mn)Si magnetic tunnel junctions 査読有り

    T. Daibou, M. Shinano, M. Hattori, Y. Sakuraba, M. Oogane, Y. Ando, T. Miyazaki

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 310 (2) 1926-1928 2007年3月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/j.jmmm.2006.10.761  

    ISSN:0304-8853

    詳細を見る 詳細を閉じる

    Magnetic tunnel junctions ( MTJs) with structure of sub ( thermal oxidized Si)/ Ta( 10 nm)/ Py( 2 nm)/ IrMn( 10 nm)/ Co75Fe25( 2 nm)/ Ru( 0.85 nm)/ Co40Fe40B20( 5 nm)/ MgO( 2.5 nm)/ poly crystalline Co2FeSi or Co2MnSi Heusler alloys/ Ta( 7)/ Ru( 7) have been grown by magnetron sputtering method. Differential resistance ( dV/ dI) and bias voltage dependence of the TMR ratio have been investigated at 6K. The shape of TMR- V curve for the MTJ with Co2MnSi showed significant voltage dependence of the TMR ratio. (c) 2006 Elsevier B. V. All rights reserved.

  284. Spin injection into organic light-emitting diodes with a ferromagnetic cathode and observation of the luminescence properties 査読有り

    Eiji Shikoh, Toru Kawai, Akihiko Fujiwara, Yasuo Ando, Terunobu Miyazaki

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 310 (2) 2052-2054 2007年3月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/j.jmmm.2006.10.981  

    ISSN:0304-8853

    詳細を見る 詳細を閉じる

    Electroluminescence ( EL) properties of organic light-emitting diodes (LEDs) under an external magnetic field were investigated for observation of spin-polarized luminescence. When an external magnetic field was applied to organic LEDs with an Fe cathode, circularly polarized light was observed, while devices with an Al cathode did not show such behavior. In order to confirm whether the circularly polarized light was certainly due to spin injection or not, photoluminescence (PL) property of Alq(3) ( tris-(8-hydroxyquinolinato)-aluminum)film on Fe and that of Alq(3) film on Al under an external magnetic field were investigated. In the case of Alq(3) on Film, the degree of circular polarization from EL was much higher than that from PL. This suggested that circular polarization on EL was mainly due to spin injection. (c) 2006 Elsevier B.V. All rights reserved.

  285. Boron effects on noise in magnetic tunnel junctions 査読有り

    A. F. Md Nor, T. Daibou, M. Oogane, Y. Ando, T. Miyazaki

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 310 (2) 1917-1919 2007年3月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/j.jmmm.2006.10.1126  

    ISSN:0304-8853

    詳細を見る 詳細を閉じる

    Normalized noise at different boron atomic percentages varying from 20%, 25%, and 30% was shown to increase with increasing boron content. The TMR% of the junction with 30% boron content shows almost 0% TMR. The X- ray diffraction patterns on these junctions, suggesting that the degree of crystallinity in MgO with increasing boron content, have deteriorated. Thus, high crystallinity is not only a vital factor for obtaining a high TMR ratio but also serve as a facilitating condition for lower noise. (c) 2006 Elsevier B. V. All rights reserved.

  286. Anisotropic intrinsic damping constant of epitaxial Co2MnSi Heusler alloy films 査読有り

    Resul Yilgin, Yuya Sakuraba, Mikihiko Oogane, Shigemi Mizukami, Yasuo Ando, Terunobu Miyazaki

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS & EXPRESS LETTERS 46 (8-11) L205-L208 2007年3月

    出版者・発行元:JAPAN SOC APPLIED PHYSICS

    DOI: 10.1143/JJAP.46.L205  

    ISSN:0021-4922

    詳細を見る 詳細を閉じる

    We investigated the Gilbert damping constant of the Heusler Co2MnSi(001) films epitaxially grown on a MgO(100) substrate by a ferromagnetic resonance technique. The angular variation in resonance field in the in-plane geometry exhibited a maximum when the field was applied parallel to the [110] direction (easy axis), and its relative minimum corresponded to the H vertical bar vertical bar [100] hard axis. Experimental results were fitted with theoretical results; the g-value, effective magnetization and anisotropy constants were determined. The magneto-crystalline anisotropy of the films decreased after the films were postannealed at 400 degrees C. The Gilbert damping parameter was anisotropic and had a minimum value at 300 degrees C.

  287. Half-metallic band structure observed in Co2MnSi-based magnetic tunnel junctions 査読有り

    Y. Sakuraba, M. Hattori, M. Oogane, H. Kubota, Y. Ando, A. Sakuma, T. Miyazaki

    JOURNAL OF PHYSICS D-APPLIED PHYSICS 40 (5) 1221-1227 2007年3月

    出版者・発行元:IOP PUBLISHING LTD

    DOI: 10.1088/0022-3727/40/5/S02  

    ISSN:0022-3727

    詳細を見る 詳細を閉じる

    Magnetic tunnel junctions ( MTJs) with stacking structures of Co2MnSi/Al-O/CoFe and Co2MnSi/Al-O/Co2MnSi were fabricated using a magnetron sputtering system. Co2MnSi/Al-O/CoFe-MTJ and Co2MnSi/Al-O/Co2MnSi-MTJ exhibited extremely large tunnelling magnetoresistance ratios of 159% and 570%, respectively, at low temperature, indicating the half-metallicity of Co2MnSi. We investigated the bias voltage dependence of tunnelling conductance ( dI/dV-V) for each MTJ in order to clarify the band structure around the Fermi level in Co2MnSi. The observed dI/dV-V curves for both MTJs reveal a clear half-metallic energy gap at 350 - 400 meV for Co2MnSi, with an energy separation of just 10 meV between the Fermi energy and the bottom edge of the conduction band.

  288. Reduction of switching fields of submicrometer sized magnetic tunnel junction with NiFe-based synthetic ferrimagnetic free layer 査読有り

    Young Min Lee, Yasuo Ando, Terunobu Miyazaki, Hitoshi Kubota

    JOURNAL OF APPLIED PHYSICS 101 (2) 023905-1-023905-3 2007年1月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.2424399  

    ISSN:0021-8979

    詳細を見る 詳細を閉じる

    We fabricated submicrometer sized magnetic tunnel junctions (MTJs) with soft NiFe-based synthetic ferrimagnet (SynF) free layers. An extremely low switching field of 13 Oe was achieved when the stacking structure of the free layer was NiFe (2 nm)/CoFe(0.2 nm)/Ru(0.4 nm)/CoFe (0.2nm)/NiFe (2.1 nm) with 0.4 mu m cell. The switching field of the SynF structure was almost independent of the cell width. Small magnetic anisotropy of NiFe and enhanced antiferromagnetic coupling strength from insertion of 0.2-nm-thick CoFe were important attributes for the low switching field in the submicrometer sized MTJs. (c) 2007 American Institute of Physics.

  289. Co<SUB>2</SUB>MnSi(110)エピタキシャル薄膜を用いた強磁性トンネル接合の作製 査読有り

    服部正志, 桜庭裕弥, 大兼幹彦, 安藤康夫, 宮崎照宣

    日本応用磁気学会誌 31 (2) 89-93 2007年

    出版者・発行元:The Magnetics Society of Japan

    DOI: 10.3379/jmsjmag.31.89  

    ISSN:0285-0192

    詳細を見る 詳細を閉じる

    According to Julliere's model, magnetic tunnel junctions (MTJs) with half-metallic electrodes lead to a large tunnel magnetoresistance (TMR) ratio. A Co<sub>2</sub>MnSi Heusler alloy is theoretically expected to exhibit half-metallicity. We fabricated (110)-oriented epitaxial Co<sub>2</sub>MnSi electrodes on sapphire substrates using W and Ta/W/Cr buffer layers. With the W buffer layer, we found that the W and Co<sub>2</sub>MnSi layers formed a twin structure. However, with the Ta/W/Cr multi-buffer layers, we succeeded in fabricating a high-quality Co<sub>2</sub>MnSi(110) epitaxial electrode. We fabricated a MTJ with the high-quality Co<sub>2</sub>MnSi(110) electrode and investigated TMR effects in the MTJ. As a result, we observed a TMR ratio of about 40% at room temperature and 120% at 2 K.

  290. コプレーナ伝送路を有する微小強磁性トンネル接合の作製 査読有り

    青木達也, 渡邉大輔, 大坊忠臣, 安藤康夫, 大兼幹彦, 宮崎照宣

    日本応用磁気学会誌 31 (2) 94-97 2007年

    出版者・発行元:The Magnetics Society of Japan

    DOI: 10.3379/jmsjmag.31.94  

    ISSN:0285-0192

    詳細を見る 詳細を閉じる

    Investigation of current induced magnetization switching properties in nanosecond regime in ferromagnetic tunnel junctions is increasing its necessity for realization of fast operating magnetic random access memory (MRAM). In this work, appropriate electrode structures for such a measurement were investigated. The electrode structure was designed as a typical coplanar waveguide with 50Ω characteristic impedance (structure A). Although the buffer layer thickness and the distance between the signal line and the ground line were altered, the large frequency dependenceof the insertion loss was not improved. The revised structure (structure B) with small cross section area between the signal line and the ground line showed very flat transmission properties over 20 GHz. Consequently, submicron sized Ta/FeNi/IrMn/CoFe/Ru/CoFeB/MgO/CoFeB/Ta/Ru ferromagnetic tunnel junctions with the electrodes of structure Bwere fabricated. The tunnel magnetoresistance ratio was 108 % after annealing at 250 °C.

  291. Co-Fe-B合金薄膜の磁気緩和定数測定 査読有り

    大兼幹彦, 渡邉美穂, 家形諭, 安藤康夫, 宮崎照宣

    日本応用磁気学会誌 31 (3) 209-212 2007年

    出版者・発行元:The Magnetics Society of Japan

    DOI: 10.3379/jmsjmag.31.209  

    ISSN:0285-0192

    詳細を見る 詳細を閉じる

    We investigated magnetic damping parameters (a) in Co-Fe-B alloy thin films having various compositions, thicknesses, and annealing temperatures. Ferromagnetic resonance (FMR) was used to determine α values. The out-of-plane angular dependencies of the resonance field and the line width of FMR spectra were measured and analyzed by using the Landau-Lifshitz-Gilbert equation, taking the effect of magnetic inhomogeneities in the films into consideration. The Co-Fe-B films with an fcc structure phase had a larger α value than that of the film with a bcc structure. The damping parameter of the Co-Fe-B film was increased by increasing the B concentration and annealing temperature, and the very thin Co-Fe-B film (~2 nm) had a large damping parameter. We discuss the advantages of Co-Fe-B thin film as a material for current-induced magnetization switching (CIMS) systems.

  292. Co<SUB>2</SUB>MnSiを用いた強磁性トンネル接合における完全スピン分極状態の実現 査読有り

    桜庭裕弥, 服部正志, 大兼幹彦, 久保田均, 安藤康夫, 佐久間昭正, N. D. Telling, P. Keatley, G. van, der Laan, E. Arenholz, R. J. Hicken, 宮崎照宣

    日本応用磁気学会誌 31 338-343 2007年

    DOI: 10.3379/jmsjmag.31.338  

  293. Interfacial structure and half-metallic ferromagnetism in Co2MnSi-based magnetic tunnel junctions 査読有り

    N. D. Telling, P. S. Keatley, G. van der Laan, R. J. Hicken, E. Arenholz, Y. Sakuraba, M. Oogane, Y. Ando, T. Miyazaki

    PHYSICAL REVIEW B 74 (22) 224439-1-224439-7 2006年12月

    出版者・発行元:AMER PHYSICAL SOC

    DOI: 10.1103/PhysRevB.74.224439  

    ISSN:2469-9950

    eISSN:2469-9969

    詳細を見る 詳細を閉じる

    X-ray absorption (XAS) and x-ray magnetic circular dichroism (XMCD) techniques are utilized to explore the ferromagnetic/barrier interface in Co2MnSi full Heusler alloy magnetic tunnel junctions. Structural and magnetic properties of the interface region are studied as a function of the degree of site disorder in the alloy and for different degrees of barrier oxidation. Photoelectron scattering features that depend upon the degree of L2(1) ordering are observed in the XAS spectra. Additionally, the moments per 3d hole for Co and Mn atoms are found to be a sensitive function of both the degree of L2(1) ordering and the barrier oxidation state. Significantly, a multiplet structure is observed in the XMCD spectra that indicates a degree of localization of the moments and may result from the half-metallic ferromagnetism (HMF) in the alloy. The magnitude of this multiplet structure appears to vary with preparation conditions and could be utilized to ascertain the role of the constituent atoms in producing the HMF, and to examine methods for preserving the half-metallic state after barrier preparation. The changes in the magnetic structure caused by barrier oxidation could be reversed by inserting a thin Mg interface layer in order to suppress the oxidation of Mn in the Co2MnSi layer.

  294. Tunnel magnetoresistance effect in CoFeB/MgO/Co2FeSi and Co2MnSi tunnel junctions 査読有り

    T. Daibou, M. Shinano, M. Hattori, Y. Sakuraba, M. Oogane, Y. Ando, T. Miyazaki

    IEEE TRANSACTIONS ON MAGNETICS 42 (10) 2655-2657 2006年10月

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

    DOI: 10.1109/TMAG.2006.879733  

    ISSN:0018-9464

    eISSN:1941-0069

    詳細を見る 詳細を閉じる

    We have fabricated MgO-based magnetic tunnel junctions (MTJs) with the CoFeB bottom electrode and top electrodes of poly crystaline Co2FeSi and Co-2 MnSi Heusler alloys. We have measured temperature dependence of the TMR ratio and TMR-V characteristics at 6 K. We have achieved a high TMR ratio of 90 % at RT for the MTJ with Co-2 FeSi electrode after annealing at 325 degrees C. The MTJ with Co-2 MnSi electrode showed a significant annealing temperature dependence of the TMR ratio. The increase of TMR ratio by annealing is due to the crystallization of the Co-2 MnSi Hensler layer. Furthermore, the strong temperature dependence of TMR ratio and the anomalous TMR-V characteristics have been observed in the MTJ with Co2MnSi.

  295. Spin injection into organic light-emitting devices with ferromagnetic cathode and effects on their luminescence properties 査読有り

    Eiji Shikoh, Akihiko Fujiwara, Yasuo Ando, Terunobu Miyazaki

    Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers 45 (9 A) 6897-6901 2006年9月7日

    DOI: 10.1143/JJAP.45.6897  

    ISSN:0021-4922 1347-4065

    詳細を見る 詳細を閉じる

    We investigated the luminescence properties of organic light-emitting devices under an external magnetic field. Circularly polarized light was observed from the devices with an Fe cathode, whereas those with an Al cathode did not show such behavior. The degree of circular polarization on the device with an Fe cathode increased with increasing applied magnetic field and decreased with increasing emissive layer thickness. These phenomena can be well explained in terms of the recombination of spin-polarized electrons injected from a ferromagnetic cathode. Consequently, spin diffusion length in the emissive layer, tris-(8-hydroxyquinolinato)-aluminum was estimated to be less than 60 nm from the thickness dependence of the degree of circular polarization. © 2006 The Japan Society of Applied Physics.

  296. Direct observation of half-metallic energy gap in Co2MnSi by tunneling conductance spectroscopy 査読有り

    Y. Sakuraba, T. Miyakoshi, M. Oogane, Y. Ando, A. Sakuma, T. Miyazaki, H. Kubota

    APPLIED PHYSICS LETTERS 89 (5) 052508-1-052508-3 2006年7月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.2335583  

    ISSN:0003-6951

    eISSN:1077-3118

    詳細を見る 詳細を閉じる

    Magnetic tunnel junctions with a Co2MnSi/Al-O/CoFe structure are prepared by magnetron sputtering and investigated with respect to the energy gap near the Fermi energy level. The plasma oxidation time for the Al-O barrier is found to affect the condition of the Co2MnSi/Al-O interface. The optimized sample (50 s oxidation time) exhibits a magnetoresistance ratio of 159% and tunneling spin polarization of 0.89 at 2 K. The bias voltage dependence of tunneling conductance (dI/dV-V) reveals a clear half-metallic energy gap at 350-400 meV for Co2MnSi, with an energy separation of just 10 meV between the Fermi energy and the bottom edge of conduction band. (c) 2006 American Institute of Physics.

  297. Preparation of silica-coated Co-Pt alloy nanoparticles 査読有り

    Yoshio Kobayashi, Mitsuru Horie, Daisuke Nagao, Yasuo Ando, Terunobu Miyazaki, Mikio Konno

    MATERIALS LETTERS 60 (16) 2046-2049 2006年7月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/j.matlet.2005.12.078  

    ISSN:0167-577X

    詳細を見る 詳細を閉じる

    A previously proposed method for silica-coating of Co nanoparticles was extended to silica-coating of Co-Pt alloy nanoparticles. The alloy nanoparticles were prepared from CoCl(2) (1.2 x 10(-3) M), H(2)PtCl(6) (1.2 x 10(-3) M), citric acid (4 x 10(-4) M) and NaBH(4) (1.2 x 10(-2) M). The silica-coating was performed in aqueous/ethanolic solution with a silane coupling agent, 3-aminopropyltrimethoxysilane (8 x 10(-5) M), and a silica source, tetraethoxyorthosilicate (7.2 x 10(-4) M) in the presence of the alloy nanoparticles. TEM observation and X-ray diffraction measurements revealed that the alloy nanoparticles were coated with silica and consisted of fee Co-Pt alloy crystallites with crystal sizes of 4.6-10.7 nm. Magnetic properties of the silica-coated particles were strongly dependent on annealing temperature. Maximum values of 1.4 emu/g-sample for saturation magnetization and 450 Oe for coercive field were obtained for the particles annealed at 300 degrees C. Annealing above 300 degrees C transformed the crystallite from the alloy to pure Pt probably through oxidation of cobalt in the alloy, resulting in reductions in saturation magnetization and coercive field. (c) 2005 Elsevier B.V. All rights reserved.

  298. Giant tunneling magnetoresistance in Co2MnSi/Al-O/Co2MnSi magnetic tunnel junctions 査読有り

    Y. Sakuraba, M. Hattori, M. Oogane, Y. Ando, H. Kato, A. Sakuma, T. Miyazaki, H. Kubota

    APPLIED PHYSICS LETTERS 88 (19) 192508-1-192508-3 2006年5月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.2202724  

    ISSN:0003-6951

    eISSN:1077-3118

    詳細を見る 詳細を閉じる

    Magnetic tunnel junctions (MTJs) with a stacking structure of Co2MnSi/Al-O/Co2MnSi were fabricated using magnetron sputtering system. Fabricated MTJ exhibited an extremely large tunneling magnetoresistance (TMR) ratio of 570% at low temperature, which is the highest TMR ratio reported to date for an amorphous Al-O tunneling barrier. The observed dependence of tunneling conductance on bias voltage clearly reveals the half-metallic energy gap of Co2MnSi. The origins of large temperature dependence of TMR ratio were discussed on the basis of the present results.(c) 2006 American Institute of Physics.

  299. Magnetic damping in ferromagnetic thin films 査読有り

    Mikihiko Oogane, Takeshi Wakitani, Satoshi Yakata, Resul Yilgin, Yasuo Ando, Akimasa Sakuma, Terunobu Miyazaki

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS 45 (5A) 3889-3891 2006年5月

    出版者・発行元:JAPAN SOC APPLIED PHYSICS

    DOI: 10.1143/JJAP.45.3889  

    ISSN:0021-4922

    詳細を見る 詳細を閉じる

    We determined the Gilbert damping constants of Fe-Co-Ni and Co-Fe-B alloys with various compositions and half-metallic Co2MnAl Heusler alloy films prepared by magnetron sputtering. The ferromagnetic resonance (FMR) technique was used to determine the damping constants of the prepared films. The out-of-plane angular dependences of the resonance field (H-R) and line width (Delta H-pp) of FMR spectra were measured and fitted using the Landau-Lifshitz-Gilbert (LLG) equation. The experimental results fitted well, considering the inhomogeneities of the films in the fitting. The damping constants of the where metallic films were much larger than those of bulk ferrimagnetic insulators and were roughly proportional to (g - 2)(2), is the Lande g factor. We discuss the origin of magnetic damping, considering spin-orbit and s-d interactions.

  300. Temperature dependences of spin-diffusion lengths of Cu and Ru layers 査読有り

    S Yakata, Y Ando, T Miyazaki, S Mizukami

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS 45 (5A) 3892-3895 2006年5月

    出版者・発行元:INST PURE APPLIED PHYSICS

    DOI: 10.1143/JJAP.45.3892  

    ISSN:0021-4922

    詳細を見る 詳細を閉じる

    Ferromagnetic resonance (FMR) was measured in Cu/Ni80Fe20/normal-metal: NM (d)/Pt, Cu/Ni80Fe20/NM (d) films with various d values to clarify the temperature dependence of spin-diffusion length induced by the precession of magnetization on Gilbert damping. The films were fabricated by rf magnetron sputtering. The out-of-plane angular dependences of FMR resonance field and linewidth were analyzed using a Landau-Lifshitz-Gilbert equation, and the Gilbert damping parameter G of NiFe was obtained. The obtained spin-diffusion lengths lambda(SD) were 350 and 950 nm at 300 and 4.5 K, respectively. The spin-flip probability of the Cu layer was obtained using the temperature dependence of FMR linewidth. These results were then compared with the calculated data of the temperature dependence of spin-diffusion length.

  301. Tunneling spectroscopy in CoFeB/MgO/CoFeB magnetic tunnel junctions 査読有り

    K Ono, T Daibou, SJ Ahn, Y Sakuraba, T Miyakoshi, T Morita, Y Kikuchi, M Oogane, Y Ando, T Miyazaki

    JOURNAL OF APPLIED PHYSICS 99 (8) 08A905-1-08A905-3 2006年4月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.2173628  

    ISSN:0021-8979

    詳細を見る 詳細を閉じる

    The d(2)V/dI(2)-V measurements were used to investigate the tunneling mechanism in CoFeB/MgO/CoFeB magnetic tunnel junctions (MTJs), which showed a giant tunnel magnetoresistance ratio up to 200% at room temperature. The d(2)V/dI(2)-V spectra of CoFeB/MgO/CoFeB junctions resemble those of single-crystal Fe(001)/MgO(001)/Fe(001) MTJs. Broad peaks appeared around +/- 600 mV in spectra for antiparallel magnetic configurations. A complex structure was apparent in the spectra for parallel configurations. We inferred that giant tunnel magnetoresistance observed in CoFeB/MgO/CoFeB junctions originates in coherent tunneling between the Delta(1) bands of crystallized CoFeB electrodes. (C) 2006 American Institute of Physics.

  302. Low-frequency noise in MgO magnetic tunnel junctions 査読有り

    AFM Nor, T Kato, SJ Ahn, T Daibou, K Ono, M Oogane, Y Ando, T Miyazaki

    JOURNAL OF APPLIED PHYSICS 99 (8) 08T306-1-08T306-3 2006年4月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.2165142  

    ISSN:0021-8979

    詳細を見る 詳細を閉じる

    Noise measurements have been performed in MgO-based tunnel junctions with normalized resistance in the range of 10(5)-10(7) Omega mu m(2) and various magnetoresistance ratios were investigated. Noise measurements in the frequency range of 1-1000 Hz shows magnetically dependent pure 1/f power spectra at low frequency. The 1/f noise scales with bias voltage, indicating that the 1/f noise can be attributed to magnetic tunnel junction resistance fluctuations. Bias voltage dependence of random telegraph noise (RTN) was observed, indicating electronic origin due to the charge-trapping mechanism. In the presence of the easy-axis bias field, our data exhibit a magnetic-field dependence of RTN that originates from magnetization fluctuations. A phenomenological noise parameter, defined for the comparison of noise levels in different junctions, was shown to be independent of the junction resistance-area product in the range investigated. This observation suggests that the decrease in tunnel resistance does not play an important role in reducing 1/f noise. (C) 2006 American Institute of Physics.

  303. Large tunnel magnetoresistance in magnetic tunnel junctions using Co2MnX (X = Al,Si) Heusler alloys 査読有り

    M Oogane, Y Sakuraba, J Nakata, H Kubota, Y Ando, A Sakuma, T Miyazaki

    JOURNAL OF PHYSICS D-APPLIED PHYSICS 39 (5) 834-841 2006年3月

    出版者・発行元:IOP PUBLISHING LTD

    DOI: 10.1088/0022-3727/39/5/S09  

    ISSN:0022-3727

    詳細を見る 詳細を閉じる

    We fabricated B2-ordered Co2MnAl and L2(1)-ordered Co2MnSi Heusler alloy films by optimizing various fabrication conditions (substrate, composition of sputtering target, substrate and post-annealing temperature, etc) and applied these films to bottom electrodes of magnetic tunnel junctions (MTJs). We used Al-oxide insulating tunnel barriers for our MTJs and varied oxidation times of Al films to control qualities of the Al-oxide insulating layer and Heusler-alloy/Al-oxide interface. Observed tunnel magnetoresistance (TMR) ratios were extremely sensitive to the structure and surface morphology of the prepared Heusler alloy films. Epitaxially grown Heusler alloy films showed very flat surfaces and enhanced TMR ratios. The good structural quality, behaviour of the TMR ratios towards oxidation time for the preparation of the Al-oxide barriers and the measurement temperature dependence of the TMR ratios were quite different between the MTJs with Co2MnAl and Co2MnSi electrodes. The obtained TMR ratio of 83% at 2 K in the MTJ with epitaxially grown B2-ordered Co2MnAl was large among the MTJs with an amorphous Al-oxide tunnel barrier. This result suggests that B2-ordered Co2MnAl is a highly spin-polarized material, as predicted by our theoretical calculation. Moreover, we observed a very large TMR ratio of 159% at 2 K in the MTJ with a high-quality epitaxially grown L2(1)-ordered Co2MnSi electrode. This TMR ratio is the highest value to date in MTJs using an amorphous M-oxide tunnel barrier. Spin-polarization of the Co2MnSi bottom electrode obtained from Julliere's formula was about 0.89. This value is also the largest achieved to date for a Heusler material and is much larger than those of conventional ferromagnetic materials such as Co-Fe. This large spin-polarization is attributed to a half-metallic band structure, as predicted by theoretical calculations.

  304. Low frequency noise in CoFeB magnetic tunnel junctions with varying boron content 査読有り

    A. F, Md. Nor, T. Daibou, M. Oogane, Y. Ando, T. Miyazaki

    J. Magn. Magn. Mater. 2006年

    DOI: 10.1109/INTMAG.2006.374889  

  305. Gilbert Damping Constants of Co2FeSi Heusler Alloy Film 査読有り

    M. Oogane, R. Yilgin, S. Shinano, S. Yakata, H. Kubota, Y. Ando, T. Miyazaki

    J. Appl. Phys. 2006年

  306. Co2MnSi (110)ホイスラー合金を用いたトンネル接合における磁気抵抗効果 査読有り

    服部正志, 桜庭裕弥, 大兼 幹彦, 安藤 康夫, 宮﨑 照宣

    日本応用磁気学会誌 2006年

  307. Magnetic tunnel junctions using B2-ordered Co2MnAl Heusler alloy epitaxial electrode 査読有り

    Y Sakuraba, J Nakata, M Oogane, Y Ando, H Kato, A Sakuma, T Miyazaki, H Kubota

    APPLIED PHYSICS LETTERS 88 (2) 022503-1-022503-3 2006年1月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.2162867  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    Magnetic tunnel junctions were fabricated with epitaxially grown Co2MnAl bottom electrodes combined with an Al-O tunnel barrier using a magnetron sputtering system. The epitaxial Co2MnAl electrode had very low surface roughness of 0.2 nm and a highly ordered B2 structure. Magnetic tunnel junctions (MTJs) with a stacking structure of epitaxial-Co2MnAl/Al-O/CoFe/IrMn exhibited large tunnel magnetoresistance (TMR) ratios of 65% at room temperature and 83% at 10 K. The TMR ratios were larger than those of a MTJ with a Co2MnAl polycrystalline electrode.

  308. FMRを用いた強磁性金属中におけるスピン拡散長の測定 査読有り

    家形諭, 安藤康夫, 大兼幹彦, 宮崎照宣

    日本応用磁気学会誌 31 2006年

  309. Intrinsic Gilbert damping constant in CO2MnAl Heusler alloy films 査読有り

    R Yilgin, M Oogane, S Yakata, Y Ando, T Miyazaki

    IEEE TRANSACTIONS ON MAGNETICS 41 (10) 2799-2801 2005年10月

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

    DOI: 10.1109/TMAG.2005.854832  

    ISSN:0018-9464

    eISSN:1941-0069

    詳細を見る 詳細を閉じる

    Intrinsic alpha-damping constants of CO2MnAl Hensler alloy films prepared by magnetron sputtering were investigated. After deposition of Co2MnAl films, the films were annealed at 200-400 degrees C to control the crystal structure and the atomic order between Co, Mn, and Al sites. Ferromagnetic resonance (FMR) technique was used to obtain alpha values of Co2MnAl films in this study. Out-of-plane angular dependences of the resonance field (H-R) and linewidth (Delta H-pp) of FMR spectra were measured and fitted using the Landau-Lifshitz-Gilbert (LLG) equation. The authors were able to fit all experimental results well because of the lack of inhomogeneities in prepared Co-2 MnAl films. The alpha-damping constants obtained from the fitting results decreased with increasing annealing temperature and showed a minimum value of 0.007 at 300 degrees C. It was found that a degree of B2 structure order can sensitively affect alpha-damping constants of Co2MnAl films.

  310. Spin-dependent tunneling spectroscopy in single-crystal Fe/MgO/Fe tunnel junctions 査読有り

    Y Ando, T Miyakoshi, M Oogane, T Miyazaki, H Kubota, K Ando, S Yuasa

    APPLIED PHYSICS LETTERS 87 (14) 142502-1-142502-3 2005年10月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.2077861  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    We report a detailed spin-dependent tunneling spectroscopy in single-crystal Fe(001)/MgO(001)/Fe(001) magnetic tunnel junctions (MTJs) that show a giant tunnel magnetoresistance effect. Spectra for antiparallel magnetic configurations show asymmetry because of extrinsic electron scatterings caused by structural defects at the barrier/electrode interfaces. Surprisingly, spectra for parallel magnetic configurations exhibit a complex oscillatory structure that has never been observed in conventional MTJs with an aluminum-oxide tunnel barrier. The complex spectra reflect the tunneling process via interface resonant states. These results provide some information that helps to elucidate the physics of spin-dependent electron tunneling and to further enhance magnetoresistance. (C) 2005 American Institute of Physics.

  311. Fabrication of Co2MnAl Heusler alloy epitaxial film using Cr buffer layer 査読有り

    Y Sakuraba, J Nakata, M Oogane, H Kubota, Y Ando, A Sakuma, T Miyazaki

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS 44 (9A) 6535-6537 2005年9月

    出版者・発行元:JAPAN SOC APPLIED PHYSICS

    DOI: 10.1143/JJAP.44.6535  

    ISSN:0021-4922

    詳細を見る 詳細を閉じる

    Thin films of the full-Heusler compound, Co(2)MnA1, were grown on Cr-buffered MgO(001) substrates at different growth temperature and post-annealing temperature by magnetron sputtering, Atomic force microscopy (AFM) and X-ray diffraction (XRD) measurements show that Cr-buffer layer can largely improve the surface morphology and structural quality of CO(2)MnA1 film. The (001)-oriented epitaxial growth and B2 structure were confirmed by XRD measurements for all prepared samples. The smallest surface roughness (similar to 2 A) and an identical M, value to the bulk value were obtained in the sample which was deposited at ambient temperature and post-annealed at 300 degrees C.

  312. Influence of diffusion of Fe atoms into the emissive layer of an organic light-emitting device on the luminescence properties 査読有り

    Eiji Shikoh, Yasuo Ando, Terunobu Miyazaki

    Journal of Applied Physics 97 (10) 10D501-1-10D501-2 2005年5月15日

    DOI: 10.1063/1.1845931  

    ISSN:0021-8979

    詳細を見る 詳細を閉じる

    This study investigated magnetic properties of multifilms, FeAl-O (Al-oxide), Fe Alq3 (tris-(8-hydroxyquinolinato)-aluminum), and FeAl-O Alq3, using vibrating sample magnetometer and ferromagnetic resonance. In the case of Fe Alq3 -films, the decrease of magnetization value of Fe was observed compared with the other two. It was explained with diffusion of Fe atoms from the underlayer into the Alq3 layer, and those diffused Fe atoms worked as quenching centers in the luminescence process of Alq3. © 2005 American Institute of Physics.

  313. Fabrication and characterization of Co-Mn-Al Heusler-type thin film 査読有り

    H Kubota, J Nakata, M Oogane, Y Ando, H Kato, A Sakuma, T Miyazaki

    JOURNAL OF APPLIED PHYSICS 97 (10) 10C913-1-10C913-3 2005年5月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.1852329  

    ISSN:0021-8979

    eISSN:1089-7550

    詳細を見る 詳細を閉じる

    Co-Mn-Al thin films were prepared using ultrahigh-vacuum magnetron sputtering on thermally oxidized silicon substrates at various substrate temperatures. Composition, crystal structure, magnetic property, and surface roughness of the films were investigated. The film prepared at a substrate temperature (T,) of around 300 degrees C had Co2MnAl B2 structure, revealing partial disorder between Mn and Al sites. Magnetization exhibited a maximum and coercive field exhibited a minimum around T-s=300 degrees C. Surface roughness increased with the substrate temperature. The film prepared at a substrate temperature of 300 degrees C was applied to a bottom electrode of a magnetic tunnel junction, thereby creating a large tunnel magnetoresistance. (c) 2005 American Institute of Physics.

  314. Fabrication of ferromagnetic single-electron tunneling devices by utilizing metallic nanowire as hard mask stencil 査読有り

    T Niizeki, H Kubota, Y Ando, T Miyazaki

    JOURNAL OF APPLIED PHYSICS 97 (10) 10C909-1-10C909-3 2005年5月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.1850408  

    ISSN:0021-8979

    詳細を見る 詳細を閉じる

    The stacked magnetic tunnel junctions (MTJs) are microfabricated into ferromagnetic single-electron tunneling devices (F-SETs) by using electron-beam lithography. The F-SETs have a couple of small MTJs (30 X 500 nm(2)-0.1 X 100 mu m(2)), which are connected via a metallic nanowire. The large tunnel magnetoresistance ratio as much as 40% (at RT) and small junction area dependence of the RA (resistance X area) are obtained. The electrostatic energy of F-SETs estimated from the minimum junction area corresponds to the temperature of 1 K, which is high enough to observe Coulomb blockade phenomena in a dilution refrigerator. (c) 2005 American Institute of Physics.

  315. Cu/NiFe<SUB>80</SUB>Fe<SUB>20</SUB>/N(N=Cu, Cu/Pt) 薄膜におけるFMR線幅とスピン拡散長 査読有り

    家形諭, 安藤康夫, 水上成美, 宮崎照宣

    日本応用磁気学会誌 29 (4) 450-454 2005年3月

    出版者・発行元:The Magnetics Society of Japan

    DOI: 10.3379/jmsjmag.29.450  

    ISSN:0285-0192

    詳細を見る 詳細を閉じる

    We have investigated the magnetic damping in two types of multilayer films, Cu(10 nm)/Ni<sub>80</sub>Fe<sub>20</sub>(3 nm)/Cu (<i>d</i><sub>Cu</sub>) and Cu(10 nm)/Ni<sub>80</sub>Fe<sub>20</sub>(3 nm)/Cu(<i>d</i><sub>Cu</sub>)/Pt(2 nm). Temperature dependence of the damping parameter and FMR linewidth with various Cu thickness <i>d</i><sub>Cu</sub> were measured. Spin diffusion length increased with decreasing temperature. We also measured the temperature dependence of FMR linewidth for the Cu/Ni<sub>80</sub>Fe<sub>20</sub>/Cu(<i>d</i><sub>Cu</sub>)/Pt films with <i>d</i><sub>Cu</sub>=400 nm, 800 nm. The increase of FMR linewidth with decreasing temperature suggested that the damping increased by spin diffusion in Cu layer.

  316. Bias-voltage dependence of magnetoresistance in magnetic tunnel junctions grown on Al2O3 (0001) substrates 査読有り

    SJ Ahn, T Kato, H Kubota, Y Ando, T Miyazaki

    APPLIED PHYSICS LETTERS 86 (10) 102506-1-102506-3 2005年3月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.1870104  

    ISSN:0003-6951

    eISSN:1077-3118

    詳細を見る 詳細を閉じる

    Magnetic tunnel junctions with the structure of Al2O3 (0001)/Pt (111) 20 nm/Ni80Fe20 (111) 50 nm/Al 1.6 nM-O/Co75Fe25 4 nm/Ir22Mn78 10 nm/Ni80Fe20 30 nm, were fabricated using UHV sputtering and photolithography process. As the annealing temperature increased up to 250 degrees C, tunnel magnetoresistance (TMR) ratio at 1 mV bias increased from 28% to 43% for t(ox)= 180 s plasma oxidation and the V-+/- 1/2, at which the zero bias TMR value is halved, is +640 mV and -650 mV for positive and negative bias voltages, respectively. The bias-voltage dependence of TMR could be explained in, terms of the relationship with V-+/- 1/2 and the interface of the ferromagnetic electrode and the Al-O insulating layer. V+1/2, which reflects the bottom ferromagnetic electrode-barrier interface state, changes with plasma oxidation time, while V-1/2, which corresponds to top ferromagnetic electrode-barrier interface, hardly changes. (c) 2005 American Institute of Physics.

  317. Temperature dependence of tunnel magnetoresistance in Co-Mn-Al/Al-oxide/Co-Fe junctions 査読有り

    M Oogane, J Nakata, H Kubota, Y Ando, A Sakuma, T Miyazaki

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS & EXPRESS LETTERS 44 (24-27) L760-L762 2005年

    出版者・発行元:INST PURE APPLIED PHYSICS

    DOI: 10.1143/JJAP.44.L760  

    ISSN:0021-4922

    詳細を見る 詳細を閉じる

    We investigated the temperature dependence of the tunnel magnetoresistance (TMR) effect in Co-Mn-Al/Al-oxide/Co-Fe tunnel junctions. The junction prepared without exposure to air during deposition showed very large TMR ratios of 65% at 10 K and 40% at room temperature. In contrast, the junction prepared with air exposure before and after Al-oxide layer fabrication showed a maximum TMR ratio of only 40% at a low temperature. Temperature dependences of tunnel conductance of these junctions were analyzed using a simple model that incorporates two contributions: elastic tunneling with decreasing spin polarization as temperature increases and spin- independent hopping tunneling through trap states in Al-oxide tunnel barriers. Results of analyses indicated that air exposure drastically reduced spin polarization and Curie temperature. It also created an inferior insulating layer at the Co-Mn-Al/Al-oxide interface.

  318. Huge spin-polarization of L2(1)-ordered Co2MnSi epitaxial Heusler alloy film 査読有り

    Y Sakuraba, J Nakata, M Oogane, H Kubota, Y Ando, A Sakuma, T Miyazaki

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS & EXPRESS LETTERS 44 (33-36) L1100-L1102 2005年

    出版者・発行元:JAPAN SOC APPLIED PHYSICS

    DOI: 10.1143/JJAP.44.L1100  

    ISSN:0021-4922

    詳細を見る 詳細を閉じる

    Magnetic tunnel junctions (MTJs) with a stacking structure of epitaxial CO2MnSi/Al-O barrier/poly-crystalline CO75Fe25 were fabricated using an ultrahigh vacuum sputtering system. The epitaxial CO2MnSi bottom electrode exhibited highly ordered L2(1) structure and very smooth surface morphology. Observed magnetoresistance (MR) ratios of 70% at room temperature (RT) and 159% at 2 K are the highest values to date for MTJs using a Heusler alloy electrode. A high spin-polarization of 0.89 at 2 K for CO2MnSi obtained from Julliere's model coincided with the half-metallic band structure that was predicted by theoretical calculations.

  319. Switching properties and dynamic domain structures in double barrier magnetic tunnel junctions 査読有り

    XF Han, SF Zhao, FF Li, T Daibou, H Kubota, Y Ando, T Miyazaki

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 282 225-231 2004年11月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/j.jmmm.2004.04.051  

    ISSN:0304-8853

    詳細を見る 詳細を閉じる

    Double barrier magnetic tunnel junctions (DBMTJs) with the layer structures of Ta (5 nm)/Ni79Fe21 (40 nm)/Ir22Mn78 (10 nm)/Co75Fe25 (4 nm)/Al (1 nm)-oxide/Co75Fe25 (8 nm)/Al (1 nm)-oxide/Co75Fe25 (4 nm)/Ir22Mn78 (10 nm)/Ni79Fe21 (30 nm)/Ta (5 nm) on Si/SiO2 wafer were micro-fabricated using a TMR R&D magnetron sputtering system and lithography method. TMR ratios of 30.0% and 22.1%, resistance-area product RS of around 32.0 and 27.5 kOmegamum(2), and free layer coercivity of 201 and 141 Oe at 4.2 K and room temperature (RT), respectively, were obtained for the MTJs with a size of 80 x 80 mum(2) . Static and dynamic domain structures occur as the DC current increases and magnetization switching properties are simulated based on micromagnetics using the energy minimization method. TMR ratios in DBMTJs that are far lower than the expected theoretical values can be clarified based on micromagnetics simulations due to the vortex domain structures formed in the free layer. (C) 2004 Elsevier B.V. All rights reserved.

  320. A simple fabrication process using focused ion beam for deep submicron magnetic tunnel junctions 査読有り

    D Watanabe, H Kubota, Y Ando, T Miyazaki

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 43 (11A) 7489-7490 2004年11月

    出版者・発行元:INST PURE APPLIED PHYSICS

    DOI: 10.1143/JJAP.43.7489  

    ISSN:0021-4922

    詳細を見る 詳細を閉じる

    Focused ion beam (FIB) induced tungsten deposition technique was applied to fabrication of small (few-hundred-nanometer scale) magnetic tunnel junctions (MTJs). The deposited tungsten pattern was used as an etching mask and a metal connection between an MTJ and a lead line. This fabrication method can eliminate some difficult process steps so that deep submicronsized MTJs can be fabricated easily and reproducibly. This technique is useful to evaluate basic properties of small MTJs for spin-electronics devices.

  321. Spin-dependent inelastic electron tunneling spectroscopy of magnetic tunnel junctions 査読有り

    M Hayashi, Y Ando, M Oogane, H Kubota, T Miyazaki

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 43 (11A) 7472-7476 2004年11月

    出版者・発行元:INST PURE APPLIED PHYSICS

    DOI: 10.1143/JJAP.43.7472  

    ISSN:0021-4922

    詳細を見る 詳細を閉じる

    We investigated the nature of spin dependent scattering by employing inelastic electron tunneling spectroscopy in magnetic tunnel junctions. In this work we introduced a comparable quantity represented as (d(2)V/dI(2))/(dV/dI) by simultaneous measurements of the dV/dI and d(2)V/dI(2) curves. In each junction we measured, a zero bias anomaly was observed close to the Fermi energy (+/-2 mV). Furthermore, a relatively large spin dependent scattering occurred around 18 mV. These peaks and zero bias anomalies were the primary cause of the drop of the tunneling magnetoresistance (TMR) ratio as the bias voltage was applied. Furthermore, insertion of a normal metal between the insulator and ferromagnetic metal was examined. Silver exhibited a reduction of spin dependent scattering, while excess aluminum induced a large zero bias anomaly.

  322. Large magnetoresistance in magnetic tunnel junctions using Co-Mn-Al full Heusler alloy 査読有り

    H Kubota, J Nakata, M Oogane, Y Ando, A Sakuma, T Miyazaki

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS & EXPRESS LETTERS 43 (7B) L984-L986 2004年7月

    出版者・発行元:JAPAN SOC APPLIED PHYSICS

    DOI: 10.1143/JJAP.43.L984  

    ISSN:0021-4922

    詳細を見る 詳細を閉じる

    Magnetic tunnel junctions with a stacking structure of Cr/Co-Mn-Al/Al-O/Co-Fe/Ir-Mn were fabricated using a UHV magnetron-sputtering machine. Co-Mn-Al films showed B2 structure, which involves partial disorder between Mn and Al sites. Tunnel magnetoresistance ratios at room temperature were 27% and 40% before and after annealing at 250degreesC, respectively. Those values are much higher than the ones obtained in previous experiments using half Heusler alloys.

  323. Measurement of magnetization precession for NM/Ni80Fe20/NM (NM = Cu and Pt) using time-resolved Kerr effect 査読有り

    H Nakamura, Y Ando, S Mizukami, H Kubota, T Miyazaki

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS & EXPRESS LETTERS 43 (6B) L787-L789 2004年6月

    出版者・発行元:INST PURE APPLIED PHYSICS

    DOI: 10.1143/JJAP.43.L787  

    ISSN:0021-4922

    詳細を見る 詳細を閉じる

    Magnetization precession of NM/Ni80Fe20/NM (NM = Cu and Pt) multilayers was measured by the time-resolved magneto-optical Kerr effect (MOKE). A MOKE measurement system equipped with a pulse laser and optical delay lines was set up and samples were combined using a photoconductive switch for pulse field generation. Clear oscillation and relaxation of the magnetization of motion in time domain were successfully observed. Gilbert damping constant alpha for Cu/Ni80Fe20/Cu multilayers was independent of the thickness of Ni80Fe20. While alpha for Pt/Ni80Fe20/Pt multilayers was enhanced as Ni80Fe20 layer became thinner. These experimental data were well fitted by LLG calculation with the same alpha obtained by ferromagnetic resonance (FMR).

  324. Tunnel spectra for Al/Al-oxide/Ni80Fe20 junctions under the superconducting transition temperature of Al films 査読有り

    M. Oogane, T. Daibou, H. Kubota, Y. Ando, T. Miyazaki

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 272 E1515-E1516 2004年5月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/j.jmmm.2003.12.318  

    ISSN:0304-8853

    詳細を見る 詳細を閉じる

    Superconductor/insulator/metal (S/I/M) tunnel junction can be used as an indicator of junction quality. For S/I/M junction, zero-bias conductance (ZBC) should be close to zero. However, leakage conductance increases the ZBC values. We measured the ZBC values of the Al/Al-oxide/ Ni80Fe20 junctions prepared with various oxidation processes. For strong plasma oxidation ( high applied power), most of the junctions showed low ZBC. However, ZBC increased with decreasing power of oxidation. It is considered that oxidation proceeds homogeneously for strong oxidation, compared with weak oxidation process. (C) 2003 Elsevier B.V. All rights reserved.

  325. CO+NH3 plasma etching for magnetic thin films 査読有り

    Hitoshi Kubota, Kousei Ueda, Yasuo Ando, Terunobu Miyazaki

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 272 E1421-E1422 2004年5月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/j.jmmm.2003.12.724  

    ISSN:0304-8853

    詳細を見る 詳細を閉じる

    Etching of magnetic thin films has been studied using CO/NH3 plasma with an electron cyclotron resonance plasma source and DC sample bias. Etch rates were proportional to bias power density. The maximum etch rate was 127 nm/ min. Both the pressure dependence of Ni - Fe etch rate and the results of appearance mass spectroscopy suggested that the chemical reaction induced by energetic CO molecules enhanced the etch rate. (C) 2003 Elsevier B. V. All rights reserved.

  326. Nanofabrication of magnetic tunnel junctions by using electron beam lithography 査読有り

    T Niizeki, H Kubota, Y Ando, T Miyazaki

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 272 1947-1948 2004年5月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/j.jmmm.2003.12.387  

    ISSN:0304-8853

    詳細を見る 詳細を閉じる

    Nanometer-sized ferromagnetic tunnel junctions (MTJs) are suitable to investigate the enhancement of tunnel magnetoresistive effect (TMR) by Coulomb blockade effect. A new fabrication process that enables us to shrink the size of MTJs down to the order of 10 nm has been developed. MTJs structured by using this process exhibited large TMR ratio of 38%. (C) 2003 Elsevier B.V. All rights reserved.

  327. Ferromagnetic tunnel junctions with high thermal stability 査読有り

    Y. Ando, S. Iura, H. Kubota, T. Miyazaki, C. S. Yoon, J. H. Lee, D. H. Im, C. K. Kim

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 272 E1507-E1509 2004年5月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/j.jmmm.2003.12.314  

    ISSN:0304-8853

    詳細を見る 詳細を閉じる

    The junctions exposed to pure oxygen at the interface between the bottom CoFe layer and Al-oxide insulator were prepared. The junctions showed high thermal stability of tunnel magnetoresistance (TMR) ratio up to 375 degrees C in comparison with the standard junction oxidized with plasma. Auger electron spectroscopy (AES) profiles revealed that the Mn diffusion occurred even for the junction with high thermal stability after annealing over 375 degrees C. A large amount of oxygen existing at the interface might oxidize the Mn diffusing at the interface. (C) 2003 Elsevier B. V. All rights reserved.

  328. Time resolved luminescence properties of Al-q3 for spin-injection into organic semiconductor 査読有り

    E Shikoh, Y Ando, T Miyazaki

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 272 1921-1923 2004年5月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/j.jmmm.2003.12.1187  

    ISSN:0304-8853

    詳細を見る 詳細を閉じる

    The electroluminescence and conduction properties of organic light emitting devices (OLEDs) with Al-q3 emissive layer and with Fe cathode were investigated. The relative luminescence intensity for the device became lower than that with Al cathode. Time resolved photoluminescence of Alq3 was measured to investigate the electronic state of the interface between Fe and A1(q3) layer of OLEDs. The difference of luminescence intensities of OLEDs could not be explained only due to the work functions, but also due to the essential increase of quenching centers. (C) 2004 Elsevier B.V. All rights reserved.

  329. Time-resolved magnetization precession and reversal dynamics investigated using tunneling current and Kerr effect 査読有り

    Y Ando, H Nakamura, S Mizukami, H Kubota, T Miyazaki

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 272 293-294 2004年5月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/j.jmmm.2003.12.1245  

    ISSN:0304-8853

    詳細を見る 詳細を閉じる

    Magnetization precession and reversal dynamics in permalloy (Py) layer was studied using ns-time-scale spin-polarized tunneling current probing and ps-time-scale Kerr microscopy. In the time-resolved magneto-optical Kerr effect measurement, the precessional frequency increased with increasing external static field. The signal was fitted well with the calculation using Landau-Lifshitz-Gilbert equation of motion with the damping parameter alpha of 0.008, which corresponded to the value obtained for the film measured using a ferromagnetic resonance. (C) 2003 Elsevier B.V. All rights reserved.

  330. Co<SUB>2</SUB>MnAlホイスラー合金を用いた強磁性トンネル接合 査読有り

    中田淳, 大兼幹彦, 久保田均, 安藤康夫, 加藤宏朗, 宮崎照宣

    日本応用磁気学会誌 28 (4) 573-576 2004年

    出版者・発行元:The Magnetics Society of Japan

    DOI: 10.3379/jmsjmag.28.573  

    ISSN:0285-0192

    詳細を見る 詳細を閉じる

    We investigated the structural and magnetic properties of Co<sub>2</sub>MnAl thin films with Cr buffer layers, and the tunnel magnetoresistance (TMR) effect of junctions using Co<sub>2</sub>MnAl Heusler alloy. The saturation magnetization of Co<sub>2</sub>MnAl film deposited at 350°C was 711 emu/cm<sup>3</sup> which was almost the same as that reported for bulk. The maximum TMR ratio of the junctions was 12% at room temperature and 26% at 25K. TMR ratio increased to 17% at room temperature after annealing at 200°C for one hour.

  331. 集束イオンビームを用いた微小強磁性トンネル接合の作製 査読有り

    渡邉大輔, 久保田均, 安藤康夫, 宮崎照宣

    日本応用磁気学会誌 28 (4) 569-572 2004年

    出版者・発行元:The Magnetics Society of Japan

    DOI: 10.3379/jmsjmag.28.569  

    ISSN:0285-0192

    詳細を見る 詳細を閉じる

    A process for fabricating small magnetic tunnel junctions (MTJs) by using focused ion beam (FIB)-assisted chemical vapor deposition was investigated. Deposited tungsten was used as an electrode, and deposited carbon was used as a mask. MTJs with a junction area of 3 × 3 μm<sup>2</sup> showed a TMR ratio of about 30 % at room temperature.

  332. Tunnel Conductance in Ni<SUB>80</SUB>Fe<SUB>20</SUB>/Al-oxide/Al Junctions below the superconducting transition temperature of the Al films 査読有り

    M. Oogane, H. Kubota, Y. Ando, T. Miyazaki

    Transactions of .Material Research Society 29 1527-1530 2004年

  333. Characterization of thermally annealed tunnel junctions with preoxidized CoFe pinned electrode 査読有り

    JH Lee, DH Im, CS Yoon, CK Kim, Y Ando, H Kubota, T Miyazaki

    JOURNAL OF APPLIED PHYSICS 94 (12) 7778-7783 2003年12月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.1628827  

    ISSN:0021-8979

    詳細を見る 詳細を閉じる

    Postannealed structure and electron transport properties of the magnetic tunnel junctions with preoxidized CoFe pinned electrode were compared with those of the conventional plasma oxidized junctions. The preoxidized junction exhibited its peak tunneling magnetoresistance ratio at 375degreesC which is well above the optimal annealing of the normal junction. Using Auger electron spectroscopy and x-ray photoelectron spectroscopy of the thermally annealed junctions, structural and chemical changes after annealing were observed in the tunnel barrier as well as near the interface for both types of the junctions and these changes closely corresponded to the respective postannealed electrical properties. X-ray magnetic circular dichroism analysis indicated that the Co moment in the preoxidized CoFe electrode rose near the tunnel barrier/electrode interface as the optimal annealing temperature was reached. Our results demonstrated that the magnitude of spin polarized tunneling current is very sensitive to the interface structure and that any changes near the barrier interface during thermal annealing can greatly alter the electrical properties of the magnetic tunnel junctions. (C) 2003 American Institute of Physics.

  334. Magnetic tunnel junctions with doubly-plasma oxidized AlOx insulation layer 査読有り

    YM Lee, O Song, CS Yoon, CK Kim, Y Ando, H Kubota, T Miyazaki

    MICROELECTRONICS JOURNAL 34 (9) 805-808 2003年9月

    出版者・発行元:ELSEVIER ADVANCED TECHNOLOGY

    DOI: 10.1016/S0026-2692(03)00138-1  

    ISSN:0026-2692

    詳細を見る 詳細を閉じる

    Magnetic tunnel junctions (MTJ), with the tunnel barrier plasma oxidized in two steps, were fabricated in order to obtain structurally uniform AlOx insulator. The doubly oxidized junctions exhibited the magnetoresistance (MR) ratio of 27-31% without showing any noticeable drop in the MR ratio even after oxidation time was extended well beyond the optimal oxidation time for the normal junctions. Transmission electron microscopy of the junctions confirmed that the AlOx thickness was thinner for the doubly oxidized junctions compared to the singly oxidized MTJ. X-ray photoelectron spectroscopy of the doubly oxidized junction also strongly suggested that the initial oxide layer prevents the over-oxidation of the bottom electrode. The AlOx tunnel barrier oxidized in two steps improved the junction performance and widened the processing window. (C) 2003 Elsevier Science Ltd. All rights reserved.

  335. Size dependence of switching field of magnetic tunnel junctions down to 50 nm scale 査読有り

    H Kubota, Y Ando, T Miyazaki, G Reiss, H Bruckl, W Schepper, J Wecker, G Gieres

    JOURNAL OF APPLIED PHYSICS 94 (3) 2028-2032 2003年8月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.1588357  

    ISSN:0021-8979

    詳細を見る 詳細を閉じる

    Tunnel magnetoresistance curves were measured in very small tunnel junctions from scales of I Am to 50 nm using conductive atomic force microscopy. The junction arrays were prepared by a simple fabrication process using electron beam lithography. In large size junctions, the minor loops shifted in the negative field direction corresponding to ferromagnetic coupling between free and pinned layers. With decreasing size, the shift changed to the positive field direction corresponding to antiparallel coupling. The dependence of the shift was quantitatively explained by a model taking account of both Neel-type and dipole coupling. The minor loops showed asymmetric shape depending on field sweep directions. (C) 2003 American Institute of Physics.

  336. Nanofabrication of magnetic tunnel junctions by using side-edge thin film deposition 査読有り

    T. Niizeki, H. Kubota, Y. Ando, T. Miyazaki

    SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS 4 (4) 347-352 2003年7月

    出版者・発行元:NATL INST MATERIALS SCIENCE

    DOI: 10.1016/j.stam.2003.08.004  

    ISSN:1468-6996

    詳細を見る 詳細を閉じる

    Nanostructured double ferromagnetic tunnel junctions (MTJs) are indispensable for investigation of spin-dependent single-electron transport at low temperature. A new fabrication process that enables us to reduce the size of MTJs down to nanometer scale by using the side edge of a patterned film were developed. The multilayers of MTJ partially replaced by thick Al2O3/Cu double layer were prepared by using electron beam lithography and lift-off, then Pt film was vacuum-evaporated onto the side edge of Al2O3/Cu film, which masked MTJ during following Ar ion milling. As a result, the double MTJs with the dimension of 10 nm x 10 mu m were formed beneath the Pt film. The large tunnel magnetoresistive ratio of 35% and symmetrical I-V characteristics were obtained at room temperature. (C) 2003 Elsevier Ltd. All rights reserved.

  337. Electron transport properties in magnetic tunnel junctions with epitaxial NiFe (111) ferromagnetic bottom electrodes 査読有り

    JH Yu, HM Lee, Y Ando, T Miyazaki

    APPLIED PHYSICS LETTERS 82 (26) 4735-4737 2003年6月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.1587271  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    By employing epitaxial NiFe (111) films as ferromagnetic bottom electrodes, magnetic tunnel junctions with layer sequence of Si (111)/epitaxial Ag/epitaxial Cu/epitaxial NiFe/Al-oxide/CoFe/IrMn/NiFe/Ta were prepared. High tunneling magnetoresistance (TMR) ratios were obtained and the bias dependence of TMR was remarkably reduced. The reason for the small bias dependence of TMR was explained by inelastic electron tunneling spectroscopy. It was clearly elucidated that a well-defined sharp interface formed between the tunnel barrier and the ferromagnetic electrode that is nearly free of crystalline defects. This magnetic tunnel junction has a large capability in engineering aspects if we can reduce the barrier thickness further by decreasing the interface roughness. (C) 2003 American Institute of Physics.

  338. Interface characterization of magnetic tunnel junctions by using tunneling spectroscopy 査読有り

    Y Ando, M Hayashi, M Oogane, H Kubota, T Miyazaki

    JOURNAL OF APPLIED PHYSICS 93 (10) 7023-7025 2003年5月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.1540172  

    ISSN:0021-8979

    eISSN:1089-7550

    詳細を見る 詳細を閉じる

    Junctions doped with a small mount of Al between the top ferromagnetic electrode and the insulator were fabricated. The tunnel magnetoresistance (TMR) ratio increased at the doped Al thickness of 0.2 nm after annealing at 250degreesC. Inelastic-electron-tunneling spectroscopy (IETS) has been applied to investigate the spin-dependent tunneling process for the tunnel junctions. The IET spectrum subtracting the spectrum at parallel magnetization configuration from that at antiparallel configuration showed a peak around 20 mV of the bias voltage especially for the junction after annealing at 250degreesC. Over the corresponding voltage the TMR ratio as a function of the bias decreased; however, the influence was relatively small. (C) 2003 American Institute of Physics.

  339. Hard mask fabrication for magnetic random access memory elements using focused ion beam assisted selective chemical vapor deposition 査読有り

    H Kubota, M Hamada, Y Ando, T Miyazaki

    JOURNAL OF APPLIED PHYSICS 93 (10) 8370-8372 2003年5月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.1540058  

    ISSN:0021-8979

    詳細を見る 詳細を閉じる

    The fabrication of carbon masks for very small magnetic tunnel junctions (MTJs) was investigated using focused ion beam assisted selective chemical vapor deposition. Gaseous phenanthrene, absorbed on the sample surface, was decomposed into solid carbon by irradiation with a Ga ion beam. The carbon layer deposited showed a lower (higher) etching rate for Ar (O-2) ion etching. The width of the carbon mask patterns varied from about 30 to 500 nm. Arrays of MTJs with size on the 100 nm scale were fabricated successfully using the carbon mask patterns. (C) 2003 American Institute of Physics.

  340. Magnetic tunnel junctions with high magnetoresistance and small bias voltage dependence using epitaxial NiFe(111) ferromagnetic bottom electrodes 査読有り

    JH Yu, HM Lee, M Hayashi, M Oogane, T Daibou, H Nakamura, H Kubota, Y Ando, T Miyazaki

    JOURNAL OF APPLIED PHYSICS 93 (10) 8555-8557 2003年5月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.1544458  

    ISSN:0021-8979

    詳細を見る 詳細を閉じる

    Magnetic tunnel junctions (MTJs) were fabricated using an Al-O insulating layer prepared on an epitaxially grown Ni80Fe20 bottom electrode and on a polycrystalline Ni80Fe20 bottom electrode. Crystallographic orientations and surface morphology of the films were examined using x-ray diffraction and atomic force microscopy, respectively. The MTJ with an epitaxial bottom electrode showed a tunnel magnetoresistance (TMR) ratio of 51% after annealing at 250 degreesC. This value was about two times larger than that of the MTJ with a polycrystalline bottom electrode (27%). The applied bias voltage dependences of the TMR ratios were also much different. The V-half values of epitaxial and polycrystalline samples were about 750 and 400 mV, respectively. (C) 2003 American Institute of Physics.

  341. 下部磁性層表面を酸化して作製したトンネル接合の高耐熱特性 査読有り

    井浦聡則, 久保田均, 安藤康夫, 宮崎照宣

    日本応用磁気学会誌 27 (4) 303-306 2003年

    出版者・発行元:The Magnetics Society of Japan

    DOI: 10.3379/jmsjmag.27.303  

    ISSN:0285-0192

    詳細を見る 詳細を閉じる

    The annealing temperature dependence of the tunnel magnetoresistance (TMR) ratio for ferromagnetic tunnel junctions with additional oxidation at the surface of the bottom ferromagnetic layer was measured. A drastic increase of TMR ratio was achieved at high temperature around 375°C. Such a tendency was very similar to the dependence for radical oxidized junctions. The enhancement of the thermal stability would be due to the existence of oxigen on the surface of the bottom ferromagnetic layer.

  342. Recent Development of MRAM Technology 査読有り

    T. Miyazaki, Y. Ando, H. Kubota

    Journal of Magnetics 8 36-44 2003年

  343. 強磁性体/非磁性体接合におけるスピンポンピング 査読有り

    水上成美, 安藤康夫, 宮崎照宣

    日本応用磁気学会誌 27 934-939 2003年

  344. Growth mechanism of thin insulating layer in ferromagnetic tunnel junctions prepared using various oxidation methods 査読有り

    Y Ando, M Hayashi, S Iura, K Yaoita, CC Yu, H Kubota, T Miyazaki

    JOURNAL OF PHYSICS D-APPLIED PHYSICS 35 (19) 2415-2421 2002年10月

    出版者・発行元:IOP PUBLISHING LTD

    DOI: 10.1088/0022-3727/35/19/314  

    ISSN:0022-3727

    eISSN:1361-6463

    詳細を見る 詳細を閉じる

    Tunnel magnetoresistance (TMR) ratio as a function of annealing temperature for ferromagnetic tunnel junctions prepared using different oxidation methods was measured. The junction with plasma oxidation showed a TMR ratio of 31% before heat treatment and it increased to 49% after annealing at 300degreesC. On the other hand, the TMR ratio for the junction with radical oxidation showed a maximum at 350degreesC. The difference of thermal stability originates from the different oxidation procedure. The initial oxidation process of thin aluminium films was investigated by scanning tunnelling microscopy (STM). The STM images revealed progression of oxygen penetration into an aluminium film composed of small grains. Oxygen first covered the aluminium grain surface homogeneously for the plasma-oxidized junction; then oxygen inserted into the aluminium grain boundaries selectively for the radical-oxidized junction.

  345. Effect of spin diffusion on Gilbert damping for a very thin permalloy layer in Cu/permalloy/Cu/Pt films 査読有り

    S. Mizukami, Y. Ando, T. Miyazaki

    Physical Review B - Condensed Matter and Materials Physics 66 (10) 1044131-1044139 2002年9月1日

    DOI: 10.1103/PhysRevB.66.104413  

    ISSN:0163-1829

    詳細を見る 詳細を閉じる

    Ferromagnetic resonance (FMR) was measured for Cu/permalloy (Py) (20, 30, 40 Å)/Cu (dCu)/Pt (0, 50 Å) films with various dCu to clarify the effect of spin diffusion driven by the precession of magnetization on Gilbert damping. The peak-to-peak linewidth ΔHpp of the FMR spectra for Cu/Py/Cu/Pt films was very large at dCu = 0 Å, and decreased remarkably at dCu = 30 Å. Above dCu = 30 Å, it decreased gradually with increasing dCu in the anomalously wide range of dCu. The out-of-plane angular dependence of the FMR of Cu/Py(30 Å)/Cu (dCu)/Pt (0, 50 Å) films was measured and analyzed using a Landau-Lifshitz-Gilbert equation that took into account the local variation of the effective demagnetizing field. The Gilbert damping coefficient G obtained from the analysis for Cu/Py/Cu/Pt films was about twice as large as that for Cu/Py/Cu films even at dCu = 100 Å and decreased gradually as dCu increased. At dCu = 2000-3000 Å, G for Cu/Py/Cu/Pt and Cu/ Py/Cu films has the same value. We discussed the influence of spin diffusion driven by the precession of magnetization in FMR on G using a previously proposed model. The calculated G vs dCu fitted well to the experimental one, and the other features of the experimental results are well explained by the model.

  346. Effect of diffusion barrier in the thermally annealed exchange-biased IrMn-CoFe electrode in magnetic tunnel junctions 査読有り

    CS Yoo, HD Jeong, JH Lee, CS Yoon, CK Kim, JH Yuh, Y Ando, H Kubota, T Miyazaki

    IEEE TRANSACTIONS ON MAGNETICS 38 (5) 2715-2717 2002年9月

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

    DOI: 10.1109/TMAG.2002.803168  

    ISSN:0018-9464

    詳細を見る 詳細を閉じる

    Exchange-biased electrodes IrMn/Ta(2 Angstrom)/CoFe/AlOx and IrMn/CoFe/Ta(2 Angstrom)-AlOx used in a magnetic tunnel junction were annealed at 300 degreesC to study the Mn diffusion characteristics. Auger electron spectroscopy and X-ray photoelectron spectroscopy analysis of the annealed electrodes show that the diffusion barrier effectively blocked the Mn migration, regardless of the barrier location. Also concluded from the study was that the Mn migration is largely enhanced by the preferential oxidation of Mn.

  347. Effect of spin diffusion on Gilbert damping for a very thin permalloy layer in Cu/permalloy/Cu/Pt films 査読有り

    S Mizukami, Y Ando, T Miyazaki

    PHYSICAL REVIEW B 66 (10) 104413-1-104413-9 2002年9月

    出版者・発行元:AMER PHYSICAL SOC

    DOI: 10.1103/PhysRevB.66.104413  

    ISSN:2469-9950

    eISSN:2469-9969

    詳細を見る 詳細を閉じる

    Ferromagnetic resonance (FMR) was measured for Cu/permalloy (Py) (20, 30, 40 Angstrom)/Cu (d(Cu))/Pt (0, 50 Angstrom) films with various d(Cu) to clarify the effect of spin diffusion driven by the precession of magnetization on Gilbert damping. The peak-to-peak linewidth DeltaH(pp) of the FMR spectra for Cu/Py/Cu/Pt films was very large at d(Cu)=0 Angstrom, and decreased remarkably at d(Cu)=30 Angstrom. Above d(Cu)=30 Angstrom, it decreased gradually with increasing d(Cu) in the anomalously wide range of d(Cu). The out-of-plane angular dependence of the FMR of Cu/Py(30 Angstrom)/Cu (d(Cu))/Pt (0, 50 Angstrom) films was measured and analyzed using a Landau-Lifshitz-Gilbert equation that took into account the local variation of the effective demagnetizing field. The Gilbert damping coefficient G obtained from the analysis for Cu/Py/Cu/Pt films was about twice as large as that for Cu/Py/Cu films even at d(Cu)=100 Angstrom and decreased gradually as d(Cu) increased. At d(Cu)=2000-3000 Angstrom, G for Cu/Py/Cu/Pt and Cu/Py/Cu films has the same value. We discussed the influence of spin diffusion driven by the precession of magnetization in FMR on G using a previously proposed model. The calculated G vs d(Cu) fitted well to the experimental one, and the other features of the experimental results are well explained by the model.

  348. Magnetic relaxation of normal-metal (NM)/80NiFe/NM films 査読有り

    S Mizukami, Y Ando, T Miyazaki

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 239 (1-3) 42-44 2002年2月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/S0304-8853(01)00525-X  

    ISSN:0304-8853

    詳細を見る 詳細を閉じる

    Ferromagnetic resonance was measured for Cu 80NiFe(Py), Cu Pt films with various thicknesses of Cu spacer (d(Cu)) in order to clarify the mechanism of the enhancement of Gilbert damping parameter (G) for Pt/Py/Pt films reported previously. The peak-to-peak linewidth (DeltaH(PP)) for the Cu/Py/Cu/Pt film was very large at d(Cu) = 0 Angstrom and decreased gradually with increasing d(Cu). The out-of-plane angular dependence of DeltaH(PP) for Cu/Py/Cu/Pt films was measured and analyzed using Landau-Lifshitz-Gilbert equation, by taking into account the magnetic inhomogeneities, The value of G obtained from analysis of the Cu/Py/Cu/Pt film was about twice larger than that for Cu/Py/Cu film even at d(Cu) = 100 Angstrom and decreased gradually as d(Cu) increased. (C) 2002 Elsevier Science B.V. All rights reserved.

  349. Micro structural and magnetic characteristics of IrMn exchange-biased tunnel junctions 査読有り

    ACC Yu, XF Han, J Murai, Y Ando, T Miyazaki, K Hiraga

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 240 (1-3) 130-133 2002年2月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/S0304-8853(01)00734-X  

    ISSN:0304-8853

    詳細を見る 詳細を閉じる

    Tunneling magnetoresistance values above 20% and 40% were obtained for as-deposited and annealed tunnel junctions, Ta/NiFe/Cu/NiFe/IrMn/CoFe/Al-oxide/CoFe/NiFe/Ta, respectively. Exchange biasing field increased from 270 to 550 Oe after annealing resulting from sharpening of the IrMn/CoFe interface. dV/dI vs. F curves showed asymmetric profiles, which were due to asymmetry of the CoFe/Al-oxide interfaces and difference in microstructure of the CoFe layers. (C) 2002 Elsevier Science B.V. All rights reserved.

  350. ラジカル酸化法で作製した高耐熱強磁性トンネル接合 査読有り

    井浦聡則, 久保田均, 安藤康夫, 宮崎照宣

    日本応用磁気学会誌 26 (6) 839-842 2002年

    出版者・発行元:公益社団法人 日本磁気学会

    DOI: 10.3379/jmsjmag.26.839  

    詳細を見る 詳細を閉じる

    The annealing temperature dependence of the tunnel magnetore-sistance (TMR) ratio for ferromagnetic tunnel junctions prepared by various oxidation methods was measured. A junction prepared by plasma oxidation showed a TMR ratio of 31.4% before heat treatment, and this ratio increased to 49% after annealing at 300&deg;C. On the other hand, the TMR ratio for a junction prepared by radical oxidation showed a maximum at 350&deg;C. The enhancement of the thermal stability resulted from the different oxidation progress depending on the oxidation method.

  351. Scanning tunneling microscopy observation of the initial state of oxidation in ferromagnetic tunnel junctions 査読有り

    M Hayashi, Y Ando, T Miyazaki

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS 40 (12A) L1317-L1319 2001年12月

    出版者・発行元:INST PURE APPLIED PHYSICS

    DOI: 10.1143/JJAP.40.L1317  

    ISSN:0021-4922

    詳細を見る 詳細を閉じる

    The initial oxidation process of thin aluminum films used in ferromagnetic tunnel junctions was investigated-by scanning tunneling microscopy (STM). The STM images reveal the progression of oxygen penetration into an aluminum film composed of small grains. The oxygen first covers the aluminum grain surface homogeneously. At the same time, the oxygen is inserted into the aluminum grain boundaries. As the oxidation proceeds, the oxygen penetrates inside the grain.

  352. Magnon excitation of CoFe/Al-oxide/CoFe ferromagnetic tunnel junctions 査読有り

    J Murai, Y Ando, T Daibou, K Yaoita, HF Han, T Miyazaki

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 226 922-923 2001年5月

    出版者・発行元:ELSEVIER SCIENCE BV

    ISSN:0304-8853

    詳細を見る 詳細を閉じる

    Inelastic-electron-tunneling(IET) spectroscopy has been applied to investigate the magnon-induced inelastic tunneling process for Ta/Ni80Fe20/Cu/Ni80Fe20/IrMn/Co75Fe25 /Al-oxide/Co75Fe25/Ni80Fe20/Ta ferromagnetic tunnel junctions. For the junction with the oxidation time. t(ox) = 40 s, which is the exact time to oxidize the 8 Angstrom Al, the subtraction spectrum of the LET spectra between the parallel and anti-parallel magnetization configurations clearly showed two peaks at +/- 3 and +/- 16mV showed. On the other hand, the spectrum for the junction with t(ox) = 120 s showed a broad peak at around 18 mV and a plateau at zero-bias. This was caused by the change of the correlation length of magnon inelastic excitation due to the over oxidation of the bottom electrode. (C) 2001 Elsevier Science B.V. All rights reserved.

  353. Optical and magnetic properties for metal halide-based organic-inorganic layered perovskites 査読有り

    E Shikoh, Y Ando, M Era, T Miyazaki

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 226 2021-2022 2001年5月

    出版者・発行元:ELSEVIER SCIENCE BV

    ISSN:0304-8853

    詳細を見る 詳細を閉じる

    Layered perovskites (RNH3)(2)CuCl4, where R was methyl-benzene C6H5-CH2, 1-methyl-naphthalene 1-C10H9-CH2, 1-propyl-naphthalene 1-C10H9-O(CH2)(3) and 1-butyl-naphthalene 1-C10H9-O(CH2)(4), were synthesized. These complexes showed ferromagnetism, with different Curie temperatures, T-C, depending on the structure of the molecule. The change of T-C by taking into account the overlap of the electronic states between the organic and the inorganic layers were discussed. (C) 2001 Elsevier Science B.V. All rights reserved.

  354. Local transport properties of ferromagnetic tunnel junctions 査読有り

    Y Ando, M Hayashi, M Kamijo, H Kubota, T Miyazaki

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 226 924-925 2001年5月

    出版者・発行元:ELSEVIER SCIENCE BV

    ISSN:0304-8853

    詳細を見る 詳細を閉じる

    The local electrical properties were measured simultaneously with the topography for a SiO2/Ta(3nm)/ I Fe20Ni80(3 nm)/Pt(20nm)/Fe20Ni80(3 nm)/IrMn(10 nm)/Co75Fe25(4 nm)/Al(0.8 nm)-oxide junction. The current image became very homogeneous and smooth after annealing at around 300 C for 1 h. Increase of tunneling magnetoresistance ratio of the junction after annealing can be well explained by taking into account both increase of the barrier height and decrease of the barrier height variation. After further annealing over 350 C. the barrier height decreased and leak currents were detected. Reduction of spin polarization of the ferromagnetic electrodes due to interface mixing or damage of the insulator due to the growth of grains of bottom electrode is a possible reason for the drastic decrease of TMR ratio for annealing at temperatures higher than 350 C. (C) 2001 Elsevier Science B.V. All rights reserved.

  355. Ferromagnetic resonance linewidth for NM/80NiFe/NM films (NM = Cu, Ta, Pd and Pt) 査読有り

    S Mizukami, Y Ando, T Miyazaki

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 226 1640-1642 2001年5月

    出版者・発行元:ELSEVIER SCIENCE BV

    ISSN:0304-8853

    詳細を見る 詳細を閉じる

    The out-of-plane angular dependence of ferromagnetic resonance linewidth of non-magnetic metal (NM)/80NiFe(Py)(20-100 Angstrom)/NM (NM = Cu, Ta, Pd and Pt) sputtered films were measured for the investigation of magnetic damping. The linewidth for NM = Pd and Pt were larger than that of NM = Cu and Ta. Analysis of the angular dependence of the linewidth using Landau-Lifshitz-Gilbert equation with magnetic inhomogeneities showed that the Gilbert damping parameter, G, for NM = Pt and Pd were larger than the bulk value of Py and were dependent on the thickness of Py. G, for NM = Cu and Ta. were same as the bulk value. These results show that the magnetization precession of Py layers sandwiched by Pt or Pd layers damps more rapidly. (C) 2001 Elsevier Science BY. All rights reserved.

  356. Inelastic magnon and phonon excitations in Al1-xCox/Al1-xCox-oxide/Al tunnel junctions 査読有り

    XF Han, J Murai, Y Ando, H Kubota, T Miyazaki

    APPLIED PHYSICS LETTERS 78 (17) 2533-2535 2001年4月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.1367882  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    Magnetoelectric properties of the tunnel junctions, Al(50 nm)/Al2O3(1.2 nm)/Al(50 nm) (x=0), Al(55 nm)/Al2O3(1.0 nm)/Co(55 nm) (x=0 and top electrode is Co), and Al1-xCox(55 nm)/Al1-xCox-oxide(d nm)/Al(55 nm) (x=0.25, 0.50, 0.75, and 1.0), were investigated. Oxides of Al1-xCox (x=0, 0.25, 0.50, 0.75, and 1.0) were chosen as barrier materials in order to modulate the magnon and phonon excitations in the barrier layer and the interfaces. It was shown that the magnon and phonon excitations were the main sources of inelastic scattering in the tunneling processes for the conduction electrons in these tunnel junctions at nonzero bias voltages. The magnon effects were enhanced in the Co-rich barrier junctions. The Al-O-Co phonon energy decreased with increasing Co composition between the Al-O and Co-O phonon energies based on an Al-O-Co stretching mode in the Al1-xCox-oxide barrier as vibrational frequency of crystal lattice decreased with increasing Co composition. (C) 2001 American Institute of Physics.

  357. Analyses of intrinsic magnetoelectric properties in spin-valve-type tunnel junctions with high magnetoresistance and low resistance 査読有り

    X. F. Han, A. C. C. Yu, M. Oogane, J. Murai, T. Daibou, H. Kubota, Y. Ando, T. Miyazaki

    Physical Review B 2001年3月

  358. Effect of microstructure on the magnetoresistive properties of NiFe/Co(CoFe)/Al(Ta)-oxide/Co(CoFe) tunnel junctions 査読有り

    H Kyung, HS Ahn, CS Yoon, CK Kim, O Song, T Miyazaki, Y Ando, H Kubota

    JOURNAL OF APPLIED PHYSICS 89 (5) 2752-2755 2001年3月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.1343519  

    ISSN:0021-8979

    詳細を見る 詳細を閉じる

    The microstructure of the NiFe/Co(CoFe)/Al(Ta)-oxide/Co(CoFe) ferromagnetic tunnel junction was investigated using cross-sectional transmission electron microscopy (TEM). The effect of the insulating layer on the magnetoresistive (MR) properties of the junction was studied. The multilayer junction was formed using magnetron sputtering and the insulating layer was created by plasma oxidation of the deposited metal film. TEM analysis showed that the MR ratio was highly dependent on the insulating layer. For the NiFe/Co/Al-oxide/Co junction, when the Al2O3 layer was 13 A, the oxide layer was flat and the highest MR ratio of 15% was attained. As the Al2O3 thickness increased, the interface roughness rapidly increased, and the MR ratio also markedly dropped. In contrast, NiFe/CoFe/Al-oxide/CoFe junction showed a comparatively flatter interface and recorded a higher MR ratio. The Ta-oxide insulating layer remained flat regardless of the thickness; however, the largest MR ratio of only 9% was obtained within a narrow thickness range. We have demonstrated that there exists a direct correlation between the microstructure of the oxide layer and the MR ratio of the junction, which could be utilized to optimize the electrical properties of the ferromagnetic tunneling junction. (C) 2001 American Institute of Physics.

  359. The study on ferromagnetic resonance linewidth for NM/80NiFe/NM (NM = Cu, Ta, Pd and Pt) films 査読有り

    S Mizukami, Y Ando, T Miyazaki

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 40 (2A) 580-585 2001年2月

    出版者・発行元:INST PURE APPLIED PHYSICS

    DOI: 10.1143/JJAP.40.580  

    ISSN:0021-4922

    詳細を見る 詳細を閉じる

    The out-of-plane angular dependence of ferromagnetic resonance (FMR) was measured for NM/80NiFe(Py)/NM (NM = Cu, Ta, Pd and Pt) films with various Py, Cu and Ta thicknesses fabricated by magnetron sputtering. The out-of-plane angular dependences of FMR resonance field and linewidth were analyzed using Landau-Lifshitz-Gilbert equation taking account of broadening of linewidth due to magnetic inhomogeneities in a film. Magnetic inhomogeneities were assumed to be the fluctuation of magnitude and direction of the effective demagnetization held which contains both demagnetization and perpendicular anisotropy field for a film. The calculations of the angular variations of linewidth agreed with the experimental ones quantitatively. The fluctuations of magnitude and direction of the effective demagnetization field, which are represented as Delta (4 pi M-eff.) and Delta theta (H), respectively, increased with decreasing Py thickness for all NM/Py/NM films, Delta theta (H) increased as the thicknesses of the buffer layers increased for Cu/Py(40 Angstrom)/Cu films and was almost constant with increasing buffer layer thickness for Ta/Py(40 Angstrom)/Ta films. Only in the case of NM = Pd and Pt films, the Gilbert damping parameter, which is the speed of decay of magnetization precession, was enhanced significantly as compared with that for the bulk sample and was dependent on Py thickness.

  360. Microfabrication and Magnetoelectric Properties of High-magnetoresistance Tunnel Junctions 査読有り

    X. F. Han, M. Oogane, T. Daibou, K. Yaoita, Y. Ando, H. Kubota, T. Miyazaki

    J. Magn. Soc. Jpn. 25 (4) 707-710 2001年

    出版者・発行元:The Magnetics Society of Japan

    DOI: 10.3379/jmsjmag.25.707  

    ISSN:0285-0192

    詳細を見る 詳細を閉じる

    Spin-valve-type tunnel junctions with structure of Ta(5nm)/Ni<sub>79</sub>Fe<sub>21</sub>(3 nm)/Cu(20 nm)/Ni<sub>79</sub>Fe<sub>21</sub>(3 nm)/Ir<sub>22</sub>Mn<sub>78</sub> (10 nm)/Co<sub>75</sub>Fe<sub>25</sub>(4 nm)/Al(0.80 nm)-oxide /Co<sub>75</sub>Fe<sub>25</sub>(4 nm)/Ni<sub>79</sub>Fe<sub>21</sub>(20 nm)/Ta(5 nm) were fabricated using a microfabrication technique. The optical lithography combined with Ar ion-beam etching and CF<sub>4</sub> active etching was used to pattern the junction area with the size from 100x100 down to 3x3 μm<sup>2</sup>. A thinner barrier layer and a short plasma-oxidation time for Al-oxide layer were used in order to reduce the junction resistance and increase the TMR ratio. High TMR ratio of 69.1% at 4.2 K and 49.7% at room temperature were achieved. A spin-electron polarization tunneling model, based on magnon emission or absorption by the tunneling electrons during the tunnel process, was extended by defining an anisotropic wavelength cutoff energy of spin-wave in this work. Intrinsic magnetoelectric properties, such as the temperature dependence of TMR ratio and resistances from 4.2 to 300 K at 1.0 mV bias can be self-consistently evaluated using this extended model and a unique set of intrinsic parameters.

  361. 強磁性トンネル接合のスピン依存局所伝導特性 査読有り

    林将光, 安藤康夫, 久保田均, 宮崎照宣

    日本応用磁気学会誌 25 (4) 759-762 2001年

    出版者・発行元:The Magnetics Society of Japan

    DOI: 10.3379/jmsjmag.25.759  

    ISSN:0285-0192

    詳細を見る 詳細を閉じる

    The local electrical properties in ferromagnetic tunnel junctions was measured using contact-mode Atomic Force Microscopy (AFM). The electrical current images reflected the barrier height distribution determined by local <i>I-V</i> curve measurement The TMR ratio was estimated from the current histogram. The estimation closely fitted the experimental temperature dependence of TMR ratio. The TMR ratio was shown to increase with a decrease in the deviation of barrier height distribution and with an increase in average barrier height The effect of the local current channel with low barrier height on the TMR ratio is also discussed.

  362. プラズマ酸化法による低抵抗強磁性トンネル接合の作製 査読有り

    矢尾板和也, 上條誠, 新関智彦, 山本直志, 久保田均, 安藤康夫, 宮崎照宣

    日本応用磁気学会誌 25 (4) 771-774 2001年

    出版者・発行元:The Magnetics Society of Japan

    DOI: 10.3379/jmsjmag.25.771  

    ISSN:0285-0192

    詳細を見る 詳細を閉じる

    Ferromagnetic tunnel junctions , Ta/Ni<sub>80</sub>Fe<sub>20</sub>/Cu/Ni<sub>80</sub>Fe<sub>20</sub>/IrMn/Co<sub>75</sub>Fe<sub>25</sub>/Al-oxide/Co<sub>75</sub>Fe<sub>25</sub>/Ni<sub>80</sub>Fe<sub>20</sub>/Ta, were fabricated using ICP oxidation, and the detailed annealing temperature dependence of the TMR effect was investigated. Thickness of the Al layer was varied from 6.6 to 7.7 Å before oxidation, and the oxidation time was optimized for each thickness. The 1-μm<sup>2</sup> junctions were micro fabricated usinge-beam lithography. When the Al thickness was 6.6 Å, the RA decreased to 60-100 Ω·μm<sup>2</sup> and the TMR ratio became 30%. The lower the <i>RA</i> was, the lower the TMR ratio became.

  363. 中間層にAl を用いた二重トンネル接合の磁気抵抗効果 査読有り

    大坊忠臣, 大兼幹彦, 安藤康夫, Changkyung Kim, Ohsung Song, 宮崎照宣

    日本応用磁気学会誌 25 (4) 767-770 2001年

    出版者・発行元:The Magnetics Society of Japan

    DOI: 10.3379/jmsjmag.25.767  

    ISSN:0285-0192

    詳細を見る 詳細を閉じる

    Tunnel magnetoresistance for double barrier tunnel junctions with an intermediate layer of metallic Al was investigated. The junction with a 40-Å intermediate layer of Al showed a about 8.5%. TMR ratio. The TMR ratio decreased with increasing Al thickness and became zero at 100 Å. At a low temperature, Al thin film was expected to be in transition to superconductor. A superconducting gap was observed in the two junctions with 40-Å and 100-Å Al at about 0.4 K.

  364. 二重強磁性トンネル接合におけるスピン依存伝導特性 査読有り

    T. Siripongsakul, 大兼幹彦, 村井純一郎, Andrew C. C. Yu, 久保田均, 安藤康夫, 宮崎照宣, Changkyung Kim, Ohsung Song

    日本応用磁気学会誌 25 (4) 763-766 2001年

    出版者・発行元:The Magnetics Society of Japan

    DOI: 10.3379/jmsjmag.25.763  

    ISSN:0285-0192

    詳細を見る 詳細を閉じる

    Ferromagnetic double barrier junctions of Co<sub>75</sub>Fe<sub>25</sub>/ Al<sub>2</sub>O<sub>3</sub>/ Co<sub>75</sub>Fe<sub>25</sub>(<i>X</i>)/ Al<sub>2</sub>O<sub>3</sub>/ Co<sub>75</sub>Fe<sub>25</sub> with discontinuous middle Co<sub>75</sub>Fe<sub>25</sub> layers (<i>X</i> = 0, 0.7, 1.3, 2.0 nm) were fabricated, and magnetoresistance of these junctions was measured by a dc-4-probe method. At low temperature, the resistance and TMR ratio increased rapidly. This result implies the existence of a charging effect due to the Coulomb-blockade. At temperatures below 50 K, an ac-modulation method was used to measure bias-voltage dependence of the TMR ratio. We observed an increase in TMR ratio for the case of dc transport at low bias voltage. On the other hand, the TMR ratio decreased for the case of ac transport. At high bias voltage and at high temperature, however, we observed no difference between these methods. Such transport properties could be explained by a co-tunneling process.

  365. 有機-無機層状ペロブスカイト錯体の磁性と光学特性 査読有り

    仕幸英治, 安藤康夫, 江良正直, 宮崎照宣

    日本応用磁気学会誌 25 (4) 755-758 2001年

    出版者・発行元:The Magnetics Society of Japan

    DOI: 10.3379/jmsjmag.25.755  

    ISSN:0285-0192

    詳細を見る 詳細を閉じる

    Layered perovskites (RNH<sub>3</sub>)<sub>2</sub>CuCl<sub>4</sub> were synthesized, where R was C<sub>6</sub>H<sub>5</sub>(CH<sub>2</sub>)-, C<sub>6</sub>H<sub>5</sub>(CH<sub>2</sub>)<sub>2</sub>-, <i>1</i>-C<sub>10</sub>H<sub>7</sub>(CH<sub>2</sub>)-, <i>2</i>-C<sub>10</sub>H<sub>7</sub>(CH<sub>2</sub>)-, <i>1</i>-C<sub>6</sub>H<sub>5</sub>N=NC<sub>6</sub>H<sub>4</sub>O(CH<sub>2</sub>)<sub>3</sub>- and <i>1</i>-C<sub>6</sub>H<sub>5</sub>COC<sub>6</sub>H<sub>4</sub>O(CH<sub>2</sub>)<sub>3</sub>-. These complexes showed ferromagnetism, with different Curie temperatures, <i>T<sub>c</sub></i>, depending on the structure of the molecules. These <i>T<sub>c</sub></i> seem to be independent of the distance of interlayer space between CuCl-based layers. The complexes with naphthalene showed lower <i>T<sub>c</sub></i> than those with benzene. Since naphthalene has more π-electrons than benzene, the degree of electronic state mixing between the organic and the inorganic layers might change and affect the interlayer magnetic interaction <i>J</i>'.

  366. Annealing effect on low-resistance ferromagnetic tunnel junctions 査読有り

    Y Ando, H Kubota, M Hayashi, M Kamijo, K Yaoita, ACC Yu, XF Han, T Miyazaki

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 39 (10) 5832-5837 2000年10月

    出版者・発行元:INST PURE APPLIED PHYSICS

    DOI: 10.1143/JJAP.39.5832  

    ISSN:0021-4922

    詳細を見る 詳細を閉じる

    The stacking structure and fabrication process of tunnel junctions were investigated. The stacking structure of the tunnel junctions fabricated was Ta/(Cu,Pt)/Fe20Ni80/IrMn/Co75Fe25/Al-oxide/Co75Fe25/Fe20Ni80/Ta. When the Al thickness, oxidation rime, and annealing temperature were 0.8 nm, 15 s (10 s), and 300 degreesC (250 degreesC), the tunnel magnetoresistance (TMR) ratio and the resistance obtained were 49% (31%) and 1.1 k Ohm mum(2) (230 Ohm mum(2)), respectively. In order to investigate the annealing temperature dependence of the TMR ratio, the local electrical properties were measured for a Ta/Fe20Ni80/Pt/Fe20Ni80/IrMn/Co-75/Fe-25/Al-oxide multilayer. The current image became very homogeneous after annealing at around 300 degreesC for Ih. The increase of the TMR ratio of the junction after annealing can be well explained by taking into account both an increase of barrier height and a decrease of barrier height fluctuation. After further annealing at above 350 degreesC, the barrier height decreased and leakage currents were detected.

  367. Enhancement of tunnel magnetoresistance in ferromagnet/granular/ferromagnet junction related to the Coulomb blockade effect (vol 87, pg 5212, 2000) 査読有り

    H Kubota, Y Fukumoto, S Thamrongsing, Y Ando, T Miyazaki, CC Yu

    JOURNAL OF APPLIED PHYSICS 88 (3) 1704-1704 2000年8月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.373881  

    ISSN:0021-8979

  368. Fabrication of high-magnetoresistance tunnel junctions using Co75Fe25 ferromagnetic electrodes 査読有り

    XF Han, M Oogane, H Kubota, Y Ando, T Miyazaki

    APPLIED PHYSICS LETTERS 77 (2) 283-285 2000年7月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.126951  

    ISSN:0003-6951

    詳細を見る 詳細を閉じる

    Temperature dependence of tunnel magnetoresistance (TMR) ratio, resistance, and coercivity from 4.2 K to room temperature and applied voltage dependence of the TMR ratio and resistance at room temperature for a tunnel junction, Ta (5 nm)/Ni79Fe21 (3 nm)/Cu (20 nm)/Ni79Fe21 (3 nm)/Ir22Mn78 (10 nm)/Co75Fe25 (4 nm)/Al (0.8 nm)-oxide/Co75Fe25 (4 nm)/Ni79Fe21 (20 nm)/Ta(5 nm), were investigated. TMR ratio, effective barrier height and width, and breakdown voltage of the junction can be remarkably enhanced after annealing at 300 degrees C for an hour. High TMR ratio of 49.7% at room temperature and 69.1% at 4.2 K were observed. The value of spin polarization of Co75Fe25, P = 50.7%, deduced from the TMR ratio at 4.2 K was corresponding well to the experimental data measured at 0.2 K in a spin polarized tunneling experiment using a superconductor/insulator/ferromagnet tunneling junction. (C) 2000 American Institute of Physics. [S0003-6951(00)05028-2].

  369. Local current distribution in a ferromagnetic tunnel junction measured using conducting atomic force microscopy 査読有り

    Y Ando, H Kameda, H Kubota, T Miyazaki

    JOURNAL OF APPLIED PHYSICS 87 (9) 5206-5208 2000年5月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.373296  

    ISSN:0021-8979

    詳細を見る 詳細を閉じる

    The local electrical properties were measured simultaneously with the topography for a Ta(50 Angstrom)/Fe20Ni80(50 )/IrMn(150 Angstrom)/Co(50 Angstrom)/Al(13 Angstrom)-oxide junction. The electrical image showed the contrast with around a few nm lateral size and a strong correlation with the topographical image was not observed. In the local current-voltage characteristics, data within the bias voltage of +/- 1.5 V were fitted well to Simmon's equation and we obtained the barrier height Phi=1.9 eV and the thickness d=12 Angstrom. On the other hand, data with the bias voltages higher than 3 V were fitted well to Fowler-Nordheim equation. The histogram of current density was calculated by taking into consideration a Gaussian distribution of the barrier thickness and the height. The distribution of the barrier height can explain the experimental result realistically. (C) 2000 American Institute of Physics. [S0021-8979(00)54308-4].

  370. High-magnetoresistance tunnel junctions using Co75Fe25 ferromagnetic electrodes 査読有り

    XF Han, T Daibou, M Kamijo, K Yaoita, H Kubota, Y Ando, T Miyazaki

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS 39 (5B) L439-L441 2000年5月

    出版者・発行元:INST PURE APPLIED PHYSICS

    DOI: 10.1143/JJAP.39.L439  

    ISSN:0021-4922

    詳細を見る 詳細を閉じる

    Tunnel magnetoresistance (TMR) effect and the applied voltage dependence of the TMR ratio in the tunnel junctions Ta(5 nm)/Ni79Fe21 (3 nm)/Cu(20 nm)/Ni79Fe21 (3 nm)/Ir22Mn78(10 nm)/Co75Fe25(4 nm)/Al(0.8 nm)-oxide/Co75Fe25 (4 nm)/Ni79Fe21(20 nm)/Ta(5 nm) were investigated. MR ratio, effective barrier height and width, and breakdown voltage of the junctions can be remarkably enhanced after annealed at 300 degreesC for an hour using Co75Fe25 as ferromagnetic electrodes and Cu as bottom conduction electrode. High MR ratio of 49.7% at room temperature and 69.1% at 4.2 K for the TMR junctions were observed.

  371. Magnon-assisted inelastic excitation spectra of a ferromagnetic tunnel junction 査読有り

    Y Ando, J Murai, H Kubota, T Miyazaki

    JOURNAL OF APPLIED PHYSICS 87 (9) 5209-5211 2000年5月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.373297  

    ISSN:0021-8979

    詳細を見る 詳細を閉じる

    Inelastic-electron-tunneling spectroscopy (IETS) has been applied to investigate the spin dependent tunneling process for a Ta(50 Angstrom)/Fe20Ni80(60 Angstrom)/IrMn(300 Angstrom)/Co(60 Angstrom)/Al(13 Angstrom)-oxide/ Co(40 Angstrom)/Fe20Ni80(200 Angstrom) spin-valve-type tunnel junction. IET spectra for both parallel and antiparallel magnetization configurations of ferromagnetic electrodes showed a strong peak at 12 mV. The subtraction spectrum defined by the difference between the spectra of both the configurations was calculated. Spin-independent inelastic excitation processes are not affected by an external magnetic field, and thus, the subtraction spectrum indicates the inelastic modes induced only by the magnetic origin. It showed a strong peak at 12 and 20 mV for the positively and negatively biased direction of the bottom electrode, respectively. The tendency of the tunneling magnetoresistance ratio to decrease with bias voltage agreed with the shape of the subtraction spectrum. By assuming the surface magnon excitation, we obtained the distributions of the correlation length and the Curie temperature for both ferromagnetic electrode surfaces faced on the insulator. (C) 2000 American Institute of Physics. [S0021-8979(00)54408-9].

  372. Enhancement of tunnel magnetoresistance in ferromagnet/granular/ferromagnet junction related to the Coulomb blockade effect 査読有り

    H Kubota, Y Fukumoto, S Thamrongsing, Y Ando, T Miyazaki, C Yu

    JOURNAL OF APPLIED PHYSICS 87 (9) 5212-5214 2000年5月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.373298  

    ISSN:0021-8979

    詳細を見る 詳細を閉じる

    We study tunnel magnetoresistance effect in ferromagnet/granular/ferromagnet tunnel junctions in the Coulomb blockade regime. The granular consists of a Al-O/Co/Al-O/Co/Al-O multilayer, which was sputtered sequentially. The magnetoresistance (MR) ratio and the resistance (R-s) of the junction increased with decreasing bias voltage at low temperatures. The MR ratio and R-s were calculated based on the theory proposed by Takahashi and Maekawa [S. Takahashi and S. Mackawa, Phys. Rev. B 90, 1758 (1998)]. Although the variation of these values on bias voltage was different from experimental results, the calculated MR ratio in the Coulomb blockade regime agreed well with the maximum value measured. (C) 2000 American Institute of Physics. [S0021-8979(00)54508-3].

  373. Effect of particle size on the magnetization process in lithographic arrays of Nd2Fe14B 査読有り

    H Kubota, T Ikari, Y Ando, H Kato, T Miyazaki

    JOURNAL OF APPLIED PHYSICS 87 (9) 6325-6327 2000年5月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.372694  

    ISSN:0021-8979

    eISSN:1089-7550

    詳細を見る 詳細を閉じる

    Controlled arrays of Nd2Fe14B were fabricated via sputtering and lithography. The arrays were fabricated via optical and electron-beam lithography combined with dry etching technique. Designed particle size varies from 10 mu mx10 mu m to 0.5 mu mx0.5 mu m. We found an increase in the coercive field with decreasing particle size. Results of the micromagnetic calculations suggest that the coercive-field increase in smaller-sized particles is originated from the effective decrease in the exchange-coupling energy owing to the relative increase in the fraction of surface grain. (C) 2000 American Institute of Physics. [S0021-8979(00)74608-1].

  374. 強磁性トンネル接合の低抵抗化と熱処理効果

    上條 誠, 村井 純一郎, 久保田 均, 安藤 康夫, 宮崎 照宣, Changkyung Kim, Ohsung Song

    日本応用磁気学会誌 24 (4) 591-594 2000年4月15日

    出版者・発行元:The Magnetics Society of Japan

    DOI: 10.3379/jmsjmag.24.591  

    ISSN:0285-0192

    詳細を見る 詳細を閉じる

    Ferromagnetic tunnel junctions of Ta/Al/Ta/Ni<sub>80</sub>Fe<sub>20</sub>/IrMn/Co/Al-oxide/Co/Ni<sub>80</sub>Fe<sub>20</sub>/Ta/Cu with various Al-oxide thicknesses were fabricated by rf magnetron sputtering and ICP oxidization. The thickness of Al was varied from 6 Å to 13 Å. With decreasing thickness, the tunnel resistance decreased from 3 x 10<sup>5</sup> Ω·μm<sup>2</sup> to 1.2 x 10<sup>2</sup>Ω·μm<sup>2</sup>. At Al thicknesses of 13 and 10 Å, the MR ratio was 22%-20%, and increased to 35%-30% after annealing. In other junctions, the MR ratios were small and increased only slightly after annealing, the <i>I-V</i> curves of all junctions were asymmetric before annealing. The curves were analyzed by taking account of both barrier heights <i>φ<sub>1</sub></i> and <i>φ<sub>2</sub></i> (upper and lower interfaces). The difference between <i>φ<sub>1</sub></i> and <i>φ<sub>2</sub></i> was reduced by annealing, and the MR ratio became large at <i>φ<sub>1</sub></i> =<i> φ<sub>2</sub></i>.

  375. スピンバルブ型トンネル接合のマグノン非弾性励起 査読有り

    村井純一郎, 安藤康夫, 上條誠, 大坊忠臣, 久保田均, 宮崎照宣

    日本応用磁気学会誌 24 (4_2) 615-618 2000年4月

  376. 強磁性トンネル接合の局所伝導特性と磁気抵抗効果 査読有り

    安藤康夫, 亀田博史, 林将光, 久保田均, 宮崎照宣

    日本応用磁気学会誌 24 (4_2) 611-614 2000年4月

    出版者・発行元:The Magnetics Society of Japan

    DOI: 10.3379/jmsjmag.24.611  

    ISSN:0285-0192

    詳細を見る 詳細を閉じる

    The local electrical properties were measured simultaneously with the topography for a Ta(50Å)/Fe<sub>20</sub>Ni<sub>80</sub>(50Å)/IrMn(150Å)/Co(50Å)/Al(<i>d</i><sub><i>Al</i></sub>Å)-oxide junction. The electrical image showed the contrast with a lateral size of around a few nm, and no strong correlation with the topography was observed. By analyzing the local current-voltage characteristics, we found that the contrast of the current image showed the distribution of the barrier height. This may be due to the lack of the oxygen from the stoichiometry of the Al<sub>2</sub>O<sub>3</sub> composition. We measured the current images for junctions with shorter oxidation times and with lower Al thicknesses. The histogram of current densities was calculated by taking into consideration the Gaussian distribution of the barrier height. It fitted the experimental results well except for the junction with thin Al; this may be due to a local leakage current. The tunneling magnetoresistance (TMR) ratio was considered to be reduced by this current.

  377. Ni<SUB>80</SUB>Fe<SUB>20</SUB>/Co/N(N=Ta, Al)/Al-oxide/Co 接合における磁気抵抗効果 査読有り

    大坊忠臣, 手束展規, 久保田均, 安藤康夫, 林将光, 宮崎照宣, Changkyung Kim, Ohsung Song

    日本応用磁気学会誌 24 (4_2) 599-602 2000年4月

    DOI: 10.3379/jmsjmag.24.599  

  378. Characterization of the Barrier Layer in Al<SUB>1-x</SUB>Co<SUB>x/(</SUB>Al<SUB>1-x</SUB>Co<SUB>x-</SUB>oxide)/Al Junctions 査読有り

    X. F. Han, J. Murai, M. Hayashi, N. Tezuka, H. Kubota, Y. Ando, T. Miyazaki

    J. Magn. Soc. Jpn. 24 (4-2) 603-606 2000年4月

    DOI: 10.3379/jmsjmag.24.603  

  379. 有機アミン-3d遷移金属錯体の磁性と光学特性 査読有り

    仕幸英治, 安藤康夫, 江良正直, 宮崎照宣

    日本応用磁気学会誌 24 (4_2) 491-494 2000年

    出版者・発行元:The Magnetics Society of Japan

    DOI: 10.3379/jmsjmag.24.491  

    ISSN:0285-0192

    詳細を見る 詳細を閉じる

    Organic-inorganic complex magnets ((RNH<sub>3</sub>)<sub>2</sub>MX<sub>4</sub>) were synthesized, where R is a simple alkylammonium molecule (CH<sub>3</sub>(CH<sub>2</sub>)<sub>17</sub>), a <i>1</i>-methy1-naphthalene (C<sub>10</sub>H<sub>9</sub>CH<sub>2</sub>), a <i>1</i>-pro-pyl-naphthalene (C<sub>10</sub>H<sub>9</sub>O(CH<sub>2</sub>)<sub>3</sub>), or a <i>1</i>-buty1-naphthalene (C<sub>10</sub>H<sub>9</sub>O(CH<sub>2</sub>)<sub>4</sub>), M is a 3d transition metal element, and X is a halide element (Cl). Their complexes had a layered perovskite structure checked by XRD. The distance of interlayer space between MCl-based layers was shorter for the complexes with <i>1</i>-buty1-naphthalene than for those with <i>1</i>-propy1-naphthalene. When R was a simple alkylammonium molecule, a <i>1</i>-methy1-naphthalene and a <i>1</i>-propy1-naphthalene, its Cu complexes showed ferromagnetism and its Mn complexes antiferromagnetism. How-ever, Cu and Mn complexes with a <i>1</i>-buty1-naphthalene did not show ferromagnetism and antiferromagnetism, respectively. The absorption spectra of Cu complexes were also measured. When R was a simple alkylammonium molecule, a <i>1</i>-methy1-naphthalene, and a <i>1</i>-propy1-naphthalene, Cu complexes showed a <i>D</i><sub><i>4th</i></sub> structure for inorganic layers, while the structure for the complex with a <i>1</i>-buty1-naphthalene was <i>D<sub>2d</sub></i>.

  380. Thickness and Oxidation Time Dependence of Tunnel Magnetoresistance in Ni-Fe/Co/Al-O/Co Junctions 査読有り

    H. Kubota, S. Otsuka, M. Kamijo, N. Tezuka, Y. Ando, C. C. Yu, T. Miyazaki

    J. Magn. Soc. Jpn. 24 (4_2) 595-598 2000年

    出版者・発行元:The Magnetics Society of Japan

    DOI: 10.3379/jmsjmag.24.595  

    ISSN:0285-0192

    詳細を見る 詳細を閉じる

    Ni-Fe/Co/Al-O/Co tunnel junctions with small active areas down to 3 x 3 μm<sup>2</sup> were fabricated by the micro-fabrication technique. The Al-O insulating layer was prepared by plasma oxidation of a thin sputtered Al film. The dependences of the tunnel magnetoresistance on the thickness of the Al film and the oxidation time were investigated. The interface structure of the junction was observed by using high-resolution electron microscopy. The relationship between the magnetoresistive properties and the interface structure is discussed.

  381. 極薄Alプラズマ酸化膜を用いた強磁性トンネル接合の磁気抵抗効果 査読有り

    上條誠, 村井純一郎, 久保田均, 安藤康夫, 宮崎照宣, Changkyung Kim, Ohsung Song

    日本応用磁気学会誌 24 (4_2) 591-594 2000年

    DOI: 10.3379/jmsjmag.24.591  

  382. Ni<SUB>80</SUB>Fe<SUB>20</SUB>薄膜における強磁性共鳴線幅の下地層依存性 査読有り

    水上成美, 安藤康夫, 宮﨑照宣

    日本応用磁気学会誌 24 (4_2) 535-538 2000年

    DOI: 10.3379/jmsjmag.24.535  

  383. Direct observation of magnon excitation in a ferromagnetic tunnel junction using inelastic-electron-tunneling spectroscopy 査読有り

    J Murai, Y Ando, M Kamijo, H Kubota, T Miyazaki

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS 38 (10A) L1106-L1108 1999年10月

    出版者・発行元:JAPAN J APPLIED PHYSICS

    DOI: 10.1143/JJAP.38.L1106  

    ISSN:0021-4922

    詳細を見る 詳細を閉じる

    Inelastic-electron-tunneling spectroscopy (IETS) is applied to investigate the spin-dependent tunneling process for a Ta/Ni80Fe20/FeMn/Ni80Fe20/Al-oxide/Co/Ni80Fe20 ferromagnetic tunnel junction. IET spec tra for ba th parallel and antiparallel magnetization configurations of ferromagnetic electrodes exhibit a strong peak at 20 mV, Using the subtraction between these spectra, we obtain the inelastic excitation spectrum induced only by the magnetic origin. This spectrum exhibits a strong peak at 18 mV and decreases monotonically with increasing bias voltage. The bias-voltage dependence of tunnel magnetoresistance (TMR) is the same. These results are discussed by considering the distribution of the surface magnon excitation energy.

  384. Enhancement of tunnel magnetoresistance effect on junction with Co cluster layers in Coulomb blockade regime 査読有り

    Y Fukumoto, H Kubota, Y Ando, T Miyazaki

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS 38 (8B) L932-L934 1999年8月

    出版者・発行元:JAPAN J APPLIED PHYSICS

    DOI: 10.1143/JJAP.38.L932  

    ISSN:0021-4922

    詳細を見る 詳細を閉じる

    Tunnel magnetoresistance (TMR) effect in ferromagnet/granular/ferromagnet (FM/GR/FM) tunnel junctions was studied, where GR = Al-O/Co/Al-O or Al-O/Co/Al-O/Co/Al-O. The magnetoresistance (MR) ratio and the resistance of the latter junction increased with decreasing bias voltage at low temperatures. These increases should be due to the cotunneling effect in the Coulomb blockade regime. In contrast, the MR ratio of the former junction exhibited a maximum of 14% near 40 mV and decreased to 10% at 1 mV. The increase of resistance in the former junction at a lower voltage was smaller than that in the latter junction. The difference was discussed using a simple model.

  385. Magnetic properties of ferrocenylmethylacrylate-N-dodecylacryl-amide copolymer Langmuir-Blodgett films 査読有り

    Y Ando, T Hiroike, T Miyashita, T Miyazaki

    THIN SOLID FILMS 350 (1-2) 232-237 1999年8月

    出版者・発行元:ELSEVIER SCIENCE SA

    DOI: 10.1016/S0040-6090(99)00271-0  

    ISSN:0040-6090

    詳細を見る 詳細を閉じる

    Langmuir-Blodgett (LB) films of the copolymer with ferrocenyl-methyl-acrylate (FcMA) and N-dodecyl-acrylamide (DDA) were fabricated. The magnetic moment of these LB films became about twenty times larger than that of the powder. In addition, the LB films had a magnetic anisotropy depending on the dipping direction. The FTIR results suggested that the polymer chains in the LB films were preferably aligned with the perpendicular of the dipping direction. These results were discussed by the intermolecular electron transfer. (C) 1999 Elsevier Science S.A. All rights reserved.

  386. Local transport property on ferromagnetic tunnel junction measured using conducting atomic force microscope 査読有り

    Y Ando, H Kameda, H Kubota, T Miyazaki

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS 38 (7A) L737-L739 1999年7月

    出版者・発行元:JAPAN J APPLIED PHYSICS

    DOI: 10.1143/JJAP.38.L737  

    ISSN:0021-4922

    詳細を見る 詳細を閉じる

    The local topographical and electrical properties were measured simultaneously for a Ni80Fe20/Co/Al-oxide junction. Images with a lateral resolution of I nm and a current sensitivity of 3 pA were successfully obtained no strong correlation between them was observed. From the results of local current-voltage characteristics also measured, it was clarified that the contrast of the current image indicated the distribution of barrier heights. The histogram of current density calculated by taking into consideration a Gaussian distribution corresponded qualitatively to the experimental result.

  387. Influence of interlayer roughness on magnetoresistive effect of ferromagnetic tunneling junctions 査読有り

    Y Ando, M Yokota, N Tezuka, T Miyazaki

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 198-99 155-157 1999年6月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/S0304-8853(98)01053-1  

    ISSN:0304-8853

    詳細を見る 詳細を閉じる

    Ferromagnetic tunneling 80NiFe/Co/Al-oxide/Co junctions with wedge shaped Al-oxide were fabricated. For preparing Al-oxide, pure Al was sputtered without exposure. The tunnel resistance for junctions with sufficiently oxidized Al increased exponentially with increasing d(Al) On the other hand, the tunnel resistance for junctions with an air-leak scattered. The tunneling magnetoresistive effect (TMR) was observed at about 7 Angstrom Al for junctions without exposure. The surface roughness of the sample without exposure was quite small, while that with an air-leak tended to be large with increasing oxidization time and also d(Al). The corresponding tunnel resistance was very small for the junction with the rough interface. (C) 1999 Elsevier Science B.V. All rights reserved.

  388. Analysis of the interface in ferromagnet insulator junctions by inelastic-electron-tunneling-spectroscopy 査読有り

    Y Ando, J Murai, T Miyazaki

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 198-99 161-163 1999年6月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/S0304-8853(98)01050-6  

    ISSN:0304-8853

    詳細を見る 詳細を閉じる

    Inelastic-electron-tunneling-spectroscopy (IETS) has been applied to investigate the electron states of the interface of Al/Al(2)O(3)/Co(d(Co) = 0 similar to 50 Angstrom)/Al and Al/Al(2)O(3)/Ni(d(Ni) = 0 similar to 50 Angstrom)/Al tunneling junctions. A positive zero-bias anomaly was observed in the conductance curve of the junction with d(Co) less than or equal to 20 Angstrom. Correspondingly, the IET spectra showed a strong negative peak at 4 mV, while another broad peak was observed for the junctions with d(Co) greater than or equal to 10 Angstrom. These results were discussed in terms of the paramagnetic impurity and magnon assisted tunneling processes. On the other hand, a positive peak was observed in the IET curves for the junction with Ni. The possibility of formation of an Ni-Al alloy was considered to explain this result. (C) 1999 Elsevier Science B.V. All rights reserved.

  389. AlをWedge状に形成した強磁性トンネル接合の磁気抵抗効果 査読有り

    安藤康夫, 横田匡史, 宮崎照宣

    日本応用磁気学会誌 23 (4_2) 1285-1288 1999年4月

    出版者・発行元:The Magnetics Society of Japan

    DOI: 10.3379/jmsjmag.23.1285  

    ISSN:0285-0192

    詳細を見る 詳細を閉じる

    Ferromagnetic tunneling 80NiFe/Co/Al oxide/Co junctions with various Al oxide thicknesses were fabricated. To prepare Al oxide, a wedge-shaped piece of pure Al was sputtered without exposure to air. The surface roughness of the unexposed samples was quite small, while that of a sample with an air-leak tended to grow larger with increasing oxidization time and also <i>d</i><sub>Al</sub>. The tunneling magnetoresistive effect (TMR) was observed at an Al thickness of about 9 Å for exposed junctions. Below this thickness, the barrier height estimated from the <i>I-V</i> curve decreased. On the other hand, the barrier height and thickness were roughly constant for junctions with <i>d</i><sub>Al</sub>>9 Å. This indicated that the metallic Al could exist, causing a reduction in the TMR.

  390. Al/Al-oxide/M/Al(M=Fe,Ni)接合の非弾性電子トンネル分光 査読有り

    村井純一郎, 安藤康夫, 宮崎照宣

    日本応用磁気学会誌 23 (4_2) 1325-1328 1999年4月

    出版者・発行元:The Magnetics Society of Japan

    DOI: 10.3379/jmsjmag.23.1325  

    ISSN:0285-0192

    詳細を見る 詳細を閉じる

    Inelastic-electron-tunneling spectroscopy (IETS) was used to investigate the electron states of the interfaces of Al/Al-oxide/Fe(<i>d<sub>Fe</sub></i>)/Al and Al/Al-oxide/Ni(<i>d<sub>Ni</sub></i>)/Al tunnel junctions. The conductance curves for all junctions showed a minimum around the zero-bias voltage. The IET spectra showed a strong positive peak around 4 mV, corresponding to the minimum of conductance curves, while another broad peaks was observed for junctions with <i>d<sub>Ni</sub></i>, <i>d<sub>Fe</sub></i>≥10Å, The peak position was different from that assigned to the Al-O LO phonon mode observed for Al/Al-oxide/Al junctions. It was confirmed by magnetization measurements that a ferromagnetic layer was formed for films with <i>d<sub>Ni</sub></i>≥30Å and <i>d<sub>Fe</sub></i>≥10Å. These results were investigated in relation to the direct and inelastic tunneling process due to magnons.

  391. Co, Ni<SUB>80</SUB>Fe<SUB>20</SUB>薄膜における強磁性共鳴の膜厚依存性 査読有り

    水上成美, 安藤康夫, 宮崎照宣

    日本応用磁気学会誌 23 (4_2) 1173-1176 1999年4月

    出版者・発行元:The Magnetics Society of Japan

    DOI: 10.3379/jmsjmag.23.1173  

    ISSN:0285-0192

    詳細を見る 詳細を閉じる

    Thickness dependence of ferromagnetic resonance (FMR) and magnetic properties were studied for cobalt and Ni<sub>80</sub>Fe<sub>20</sub> thin films prepared on glass substrates by magnetron, sputtering. Resonance field and linewidth increased with decreasing film thickness, while saturation magnetization and square ratio decreased. Thickness dependence of 4π<i>M</i><sub>eff.</sub> estimated from resonance field by using Kittel's formula was consistent with 4π<i>M</i><sub>s</sub> from hysteresis loops. Linewidth was assumed to have two components: zero-frequency linewidth, <i>ΔH</i><sub>0</sub>, caused by magnetic inhomogeneities in films and viscous damping. <i>ΔH</i><sub>0</sub> estimated from the experimental linewidth was, above 40 Å thick, nearly constant with film thickness. Below 30 Å, however, <i>ΔH</i><sub>0</sub> for both films rapidly increased. These results were discussed by taking account of the structural inhomogeneity in the thin magnetic layer region.

  392. Synthesis and the Magnetism of the Metal Halide-based Organic/Inorganic Layered Perovskite 査読有り

    Y. Ando, E. Shikoh, T. Miyazaki

    J. Magn. Soc. Jpn. 23 (1_2) 596-598 1999年1月

    出版者・発行元:The Magnetics Society of Japan

    DOI: 10.3379/jmsjmag.23.596  

    ISSN:0285-0192

    詳細を見る 詳細を閉じる

    Metal halide-based layered perovskites, (RNH<sub>3</sub>)<sub>2</sub>MCl<sub>4</sub>, self-organized organic/inorganic multilayer structure were synthesized, where R is a simple alkylammonium molecule with a long chain length, (CH<sub>3</sub>(CH<sub>2</sub>)<sub>17</sub>) or a <i>l</i>-methyl-naphthalene (C<sub>10</sub>H<sub>9</sub>CH<sub>2</sub>), M is 3<i>d</i> transition metal elements. Its layered pcrovskite structure was checked by a FT-IR method. The perovskites of CH<sub>3</sub>(CH<sub>2</sub>)<sub>17</sub>NH<sub>3</sub> with Cu and Cr showed ferromagnetism (<i>T</i><sub>C</sub>= 10 K and 42 K, respectively), and Mn and Fe antifcrromagnetism (<i>T</i><sub>N</sub>=41 K and 95 K, respectively). These results roughly corresponded to the results for methyl and ethyl ammonium complexes reported. The naphthlene complex with Cu also showed ferromagnetism, however, the Curie temperature became low. It was considered that the relative large chromophore might disturb the Jahn-Teller distortion of CuCl<sub>6</sub> octahedra. <i>l</i>-methyl-naphthylamine- hydrochloride was luminous with the wavelength of 350 nm under ultraviolet light irradiation, but its Cu complex was quenched.

  393. Analysis of the Interlayer in Al/Al<SUB>2</SUB>O<SUB>3/</SUB>/Co/Al Junction by Inelastic-Electron-Tunneling-Spectroscopy 査読有り

    J. Murai, Y. Ando, T. Miyazaki

    J. Magn. Soc. Jpn. 23 (1_2) 64-66 1999年1月

    出版者・発行元:The Magnetics Society of Japan

    DOI: 10.3379/jmsjmag.23.64  

    ISSN:0285-0192

    詳細を見る 詳細を閉じる

    Inelastic-Electron-Tunneling-Spectroscopy (IETS) has been applied to investigate the electron states of the interface of Al/Al<sub>2</sub>O<sub>3</sub>/Co(<i>d</i><sub><i>Co</i></sub>)/Al tunneling junctions. A zero-bias anomaly was observed in the conductance curve of the junction with <i>d</i><sub><i>Co</i></sub> of 2 Å and decreased with increasing <i>d</i><sub><i>Co</i></sub>. The IET spectra of these junctions showed a strong negative peak at 4 mV, corresponding to the zero- bias anomaly, while the another broad peak was observed for the junctions with <i>d</i><sub><i>Co</i></sub> ≥10Å. The peak was different in the position from that assigned to the Al-O LO phonon mode observed for Al/Al<sub>2</sub>O<sub>3</sub>/Al junction. From the magnetization measurement, it is confirmed that the ferromagnetic layer was formed for the junctions with <i>d</i><sub><i>Co</i></sub> ≥10 Å These results were discussed with the paramagnetic impurity and magnon assisted tunneling process.

  394. Magnetic properties of random-anisotropy amorphous magnets (RxFe1-x)(80)Si12B8 with R = Pr, Nd, Sm, Tb, Dy and Er 査読有り

    H Kato, N Kurita, Y Ando, T Miyazaki, M Motokawa

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 189 (3) 263-273 1998年11月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/S0304-8853(98)00285-6  

    ISSN:0304-8853

    詳細を見る 詳細を閉じる

    Magnetic properties of rapidly quenched amorphous alloys (RxFe1-x)(80)Si12B8 with R = Pr, Nd, Sm, Tb, Dy and Er (0.1 less than or equal to x less than or equal to 1.0) have been investigated systematically by Mossbauer absorption and magnetization measurements in fields of up to 300 kOe. Mossbauer experiments have shown that the averaged Fe magnetic moment decreases rapidly with increasing x. Low-held magnetic measurements have exhibited a spin-freezing behavior at low temperatures in all R-rich samples. The freezing temperature T-f rapidly decreases with increasing magnitude of magnetic field H. High-held magnetization isotherms at low temperatures showed a large hysteresis, in which the coercive field H-c increases rapidly with decreasing temperature. In H-T space, the lines of H-c(T) and T-f(H) are found to be almost identical, which have therefore been regarded as a boundary between reversible and irreversible regions in the magnetic phase diagram. Upward concavity in the high-field magnetization curve has been observed in R = Tb and Dy samples with x = 0.2, which was suggested to be an incipient stage of a transition from sperimagnetic to asperomagnetic state, based on the numerical calculations. (C) 1998 Elsevier Science B.V. All rights reserved.

  395. Spin dependent tunneling in 80NiFe/LB film with ferrocene and tris(bipyridine)ruthenium derivatives Co junctions 査読有り

    Y Ando, J Murai, T Miyashita, T Miyazaki

    THIN SOLID FILMS 331 (1-2) 158-164 1998年10月

    出版者・発行元:ELSEVIER SCIENCE SA

    DOI: 10.1016/S0040-6090(98)00913-4  

    ISSN:0040-6090

    詳細を見る 詳細を閉じる

    80NiFe/LB-film/Co tunnel junctions with poly-N-dodecyl-acrylamide and its copolymer with the ferrocene derivative (Fc) or the tris(bipyridine)ruthenium complex (Ru) have been fabricated. FTIR spectra and small angle X-ray diffraction patterns for Fc, Ru and their mixture LB films indicated the formation of highly ordered molecular structure. The Bohr magneton number per one ferrocene moiety showed no difference between the him of Fe and the mixed film with Ru in the dark. However, UV-visible absorption and fluorescence spectra indicated that the electron transfer process in the mixed LB films occurred by an irradiation of light. The tunnel junctions using these LB films showed tunnel magnetoresistive effect. Its magnetoresistive ratio was 0.4% at room temperature being very small in comparison with the tunnel junction with Al2O3 tunnel barrier. The reason for this was considered to be residual water in the LB film causing a structural change of Co or the oxidation of thtr Co surface, so that the spin polarization could have become low. (C) 1998 Elsevier Science S.A. All rights reserved.

  396. Spin-polarized magnetic tunnelling magnetoresistive effects in various junctions 査読有り

    T Miyazaki, N Tezuka, S Kumagai, Y Ando, H Kubota, J Murai, T Watabe, M Yokota

    JOURNAL OF PHYSICS D-APPLIED PHYSICS 31 (6) 630-636 1998年3月

    出版者・発行元:IOP PUBLISHING LTD

    DOI: 10.1088/0022-3727/31/6/009  

    ISSN:0022-3727

    詳細を見る 詳細を閉じる

    Recent progress concerning spin-polarized magnetic tunnelling effects for (i) trilayer standard ferromagnet (F)/insulator (I)/ferromagnet (F) junctions, (ii) spin-valve-type junctions, (iii) trilayer or multilayer ferromagnet/granular/ferromagnet junctions and (iv) F/I/F junction with a 'wedge-geometry' insulator is reviewed. Special emphasis is placed on the dependence of the tunnel magnetoresistance ratio on temperature and also the intensity of the applied voltage. It was found that the resistiance for the saturation magnetization state, R-S, and the tunnelling magnetoresistance ratio, TMR, of an Fe/Al(2)O3/Fe junction decreased rapidly with increasing temperature, whereas those of a NiFe/Al2O3/Co junction were insensitive to temperature. Concerning the bias voltage dependence of Rs and TMR, the same tendency with temperature was observed for Fe/Al2O3/Fe and NiFe/Al2O3/Co junctions. Spin-valve-type junction exchange biased by a FeMn layer exhibits a relatively large TMR ratio up to about 400 K.

  397. 非弾性電子トンネル分光法(IETS)を用いた強磁性体/絶縁体界面の解析 査読有り

    村井純一郎, 安藤康夫, 手束展規, 宮崎照宣

    日本応用磁気学会誌 22 (4) 573-576 1998年

    出版者・発行元:The Magnetics Society of Japan

    DOI: 10.3379/jmsjmag.22.573  

    ISSN:0285-0192

    詳細を見る 詳細を閉じる

    Inelastic electron-tunneling spectroscopy (IETS) has been used to investigate the vibrational spectrum in Al/Al<sub>2</sub>O<sub>3</sub>/CO/AI tunneling junctions with various Co thicknesses (<i>d</i> <sub>Co</sub>). A zero-bias anomaly was observed in the conductance curve of the junction with <i>d</i><sub>Co</sub> of 2Å, and decreased with increasing <i>d</i><sub>Co</sub>. The IET spectra of these junctions showed strong negative peaks at 4 mV, corresponding to the zero-bias anomaly, while phonon spectra were observed for the junction with <i>d</i><sub>Co</sub> ≥ 10Å. The peak position was different from that of Al/Al<sub>2</sub>O<sub>3</sub>/Al. After annealing of the junction with <i>d</i><sub>Co</sub> of 2Å at 250°C for one hour, the zero-bias anomaly decreased and the phonon spectrum appeared.

  398. wedge状のAl-O絶縁層を有する強磁性トンネル接合の磁気抵抗 査読有り

    横田匡史, 安藤康夫, 手束展規, 宮崎照宣

    日本応用磁気学会誌 22 (4) 569-572 1998年

    出版者・発行元:The Magnetics Society of Japan

    DOI: 10.3379/jmsjmag.22.569  

    ISSN:0285-0192

    詳細を見る 詳細を閉じる

    Ferromagnetic tunneling junctions of Ni<sub>80</sub>Fe<sub>20</sub> (Py)/Co/Al oxide/Co with wedge-shaped insulators were fabricated. Al oxide films were formed by natural oxidization with various conditions and were checked by FT-IR spectroscopy. The peak intensity and the position depending on the Al thickness were explained by using the 1-D Einstein model. When the oxidization time was less than 50 h, tunneling magnetoresistance (TMR) was observed at about 13 Å of the Al thickness. When the oxidization time became more than 50 h, the thickness shifted to less than 10 Å. The reason for this was considered that Co oxide was formed on the surface of the bottom electrode and became a tunneling barrier with increasing oxidization time. On the other hand, the TMR decreased rapidly with increasing Al thickness. To determine the reason for this, AFM images of the Py/Co/Al surface with various oxidization times were measured. The surface roughness of the Al increased with increasing oxidization time, corresponding to the TMR results.

  399. Exchange coupling energy determined by ferromagnetic resonance in 80Ni-Fe/Cu multilayer films 査読有り

    Y Ando, H Koizumi, T Miyazaki

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 166 (1-2) 75-81 1997年2月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/S0304-8853(96)00413-1  

    ISSN:0304-8853

    詳細を見る 詳細を閉じる

    Ferromagnetic resonance (FMR) experiments were carried out for [80Ni-Fe(60 Angstrom)/Cu(d(Cu) Angstrom)](N), (d(Cu) = 10-12, N = 2-5) multilayer films fabricated by a sputtering method. The main resonance peak had a broad shoulder located on the higher magnetic field side. Namely, the exchange energy between the magnetic layers was antiferromagnetic. In order to estimate the exchange energy, the FMR absorption spectrum was calculated using the Landau-Lifshitz equation of motion. The calculation model was improved so that we were able to analyze the spectrum for a multilayer with N magnetic layers. The exchange energy obtained from FMR analysis was compared with that estimated from the saturation magnetic field in the magnetoresistance (MR) curve. The positions and the intensity ratio of the resonance peaks were dependent on merely the exchange energy but not on the number of layers. The MR ratio was roughly proportional to the exchange energy.

  400. 強磁性体-有機分子接合における強磁性トンネル効果に及ぼす分子構造の影響 査読有り

    安藤康夫, 村井純一郎, 宮崎照宣

    日本応用磁気学会誌 21 (4) 497-500 1997年

    出版者・発行元:The Magnetics Society of Japan

    DOI: 10.3379/jmsjmag.21.497  

    ISSN:0285-0192

    詳細を見る 詳細を閉じる

    Ferromagnet/insulator/ferromagnet junctions with Langmuir-Blodgett (LB) films were fabricated. The LB films used were poly-<i>N</i>-dodecylacrylamide (PDDA) and merocyanine (MC) dye. A magnetoresistance ratio of 0.3% at 300 K was observed in the junction with PDDA. This value was small in comparison with the theoretical values. One possible reason for this was the presence of an inelastic tunnel with a molecular vibration. To confirm this possibility, inelastic tunnel spectroscopy was performed. A shift of the peak assigned to the C=O stretching vibration was observed, indicating that electrons are trapped at the carbonyl group and can tunnel between the electrode and the carbonyl group. The junction with MC did not show the magnetic tunneling effect. MC relaxed rapidly to spiropyran (SP) form on the water surface, and the homogeneity of the LB film was lost.

  401. 70CoNi/Cu/80NiFe三層膜と70CoNi/Cu/80NiFe/Cu/70CoNi五層膜における強磁性共鳴 査読有り

    水上成美, 安藤康夫, 宮崎照宣

    日本応用磁気学会誌 21 (4) 445-448 1997年

    出版者・発行元:The Magnetics Society of Japan

    DOI: 10.3379/jmsjmag.21.445  

    ISSN:0285-0192

    詳細を見る 詳細を閉じる

    Interlayer exchange-coupling strength, <i>J</i>, was studied by measuring the ferromagnetic resonance (FMR) of 70CoNi/ Cu/80NiFe trilayers and 70CoNi/Cu/80NiFe/Cu/70CoNi five-layers prepared on glass substrates by magnetron sputtering. In the trilayers, <i>J</i> oscillated between positive and negative values a function of the spacer Cu layer thickness, and two peaks as in the negative value of <i>J</i> were observed. In the five-layers, on the other hand, two values of <i>J</i> were observed. One of those corresponded to <i>J</i> in the trilayers, while the other was positive and decreased monotonically with increasing the Cu spacer layer thickness. These results are consistent with that for the magnetoresistance.

  402. 強磁性トンネリング接合における絶縁障壁と磁気抵抗 査読有り

    手束展規, 安藤康夫, 宮崎照宣

    日本応用磁気学会誌 21 (4) 493-496 1997年

    出版者・発行元:The Magnetics Society of Japan

    DOI: 10.3379/jmsjmag.21.493  

    ISSN:0285-0192

    詳細を見る 詳細を閉じる

    The dependence of the tunneling magnetoresistive effect on the barrier height was investigated. The magnitude of the barrier height increased with increasing aluminum oxidation temperature and time from 0.3 to 2.3 eV in Fe/Al oxide/Fe junctions. However, those values are smaller than those reported for an Al<sub>2</sub>O<sub>3</sub> barrier. A possible reason for this is that the barrier is not pure Al<sub>2</sub>O<sub>3</sub>, but AIO<sub><i>x</i></sub>, or another oxide created by interface mixing between Fe and Al oxide. On the other hand, the magnetoresistance ratio in these junctions varied up to 18% at room temperature and up to 18% at 4.2 K. The dependence of the magnetoresistance ratio at 4.2 K on the barrier height is roughly the same as predicted by Slonczewski's theory. This result shows that the effective spin polarization of ferromagnetic electrodes changes according to the barrier height.

  403. Ferromagnetic resonance in 80Ni-Fe/Cu/Co multilayer films 査読有り

    H Koizumi, Y Ando, T Miyazaki

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 164 (3) 293-299 1996年12月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/S0304-8853(96)00418-0  

    ISSN:0304-8853

    詳細を見る 詳細を閉じる

    Trilayers and multilayers containing ferromagnetic 80Ni-Fe,Co layers separated by nonmagnetic Cu layers were fabricated using the magnetron sputtering method. For 80Ni-Fe(60 Angstrom)/Cu(d(Cu))/Co(60 Angstrom) trilayer films, the MR ratio and the exchange coupling strength oscillated with increasing d(Cu). For 80Ni-Fe(60 Angstrom)/Cu(d(Cu))/Co(60 Angstrom)/Cu(d(Cu))/80Ni-Fe(60 Angstrom) multilayer films, however, the exchange coupling between the bottom 80Ni-Fe and the Co layers oscillated,while that between the Co and the top 80Ni-Fe layers decreased monotonously with increasing de, Consequently, antiferromagnetic exchange coupling was not achieved between the Co(60 Angstrom) and the top magnetic layer. The reason for the nonexistence of antiferromagnetic exchange coupling is discussed by taking into account the rougher surface of the Co(60 Angstrom) layer caused by the growth of the different crystalline structures.

  404. Magnetic properties of stearate films with 3d transition metal ions fabricated by the Langmuir-Blodgett method 査読有り

    Y Ando, T Hiroike, T Miyashita, T Miyazaki

    THIN SOLID FILMS 278 (1-2) 144-149 1996年5月

    出版者・発行元:ELSEVIER SCIENCE SA LAUSANNE

    DOI: 10.1016/0040-6090(95)08146-1  

    ISSN:0040-6090

    詳細を見る 詳細を閉じる

    Stearate films with 3d transition metal ions, such as Mn, Fe, Co and Ni, were fabricated by the Langmuir-Blodgett (LB) method. The formation of salts was determined by Fourier transform infrared (FTIR) analysis, and the structure oriented two-dimensionally was confirmed by X-ray analysis and electron spin resonance (ESR) spectroscopy. The hydrocarbon chains with Fe, Co and Ni ions are arranged in a hexagonal unit cell aligned vertically to the film surface. However, the packing arrangement of the hydrocarbon chain with an Mn ion is orthorhombic with a tilt angle of 10 degrees to the film normal direction. The magnetization curves were measured at 4.5 K and the temperature dependence of the magnetic susceptibility was measured in the range 4.5-100 K. The susceptibility of the films showed a Curie-Weiss behaviour, The asymptotic temperature theta(p) of the Ni stearate film was positive, i.e. the film exhibited ferromagnetic interaction. This was explained by assuming the presence of a superexchange interaction of cation-anion-cation type making an angle of 103 degrees-109 degrees.

  405. Magnetic properties of polymer LB films containing ferrocene derivatives 査読有り

    Y Ando, T Hiroike, T Miyazaki, A Aoki, T Miyashita

    MOLECULAR CRYSTALS AND LIQUID CRYSTALS SCIENCE AND TECHNOLOGY SECTION A-MOLECULAR CRYSTALS AND LIQUID CRYSTALS 285 411-416 1996年

    出版者・発行元:GORDON BREACH SCI PUBL LTD

    ISSN:1058-725X

    詳細を見る 詳細を閉じる

    Langmuir-Blodgett (LB) films of copolymer with fenocenyl-methylacrylate(FcMA) and N-dodecyl-acrylamide(DDA) were fabricated. The FcMA moiety is supposed to enter into the alkyl chains of DDA and be arranged two-dimensionally form the X-ray diffraction analysis. The magnetization curve showed a steep rise up to several kOe and a gentle increase with the magnetic field up to 55 kOe. This behavior seems to be ferromagnetic. Even more than room temperature, the half of the magnetic moment at 4.5K remained, and the magnetization curve showed ferromagnetic. Furthermore, this LB film had a magnetic anisotropy depending on the dipping direction. On the other hand, the magnetization curves for the powder and the cast film of the copolymer were paramagnetic. The magnetic moment of the LB film is about 30 times larger than those of the powder and the cast film. These results indicate that a configurational interaction is important to explain the enhancement of magnetic moment of this copolymer.

  406. Magnetic Properties of Polymer LB Films Containing Ferrocene Derivatives 査読有り

    Y.Ando, T.Hiroike, A.Aoki, T.Miyashita, T.Miyazaki

    Mol. Cryst. Liq. Cryst. 286 89-94 1996年

  407. FABRICATION OF FERROUS STEARATE MULTILAYER FILMS BY THE LANGMUIR-BLODGETT METHOD 査読有り

    Y ANDO, T HIROIKE, T MIYASHITA, T MIYAZAKI

    THIN SOLID FILMS 266 (2) 292-297 1995年10月

    出版者・発行元:ELSEVIER SCIENCE SA LAUSANNE

    DOI: 10.1016/0040-6090(95)06731-0  

    ISSN:0040-6090

    詳細を見る 詳細を閉じる

    Ferrous stearate multilayer films were successfully deposited by the Langmuir-Blodgett method. The difficulty in fabrication of these films is due to the hydrolysis of ferrous or ferric ions generated by oxidation of ferrous ions. We investigated the fabrication condition of the films; the concentrations of the ferrous ions and the pH values in the subphase were controlled. The fraction of stearates in the films was obtained from Fourier transform infrared spectroscopy and structural studies were performed by X-ray diffraction in the low-angle region. We also investigated the magnetic properties of the multilayer films at 4.5 K. The magnetization curve behaved paramagnetically but the magnetic moment per atom was very small in comparison with that of one free ferrous ion. The result indicates a possibility of existence of both ferrous ions with high and low spin states.

  408. 液体急冷(Gd-M)<SUB>80</SUB>Si<SUB>12</SUB>B<SUB>8</SUB>アモルファス合金の磁気特性 査読有り

    栗田直幸, 安藤康夫, 石尾俊二, 宮崎照宣

    日本応用磁気学会誌 18 231-234 1995年

    DOI: 10.3379/jmsjmag.18.231  

  409. 強磁性/Al<SUB>2</SUB>O<SUB>3</SUB>/強磁性接合の磁気トンネリング効果 査読有り

    手束展規, 安藤康夫, 宮崎照宣

    日本応用磁気学会誌 19 (2) 369-372 1995年

    DOI: 10.3379/jmsjmag.19.369  

  410. 80Ni-Fe/Cu/Co三層膜における強磁性共鳴 査読有り

    古泉浩, 久保田均, 安藤康夫, 石尾俊二, 宮崎照宣

    日本応用磁気学会誌 19 (2) 389-392 1995年

    DOI: 10.3379/jmsjmag.19.389  

  411. MAGNETIC PROPERTIES OF ORGANIC MULTILAYER FILMS FABRICATED BY LANGMUIR-BLODGETT METHOD. 査読有り

    Y.Ando, T.Hiroike, A.Aoki, T.Miyashita, T.Miyazaki

    Proceedings of the Third International Symposium on Physics of Magnetic Materials 40-44 1995年

  412. HIGH FIELD MAGNETIZATION AND MOSSBAUER ABSORPTION IN (R<SUB>X</SUB>Fe<SUB>1-X</SUB>)<SUB>80</SUB>Si<SUB>12</SUB>B<SUB>8</SUB> AMORPHOUS ALLOYS (R-Pr,Nd,Sm,Tb,Dy AND Er) 査読有り

    N.Kurita, H.Kato, Y.Ando, T.Miyazaki

    Proceedings of the Third International Symposium on Physics of Magnetic Materials 805-808 1995年

  413. LINEAR AC MAGNETIC RESPONSE NEAR THE VORTEX-GLASS TRANSITION IN SINGLE-CRYSTALLINE YBA2CU3O7 査読有り

    Y ANDO, H KUBOTA, Y SATO, TERASAKI, I

    PHYSICAL REVIEW B 50 (13) 9680-9683 1994年10月

    出版者・発行元:AMERICAN PHYSICAL SOC

    DOI: 10.1103/PhysRevB.50.9680  

    ISSN:0163-1829

    詳細を見る 詳細を閉じる

    By using a miniature two-coil mutual-inductance method and an exact inversion scheme, the ac penetration depth lambda(ac) was measured in a twinned YBa2Cu3O7 crystal in dc fields parallel to the c axis. The Ohmic dc resistance was also measured on the same crystal. The behavior of these quantities was altogether consistent with the vortex-glass-transition scaling. However, if we calculate the Labusch parameter and the pinning relaxation time from lambda(ac), they show unexpectedly large frequency dependencies, which can hardly be explained by the standard theory of the linear ac response of pinned vortices.

  414. Magnetic Properties of Rapidly Quenched (Gd-M)&lt;inf&gt;80&lt;/inf&gt;Si&lt;inf&gt;12&lt;/inf&gt;B&lt;inf&gt;8&lt;/inf&gt; Amorphous Alloys 査読有り

    N. Kurita, Y. Ando, T. Miyazaki

    IEEE Translation Journal on Magnetics in Japan 9 (6) 185-190 1994年

    DOI: 10.1109/TJMJ.1994.4565978  

    ISSN:0882-4959

    詳細を見る 詳細を閉じる

    The magnetization and Curie temperature of rapidly quenched (Gd0.7M0.3)80Si12B2 (M=Y, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Al) amorphous alloys were investigated. The Curie temperatures of alloys with M=Mn, Fe are higher by about 70K and 120K than that of Gd80Si12B8 amorphous alloy. The magnetic moments of Mn, Fe and Co atoms are 2, 1 and 1µg respectively. These magnetic moments are antiparallel to that of the Gd atoms. The magnetic moment of Ni atoms nearly disappears the magnetic moments of Y and V atoms are 1.7 and 2.1µB respectively. The magnetic moment of Y atoms is antiparallel to that of Gd atoms, while that of V atoms is parallel to the latter. We conclude that alloys with nonmagnetic elements M exhibit asperomagnetism in which the Gd moments are distributed, while alloys with magnetic elements M have a ferrimagnetic order. © 1994 IEEE.

  415. FMR Study of Ni-Fe/Cu Multilayer Films 査読有り

    H. Koizumi, M. Sato, Y. Ando, T. Miyazaki

    IEEE Translation Journal on Magnetics in Japan 9 (6) 242-246 1994年

    DOI: 10.1109/TJMJ.1994.4565987  

    ISSN:0882-4959

    詳細を見る 詳細を閉じる

    The interlayer exchange coupling strength of 80Ni-Fe/Cu multilayer films prepared on a glass substrate by magnetron sputtering was studied by ferromagnetic resonance. The exchange coupling strength was evaluated by assuming a weak perpendicular magnetic anisotropy and fitting the data of the resonance fields and peak intensities. It exhibited a broad peak when the Cu thickness was 10.8Å, and increased linearly in proportion to the number of bilayers. © 1994 IEEE.

  416. Ni-Fe/Cu人工格子における強磁性共鳴 査読有り

    古泉浩, 佐藤雅重, 安藤康夫, 石尾俊二, 宮崎照宣

    日本応用磁気学会誌 18 361-364 1994年

    DOI: 10.3379/jmsjmag.18.361  

  417. FMR STUDY ON PERMALLOY/CU/PERMALLOY TRILAYER FILMS FABRICATED ON CU BUFFER LAYERS 査読有り

    S ISHIO, H KOIZUMI, H KUBOTA, Y ANDO, T MIYAZAKI

    PHYSICA STATUS SOLIDI A-APPLIED RESEARCH 139 (2) K125-K128 1993年10月

    出版者・発行元:AKADEMIE VERLAG GMBH

    DOI: 10.1002/pssa.2211390239  

    ISSN:0031-8965

  418. SIZE EFFECT IN THE VORTEX-GLASS TRANSITION IN SUBMICRON YBA2CU3OY STRIPS - EVIDENCE FOR SOFTENING OF VORTEX MATTER 査読有り

    Y ANDO, H KUBOTA, S TANAKA

    PHYSICAL REVIEW LETTERS 69 (19) 2851-2854 1992年11月

    出版者・発行元:AMERICAN PHYSICAL SOC

    ISSN:0031-9007

    詳細を見る 詳細を閉じる

    The I-V curves of YBa2Cu3Oy strips, with widths of 0.54 to 5.6 mum, were measured in magnetic fields. All the strips showed critical scaling behavior, and a clear decrease in the vortex-glass (VG) transition temperature with decreasing width was observed. This finding proves that the interaction range of vortices is relevant in characterizing the phase transition, and that softening of the vortex-matter elasticity occurs upon approaching this scale. Moreover, the results are not easily explained by the flux-creep picture and give strong support to the VG picture.

  419. 重層媒体におけるビデオ信号の磁気記録シミュレ-ション解析 査読有り

    安藤康夫, 田河育也, 中村慶久

    テレビジョン学会誌 46 (10) 1286-1294 1992年10月

    出版者・発行元:一般社団法人映像情報メディア学会

    DOI: 10.3169/itej1978.46.1286  

    ISSN:0386-6831

    詳細を見る 詳細を閉じる

    We incorporate a magnetization model into the finite element method to calculate the recording characteristics for a VTR signal. The fact that calculated results agree with measured ones shows that this method is effective in the analysis of VTR signal recording. In addition we use the Fourier transfer to analyze magnetization distribution. This analysis clearly shows that the appearance of a spurious signal is caused by a nonlinear magnetization process. We also show that a video luminance signal can be recorded on a medium surface and that a video chrominance signal can be recorded on the middle layer of a medium. Therefore, a double-layered medium having a high coercive force in the surface layer and a low coercive force in the underlayer, is effective for the recording of a signal with a wide frequency region. Moreover, a double-layered medium with a perpendicularly oriented surface is excellent for high density recording.

  420. 重層塗布型媒体の電磁変換特性 査読有り

    安藤康夫, 川上晃, れん理英子, 西川卓男

    日本応用磁気学会誌 15 109-112 1991年

    DOI: 10.3379/jmsjmag.15.109  

  421. A SIMULATION FOR VIDEO SIGNAL RECORDING ON DOUBLE LAYERED COATING MEDIA . 査読有り

    Y.Ando, I.Tagawa, Y.Nakamura

    J. Magn. Soc. Jpn. 15 (S2) 215-220 1991年

  422. CLASSICAL AND RE-ENTRANT SPIN-GLASS BEHAVIOR IN AMORPHOUS (FE1-XVX)77SI10B13, (FE1-XCRX)77SI10B13, (FE1-XMNX)77SI10B13, (FE1-XNIX)77SI10B13 ALLOYS 査読有り

    T MIYAZAKI, OKAMOTO, I, Y ANDO, M TAKAHASHI

    JOURNAL OF PHYSICS F-METAL PHYSICS 18 (7) 1601-1610 1988年7月

    出版者・発行元:IOP PUBLISHING LTD

    ISSN:0305-4608

  423. CLASSICAL AND RE-ENTRANT SPIN-GLASS BEHAVIOR IN AMORPHOUSFe<SUB>1-x</SUB>M<SUB>x</SUB>)<SUB>77</SUB>Si<SUB>10</SUB>B<SUB>13</SUB> (M=Cr,Mn,Ni) ALLOY. 査読有り

    T.Miyazaki, I.Okamoto, Y.Ando, M.Takahashi

    Journal of Physics F Metallic Physics 18 1601-1610 1988年

    DOI: 10.1088/0305-4608/18/7/026  

  424. MAGNETIZATION AND MOSSBAUER-EFFECT INVESTIGATIONS IN AMORPHOUS (FE1-XMNX)77SI10B13 ALLOYS 査読有り

    T MIYAZAKI, K YAMADA, Y ANDO, OKAMOTO, I, M TAKAHASHI

    IEEE TRANSACTIONS ON MAGNETICS 23 (5) 3584-3586 1987年9月

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

    ISSN:0018-9464

  425. LOW-FIELD MAGNETIZATION AND MOSSBAUER-EFFECT INVESTIGATIONS IN (FE65NI35)1-X(FE84MN16)X ALLOYS 査読有り

    T MIYAZAKI, Y ANDO, M TAKAHASHI

    PHYSICAL REVIEW B 34 (9) 6334-6340 1986年11月

    出版者・発行元:AMERICAN PHYSICAL SOC

    DOI: 10.1103/PhysRevB.34.6334  

    ISSN:0163-1829

  426. ANOMALOUS TEMPERATURE-DEPENDENCE OF MAGNETIZATION IN SINGLE-CRYSTAL FE65NI35 ALLOY 査読有り

    T MIYAZAKI, Y ANDO, M TAKAHASHI

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 60 (2-3) 227-235 1986年8月

    出版者・発行元:ELSEVIER SCIENCE BV

    ISSN:0304-8853

  427. ANOMALOUS TEMPERATURE-DEPENDENCE OF MAGNETIZATION IN POLYCRYSTALLINE FE65NI35 ALLOY 査読有り

    T MIYAZAKI, Y ANDO, M TAKAHASHI

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 60 (2-3) 219-226 1986年8月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/0304-8853(86)90104-6  

    ISSN:0304-8853

  428. ANOMALOUS TEMPERATURE-DEPENDENCE OF MAGNETIZATION IN POLYCRYSTALLINE FE65NI35 ALLOY 査読有り

    T MIYAZAKI, Y ANDO, M TAKAHASHI

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 60 (2-3) 219-226 1986年8月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/0304-8853(86)90105-8  

    ISSN:0304-8853

  429. SPIN-GLASS IN FE-NI INVAR-ALLOYS 査読有り

    T MIYAZAKI, Y ANDO, M TAKAHASHI

    JOURNAL OF APPLIED PHYSICS 57 (8) 3456-3458 1985年

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.335075  

    ISSN:0021-8979

︎全件表示 ︎最初の5件までを表示

MISC 144

  1. TMRセンサによる生体磁場計測の進展

    大兼幹彦, 大兼幹彦, 藤原耕輔, 菅野彰剛, 中野貴文, 我妻宏, 有本直, 水上成美, 水上成美, 熊谷静似, 松崎斉, 松崎斉, 中里信和, 安藤康夫, 安藤康夫

    応用物理学会春季学術講演会講演予稿集(CD-ROM) 70th 2023年

    ISSN:2436-7613

  2. トンネル磁気抵抗センサによるサブピコテスラ磁界検出

    大兼幹彦, 大兼幹彦, 藤原耕輔, 菅野彰剛, 中野貴文, 我妻宏, 有本直, 水上成美, 水上成美, 熊谷静似, 松崎斉, 松崎斉, 中里信和, 安藤康夫, 安藤康夫

    応用物理学会春季学術講演会講演予稿集(CD-ROM) 70th 2023年

    ISSN:2436-7613

  3. 頭皮上に密着可能なトンネル磁気抵抗素子を用いた室温脳磁計の開発

    菅野彰剛, 大兼幹彦, 藤原耕輔, 柿坂庸介, 松崎斉, 安藤康夫, 中里信和

    臨床神経生理学(Web) 49 (5) 2021年

    ISSN:2188-031X

  4. TMRセンサの原理と心磁図計測

    大兼幹彦, 大兼幹彦, 大兼幹彦, 菅野彰剛, 藤原耕輔, 中野貴文, 熊谷静似, 松崎斉, 中里信和, 安藤康夫

    臨床神経生理学(Web) 49 (5) 2021年

    ISSN:2188-031X

  5. 頭皮上に密着可能なトンネル磁気抵抗素子を用いた室温脳磁計の開発

    菅野彰剛, 大兼幹彦, 藤原耕輔, 柿坂庸介, 松崎斉, 安藤康夫, 中里信和

    臨床神経生理学(Web) 49 (5) 2021年

    ISSN:2188-031X

  6. TMRセンサを用いたリアルタイム心磁図計測

    大兼幹彦, 菅野彰剛, 藤原耕輔, 松崎斉, 中里信和, 安藤康夫

    日本生体医工学会大会プログラム・抄録集(Web) 60th 2021年

  7. トンネル磁気抵抗素子を用いた室温脳磁計による体性感覚誘発磁界の測定

    菅野彰剛, 大兼幹彦, 藤原耕輔, 松崎斉, 安藤康夫, 中里信和

    日本生体磁気学会誌 34 (1) 2021年

    ISSN:0915-0374

  8. スピントロニクス技術を応用した高感度生体磁気センサ技術 招待有り

    安藤 康夫

    機能材料 38 40-47 2018年

  9. Anisotropic magnetic property of nanocomposite Nd<inf>2</inf>Fe<inf>14</inf>B/Mo/α-Fe multilayer films

    K. Kobayashi, D. Ogawa, K. Koike, H. Kato, M. Oogane, T. Miyazaki, Y. Ando, M. Itakura

    Journal of Physics: Conference Series 903 2017年10月28日

    DOI: 10.1088/1742-6596/903/1/012015  

    ISSN:1742-6588

    詳細を見る 詳細を閉じる

    © 2016 Published under licence by IOP Publishing Ltd. We fabricated the MgO(100)/Mo/[Nd2Fe14B/Mo/Fe/Mo]5/Mo multilayer films, in which we tried to avoid the negative Jexinterfaces and thermal diffusion between Nd2Fe14B and α-Fe layers by forming the stacked structure with ultra thin Mo interlayer. The films without Mo interlayer showed isotropic magnetic properties, while films with Mo interlayer thickness tMo= 1 nm exhibited the perpendicular anisotropy with the coercivity of 7 kOe. Shapes for the major loop and the first order reversal curves (FORCs) suggested an existence of positive exchange coupling between the Nd-Fe-B and the α-Fe layers via the 1 nm thick Mo interlayer.

  10. 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

  11. 生体磁場測定応用の為の高感度TMRセンサの開発 (高周波用磁気デバイス・材料・評価技術の現状と新展開)

    城野 純一, 藤原 耕輔, 大兼 幹彦, 寺内 孝, 土田 匡章, 安藤 康夫

    社団法人日本磁気学会研究会資料 = Bulletin of Topical Symposium of the Magnetics Society of Japan 212 33-38 2017年2月21日

    出版者・発行元:日本磁気学会

    ISSN:1882-2940

  12. 強磁性トンネル磁気抵抗素子センサ 招待有り

    安藤 康夫

    電気学会誌 136 22-25 2016年

  13. 強磁性トンネル接合を用いた高感度磁場センサの開発と展望 (大型プロジェクトによる磁気・スピン新機能デバイス研究開発の最前線)

    安藤 康夫

    社団法人日本磁気学会研究会資料 = Bulletin of Topical Symposium of the Magnetics Society of Japan 203 21-30 2015年7月24日

    出版者・発行元:日本磁気学会

    ISSN:1882-2940

  14. Systematic investigation on correlation between sensitivity and nonlinearity in magnetic tunnel junction for magnetic sensor.

    T. Nakano, M. Oogane, H. Naganuma, Y. Ando

    2015 IEEE MAGNETICS CONFERENCE (INTERMAG) 2015年

    出版者・発行元:IEEE

  15. Temperature Dependence of Low Frequency Noise in Magnetic Tunneling Junctions with Co40Fe40B20/Co70.5Fe4.5Si15B10 Composed Free Layer.

    Z. Yuan, J. Feng, P. Guo, T. Nakano, S. Ali, X. Han, H. Naganuma, Y. Ando

    2015 IEEE MAGNETICS CONFERENCE (INTERMAG) 2015年

    出版者・発行元:IEEE

  16. Coercivity Enhancement in la Coated Nd-Fe-B Thin Films

    Kunihiro Koike, Hiroya Ishikawa, Daisuke Ogawa, Hiroaki Kato, Takamichi Miyazaki, Yasuo Ando, Masaru Itakura

    Physics Procedia 75 1294-1299 2015年1月1日

    DOI: 10.1016/j.phpro.2015.12.144  

    ISSN:1875-3884

    詳細を見る 詳細を閉じる

    © 2015 The Authors. Published by Elsevier B.V. The Nd-Fe-B/La thin films were deposited on the Al2O3(0001) substrate in order to investigate the effect of rare earth overlayer on the coercivity Hc. Highly textured Nd2Fe14B grains were grown by inserting the Mo(111) single crystal buffer layer. By depositing the La overlayer onto Nd2Fe14B thin films and subsequently post-annealing at 470 °C, the Hc value increased from about 10.5 kOe to 15.0 kOe. The amount of Hc increase by the combination of the La coating and post-annealing was about 4.5 kOe. After the post annealing, La oxide (hcp La2O3) was formed in the La layer, which was confirmed by means of XRD and SIMS depth profile measurements.

  17. Spintronics technology and device development

    Yasuo Ando

    Jpn. J. Appl. Phys. 54 070101-1-070101-10 2015年

    DOI: 10.7567/JJAP.54.070101  

  18. 界面装飾した強磁性トンネル接合の作製と磁気抵抗効果

    安藤 康夫, 大兼 幹彦, 永沼 博

    東北大学極低温科学センターだより (15) 3-6 2014年11月

    出版者・発行元:東北大学極低温科学センター

  19. スピントロニクス技術とデバイス開発 招待有り

    安藤 康夫

    応用物理 83 (3) 184-193 2014年

    出版者・発行元:応用物理学会

    ISSN:0369-8009

  20. 磁気抵抗素子センサを用いた生体磁場計測 招待有り

    安藤康夫, 西川卓男

    検査技術 6 2014年

  21. 技術シーズを活用した研究開発テーマの発掘

    安藤康夫

    (株)技術情報協会 223-229 2013年7月

  22. Nd<sub>2</sub>Fe<sub>14</sub>B系バルク単結晶の表面状態と磁化反転

    小川大介, 齋藤龍真, 水野善幸, 小池邦博, 加藤宏朗, 宮崎孝道, 安藤康夫

    日本磁気学会学術講演概要集 37th 2013年

    ISSN:1882-2959

  23. 磁気抵抗素子センサーを用いた生体磁場計側

    安藤康夫

    工業材料 8 38-41 2013年

  24. 低磁気緩和を有するハーフメタルホイスラー合金

    大兼 幹彦, 水上 成美, 窪田 崇秀, 小田 洋平, 佐久間 昭正, 永沼 博, 安藤 康夫

    日本磁気学会研究会資料 = Bulletin of Topical Symposium of the Magnetics Society of Japan 183 21-24 2012年3月22日

    出版者・発行元:日本磁気学会

    ISSN:1882-2940

  25. スピントロニクスとは何か

    安藤康夫

    OHM 99 (1) 17-20 2012年

    出版者・発行元:オーム社

  26. Pressure-induced half-metallic gap transformation in Co2MnSi observed by tunneling conductance spectroscopy

    M. Nobori, Y. Sakuraba, Y. Miura, T. Nakano, J. Hasegawa, Y. Ohdaira, Y. Ando, K. Takanashi, G. Oomi

    Physical Review B 83 (10) 104410 2011年

    DOI: 10.1103/PhysRevB.83.104410  

    ISSN:1098-0121

  27. Optically induced magnetization dynamics and variation of damping parameter in epitaxial Co2MnSi Heusler alloy films

    Y. Liu, L. R. Shelford, V. V. Kruglyak, Y. Sakuraba, M. Oogane, R. J. Hicken, Y. Ando

    Physical Review B 81 (9) 094402 2010年

    DOI: 10.1103/PhysRevB.81.094402  

    ISSN:1098-0121

  28. Evidence of Fermi level control in a half-metallic Heusler compound Co2MnSi by Al-doping: Comparison of measurements with first-principles calculations

    Y. Sakuraba, Y. Kota, T. Kubota, M. Oogane, A. Sakuma, Y. Ando, K. Takanashi

    Physical Review B 81 (14) 144422 2010年

    DOI: 10.1103/PhysRevB.81.144422  

    ISSN:1098-0121

  29. 26aVD-7 垂直磁化Pt/Co/Pt三層膜における時間分解磁気光学効果(スピン流・スピンホール,領域3,磁性,磁気共鳴)

    水上 成美, Sajitha E. P., 渡邉 大輔, Wu F., 大兼 幹彦, 永沼 博, 安藤 康夫, 宮崎 照宣

    日本物理学会講演概要集 64 (2) 360-360 2009年8月18日

    出版者・発行元:一般社団法人日本物理学会

    ISSN:1342-8349

  30. Fe-Co-NiおよびCo基フルホイスラー合金薄膜における磁気緩和

    水上成美, 大兼幹彦, 窪田嵩秀, 渡邉大輔, 永沼博, 安藤康夫, 宮崎照宣

    日本磁気学会誌 まぐね 4 (5) 229-235 2009年4月

  31. スピントルク磁化反転におけるスピンダイナミクス

    安藤 康夫, 青木 達也, 玉川 聖, 渡邉 大輔, 水上 成美, 家形 諭, 谷口 知大, 今村 裕志, 永沼 博, 大兼 幹彦, 井波 暢人, 宮崎 照宣

    日本磁気学会研究会資料 = Bulletin of Topical Symposium of the Magnetics Society of Japan 165 25-30 2009年3月13日

    出版者・発行元:日本磁気学会

    ISSN:1882-2940

  32. 27aTF-12 磁性金属薄膜のスピン緩和の光学的検出(27aTF スピンホール・磁気渦・ダイナミクス,領域3(磁性,磁気共鳴))

    水上 成美, 大兼 幹彦, 安藤 康夫, 宮崎 照宣

    日本物理学会講演概要集 64 (1) 431-431 2009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

  33. スピンポンピングによるスピン流の創出と物理現象

    安藤康夫, 水上成美, 家形諭, 谷口知大, 今村裕志, 大兼幹彦, 宮﨑照宣

    まぐね 4 73-81 2009年

  34. ホイスラー合金Co2MnSiを用いた高感度磁気抵抗素子の開発

    桜庭裕弥, 岩瀬拓, 常木澄人, 斉藤今朝美, 大兼幹彦, 安藤康夫, 佐久間昭正, 高梨弘毅

    IEICE Technical Report (MR2008) 32 2008年11月

    詳細を見る 詳細を閉じる

    Development of high-sensitive magnetoresistance devices using half-metallic Heusler alloy Co2MnSi

  35. BiFeO<sub>3</sub>-BiCoO<sub>3</sub>固溶体薄膜の磁気特性および強誘電性

    永沼博, 安井伸太郎, 西田謙, 飯島高志, 舟窪浩, 岡村総一郎, 安藤康夫

    応用物理学会学術講演会講演予稿集 69th (2) 2008年

  36. MPBを有するBiFcO<sub>3</sub>-BiCoO<sub>3</sub>エピタキシャル薄膜の磁性と強誘電性

    永沼博, 安井伸太郎, 西田謙, 舟窪浩, 飯島高志, 安藤康夫, 岡村総一郎

    日本磁気学会学術講演概要集 32nd 2008年

    ISSN:1882-2959

  37. Evidence of local moment formation in Co-based Heusler alloys

    N. D. Telling, P. S. Keatley, G. van, der Laan, R. J. Hicken, E. Arenholz, Y. Sakuraba, M. Oogane, Y. Ando, K. Takanashi, T. Miyazaki

    Physical Review B 78 (18) 184438 2008年

    DOI: 10.1103/PhysRevB.78.184438  

    ISSN:1098-0121

  38. Synthesis and Properties of Co-Pt Alloy-Silica Core-Shell Particles

    Yoshio Kobayashi, Hidekazu Kakinuma, Daisuke Nagao, Yasuo Ando, Terunobu Miyazaki, Mikio Konno

    Journal of Sol-Gel Science and Technology 47 (1) 16-22 2008年

    DOI: 10.1007/s10971-008-1740-1  

  39. 強磁性共鳴を用いたMRAMフリー層材料の磁気緩和定数測定

    安藤 康夫, 大兼 幹彦, 渡邉 大輔, 渡邉 美穂, YILGIN R., 家形 諭, 宮崎 照宣

    日本応用磁気学会研究会資料 153 7-14 2007年2月27日

    ISSN:1340-7562

  40. IETS法によるMgO-TMR膜のバリア構造観測

    玉野井健, 大兼幹彦, 安藤康夫, 田中努, 上原裕二, 渦巻拓也

    次世代磁気記録材料・システムへの挑戦 2007年

  41. MgOバリアTMR膜の電気伝導特性

    玉野井健, 大兼幹彦, 安藤康夫, 田中努, 上原裕二, 渦巻拓也

    日本応用磁気学会学術講演概要集 31st 2007年

    ISSN:1340-8100

  42. Synthesis of SiO<SUB>2</SUB>-Coated Magnetite Nanoparticles and Immobilization of Proteins on Them

    Yoshio Kobayashi, Mayumi Yoshida, Daisuke Nagao, Yasuo Ando, Terunobu Miyazaki, Mikio Konno

    Ceramic Transactions 198 135-141 2007年

  43. Nearly ideal half-metallic spin-polarization in Co2MnSi based magnetic tunnel junctions

    Y. Sakuraba, M. Hattori, M. Oogane, H. Kubota, Y. Ando, A. Sakuma, N. D. Telling, P. Keatley, G. van, der Laan, E. Arenholz, R. J. Hicken, T. Miyazaki

    Journal of Magnetic Society of Japan 31 (4) 338-343 2007年

    DOI: 10.3379/jmsjmag.31.338  

    ISSN:0285-0192 1880-4004

  44. スピンエレクトロニクスが先導する高効率デバイス開発の未来―磁気抵抗比向上とMgO―

    安藤康夫

    マグネシア・ミュー,タテホ化学 2007年

  45. 27pPSA-7 磁性薄膜における強磁性共鳴の電気的検出および周波数依存性(27pPSA 領域3ポスターセッション 薄膜・人工格子磁性,表面・界面磁性,微小領域磁性,遍歴磁性,化合物磁性,f電子系磁性磁性,領域3(磁性,磁気共鳴))

    水上 成美, 永嶋 誠一, 安藤 康夫, 宮崎 照宣

    日本物理学会講演概要集 61 (1) 437-437 2006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

  46. Interfacial structure and half-metallic ferromagnetism in Co2MnSi-based magnetic tunnel junctions

    N. D. Telling, P. Keatley, G. van, der Laan, R. J. Hicken, E. Arenholz, Y. Sakuraba, M. Oogane, Y. Ando, T. Miyazaki

    Physical Review B 74 (22) 224439-1-224439-7 2006年

    出版者・発行元:American Physical Society

    DOI: 10.1103/PhysRevB.74.224439  

    ISSN:1098-0121

  47. MRAMの研究開発動向

    安藤康夫

    講習会資料 2006年

  48. 24aXN-3 強磁性体二重トンネル接合を利用した超伝導体中へのスピン注入とその磁気抵抗効果(薄膜・人工格子磁性,表面・界面磁性,トンネル分光,領域3(磁性,磁気共鳴))

    大坊 忠臣, 大兼 幹彦, 安藤 康夫, 宮崎 照宜

    日本物理学会講演概要集 60 (1) 407-407 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

  49. 24aXN-1 Fe/MgO/Fe強磁性トンネル接合の非弾性電子トンネル分光(薄膜・人工格子磁性,表面・界面磁性,トンネル分光,領域3(磁性,磁気共鳴))

    宮越 健史, 安藤 康夫, 大兼 幹彦, 宮崎 照宜, 久保田 均, 福島 章雄, 長浜 太郎, 湯浅 新治

    日本物理学会講演概要集 60 (1-3) 407-407 2005年3月4日

    出版者・発行元:社団法人日本物理学会

    ISSN:1342-8349

  50. スピンダイナミクスとスピントロニクスデバイス

    安藤康夫, 水上成美, 宮崎照宣

    固体物理 45 35-43 2005年

  51. Co_2MnAlを用いた強磁性トンネル接合の磁気抵抗効果

    中田 淳, 大兼 幹彦, 久保田 均, 安藤 康夫, 加藤 宏朗, 佐久間 昭正, 宮崎 照宣

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 28 395-395 2004年9月21日

  52. スパッタリング法によるCo_2MnAlエピタキシャル薄膜の作製

    桜庭 裕弥, 中田 淳, 大兼 幹彦, 久保田 均, 安藤 康夫, 加藤 宏朗, 佐久間 昭正, 宮崎 照宣

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 28 394-394 2004年9月21日

  53. TMR素子の高速磁化反転測定

    安藤 康夫, 中村 洋明, 劉 智亨, 久保田 均, 宮崎 照宣

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 28 214-214 2004年9月21日

  54. 積層フェリフリー層を用いたサブミクロンMTJにおけるスイッチング磁界の低減

    李 永〓, 久保田 均, 安藤 康夫, 宮崎 照宣

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 28 215-215 2004年9月21日

  55. 下部強磁性電極の結晶性と強磁性トンネル接合のバイアス電圧依存性

    安 成眞, 加藤 丈晴, 安藤 康夫, 久保田 均, 宮崎 照宣

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 28 109-109 2004年9月21日

  56. Cu/Ni_<80>Fe_<20>/N(N=Cu, Cu/Pt)薄膜におけるFMR線幅とスピン拡散長

    家形 諭, 安藤 康夫, 水上 成美, 宮崎 照宣

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 28 125-125 2004年9月21日

  57. 金属ナノ細線をハードマスクに用いた強磁性単一電子素子の作製と特性評価

    新関 智彦, 久保田 均, 安藤 康夫, 宮崎 照宣

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 28 122-122 2004年9月21日

  58. FIBによるサブミクロンMTJの作製プロセス

    渡邉 大輔, 久保田 均, 安藤 康夫, 宮崎 照宣

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 28 121-121 2004年9月21日

  59. 強磁性体二重トンネル接合による超伝導体へのスピン注入

    大坊 忠臣, 大兼 幹彦, 安藤 康夫, 宮崎 照宣

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 28 123-123 2004年9月21日

  60. 27pXJ-4 強磁性体/非磁性体接合におけるスピンポンピング(領域3シンポジウム : スピン注入現象の新展開)(領域3)

    安藤 康夫, 中村 洋明, 家形 諭, 水上 成美, 久保田 均, 宮崎 照宣

    日本物理学会講演概要集 59 (1) 464-464 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

  61. ユニバーサルメモリMRAM

    安藤康夫

    応用物理 73 390-393 2004年

  62. 高密度磁気メモリ

    安藤康夫, 手束展規, 大野裕三, 栗野浩之, 久保田均, 大野英男

    電子材料 43 (1) 136-141 2004年

  63. 高速磁化反転測定のための埋め込みコプレナーガイドの作製

    花田 成, 中村 洋明, 久保田 均, 安藤 康夫, 宮崎 照宣

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 27 274-274 2003年9月1日

    ISSN:1340-8100

  64. サイドエッジ薄膜堆積法を用いた微小二重強磁性トンネル接合の作製

    新関 智彦, 久保田 均, 安藤 康夫, 宮崎 照宣

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 27 272-272 2003年9月1日

    ISSN:1340-8100

  65. CO-NH_3ガスを用いた磁性薄膜のドライエッチング

    久保田 均, 上田 幸生, 安藤 康夫, 宮崎 照宣

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 27 270-270 2003年9月1日

    ISSN:1340-8100

  66. 多層膜中の強磁性薄膜における動的磁化過程

    中村 洋明, 水上 成美, 安藤 康夫, 久保田 均, 宮崎 照宣

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 27 275-275 2003年9月1日

    ISSN:1340-8100

  67. ホイスラー系合金Co_2MnAlを用いた強磁性トンネル接合

    中田 淳, 大兼 幹彦, 久保田 均, 安藤 康夫, 加藤 宏朗, 宮崎 照宣

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 27 266-266 2003年9月1日

    ISSN:1340-8100

  68. 集束イオンビームを用いた微小強磁性トンネル接合の作製

    渡邉 大輔, 久保田 均, 安藤 康夫, 宮崎 照宣

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 27 271-271 2003年9月1日

    ISSN:1340-8100

  69. MTJに用いる Synthetic ferrimagnet フリー層の熱安定性

    李 永〓, 久保田 均, 安藤 康夫, 宮崎 照宣

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 27 277-277 2003年9月1日

    ISSN:1340-8100

  70. スピンダイナミクスの電気的および光学的アプローチ

    安藤 康夫, 中村 洋明, 水上 成美, 花田 成, 久保田 均, 宮崎 照宣

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 27 158-159 2003年9月1日

    ISSN:1340-8100

  71. トンネルスピン分極率の強磁性層作製条件依存性

    大兼 幹彦, 大坊 忠臣, 久保田 均, 安藤 康夫, 宮崎 照宣

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 27 434-434 2003年9月1日

    ISSN:1340-8100

  72. Al_2O_3(0001)基板上のエピタキシャルトンネル接合のバイアス電圧依存性

    安 成眞, 久保田 均, 安藤 康夫, 宮崎 照宣

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 27 429-429 2003年9月1日

    ISSN:1340-8100

  73. 強磁性体//超伝導体//強磁性体二重接合の磁気抵抗効果

    大坊 忠臣, 大兼 幹彦, 久保田 均, 安藤 康夫, 宮崎 照宣

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 27 435-435 2003年9月1日

    ISSN:1340-8100

  74. 下部電極をエピタキシャル成長させた強磁性トンネル接合の局所伝導特性

    加藤 丈晴, 劉 智亨, 安藤 康夫, 久保田 均, 宮崎 照宣

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 27 431-431 2003年9月1日

    ISSN:1340-8100

  75. 陰極に強磁性金属を用いた有機EL素子の発光特性

    仕幸 英治, 安藤 康夫, 宮崎 照宣

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 27 62-62 2003年9月1日

    ISSN:1340-8100

  76. スピン物性の制御はどこまで可能になったか?

    宮崎 照宣, 安藤 康夫

    應用物理 72 (6) 773-774 2003年6月10日

    ISSN:0369-8009

  77. Hard mask fabrication for MRAM elements using FIB assisted selective CVD

    H. Kubota, M. Hamada, Y. Ando, T. Miyazaki

    J. Appl. Phys 2003年

  78. スピンダイナミックス

    宮崎照宣, 安藤康夫, 水上成美, 中村洋明

    マテリアルインテグレーション 16 23-28 2003年

  79. 100nmスケールの微小強磁性トンネル接合の作製と評価

    久保田 均, 濱田 致知, 安藤 康夫, 宮崎 照宣

    日本応用磁気学会研究会資料 126 27-34 2002年11月22日

    ISSN:1340-7562

  80. Magnetic tunnel junction using an epitaxial Ni_<80>Fe_<20> thin film grown on a a single crystal Si substrate

    YU J. H., LEE H. M., HAYASHI M., OOGANE M., KUBOTA H., ANDO Y., MIYAZAKI T.

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 26 10-10 2002年9月1日

    ISSN:1340-8100

  81. Al/Al-oxide/ 強磁性体接合のトンネルコンダクタンス特性

    大兼 幹彦, 大坊 忠臣, 久保田 均, 安藤 康夫, 宮崎 照宣

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 26 9-9 2002年9月1日

    ISSN:1340-8100

  82. TMR素子の動的磁化反転過程の測定

    中村 洋明, 安藤 康夫, 久保田 均, 宮崎 照宣

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 26 16-16 2002年9月1日

    ISSN:1340-8100

  83. 電子線リソグラフィを用いたナノメーターサイズTMR素子の作製

    新関 智彦, 久保田 均, 安藤 康夫, 宮崎 照宣

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 26 11-11 2002年9月1日

    ISSN:1340-8100

  84. 高耐熱・高耐電圧強磁性トンネル接合の作製

    井浦 聡則, 久保田 均, 安藤 康夫, 宮崎 照宣

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 26 14-14 2002年9月1日

    ISSN:1340-8100

  85. TMR素子における絶縁層/強磁性層界面の評価と伝導特性

    安藤 康夫, 林 将光, 久保田 均, 宮崎 照宣

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 26 8-8 2002年9月1日

    ISSN:1340-8100

  86. Fabrication of magnetic tunnel junctions using epitaxial NiFe (111) ferromagnetic bottom electrodes

    H. Yu, M. Hayashi, M. Oogane, H. Kubota, Y. Ando, T. Miyazaki, H. M. Lee

    Appl. Phys. Lett 2002年

  87. トンネル磁気抵抗効果とスピンエレクトロニクスの展開

    宮崎照宣, 安藤康夫, 久保田均

    固体物理 38 109-124 2002年

  88. 強磁性トンネル接合の絶縁障壁とスピン依存伝導

    安藤 康夫, 林 将光, 久保田 均, 宮崎 照宣

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 25 144a-144b 2001年9月1日

    ISSN:1340-8100

  89. 金属キレート錯体Alq_3の磁性と伝導特性

    仕幸 英治, 安藤 康夫, 宮崎 照宣

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 25 190-190 2001年9月1日

    ISSN:1340-8100

  90. 様々な酸化方法で作製した強磁性トンネル接合

    井浦 聡則, 久保田 均, 安藤 康夫, 宮崎 照宣

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 25 337-337 2001年9月1日

    ISSN:1340-8100

  91. TMR素子における極薄Alプラズマ酸化膜の特性

    矢尾板 和也, 久保田 均, 安藤 康夫, 宮崎 照宣

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 25 338-338 2001年9月1日

    ISSN:1340-8100

  92. Magnetoresistance mesurement for ultra small TMR junctions using conductive AFM

    KUBOTA H., ANDO Y., MIYAZAKI T., REISS G., BRUCKL H., SCHEPPER W., WECKER J., GIERES G.

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 25 341-341 2001年9月1日

    ISSN:1340-8100

  93. トンネル分光法を用いたスピン分極率測定

    大兼 幹彦, 久保田 均, 安藤 康夫, 宮崎 照宣

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 25 336-336 2001年9月1日

    ISSN:1340-8100

  94. 中間層を超伝導体とする二重トンネル接合の磁気抵抗効果

    大坊 忠臣, 大兼 幹彦, 久保田 均, 安藤 康夫, 宮崎 照宣

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 25 344-344 2001年9月1日

    ISSN:1340-8100

  95. 強磁性トンネル接合における絶縁層の酸化過程

    林 将光, 安藤 康夫, 大兼 幹彦, 久保田 均, 宮崎 照宣

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 25 339-339 2001年9月1日

    ISSN:1340-8100

  96. 28aYE-5 中間層を超伝導体とする二重トンネル接合の磁気抵抗効果

    大坊 忠臣, 大兼 幹彦, 安藤 康夫, Kim C., Song O., 宮崎 照宣

    日本物理学会講演概要集 56 (1) 711-711 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

  97. スピンが担うエレクトロニクスの未来

    安藤康夫

    パリティ 16-12 23-29 2001年

  98. 強磁性トンネル接合の絶縁障壁と高速スイッチング特性

    安藤康夫, 林将光, 中村洋明, 井浦聡則, 水上成美, 久保田均, 宮崎照宣

    日本応用磁気学会第121回研究会資料 11-18 2001年

  99. 有機無機層状ペロブスカイト錯体の磁性と光学特性

    仕幸 英治, 安藤 康夫, 江良 正直, 宮崎 照宣

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 24 188-188 2000年9月1日

    ISSN:1340-8100

  100. Ni_<80>Fe_<20>薄膜における磁気緩和

    水上 成美, 安藤 康夫, 宮崎 照宣

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 24 183-183 2000年9月1日

    ISSN:1340-8100

  101. 強磁性トンネル接合のスピン依存局所伝導特性

    林 将光, 安藤 康夫, 久保田 均, 宮崎 照宣

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 24 45-45 2000年9月1日

    ISSN:1340-8100

  102. 異なる酸化条件により作製したTME素子のIETS

    村井 純一郎, 安藤 康夫, 大坊 忠臣, 矢尾板 和也, 宮崎 照宣

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 24 39-39 2000年9月1日

    ISSN:1340-8100

  103. プラズマ酸化法による低抵抗強磁性トンネル接合の作製

    矢尾板 和也, 上條 誠, 新関 智彦, 山本 直志, 久保田 均, 安藤 康夫, 宮崎 照宣

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 24 47-47 2000年9月1日

    ISSN:1340-8100

  104. Fabrication and magnetoelectric properties of high-magnetoresistance tunnel junctions

    HAN X. F., DAIBOU T., YAOITA K., ANDO Y., KUBOTA H., MIYAZAKI T.

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 24 46-46 2000年9月1日

    ISSN:1340-8100

  105. 中間層にAlを用いた二重トンネル接合の磁気抵抗効果

    大坊 忠臣, 大兼 幹彦, 安藤 康夫, KIM Changkyung, SONG Ohsung, 宮崎 照宣

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 24 52-52 2000年9月1日

    ISSN:1340-8100

  106. Transport properties in ferromagnetic double barrier junctions

    SIRIPONGSAKUL T., OOGANE M., MURAI J., YU Andrew C. C., KUBOTA H., ANDO Y., MIYAZAKI T., KIM Changkyung, SONG Ohsung

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 24 51-51 2000年9月1日

    ISSN:1340-8100

  107. 23aE-13 マグノン非弾性励起の熱処理温度依存性

    村井 純一郎, 安藤 康夫, 宮崎 照宣

    日本物理学会講演概要集 55 (1) 361-361 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

  108. 24pPSB-30 トンネル分光法によるFe,Co,Niのスピン分極率測定

    大兼 幹彦, 手束 展規, 久保田 均, 安藤 康夫, 宮崎 照宣

    日本物理学会講演概要集 55 (1) 410-410 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

  109. 24pPSA-38 (80NiFe)_<1-x>Pt_x薄膜における強磁性共鳴線幅

    水上 成美, 安藤 康夫, 宮崎 照宣

    日本物理学会講演概要集 55 (1) 402-402 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

  110. Co/Al/Al-Oxide/Co接合界面のマグノン非弾性励起

    村井純一郎, 安藤康夫, 上條誠, 大坊忠臣, 久保田均, 宮崎照宣

    日本応用磁気学会誌 24 (4-2) 615-618 2000年

    出版者・発行元:The Magnetics Society of Japan

    DOI: 10.3379/jmsjmag.24.615  

    ISSN:0285-0192

    詳細を見る 詳細を閉じる

    Inelastic-electron-tunneling spectroscopy (IETS) was used to investigate the electron states of the Co/Al(<i>d</i><sub>Al</sub>)/Al-oxide/Co interface in ferromagnetic tunnel junctions. The IET spectra for both parallel and anti-parallel magnetization configurations of ferromagnetic electrodes showed a strong positive peak for <i>d</i><sub>Al</sub> = 0 Å. The subtraction spectrum defined by the difference between the spectra of the two configurations was calculated. The subtraction spectrum indicates only a magnon-assisted inelastic tunneling process. The tendency of the tunneling magnetoresistance (TMR) ratio to decrease with bias voltage agreed with the shape of the subtraction spectrum. By assuming surface magnon inelastic excitation, we obtained the distributions of correlation length and Curie temperature for both ferromagnetic electrode surfaces on the insulator. If an Al layer was inserted between a ferromagnet and an insulator, the subtraction spectrum showed an asymmetry to the bias voltage and magnon inelastic excitation at the interface decreased.

  111. 有機アミン-3d遷移金属錯体の磁性と光学特性

    仕幸 英治, 安藤 康夫, 江良 正直, 宮崎 照宣

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 23 312-312 1999年10月1日

  112. スピンバルブ型トンネル接合のマグノン非弾性励起

    村井 純一郎, 安藤 康夫, 上條 誠, 久保田 均, 宮崎 照宣

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 23 425-425 1999年10月1日

  113. Ni_<80>Fe_<20>薄膜における強磁性共鳴線幅の下地層依存性

    水上 成美, 安藤 康夫, 宮崎 照宣

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 23 379-379 1999年10月1日

  114. Coナノ微粒子を含むトンネル接合の TMRとクーロンブロッケード

    久保田 均, 福本 能之, THAMRONGSING S., 安藤 康夫, 宮崎 照宣

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 23 284-284 1999年10月1日

  115. 強磁性トンネル接合用Al酸化膜の局所伝導

    安藤 康夫, 亀田 博史, 久保田 均, 宮崎 照宣

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 23 275-275 1999年10月1日

  116. Ni_<80>Fe_<20>Co/N(N=Ta, Al)/Al-oxide/Co接合における磁気抵抗効果

    大坊 忠臣, 手束 展規, 久保田 均, 安藤 康夫, 宮崎 照宣

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 23 273-273 1999年10月1日

  117. 極薄Alプラズマ酸下膜を用いた強磁性トンネル接合の磁気抵抗効果

    上條 誠, 久保田 均, 安藤 康夫, 宮崎 照宣

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 23 271-271 1999年10月1日

  118. Ni-Fe/Co/Al-O/Co接合におけるTMRのプラズマ酸化時間及びAl膜厚依存性

    久保田 均, 大塚 茂樹, 上條 誠, YU C. C., 手束 展規, 安藤 康夫, 宮崎 照宣

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 23 272-272 1999年10月1日

  119. 26pPSA-49 Co/Co-AlO_x/Co接合のTMRとクーロンブロッケード

    久保田 均, シリポンサクン タムロンシン, 福本 能之, 安藤 康夫, 宮崎 照宣

    日本物理学会講演概要集 54 (2) 420-420 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

  120. 26pPSA-46 Ni_<80>Fe_<20>/Co/N/N-oxide/Co(N=Ta, Al)接合における磁気抵抗効果

    大坊 忠臣, 手束 展規, 久保田 均, 安藤 康夫, 宮崎 照宣

    日本物理学会講演概要集 54 (2) 420-420 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

  121. 26pPSA-45 トンネル分光法によるスピン分極率測定

    大兼 幹彦, 手束 展規, 久保田 均, 安藤 康夫, 宮崎 照宣

    日本物理学会講演概要集 54 (2) 419-419 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

  122. 26pPSA-47 Ni_<80>Fe_<20>/Co/Al(d_<Al>)/Al-oxide/Co接合の非弾性電子トンネル分光

    村井 純一郎, 安藤 康夫, 大坊 忠臣, 宮崎 照宣

    日本物理学会講演概要集 54 (2) 420-420 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

  123. 26aYQ-7 非磁性体(NM)/80NiFe/NM膜におけるFMR線幅に対するNMの効果

    水上 成美, 安藤 康夫, 宮崎 照宣

    日本物理学会講演概要集 54 (2) 397-397 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

  124. 29a-J-3 80NiFe並びにCo超薄膜のFMR線幅

    水上 成美, 安藤 康夫, 宮崎 照宣

    日本物理学会講演概要集 54 (1) 420-420 1999年3月15日

    出版者・発行元:一般社団法人日本物理学会

    ISSN:1342-8349

  125. ナフチルアミン-3d遷移金属錯体の合成とその磁性

    安藤 康夫, 仕幸 英治, 宮崎 照宣

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 22 257-257 1998年9月1日

  126. Co, 80NiFe薄膜における強磁性共鳴の膜厚依存性

    水上 成美, 安藤 康夫, 宮崎 照宣

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 22 261-261 1998年9月1日

  127. wedge状に絶縁層を形成した強磁性トンネル接合の磁気抵抗効果

    安藤 康夫, 横田 匡史, 宮崎 照宣

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 22 453-453 1998年9月1日

  128. 1p-W-8 Al/Al_2O_3/Co/Al接合の非弾性電子トンネル分光

    村井 純一郎, 安藤 康夫, 宮崎 照宣

    日本物理学会講演概要集 53 (1) 427-427 1998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

  129. 高分子化合物を用いた機能性LB膜組織体の形成

    宮下徳治, 安藤康夫, 宮崎照宣

    日本油学会誌 47 (4) 323-331 1998年

    出版者・発行元:Japan Oil Chemists' Society

    DOI: 10.5650/jos1996.47.323  

    ISSN:1341-8327

    詳細を見る 詳細を閉じる

    近年,高分子化合物を用いたLB膜が興味を持たれ始めている。高分子化合物の単分子膜形成やそのLB膜形成に影響する因子について低分子両親媒性化合物との違いなどの観点から,実際の高分子LB膜形成の例をもとに解説を行う。新規な高分子LB膜としてそれまであまり報告例のないフッ素系の高分子LB膜についても紹介を行う。また,高分子LB膜への機能性の導入法の検討と実際の興味ある例として磁気機能団を導入した高分子LB膜の解説を行った。

  130. 有機アミン-3d遷移金属錯体の合成とその磁性

    安藤 康夫, 仕幸 英治, 宮崎 照宣

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 21 79-79 1997年10月1日

  131. 非弾性電子トンネル分光法(IETS)を用いた強磁性体/絶縁体界面の解析

    村井 純一郎, 安藤 康夫, 手束 展規, 宮崎 照宣

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 21 174-174 1997年10月1日

  132. Wedge状の絶縁層を有する強磁性トンネル接合の磁気抵抗効果

    横田 匡史, 安藤 康夫, 手束 展規, 宮崎 照宣

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 21 173-173 1997年10月1日

  133. 強磁性体-有機色素接合における偏極スピン伝導

    安藤 康夫, 村井 純一郎, 宮崎 照宣

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 20 137-137 1996年9月1日

  134. 強磁性トンネル接合における絶縁障壁と磁気抵抗効果

    手束 展規, 安藤 康夫, 宮崎 照宣, TOMPKINS H. G., TEHRANI S. T., GORONKIN H. G.

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 20 136-136 1996年9月1日

  135. 70CoNi/Cu/80NiFe三層膜の強磁性共鳴

    水上 成美, 安藤 康夫, 宮崎 照宣

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 20 54-54 1996年9月1日

  136. 80Ni-Fe/Cu/Co/Cu80Ni-Fe人工格子薄膜の強磁性共鳴

    安藤 康夫, 古泉 浩, 宮崎 照宣

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan 19 343-343 1995年9月1日

  137. 29a-PS-14 擬二元R-Fe(R=Pr, Nd, Sm, Tb, Dy, Er)アモルファス合金の強磁場磁化

    栗田 直幸, 加藤 宏朗, 安藤 康夫, 宮崎 照宣

    日本物理学会講演概要集. 年会 50 (3) 41-41 1995年3月16日

    出版者・発行元:一般社団法人日本物理学会

  138. 3a-YA-12 ランダム異方性を有するR-Fe擬二元アモルファス合金の磁気相図

    栗田 直幸, 加藤 宏朗, 安藤 康夫, 石尾 俊二, 宮崎 照宣

    日本物理学会講演概要集. 秋の分科会 1994 (3) 67-67 1994年8月16日

    出版者・発行元:一般社団法人日本物理学会

  139. 3p-YA-7 強磁性/Al-Al_2O_3/強磁性接合の磁気トンネリング効果

    手束 展規, 安藤 康夫, 宮崎 照宜

    日本物理学会講演概要集. 秋の分科会 1994 (3) 84-84 1994年8月16日

    出版者・発行元:一般社団法人日本物理学会

  140. 1a-S-4 80Ni-Fe/Cu人工格子における強磁性共鳴

    古泉 浩, 佐藤 雅重, 安藤 康夫, 石尾 俊二, 宮崎 照宣

    日本物理学会講演概要集. 年会 48 (3) 142-142 1993年3月16日

    出版者・発行元:一般社団法人日本物理学会

  141. 31p-PS-15 Fe-Ni-Mn合金のリエントラントスピングラス(磁性(磁性理論及びスピングラス))

    宮崎 照宣, 安藤 康夫, 高橋 実

    年会講演予稿集 41 (3) 137-137 1986年3月29日

    出版者・発行元:一般社団法人日本物理学会

  142. 3a-PS-9 Fe_<65>(Ni_<1-x>Mn_x)_<35>(0≦x≦0.3)合金のスピングラス

    宮崎 照宣, 安藤 康夫, 高橋 実

    秋の分科会講演予稿集 1985 (3) 119-119 1985年9月13日

    出版者・発行元:一般社団法人日本物理学会

  143. 31a-D3-10 Fe_<65>Ni_<35>インバー合金のリエントラントスピングラス(磁性(スピングラス))

    高橋 実, 安藤 康夫, 宮崎 照宜

    年会講演予稿集 40 (3) 69-69 1985年3月31日

    出版者・発行元:一般社団法人日本物理学会

  144. 12a-T-4 Fe-Niインバー合金のスピングラス

    高橋 実, 岡本 巌, 安藤 康夫, 宮崎 照宣

    秋の分科会講演予稿集 1983 (3) 88-88 1983年9月13日

    出版者・発行元:一般社団法人日本物理学会

︎全件表示 ︎最初の5件までを表示

書籍等出版物 8

  1. 生体情報センシングとヘルスケアへの最新応用

    安藤 康夫

    技術情報協会 2017年6月

  2. 新しい磁気センサとその応用

    安藤康夫

    (株)トリケップス 2013年

  3. 技術シーズを活用した研究開発テーマの発掘

    安藤 康夫

    技術情報協会 2013年

  4. スピンポンピングと磁化ダイナミクス

    安藤康夫

    シーエムシー出版 2009年

  5. Optically stimulated magnetization dynamics of epitaxial Heusler alloy films

    Y. Liu, L. R. Shelford, V. V. Kruglyak, R. J. Hicken, Y. Sakuraba, M. Oogane, Y.Ando, T. Miyazaki

    Research Signpost 2009年

  6. 磁気抵抗効果再生磁気ヘッドの基本原理

    安藤康夫

    シーエムシー出版 2007年

  7. トンネル磁気抵抗材料

    安藤康夫

    株式会社 フジ・テクノシステム 2005年

  8. スピンダイナミクス

    安藤康夫, 水上成美, 中村洋明, 久保田均, 宮﨑照宣

    シーエムシー出版 2004年12月

︎全件表示 ︎最初の5件までを表示

講演・口頭発表等 86

  1. 超高感度磁気センサの可能性 招待有り

    安藤 康夫

    第33回 東北地域の車を考える会 2018年9月21日

  2. Recent progress of biomagnetic field sensors with ferromagetic tunnel junctions 招待有り

    安藤 康夫

    第42回日本磁気学会講演会 2018年9月12日

  3. Recent Progress of Bio-magnetic Field Sensors with Ferromagnetic Tunnel Junctions (MTJs) 国際会議 招待有り

    安藤 康夫

    Annual World Congress of Smart Materials 2018 “Weaving an Avatar Dream Together” 2018年4月7日

  4. Recent progress of bio-magnetic field sensors with ferromagnetic tunnel junctions (MTJs) 国際会議 招待有り

    安藤 康夫

    Tohoku/SG-Spin Workshop on Spintronics 2018年2月21日

  5. トンネル磁気抵抗素子を用いた生体磁場測定装置の開発と展望 招待有り

    安藤 康夫

    日本学術振興会「先端ナノデバイス・材料テクノロジー」151委員会 平成29年度第5回研究会 2018年1月24日

  6. トンネル磁気抵抗素子を用いた生体磁場測定装置の開発 招待有り

    安藤 康夫

    東北大学レアメタル・グリーンイノベーション研究開発センター 第3回フォーラム~クリーンエネルギー関連デバイス部門研究成果~ 2017年12月22日

  7. TMRを用いた生体磁気センサの開発 「社会基盤の向上につながる磁気センサとその活用」 招待有り

    安藤 康夫

    第5回 岩崎コンファレンス 2017年11月27日

  8. Bio-magnetic field sensor application of magnetic tunnel junctions 国際会議 招待有り

    安藤 康夫

    2017 Lorraine-Mainz-Tohoku Joint Seminar 2017年11月3日

  9. Magnetic field sensor application of magnetic tunnel junctions 国際会議 招待有り

    安藤 康夫

    SSDM 2017 2017年9月21日

  10. Development of Spintronics and Device Application 国際会議 招待有り

    安藤 康夫

    The 2017 International Meeting for Future of Electron Devices 2017年6月29日

  11. Development of bio-magnetic sensors operating at room temperature with ferromagnetic tunnel junctions 国際会議 招待有り

    安藤 康夫

    Biomagnetic Sendai 2017 2017年5月23日

  12. トンネル磁気抵抗磁場センサの開発と生体磁場計測への応用 招待有り

    安藤 康夫

    第64回応用物理学会春季学術講演会 2017年3月16日

  13. Bio-magnetic field sensor application of magnetic tunnel junctions 国際会議 招待有り

    安藤 康夫

    4th JSPS Core-to-Core Workshop on “New concept Spintronic Devices” 2016年11月20日

  14. Development of bio-magnetic field measurement system with tunnel magnetoresistance devices 国際会議 招待有り

    安藤 康夫

    2016 DISKCON JAPAN 2016年5月26日

  15. ホイスラー合金を用いた強磁性トンネル接合のデバイス応用の展望 招待有り

    安藤 康夫

    日本金属学会 2015年秋季講演大会 2015年9月17日

  16. “強磁性トンネル接合を用いた高感度磁場センサの開発と展望” 招待有り

    日本磁気学会第203回研究会 2015年7月24日

  17. “高感度TMRを用いた生体磁場測定デバイス” 招待有り

    日本学術振興会薄膜第131委員会、半導体界面制御技術第154委員会合同研究会 2015年2月24日

  18. “高感度TMRを用いた生体磁場測定デバイス” 招待有り

    JR東海第25回技術開発部セミナー 2014年11月11日

  19. ”Bio-magnetic field sensor application of magnetic tunnel junctions” 国際会議 招待有り

    The 6th IEEE international Nanoelectronics Conference 2014 (IEEE INEC 2014) 2014年7月29日

  20. “強磁性トンネル接合を用いた高感度磁気センサの応用と展望” 招待有り

    日本磁気学会 第197回研究会 「高感度磁気センサの研究と製品」 2014年7月11日

  21. ”強磁性トンネル接合を用いた生体磁気計測の現状と進歩” 招待有り

    第53回日本生体医工学会 オーガナイズドセッション 「生体磁気計測技術の進歩」 2014年6月24日

  22. ”Bio-magnetic field sensor application of magnetic tunnel junctions” 国際会議 招待有り

    Yasuo Ando, Daiki Kato, Kosuke Fujiwara, Hiroshi Naganuma, Mikihiko Oogane, T. Nishikawa

    The AIMR International Symposium 2014 (AMIS 2014) “Toward emergence of new materials science with mathematics collaboration” 2014年2月18日

  23. “Magnetic materials with high thermal stability and low magnetic damping” 国際会議 招待有り

    The 2nd SRJ MRAM Forum 2013 2013年11月20日

  24. “MTJ-based Spintronics” 国際会議 招待有り

    SSDM2013 SHORT COURSE B. “Fundamentals and Applications of Spintronics Frontier” 2013年9月24日

  25. “強磁性トンネル接合を用いた生体磁気計測の現状と展望” 招待有り

    第28回日本生体磁気学会 2013年6月7日

  26. “トンネル磁気抵抗素子を用いた心磁場および脳磁場の計測” 招待有り

    安藤 康夫, 藤原耕輔, 大兼幹彦, 永沼博, 西川卓男

    日本磁気学会第44回スピンエレクトロニクス専門研究会 2013年3月6日

  27. “スピンによる生体磁場計測 -革新的スピントロニクス医療デバイスの創成の可能性-” 招待有り

    安藤康夫, 西川卓男

    平成24年度東北地区高等専門学校専攻科産学連携シンポジウム 2013年3月2日

  28. “XMCDを用いた強磁性トンネル接合界面の解析と伝導特性” 招待有り

    第二回 東北大学 光・量子ビーム科学連携ワークショップ 2013年1月8日

  29. スピンによる心磁図・脳磁図計測 -革新的スピントロニクス医療デバイスの創成の可能性 招待有り

    第7回 ATI合同研究会『スピンと生命の融合』—バイオスピントロニクスの可能性を探る 2012年11月27日

  30. “Large magnetoresistance effect in Epitaxial Co2FexMn1-xSi/Ag/ Co2FexMn1-xSi Devices” 招待有り

    Jo Sato, Mikihiko Oogane, Hiroshi Naganuma, Yasuo Ando

    第73回応用物理学会学術講演会応用物理学会優秀論文賞受賞記念講演 2012年9月13日

  31. “スピントロニクス技術による生体磁場センサ” 招待有り

    安藤 康夫, 藤原耕輔, 大兼幹彦, 永沼博, 西川卓男

    第73回応用物理学会学術講演会 2012年9月12日

  32. Advanced spintronic materials and transport phenomena 国際会議 招待有り

    Japan-Germany Progress Seminar “Spin and Quantum Information” 2011年11月24日

  33. スピントロニクスの現状と今後の展開 招待有り

    デンソー共同研究講演会 2011年11月4日

  34. 二重強磁性トンネル接合の磁気抵抗効果 招待有り

    第71回応用物理学会学術講演会 2011年9月14日

  35. Progress of magnetoresistance effect in MTJs with Heusler alloys 国際会議 招待有り

    2nd Meeting of Strategic Japanese-German Joint Research Program“ASPIMATT” : Advanced spintronic materials and transport phenomena 2010年10月19日

  36. 強磁性トンネル接合を用いた極微小磁界検出の可能性 招待有り

    コニカミノルタオプト講演会 2010年10月1日

  37. 二重強磁性トンネル接合の磁気抵抗効果 招待有り

    第34回日本磁気学会学術講演会 2010年9月4日

  38. 二重障壁強磁性トンネル素子およびホイスラー合金を用いた素子における磁気抵抗効果 招待有り

    International Disk Forum 国際ディスクフォーラム2010 (DISKCON) 2010年7月30日

  39. MgO二重障壁強磁性トンネル接合における巨大磁気抵抗効果 招待有り

    Lixian Jiang, 永沼 博, 大兼 幹彦

    春季第 57回応用物理学関係連合講演会 2010年3月18日

  40. MgO障壁層を用いた二重強磁性トンネル接合における巨大磁気抵抗効果 招待有り

    IDEMA JAPAN 合同部会講演会 2009年12月4日

  41. MgO障壁層を用いた二重強磁性トンネル接合における磁気抵抗効果 招待有り

    第4回 スピントロニクス技術分科会 2009年11月12日

  42. ホイスラー合金を用いた強磁性トンネル接合の磁気抵抗効果と界面制御 招待有り

    応用物理学会シリコンテクノロジー分科会 2009年3月16日

  43. スピントルク磁化反転におけるスピンダイナミクス 招待有り

    安藤康夫, 青木達也, 玉川聖, 渡邉大輔, 水上成美, 家形諭, 谷口知大, 今村裕志, 永沼博, 大兼幹彦, 宮崎照宣

    日本磁気学会第165回研究会 2009年3月13日

  44. Perspective of High Tunnel Magnetoresistance in Magnetic Tunnel Junctions with Heusler Alloy Electrodes and MgO Barrier 国際会議 招待有り

    Y. Ando, S. Tsunegi, T. Kubota, G. Kim, T. Hiratsuka, Y. Sakuraba, M. Oogane, K. Takanashi, S. Mizukami, T. Miyazaki

    Tohoku-York Research Seminar 2009年1月20日

  45. 強磁性トンネル接合における磁気抵抗効果と界面制御 招待有り

    第1回界面科学研究会,表面・界面制御による新物質層の探索 2008年12月19日

  46. 新潟高校特別授業 招待有り

    安藤康夫

    最先端技術と産業を支える工学研究~磁石で考えるナノテクノロジー 2008年3月24日

  47. スピンエレクトロニクス技術の現状と将来展望 招待有り

    富士電機デバイステクノロジー株式会社 技術講演会 2007年10月10日

  48. MRAMの研究開発動向 招待有り

    次世代不揮発メモリのデバイス原理と研究開発動向 2007年4月26日

  49. Preparation of magnetic tunnel junctions with ferromagnetic electrodes of high spin polarization 国際会議 招待有り

    FG559 meeting, Mainz, Germany 2007年4月16日

  50. 強磁性共鳴を用いたMRAMフリー層材料の磁気緩和定数測定 招待有り

    大兼幹彦, 渡邉大輔, 渡邉美穂, Resul Yilgin, 家形諭, 宮崎照宣

    日本応用磁気学会第153回研究会,第15回スピンエレクトロニクス専門研究会 2007年2月27日

  51. High spin-polarized state observed in magnetic tunnel junctions with Co2MnSi electrodes 国際会議 招待有り

    Y. Ando, Y. Sakuraba, M. Oogane, A. Sakuma, T. Miyazaki

    Japan-Germany Joint Workshop 2006, “Nano-Electronics” 2006年11月30日

  52. マイクロ波とスピンダイナミクス 招待有り

    東北大学電気通信研究所共同プロジェクト研究会 2006年9月28日

  53. Recent progress in tunnel magnetoresistance effect and the application to spintronics devices 国際会議 招待有り

    Y. Ando

    KINKEN-WAKATE 2006年8月26日

  54. ナノテクノロジーと私たちの生活~究極の微小磁石-スピン-を利用したナノテク~ 招待有り

    佐沼高校 2006年8月1日

  55. 強磁性トンネル接合における巨大磁気抵抗効果の進展と磁気メモリへの応用 招待有り

    安藤康夫, 大兼幹彦, 宮崎照宣

    東北大学多元研研究会 2006年6月3日

  56. Spin-dependent spectroscopy of MTJs with high spin polarization materials 国際会議 招待有り

    Y. Ando, T. Miyakoshi, T. Daibou, M. Oogane, T. Miyazaki, S. Yuasa

    3rd Int. Symposium “Thin Films of Heusler Compounds, a Challenge 2005年11月12日

  57. Large magnetoresistance in MTJs with full-Heusler alloy electrode 国際会議 招待有り

    Y. Ando, Y. Sakuraba, M. Oogane, H. Kubota, T. Miyazaki

    3rd Int. Symposium Thin Films of Heusler Compounds, a Challenge 2005年11月11日

  58. Recent progress in magnetic tunnel junctions with MgO barrier 国際会議 招待有り

    Y. Ando, M Oogane, T. Daibou, T. Miyakoshi, S. Yuasa, T. Miyazaki

    Johannes Gutenberg-Universität seminar 2005年6月24日

  59. Recent development of MRAM (magnetic random access memory) and related phenomena 国際会議 招待有り

    Y. Ando, M. Oogane, Y. Sakuraba, Y.M. Yi, J. Nakata, R. Yilgin, H. Kubota, T. Miyazaki

    Physikalisches Kolloquium, Fachbereich Physik 2005年5月2日

  60. Large magnetoresistance in magnetic tunnel junctions using Co-Mn-Al full Heusler alloy 国際会議 招待有り

    Y. Ando, M. Oogane, Y. Sakuraba, J. Nakata, R. Yilgin, H. Kubota, T. Miyazaki

    Johannes Gutenberg-Universität seminar 2005年3月18日

  61. スピン緩和とスピンデバイスへの展開 招待有り

    安藤康夫, 水上成美, 中村洋明, 家形諭, 大坊忠臣, 宮崎照宣

    日本応用磁気学会第8回ナノマグネティックス専門研究会 2004年10月22日

  62. 強磁性体/非磁性体接合におけるスピンポンピングとスピン拡散長 招待有り

    安藤康夫, 家形諭, 中村洋明, 水上成美, 宮崎照宣

    日本金属学会 2004年秋期大会シンポジウム 2004年9月29日

  63. 強磁性体/非磁性体接合におけるスピンポンピング 招待有り

    安藤康夫, 家形諭, 水上成美, 中村洋明, 久保田均, 宮崎照宣

    日本物理学会第59回年次大会シンポジウム 2004年3月27日

  64. メタル系スピントロニクスデバイスとダイナミクス 招待有り

    安藤康夫, 水上成美, 中村洋明, 家形諭, 久保田均, 宮崎照宣

    文部科学省科学研究費補助金特定領域研究「半導体ナノスピントロニクス」平成15年度報告会 2004年1月27日

  65. TMR素子の分極率とトンネル分光 招待有り

    NHK技術研究会 2004年1月8日

  66. Effect of spin pumping on Gilbert damping for thin permalloy films detected by using time-resolved Kerr effect 国際会議 招待有り

    Y. Ando, S. Mizukami, H. Nakamura, H. Kubota, T. Miyazaki

    International Symposium on Magnetic Materials and Application 2003年12月4日

  67. Magnetic tunnel junctions with epitaxially-grown bottom electrodes 国際会議 招待有り

    Y. Ando, J.H. Yu, S.J. Ahn, T. Kato, M. Oogane, H. Kubota, T. Miyazaki

    International workshop on Nano-scale Magnetoelectronics 2003年11月25日

  68. コンタクトAFM同時電流測定による強磁性トンネル接合絶縁層の局所評価 招待有り

    JEOL仙台表面分析懇話会 2003年11月6日

  69. TMR素子の基礎と物性 招待有り

    NHK技術研究会 2003年10月6日

  70. スピンダイナミクスの電気的および光学的アプローチ 招待有り

    安藤康夫, 中村洋明, 水上成美, 花田成, 久保田均, 宮崎照宣

    第27回応用磁気学会学術講演会シンポジウム 2003年9月17日

  71. Interface Characterization of Magnetic Tunnel Junctions 国際会議 招待有り

    Y. Ando, H. Kubota, T. Miyazaki

    KIST seminar 2002年10月29日

  72. MRAMに関わるTMR素子の絶縁特性とスピン反転 招待有り

    安藤康夫, 林将光, 中村洋明, 久保田均, 宮崎照宣

    第49回応用物理学関係連合講演会シンポジウム 2002年3月29日

  73. Growth Mechanism of Thin Insulating Layer in Ferromagnetic Tunnel Junctions Prepared by Various Oxidation Methods 国際会議 招待有り

    Y. Ando, M. Hayashi, S. Iura, K. Yaoita, H. Kubota, T. Miyazaki

    International 17th International Colloquium on Magnetic Films and Surfaces 2002年3月4日

  74. 強磁性トンネル接合における絶縁層/強磁性層界面状態と耐熱特性 招待有り

    安藤康夫, 林将光, 久保田均, 宮崎照宣

    金研ワークショップ「遷移金属酸化物薄膜における新機能創製の研究」 2001年11月25日

  75. 強磁性トンネル接合の絶縁障壁と高速スイッチング特性 招待有り

    安藤康夫, 林将光, 中村洋明, 井浦聡則, 水上成美, 久保田均, 宮崎照宣

    応用磁気学会研究会「スピンエレクトロニクスの現状と将来展望」 2001年10月23日

  76. 強磁性トンネル接合の絶縁障壁とスピン依存伝導 招待有り

    安藤康夫, 林将光, 久保田均, 宮崎照宣

    第25回日本応用磁気学会学術講演会シンポジウム 2001年9月26日

  77. 強磁性トンネル接合の絶縁障壁とスピン依存伝導 招待有り

    安藤康夫, 林将光, 久保田均, 宮崎照宣

    第45回日本学術会議材料研究連合講演会 2001年9月18日

  78. テラビット開発に向けたTMR素子の要件と課題 招待有り

    情報ストレージ技術専門委員会 2001年7月31日

  79. Growth Mechanism of Thin Insulating Layer in Ferromagnetic Tunnel Junctions Analyzed by Conducting AFM Method 国際会議 招待有り

    Y. Ando, M. Hayashi, K. Yaoita, S. Iura

    International Symposium on Physics of Magnetic Materials 2001年5月13日

  80. TMR素子の局所伝導特性と磁気抵抗効果 招待有り

    第40回磁性多層膜の新しい機能専門研究会 2001年1月21日

  81. Recent Development for Ferromagnetic Tunnel Junctions 国際会議 招待有り

    2nd Workshop for 21C Frontier Project 2000年11月2日

  82. Spin Dependent Tunneling in Ferromagnet/Insulator/Ferromagnet Junctions with poly-N dodecyl-acrylamide LB Film 国際会議 招待有り

    Nano-molecular Electronics '97 1997年12月10日

  83. 高分子フェロセン誘導体LB膜の構造と磁性 招待有り

    第46回高分子討論会 1997年10月2日

  84. 金属人工格子における磁性層間相互作用とスピントランスポート 招待有り

    安藤康夫, 手束展規, 水上成美, 古泉浩, 宮崎照宣

    東大COE研究会 1996年3月

  85. Langmuir-Blodgett法による有機分子強磁性体薄膜の作製 招待有り

    秋田大学薄膜研究会「磁性薄膜の基礎・応用研究の進展」 1995年11月17日

  86. 高分子LB膜を用いた80NiFe/PDDA/Co接合の磁気トンネリング効果 招待有り

    安藤康夫, 廣池太郎, 宮崎照宣

    磁性多層膜の新しい機能専門研究会 1995年7月18日

︎全件表示 ︎最初の5件までを表示

産業財産権 69

  1. Mn系強磁性薄膜の製造方法およびMn系強磁性薄膜

    大兼 幹彦, 安藤 康夫, 渡部 健太

    産業財産権の種類: 特許権

  2. 磁気センサおよびその製造方法

    古市 喬干, 青 建一, 阿部 竜一郎, 安藤 康夫, 大兼 幹彦, 中野 貴文

    産業財産権の種類: 特許権

  3. 磁気抵抗素子、磁気検出装置、及び磁気抵抗素子の製造方法

    古市 喬干, 青 建一, 安藤 康夫, 大兼 幹彦, 中野 貴文

    産業財産権の種類: 特許権

  4. 磁気センサ

    古市 喬干, 青 建一, 安藤 康夫, 大兼 幹彦, 中野 貴文

    産業財産権の種類: 特許権

  5. トンネル磁気抵抗素子及びその製造方法

    安藤 康夫, 大兼 幹彦, 藤原 耕輔, 城野 純一, 土田 匡章

    産業財産権の種類: 特許権

  6. トンネル磁気抵抗素子及びその製造方法

    安藤 康夫, 大兼 幹彦, 藤原 耕輔, 城野 純一

    産業財産権の種類: 特許権

  7. 磁気センサー、センサーユニット、磁気検出装置、及び磁気計測装置

    藤原 耕輔, 大兼 幹彦, 安藤 康夫, 城野 純一, 寺内 孝

    産業財産権の種類: 特許権

  8. Mn系強磁性薄膜およびその製造方法、ならびにMn系強磁性薄膜を有する磁気トンネル接合素子

    大兼 幹彦, 安藤 康夫, 栗本 雄太, 渡部 健太, 窪田 美穂

    産業財産権の種類: 特許権

    詳細を見る 詳細を閉じる

    【優先権主張番号】特願2015-210894,【優先日】平成27年10月27日

  9. 磁気センサ

    矢野 敏史, 青 建一, 安藤 康夫, 大兼 幹彦

    産業財産権の種類: 特許権

  10. マルチフェロイック素子

    永沼 博, 一ノ瀬 智浩, 大兼 幹彦, 安藤 康夫

    産業財産権の種類: 特許権

  11. 磁気抵抗素子

    矢野敏史, 青建一, 安藤康夫, 大兼幹彦, 中野貴文

    産業財産権の種類: 特許権

  12. 磁気センサ

    矢野敏史, 青建一, 古市喬干, 安藤康夫, 大兼幹彦, 中野貴文

    産業財産権の種類: 特許権

  13. 磁気抵抗素子およびそれを用いた磁気センサ

    矢野敏史, 青建一, 安藤康夫, 大兼幹彦, 中野貴文

    産業財産権の種類: 特許権

  14. 磁気センサー及びその製造方法

    西川卓男, 安藤康夫

    産業財産権の種類: 特許権

    詳細を見る 詳細を閉じる

    【優先権主張番号】特願2013-150339,【優先日】平成25年7月19日

  15. マルチフェロイック薄膜及びそれを用いたデバイス

    永沼博, フスネ アラ ベガン, 窪田美穂, 佐藤敬, 大兼幹彦, 安藤康夫

    産業財産権の種類: 特許権

  16. 磁気抵抗素子及びそれを用いた磁気メモリ

    永沼博, モハメド ナズルル, イスラム カーン, 井波暢人, 大兼幹彦, 安藤康夫

    産業財産権の種類: 特許権

  17. 生体磁気センサー及びその製造方法

    西川卓男, 荒川裕明, 安藤康夫, 大兼幹彦, 藤原耕輔

    産業財産権の種類: 特許権

  18. 磁気抵抗効果素子および磁気デバイス

    大兼幹彦, 永沼博, 安藤康夫, 佐藤丈

    産業財産権の種類: 特許権

  19. スピントランジスタおよび磁気デバイス

    大兼幹彦, 永沼博, 安藤康夫, 大平祐介

    産業財産権の種類: 特許権

  20. 生体磁気計測装置、生体磁気計測システム、及び、生体磁気計測方法

    西川卓男, 安藤康夫

    産業財産権の種類: 特許権

    詳細を見る 詳細を閉じる

    【優先権主張番号】特願2010-202540,【優先日】平成22年9月10日

  21. 二重障壁強磁性トンネル接合および磁気デバイス

    姜麗仙, 永沼博, 大兼幹彦, 安藤康夫

    産業財産権の種類: 特許権

  22. ホイスラー合金材料、磁気抵抗素子および磁気デバイス

    大兼幹彦, 佐藤丈, 窪田崇秀, 永沼博, 安藤康夫

    産業財産権の種類: 特許権

  23. 反平行結合膜構造体、トンネル磁気抵抗素子および磁気デバイス

    大兼幹彦, 西村真之, 安藤康夫

    産業財産権の種類: 特許権

  24. 磁気抵抗素子及び磁気メモリ

    西山勝哉, ファン ウ, 水上成美, 宮崎照宣, 與田博明, 甲斐正, 岸達也, 渡邉大輔, 大兼幹彦, 安藤康夫, 吉川将寿, 永瀬俊彦, 北川英二, 大坊忠臣, 長嶺真夫

    産業財産権の種類: 特許権

  25. 磁性材料及びそれを用いた磁気抵抗素子

    久保田均, 福島章雄, 薬師寺啓, 長浜太郎, 湯浅新治, 安藤功兒, 大兼幹彦, 渡邉美穂, 安藤康夫, 宮﨑照宣

    産業財産権の種類: 特許権

  26. 磁気抵抗素子の製造方法、磁気デバイスの製造方法、磁気抵抗素子の製造装置および磁気デバイスの製造装置

    森田正, 小野一修, 菊地幸男, 大兼幹彦, 大坊忠臣, 安藤康夫, 宮﨑照宣

    産業財産権の種類: 特許権

  27. トンネル磁気抵抗効果素子

    大兼幹彦, 宮﨑照宣, 桜庭裕弥, 服部正志, 安藤康夫

    産業財産権の種類: 特許権

  28. トンネル磁気抵抗効果素子

    大兼幹彦, 宮﨑照宣, 桜庭裕弥, 服部正志, 安藤康夫

    産業財産権の種類: 特許権

  29. 低磁気緩和定数トンネル磁気抵抗素子

    安藤康夫, 渡邉大輔, 大兼幹彦, 宮﨑照宣

    産業財産権の種類: 特許権

  30. スピントランジスタ

    大兼幹彦, 宮﨑照宣, 桜庭裕弥, 安藤康夫, 久保田均

    産業財産権の種類: 特許権

  31. トンネル磁気抵抗効果素子

    大兼幹彦, 宮﨑照宣, 桜庭裕弥, 安藤康夫, 久保田均

    産業財産権の種類: 特許権

  32. 磁気記録媒体

    竹田克之, 清水雄二, 溝口康正, 安藤康夫

    産業財産権の種類: 特許権

  33. 磁気記録媒体

    清水雄二, 竹田克之, 溝口康正, 安藤康夫

    産業財産権の種類: 特許権

  34. 磁気記録媒体

    川上晃, 安藤康夫, 西川卓男, れん理英子, 枝松美紀

    産業財産権の種類: 特許権

  35. 磁気記録媒体

    川上晃, 安藤康夫, 西川卓男, 瑓理英子, 枝松美紀

    産業財産権の種類: 特許権

  36. 磁気記録媒体およびその製造方法

    瑓理英子, 安藤康夫

    産業財産権の種類: 特許権

  37. 磁気記録媒体

    西川卓男, 安藤康夫

    産業財産権の種類: 特許権

  38. 磁気記録媒体

    西川卓男, 安藤康夫

    産業財産権の種類: 特許権

  39. 磁気記録媒体

    安藤康夫, 西川卓男

    産業財産権の種類: 特許権

  40. 磁気記録媒体

    安藤康夫, 西川卓男

    産業財産権の種類: 特許権

  41. 磁気記録媒体

    川上晃, 安藤康夫, 西川卓男, 瑓理英子, 枝松美紀

    産業財産権の種類: 特許権

  42. 磁気記録媒体

    川上晃, 安藤康夫, 西川卓男, 瑓理英子, 枝松美紀

    産業財産権の種類: 特許権

  43. 磁気記録媒体

    河原説子, 中野寧, 小山曻, 安藤康夫, 川上晃

    産業財産権の種類: 特許権

  44. 磁気記録媒体

    西川卓男, 安藤康夫

    産業財産権の種類: 特許権

  45. 磁気記録媒体

    安藤康夫, 見寶勉

    産業財産権の種類: 特許権

  46. 磁気記録媒体

    松田敦子, 安藤康夫

    産業財産権の種類: 特許権

  47. 磁気記録媒体

    松田敦子, 安藤康夫

    産業財産権の種類: 特許権

  48. 磁気記録媒体

    後藤成人, 安藤康夫

    産業財産権の種類: 特許権

  49. 磁気記録媒体及びその製造方法

    西川卓男, 安藤康夫

    産業財産権の種類: 特許権

  50. 磁気記録媒体

    後藤成人, 安藤康夫

    産業財産権の種類: 特許権

  51. 磁気記録媒体

    後藤成人, 安藤康夫

    産業財産権の種類: 特許権

  52. 磁気記録媒体

    安藤康夫, 西川卓男

    産業財産権の種類: 特許権

  53. 磁気記録媒体

    後藤成人, 安藤康夫

    産業財産権の種類: 特許権

  54. 磁気記録媒体

    安藤康夫, 西川卓男

    産業財産権の種類: 特許権

  55. 磁気記録媒体

    安藤康夫, 西川卓男

    産業財産権の種類: 特許権

  56. 磁気記録媒体の製造方法

    川上晃, 安藤康夫

    産業財産権の種類: 特許権

  57. 磁気記録媒体の製造方法及びその装置

    川上晃, 安藤康夫

    産業財産権の種類: 特許権

  58. 磁気記録媒体の製造方法

    安藤康夫, 飛沢誠一

    産業財産権の種類: 特許権

  59. 磁気記録媒体の製造方法

    佐々木邦綱, 安藤康夫, 飛沢誠一

    産業財産権の種類: 特許権

  60. 磁気記録媒体の製造方法

    安藤康夫, 佐々木邦綱, 飛沢誠一

    産業財産権の種類: 特許権

  61. 磁気記録媒体

    磯辺亮介, 安藤康夫

    産業財産権の種類: 特許権

  62. 磁気記録媒体

    磯辺亮介, 安藤康夫

    産業財産権の種類: 特許権

  63. 磁気記録媒体

    磯辺亮介, 安藤康夫

    産業財産権の種類: 特許権

  64. 磁気記録媒体

    磯辺亮介, 安藤康夫

    産業財産権の種類: 特許権

  65. 磁気記録媒体の製造方法

    奈良仁司, 川上晃, 松田敦子, 後藤成人, 安藤康夫

    産業財産権の種類: 特許権

  66. 磁気記録媒体の製造方法

    奈良仁司, 見寶勉, 川上晃, 安藤康夫, 松田敦子

    産業財産権の種類: 特許権

  67. 磁気記録媒体の製造方法

    奈良仁司, 見寶勉, 川上晃, 安藤康夫, 松田敦子

    産業財産権の種類: 特許権

  68. 磁気記録媒体の製造方法

    奈良仁司, 見寶勉, 川上晃, 安藤康夫, 後藤成人

    産業財産権の種類: 特許権

  69. 磁気記録媒体の製造方法

    川上晃, 奈良仁司, 見寶勉, 松田敦子, 安藤康夫

    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 47

  1. トンネル磁気抵抗素子を用いた心磁図および脳磁図と核磁気共鳴像の室温同時測定装置の開発 競争的資金

    安藤 康夫

    2011年 ~ 2020年

  2. 高機能・超低消費電力スピンデバイス・ストレージ基盤技術の開発 競争的資金

    大野 英男

    2007年 ~ 2019年

  3. 規則合金系ヘテロ接合における多彩な物理現象とスピンデバイス創製 競争的資金

    安藤 康夫

    2012年 ~ 2016年

  4. 規則合金系ヘテロ接合における多彩なスピンデバイス創製(辞退) 競争的資金

    安藤 康夫

    2012年 ~ 2014年

  5. 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 競争的資金

    大野 英男

    2009年 ~ 2014年

  6. 先端スピントロニクス材料と伝導現象(ASPIMATT) 競争的資金

    安藤 康夫

    2010年 ~ 2012年

  7. MgOおよびAlOトンネル接合におけるスピントランスファー磁化反転 競争的資金

    安藤 康夫

    2009年 ~ 2011年

  8. 材料インテグレーション国際教育研究拠点 競争的資金

    後藤 孝

    2007年 ~ 2011年

  9. Design of Materials and Structures for Reduction in Spin Transfer Noise for Heusler Alloy Based CPP GMR Structures 競争的資金

    安藤 康夫

    2008年 ~ 2010年

  10. 金属ナノへテロ接合におけるスピン波励起と高周波デバイスの創製 競争的資金

    安藤 康夫

    2008年 ~ 2010年

  11. スピン流と光物性調製班

    大野 裕三, 宗片 比呂夫, 安藤 康夫, 永長 直人

    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

    2007年 ~ 2010年

    詳細を見る 詳細を閉じる

    スピン流と光物性に関し,半導体量子構造における電子・核スピン物性の光制御とその光検出,強磁性半導体の光励起による新物性の発現,強磁性金属多層膜の光物性,さらにスピンと光の結合理論について研究を行い,実験研究および理論研究のグループ間の連携を進めながら多くの知見を得た.

  12. 磁性薄膜材料.MRAMの磁化反転に関する研究 競争的資金

    安藤 康夫

    2007年 ~ 2010年

  13. 金属系多層膜におけるスピン流と磁気緩和 競争的資金

    安藤 康夫

    2007年 ~ 2010年

  14. NEDOスピントロニクス不揮発性機能技術プロジェクト 競争的資金

    安藤 功兒

    2006年 ~ 2010年

  15. 高密度情報ストレージコンポーネント,研究代表者 競争的資金

    宮﨑 照宜

    1998年 ~ 2010年

  16. 高分極率を有する新しいホイスラー合金に関する研究 競争的資金

    安藤 康夫

    2007年 ~ 2009年

  17. New materials with High Spin Polarization 競争的資金

    安藤 康夫

    2007年 ~ 2009年

  18. TMRセンサーに関する研究 競争的資金

    安藤 康夫

    2007年 ~ 2009年

  19. TMR材料の研究 競争的資金

    安藤 康夫

    2007年 ~ 2009年

  20. ホイスラー合金を用いた高トンネル磁気低抗素子の創製とスピン注入磁化反転

    宮崎 照宣, 安藤 康夫, 久保田 均, 水上 成美, 大兼 幹彦

    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:Tohoku University

    2005年 ~ 2007年

    詳細を見る 詳細を閉じる

    1.エピタキシャルホイスラー系合金電極トンネル接合の作製 高品位なホイスラー合金電極と結晶質の酸化マグネシウムを組み合わせたCo_2MnSi/MgO/CoFe-トンネル接合において,217%(室温),753%(低温)の巨大なTMR比を観測することに成功した.このTMR比はホイスラー合金を用いたトンネル接合において世界最高の値である.また,このTMR接合のコンダクタンス特性を詳細に調べた結果,巨大TMR比の原因は結晶質のMgO絶縁層を介したコヒーレントトンネリング過程によるものと示唆された. 2.微細化とスピン注入磁化反転 磁化反転層に(Co_<50>Fe_<50>)_<100-x>B_x(x=20,25,30,膜厚d=2nm)を用いたCoFeB/MgO/CoFeB接合を作製し,スピン注入磁化反転の観測に成功した.その結果,反転電流密度は理論予測どおり,強磁性層の飽和磁化,ダンピング定数およびスピン分極率に依存することが明らかとなり,飽和磁化およびダンピング定数の低減が反転電流密度を低減するために非常に有効であることが分かった. 3.ダンピング定数αに関して 強磁性共鳴を用いて,種々の強磁性体のダンピング定数を系統的に明らかにした.さらに,トンネル接合構造における磁化反転層のダンピング定数を測定する方法を世界で初めて確立した.その結果,2nm程度の非常に薄いCoFeB磁化反転層のダンピング定数は,バルクの約5倍程度増大することが分かった.また,磁化反転層の隣接層がダンピング定数に大きな影響を及ぼすことを明らかにした.

  21. 電子内部自由度制御型ナノデバイス創製原理の構築 競争的資金

    前川 禎通

    2004年 ~ 2007年

  22. スピンエンジニアリングのための新材料と新機能 競争的資金

    安藤康夫

    制度名:International Joint Research Projects

    2004年 ~ 2007年

  23. 超ギガビット磁気メモリの基盤技術の開発 競争的資金

    宮﨑 照宜

    2003年 ~ 2007年

  24. スピントロニクスデバイスに関する研究 競争的資金

    安藤 康夫

    2007年 ~

  25. 共鳴磁気トンネル・ナノドット不揮発性メモリの創製 競争的資金

    小柳 光正

    2002年 ~ 2006年

  26. 高機能・超低消費電力メモリの開発 競争的資金

    大野 英男

    2002年 ~ 2006年

  27. 微細加工した強磁性トンネル接合の動的磁区構造と磁化反転特性 競争的資金

    安藤 康夫

    2004年 ~ 2005年

  28. スピンバッテリーの強磁性共鳴を用いた動作実証 競争的資金

    安藤 康夫

    2004年 ~ 2005年

  29. 微小強磁性トンネル接合のスピンダイナミクス 競争的資金

    安藤 康夫

    2003年 ~ 2005年

  30. 固体中へのスピン注入による新機能創製 競争的資金

    鈴木 義茂

    2000年 ~ 2004年

  31. (独)日本学術振興会日韓科学技術協力事業共同研究 競争的資金

    安藤 康夫

    2002年 ~ 2003年

  32. 高品位微小トンネル接合へのスピン注入

    宮崎 照宣, 鈴木 義茂, 久保田 均, 安藤 康夫, 余 澤中

    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

    2001年 ~ 2003年

    詳細を見る 詳細を閉じる

    微小トンネル接合の作製と評価 ・集束イオンビームを用いて,100nmスケールのカーボンならびにタングステンマスクパターンを作製し,これらを用いることにより,最小400×400nm^2のトンネル微小接合を作製し,約30%のMR比を得た. ・電子ビームリソグラフィーと用いることで,0.25〜100μm^2の接合を作製した. ・原子間力顕微鏡(コンタクトモード)で微小トンネル接合の磁気抵抗曲線(MR曲線)を測定する装置を製作した.これを用いて2×0.7μm^2の接合のMR曲線を測定し,29%のMR比を得た. 素子界面におけるスピン緩和 ・Cu/Al-oxide/FeNi/Cu積層膜の強磁性共鳴(FMR)スペクトル,ならびに電流検出共鳴(EDMR)スペクトルを測定し,FMRに対応したEDMR信号が観測された. ・強磁性体の才差運動に伴うスピンポンピングにより,非磁性体中にスピンが注入されたことによると結論した. コプレーナ線路からの高速パルス磁界応答信号の測定 ・トンネル接合における強磁性電極の磁化反転に伴うトンネル電流の応答信号測定用プローブシステムを製作した.パルスの立ち上がり時間が50ps,応答信号の帯域が20GHz,に対応できた. ・トンネル接合のパーマロイ層の磁化反転信号を測定し,500ps以下の反転時間および反転後の才差運動を観測した.これらの信号はLLG方程式による計算結果とほぼ一致した. ポンププローブ方による磁化の才差運動の測定 ・ポンププローブ測定が可能な光学系を構築した. ・180×90μm^2のパーマロイ薄膜の磁化の才差運動によるシグナルを測定し,1ns以下の振動周期を観測した. ・Pt/パーマロイ/Pt接合の磁化の才差運動を測定し,Ptでパーマロイを挟むことにより振動の減衰が増大する(αが増大する)ことを直接的に観測した.

  33. スピンバルブタイプTMRを利用した高感度再生用ヘッド素子 競争的資金

    宮﨑 照宜

    1995年 ~ 2003年

  34. スピントンネル磁気抵抗デバイスの試作と評価

    久保田 均, 熊谷 静似, 宮崎 照宣, 安藤 康夫, 中塩 栄治, 余 澤中

    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

    2001年 ~ 2002年

    詳細を見る 詳細を閉じる

    サブミクロンスピントンネル接合セルの作製プロセスでは微小サイズのマスクパターンの形状及び位置の制御が非常に難しい.これらの問題を解決するため本研究では収束イオンビーム(FIB)を用いたマスクパターンの形成を試みた.スパッタ法により作製したスピントンネル接合薄膜の上にカーボン(C)及びタングステン(W)をFIB誘起堆積法により作製した.最小100nm角,高さは約300nmのCパターンを作製することができた.従って,アスペクト比>3を確保することができた.CパターンはArイオンエッチングに対しては比較的硬く,酸素アッシングに対しては十分柔らかいことが確認できた.最小140X 180nm^2の長方形で高さ約1ミクロンのWパターンに形成することができた。Wパターンの電気抵抗は接合抵抗に比べ十分低いことが確認できた.しかし,いずれのマスクにおいてもArイオンエッチング中の最付着が生じた.この際付着を防止することで,サブミクロンスピントンネル接合セルの作製が可能となると考えられる. トンネル接合の絶縁層の質的向上のため,Si(111)単結晶表面上にエピタキシャル成長させた下部電極Ag/Cu/Ni-Feを用いてトンネル接合を作製した.X線および低速電子線回折の実験により下部電極のエピタキシャル成長を確認した.この接合の室温の磁気抵抗比は50%と高く,かつバイアス電圧依存性が非常に小さい.酸化時の粒界をとおした酸素の拡散が抑制され,絶縁層および下部電極表面での欠陥密度が減少したことが原因と考えられる. 今後の課題は前述の微細加工プロセスを完成し,エピタキシャル成長した高品位トンネル接合を一辺100nm以下の微小接合に加工し,形状とスイッチング特性の関係を明らかにすることである.

  35. プローブ顕微鏡探針からの弾道電子放出による局所トンネルスピン伝導 競争的資金

    安藤 康夫

    2001年 ~ 2002年

  36. ナノサイズ強磁性トンネル接合への高密度スピン注入 競争的資金

    安藤 康夫

    2002年 ~

  37. スピントンネル再生磁気ヘッドの開発

    宮崎 照宣, 熊谷 静似, 久保田 均, 安藤 康夫, 菅原 淳一, 中塩 栄治, 韓 秀峰

    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 University and Society Collaboration

    研究機関:Tohoku University

    1999年 ~ 2001年

    詳細を見る 詳細を閉じる

    スピントンネル素子は高感度再生磁気ヘッドとして実用化されることが期待されている.しかし,実用化にあたっては,高い素子抵抗に起因する高ノイズ,低転送速度の問題を解決しなければならない.また,ヘッド作製プロセスの面では現在実用化されているGMRヘッドのデザイン,バイアス磁界印加法を直接適用できない問題がある.本研究ではこれら実用化にあたって解決すべき課題に対して東北大学のグループとソニー(株)のグループが協力して研究をすすめた.東北大学のグループは低抵抗化のアプローチとして絶縁層の薄膜化を目指した.絶縁層表面を伝導性原子間力顕微鏡(c-AFM)を用いて局所的伝導特性を調べ,Al膜厚8Å下では絶縁層にピンホール欠陥があることを明らかにした.ピンホールを低減するため,種々のバッファー層の材料を検討し,Cuバッファーを用いAl膜厚が6.6Åのとき最も抵抗化(80Ω・μm^2)かつ高TMR比(30%)の接合を得た.Fe-Niバッファーの場合,更に絶縁層を薄膜化できる可能性を示した.また,c-AFMを用いた電流分布の解析により,熱処理時に絶縁層面内の均質化がおこりTMR比が増加すること,及び,抵抗値の減少に伴い低絶縁障壁部分が増加しTMRが減少することを示した.ソニーグループはヘッドのデザインの検討を行った.フラックスガイドを用いて絶縁層を記録媒体に直接接触しないデザインを考案し,かつ,接合面積の増加による低抵抗化を図った.現行のGMRヘッドで用いられている永久磁石によるバイアス磁界印加方法はトンネル素子の電気的ショートを招く可能性が高い.そこで,フラックスガイド部のFe-Ni上にCu/Ir-Mnを積層し,Cuを介した長距離交換相互作用によりFe-Niにバイアス磁界を印加することを考案した.以上のデザインに基づきAl膜厚8Åの絶縁層を持つスピントンネル再生磁気ヘッドを試作した.試作したヘッドをヘリカルスキャン方式の磁気テープ再生システムに組み込み,再生波形を得た.長さ0.1μmのフラックスガイドを持つヘッドの出力は1.75mVp-pであり,従来方式のヘッドにくらべ2.4dB高い出力電圧を得た.この結果より,長距離交換相互作用およびフラックスガイドを組み合わせた用いたヘッド構造がスピントンネル再生磁気ヘッドに非常に適していることを実証した.

  38. ハイブリット磁性体の微細化プロセスとトンネル再生磁気ヘッドの作製

    宮崎 照宣, 熊谷 静似, 久保田 均, 安藤 康夫, 中谷 功, 韓 秀峰

    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 ~ 2001年

    詳細を見る 詳細を閉じる

    強磁性トンネル接合を再生磁気ヘッドとしてデバイス化するために、トンネル素子の最適化、微小トンネル素子作製プロセスの検討および再生磁気ヘッドの作製を行った.以下に主な成果を記す. (1)トンネル接合の積層構造、絶縁層の膜厚および熱処理条件について検討した結果、Ta30(Å)/Ni_<80>Fe_<20>(30Å)/Cu(200Å)/IrMn(100Å)/CoFe(40Å)/Al-oxide/CoFe(40Å)/Ni_<80>Fe_<20>(200Å)/Ta(50Å)の積層構造で,250℃-1時間磁界中で熱処理をすることにより,抵抗と接合面積の積が78Ω・μm^2,磁気抵抗比33%の値を得た. (2)フォトリソグラフィーおよびArイオンミリングを用いて3x3μm^2までめ微小トン接合を作製した.トンネル接合上部と電極間のわずかな汚染は2種類のレジストを用いたリフトオフプセスで防いだ.また、電子線リソグラフィーを用いて0.5x0.5μm^2までの微小トンネル接合を作製するプロセスを確立し、加工前の素子特性と比較して損傷のないことを確認した. (3)8ÅのAlを酸化した絶縁層を持つトンネル接合を微細加工プロセスによりフラックスガイド方式の再生ヘッドを試作した.フラックスガイドにはパーマロイを用い,その上にCu(15Å)/PtMn(200Å)/Ta(50Å)をスッパタし,長距離の交換相互作用を利用して、パーマロイの磁区を安定化した.試作したヘッドをヘリカルスキャン方式の磁気テープ再生システムに繰り込み,再生波形を得た.長さ0.1μmのフラックスガイドを持つヘッドの出力は1.75mV_<p-p>で,従来方式(AMRヘッド>に較べ1.5dB高い出力電圧を得た.また、HDD用の再生ヘッドを作製し、10Gbit/in^2相当の出力を得た.

  39. 有機・無機ペロブスカイトナノ構造薄膜における光誘起による磁性と伝導に関する研究 競争的資金

    安藤 康夫

    1997年 ~ 2000年

  40. None 競争的資金

    安藤 康夫

    2000年 ~

  41. 有機・無機ペロブスカイトナノコンポジットにおける光誘起による磁性と伝導に関する研究 競争的資金

    安藤 康夫

    1999年 ~

  42. 希土類超薄膜のスピン構造と磁気光学スペクトル

    宮崎 照宜, 安藤 康夫

    1997年 ~ 1998年

    詳細を見る 詳細を閉じる

    1. 低温,高磁界中表面磁気光学効果測定装置の製作 製作した装置の主な仕様は,(1)最大印加磁界:20kOe,(2)測定温度保持時間:10時間以上,(3)到達最低温度:12Kである.これを達成するために,マグネットのポールピースをクライオスタットの内部に挿入した形状に設計した.製作した低温,高磁界中表面磁気光学効果測定装置の動作検証を行い,以下の結果を得た. (1) Ni薄膜を用い磁気光学スペクトルを測定した.圧縮冷凍機動作時の機械的振動が測定に問題ないことを確認した. (2) 試料ホルダー上の温度を測定し,設定温度に対して1度以内の精度に10分以内で制御できた. (3) 光導入用の石英窓をマグネットヨークの外側に配置し,漏れ磁界によるバックグラウンドシフトの影響がほとんどないことを確認した. 2. Gd薄膜の作製と磁気光学スペクトル ガラス基板上に5×10^<-10>Torrの超高真空中電子ビーム蒸着法でGd薄膜(1000,250Å)を作製した.膜表面に酸化防止膜としてMgF_2を100Åコーティングした.この磁気光学スペクトルおよび磁化曲線を測定した.結果は以下の通りである. (1) カーヒステリシスの温度依存性を測定した.カー回転角および保磁力の温度依存性は磁気特性測定の結果と対応した. (2) 測定温度20〜350Kで磁気光学スペクトルを得た.伝導率スペクトルの非対角成分σ_<xy>"のスペクトルにおいて,バルクの報告と比較してシャープなピークが1.9eVのエネルギー位置に見られた.これはフェルミレベル付近から,分裂したdバンドへの遷移に対応する.膜厚250Åのスペクトルは,1000Åの場合と比較して構造的な変化は特に観測されなかった.

  43. スピントランスポートデバイスに関する研究

    宮崎 照宣, 久保田 均, 安藤 康夫

    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

    1996年 ~ 1998年

    詳細を見る 詳細を閉じる

    トンネルスピン磁気抵抗効果を用いたデバイスを作製するため,過去3年間にトンネル接合の基礎物性,接合素子の評価のための装置の作製並びにデバイス化に直接かかわる微細加工プロセスの確立に関して研究を行なってきた.それぞれについて主な成果をまとめる. 1. トンネル接合の基礎物性に関して トンネル磁気抵抗(TMR)変化率は両磁性層のスピン分極率,絶縁障壁の高さおよび幅に依存する.これらの点について実験的に明らかにし,その間に報告された理論的研究の比較検討も併せて行なった.また,TMR比の温度並びに印加電圧依存性はデバイス化にとって重要である.種々の接合についてこれらの依存性を調べその原因を明らかにした.更に,強磁性層の一つをFeMn又はIrMn反強磁性層でピンすることにより,温度変化が少なく,V_<1/2>が0.5Vと印加電圧依存性の少ない接合を作製することができた. 2. 評価装置の製作 トンネル接合素子の絶縁層(アルミナ)は約13Åと非常に薄く,その絶縁性は酸化の状態により著しく変わる.また,絶縁層は強磁性層と接しているため両者の界面構造がTMR比の温度依存性等に大きく影響する.これらの点を解明する非弾性電子トンネル分光(IETS)装置の開発を行ない,界面状態の構造と分光スペクトルとの対応を明らかにした.また,カー効果を利用して40×40μm^2の微小接合部のカーヒステリシスを測定できる装置を製作し,接合部の磁化と接合の磁気抵抗曲線が対応することを明らかにした. 3. 微細加工プロセスの検討と微小トンネル接合素子の作製 フォトリソグラフィーおよびArイオンミリングを用いて,微小トンネル接合を作製するプロセスを検討した.プロセス中の再付着が接合をショートし,電磁気特性が劣化するが,Arイオンのミリング入射角度,ミリングの深さを最適化することにより,再付着フリーの接合を作製できることを明らかにした.また,リード電極内の電気的絶縁に用いたSiO_2膜にコンタクトホールを作製するプロセスとして,CF_4ガスを用いたプラズマエッチング法が適していることを明らかにした. 確立したプロセスにより,最少接合面積3×3μm^2,トンネル抵抗値500Ω,TMR比の15%の微小トンネル接合素子ができ,これらの特性を有する素子は再生磁気ヘッド,MRAM等のデバイスとして非常に有望であることを示した.

  44. 層状ペロブスカイト構造を有する有機・無機ナノコンポジット薄膜における光誘起による磁性と伝導に関する研究 競争的資金

    安藤 康夫

    1998年 ~

  45. 分子構造の制御されたLB膜を用いたMIM接合の磁気トンネリング効果に関する研究 競争的資金

    安藤 康夫

    1995年 ~ 1997年

  46. 高分子LB膜を用いた金属/絶縁体/金属接合の作製と磁気トンネリング効果に関する研究 競争的資金

    安藤 康夫

    1995年 ~

  47. LB法による有機磁性薄膜の作製並びに基礎物性に関する研究 競争的資金

    安藤 康夫

    1994年 ~

︎全件表示 ︎最初の5件までを表示

社会貢献活動 63

  1. 応用物理学会リフレッシュ理科教室

    応用物理学会リフレッシュ理科教室

    2001年8月7日 ~ 2001年8月8日

    詳細を見る 詳細を閉じる

    仙台市の中学生を対象に理科教室を開いた

  2. 医療センサーのベンチャー 東北大教授ら設立 上場目指す

    日本経済新聞

    2018年12月4日 ~

  3. 東北大,磁気センサー技術のベンチャー企業設立

    OPTRONICS ONLINE

    2018年12月3日 ~

  4. <東北大>医療用センサー開発へベンチャー設立 高度な診断を容易に、5年後上場目指す

    河北新聞

    2018年12月3日 ~

  5. 医療用センサー開発へベンチャー設立

    東北放送,Nスタみやぎ

    2018年11月30日 ~

  6. 液体ヘリウムを使わず簡単に低コストで脳磁場を測定する高感度センサーを開発

    JSTnews

    2018年2月 ~

  7. 脳・心磁場計測用の「TMR素子生体磁気センサ

    MED+Fit

    2018年1月17日 ~

  8. コニカミノルタ 東北大学と脳磁場を簡便に低コストで計測する高感度センサを開発

    インナービジョン

    2018年 ~

    詳細を見る 詳細を閉じる

    インナービジョン 第33巻第1号 2018 JANUARY

  9. コニカミノルタ、脳磁場を簡易に低コストで計測する高感度センサを開発 ~心磁場測定の高速化も同時に実現-革新的な医用計測技術~

    映像情報Medical

    2018年 ~

    詳細を見る 詳細を閉じる

    映像情報Medical Vol.50 No.1 JANUARY 2018

  10. トンネル磁気抵抗素子を用いた心磁図及び脳磁図と核磁気共鳴像の室温同時測定装置の開発

    東北大学レアメタル・グリーンイノベーション研究開発センターフォーラム2017 東北大学レアメタル・グリーンイノベーション研究開発センター

    2017年12月22日 ~

  11. 磁石を使って体内を見る!

    平成27年度第5学年「2015 出前授業」 仙台市立泉松陵小学校

    2017年12月10日 ~

  12. 脳磁場を簡易、低コストで計測する 高感度センサを開発 東北大学、コニカミノルタ

    病院新聞

    2017年12月7日 ~

  13. スピンを用いた最先端デバイスの開発 ~工学とは、医工学とは~

    新潟高校模擬講義 新潟県立新潟高等学校

    2017年12月6日 ~

  14. TMR磁気センサを高感度化・低ノイズ化、α波の検出に成功-東北大, 医療

    NEWS QLifePro

    2017年11月28日 ~

  15. 東北大学、簡便かつ低コストで脳磁場を計測する高感度センサを開発

    Answers

    2017年11月27日 ~

  16. 診療所レベルでの脳磁場測定へ - 東北大、液体Heを使わない新センサを開発

    マイナビニュース

    2017年11月27日 ~

  17. 脳・心臓の磁場、室温で簡易計測 東北大・コニカミノルタなどが手法開発

    日刊工業新聞オンライン

    2017年11月27日 ~

  18. コニカミノルタ、東北大と脳磁場を簡便に低コストで計測する高感度センサーを開発

    MORNINGSTAR

    2017年11月27日 ~

  19. 脳・心臓磁場を簡易計測 東北大・コニカミノルタなど、室温利用センサー作製

    日刊工業新聞

    2017年11月27日 ~

  20. 東北大とコニカミノルタ、脳磁場を安価に計測できる高感度センサを開発

    財経新聞

    2017年11月25日 ~

  21. 東北大とコニカミノルタ、脳磁場を安価に計測できる高感度センサを開発

    livedoor NEWS

    2017年11月25日 ~

  22. 脳磁場を簡便に低コストで計測する高感度センサを開発

    J-Net21

    2017年11月24日 ~

  23. コニカミノルタ/東北大との共同研究で脳磁場を簡便に低コストで計測する高感度センサを開発

    月刊新医療

    2017年11月24日 ~

  24. 磁石を使うと心臓や脳の状態がわかる?

    サイエンススクール 生出中学校

    2017年11月21日 ~

    詳細を見る 詳細を閉じる

    磁石を使うと心臓や脳の状態がわかる?

  25. 生体活動情報を磁場で捉える高感度磁場センシング装置

    JSTフェア2017 東京

    2017年8月31日 ~

  26. 室温脳磁計による脳機能のワイドバンドマッピング

    第3回みやぎみやぎ医療機器創生産学官金連携フェア 仙台

    2017年7月15日 ~

  27. 認知症予防にも期待、室温動作の生体磁場センサ高出力化に成功

    niftyニュース

    2017年6月12日 ~

  28. 生体磁場センサーの高出力化に成功、MRIイメージングとの同時測定も

    MONOist

    2017年6月7日 ~

  29. 心臓や脳の検査、気軽にできる環境へ

    QLifePro 医療ニュース

    2017年5月25日 ~

  30. 室温で動作するMTJ生体磁場センサの高出力化に成功

    医療NEWS

    2017年5月24日 ~

  31. 東北大,室温動作の生体磁場センサーを高出力化

    OPTRONICS ONLINE

    2017年5月23日 ~

  32. 室温で動作する生体磁場検出用センサで従来素子の1500倍の出力

    マイナビニュース

    2017年5月22日 ~

  33. 東北大、室温動作の生体磁場センサの高出力化に成功

    日本経済新聞

    2017年5月22日 ~

  34. 室温脳磁計による脳機能のワイドバンドマッピング

    知と医療機器創生宮城県エリア 総括報告会 仙台

    2017年3月2日 ~

  35. スピンを用いた最先端デバイスの開発 ~工学とは、医工学とは~

    宮城県仙台第二高等学校出前講義 宮城県仙台第二高等学校

    2016年12月8日 ~

  36. 磁石を使って体内を見る!

    平成28年度第5学年「2016出前授業」 仙台市立錦ヶ丘小学校

    2016年11月22日 ~

  37. 磁石を使って体内を見る!

    平成28年度第5学年「2016出前授業」 仙台市立幸町小学校

    2016年11月15日 ~

  38. スピンを用いた最先端デバイスの開発 ~工学とは、医工学とは~

    横手高校出前講義 秋田県立横手高等学校

    2016年9月13日 ~

  39. 室温で動作する高感度の生体磁場検出用センサの開発

    JSTフェア2016 東京

    2016年8月24日 ~

  40. スピンを用いた最先端デバイスの開発 ~工学とは、医工学とは~

    新潟高校模擬講義 新潟県立新潟高等学校

    2016年7月8日 ~

  41. 磁石を使って体内を見る!

    平成27年度第5学年「2015 出前授業」 仙台市立住吉台小学校

    2015年12月1日 ~

  42. 特別授業「スピンを用いた最先端デバイスの開発 ~工学とは,医工学とは~」を行った

    第1学年「大学出張講義」宮城県立宮城県泉高等学校

    2014年11月12日 ~

  43. トンネル磁気抵抗素子を用いた心磁図および脳磁図と核磁気共鳴像の室温同時測定装置の開発

    東北大学イノベーションフェア2014 仙台国際センター

    2014年1月28日 ~

  44. 「微小磁石を用いた生体磁場センサの開発 -ナノテク材料から最先端機器 開発の方法-」

    東北大学進路講演会 神奈川県立小田原高等学校

    2013年11月26日 ~

  45. 「磁石の神秘」

    第13回 東北大学出前授業 仙台市立桜丘中学校

    2013年11月12日 ~

  46. 「磁石で考えるナノテクの世界」

    平成25年度 第2学年 大学・学問体験講座 福島県立安積黎明高等学校

    2013年11月6日 ~

  47. 「磁石の不思議にふれてみよう!」

    学都「仙台・宮城」サイエンス・デイ2013

    2013年7月21日 ~

  48. 「微小磁石を用いた生体磁場センサの開発 ~ナノテク材料から最先端機器開発へ~」

    平成25年度ユニバーサイエンス 学校法人ノートルダム新潟清心学園 新潟清心女子高等学校

    2013年7月5日 ~

  49. 「科学の不思議を体験しよう」

    平成25年度リフレッシュ理科教室 仙台市立中野小学校

    2013年6月28日 ~

  50. 平成24年度東北地区高等専門学校専攻科 産学連携シンポジウム

    仙台高等専門学校

    2013年3月3日 ~

    詳細を見る 詳細を閉じる

    「医工連携の現状と未来」,「スピンによる生体磁場計測 -革新的スピントロニクス医療デバイスの創成の可能性-」

  51. 「磁石の神秘」

    第12回サイエンス・スクール 仙台市立木町通小学校

    2012年12月17日 ~

  52. 東北大が開発に成功 超高密度HDD用巨大磁気抵抗素子

    科学新聞

    2011年10月21日 ~

  53. 東北大学、超高密度ハードディスク用の巨大磁気抵抗素子を開発 超高密度ハードディスク用巨大磁気抵抗素子の開発に成功 -1平方インチ当たり5 テラビット容量の次世代ハードディスクに適用可能な技術-

    日経プレスリリース

    2011年9月30日 ~

  54. 東北大,1平方インチ当たり5Tbクラスの次世代HDDヘッド用素子を開発

    財経新聞

    2011年9月30日 ~

  55. 東北大、5Tビット/平方インチの記録が可能となるHDD用磁気抵抗素子を開発

    マイコミジャーナル

    2011年9月30日 ~

  56. HDD,記録密度7倍に 東北大,新型の磁気ヘッド

    日経産業新聞

    2011年9月30日 ~

  57. 磁石で考えるナノテクの世界 ~最先端電子デバイスと支えるナノサイエンス~オープンキャンパス模擬授業

    オープンキャンパス模擬授業

    2009年7月31日 ~

  58. 磁化ダイナミクスとスピントロニクス

    リカレント教育公開講座

    2008年8月1日 ~

  59. オー磁石で考えるナノテクの世界 ~最先端電子デバイスと支えるナノサイエンス~プンキャンパス模擬授業

    オープンキャンパス模擬授業

    2008年7月31日 ~

  60. 最先端技術と産業を支える工学研究~磁石で考えるナノテクノロジー~新潟高校特別授業

    新潟高校特別授業

    2008年3月3日 ~

  61. メモリのデバイス原理と研究開発動向

    2007年4月26日 ~

    詳細を見る 詳細を閉じる

    「MRAMの研究開発動向」

  62. 高大連携特別授業

    2006年8月1日 ~

    詳細を見る 詳細を閉じる

    特別授業を行った

  63. スピンを用いた最先端デバイスの開発 ~ナノテクから生体医工まで~」 (理数セミナーⅠ)

    平成25年度模擬授業 山形県立鶴岡南高等学校

︎全件表示 ︎最初の5件までを表示

その他 27

  1. 先端スピントロニクス材料と伝導現象(ASPIMATT)

    詳細を見る 詳細を閉じる

    先端スピントロニクス材料と伝導現象(ASPIMATT)に関する研究

  2. MgOおよびAlOトンネル接合におけるスピントランスファー磁化反転

    詳細を見る 詳細を閉じる

    MgOおよびAlOトンネル接合におけるスピントランスファー磁化反転

  3. スピントロニクスデバイスに関する研究

    詳細を見る 詳細を閉じる

    スピントロニクスデバイスに関する研究

  4. Design of Materials and Structures for Reduction in Spin Transfer Noise for Heusler Alloy Based CPP GMR Structures

    詳細を見る 詳細を閉じる

    Design of Materials and Structures for Reduction in Spin Transfer Noise for Heusler Alloy Based CPP GMR Structures

  5. 高分極率を有する新しいホイスラー合金に関する研究

    詳細を見る 詳細を閉じる

    高分極率を有する新しいホイスラー合金に関する研究

  6. New materials with High Spin Polarization

    詳細を見る 詳細を閉じる

    New materials with High Spin Polarization

  7. 高機能・超低消費電力スピンデバイス・ストレージ基盤技術の開発

    詳細を見る 詳細を閉じる

    高機能・超低消費電力スピンデバイス・ストレージ基盤技術の開発

  8. 磁性薄膜材料.MRAMの磁化反転に関する研究

    詳細を見る 詳細を閉じる

    磁性薄膜材料.MRAMの磁化反転に関する研究

  9. TMR材料の研究

  10. TMRセンサーに関する研究

    詳細を見る 詳細を閉じる

    TMRセンサーに関する研究

  11. スピントロニクスデバイスに関する研究

    詳細を見る 詳細を閉じる

    スピントロニクスデバイスに関する研究

  12. NEDOスピントロニクス不揮発性機能技術プロジェクト

    詳細を見る 詳細を閉じる

    NEDOスピントロニクス不揮発性機能技術プロジェクト

  13. スピンエンジニアリングのための新材料と新機能

    詳細を見る 詳細を閉じる

    スピンエンジニアリングのための新材料と新機能

  14. 微細加工した強磁性トンネル接合の動的磁区構造と磁化反転特性

    詳細を見る 詳細を閉じる

    微細加工した強磁性トンネル接合の動的磁区構造と磁化反転特性

  15. 電子内部自由度制御型ナノデバイス創製原理の構築

    詳細を見る 詳細を閉じる

    電子内部自由度制御型ナノデバイス創製原理の構築

  16. 超ギガビット磁気メモリの基盤技術の開発

    詳細を見る 詳細を閉じる

    超ギガビット磁気メモリの基盤技術の開発

  17. ナノサイズ強磁性トンネル接合への高密度スピン注入

    詳細を見る 詳細を閉じる

    ナノサイズ強磁性トンネル接合への高密度スピン注入

  18. 強磁性トンネル接合の耐熱特性改善に関する研究

    詳細を見る 詳細を閉じる

    強磁性トンネル接合の耐熱特性改善に関する研究

  19. 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

  20. 共鳴磁気トンネル・ナノドット不揮発性メモリの創製

    詳細を見る 詳細を閉じる

    共鳴磁気トンネル・ナノドット不揮発性メモリの創製

  21. 固体中へのスピン注入による新機能創製

    詳細を見る 詳細を閉じる

    固体中へのスピン注入による新機能創製

  22. 走査型プローブ顕微鏡を用いた強磁性トンネル接合の局所磁気抵抗効果に関する研究

    詳細を見る 詳細を閉じる

    走査型プローブ顕微鏡を用いた強磁性トンネル接合の局所磁気抵抗効果に関する研究

  23. 有機・無機ペロブスカイトナノコンポジットにおける光誘起による磁性と伝導に関する研究

    詳細を見る 詳細を閉じる

    有機・無機ペロブスカイトナノコンポジットにおける光誘起による磁性と伝導に関する研究

  24. 層状ペロブスカイト構造を有する有機・無機ナノコンポジット薄膜における光誘起による磁性と伝導に関する研究

    詳細を見る 詳細を閉じる

    層状ペロブスカイト構造を有する有機・無機ナノコンポジット薄膜における光誘起による磁性と伝導に関する研究

  25. 高密度情報ストレージコンポーネント

    詳細を見る 詳細を閉じる

    高密度情報ストレージコンポーネント

  26. 高分子LB膜を用いた金属/絶縁体/金属接合の作製と磁気トンネリング効果に関する研究

    詳細を見る 詳細を閉じる

    高分子LB膜を用いた金属/絶縁体/金属接合の作製と磁気トンネリング効果に関する研究

  27. スピンバルブタイプTMRを利用した高感度再生用ヘッド素子

    詳細を見る 詳細を閉じる

    スピンバルブタイプTMRを利用した高感度再生用ヘッド素子

︎全件表示 ︎最初の5件までを表示