Details of the Researcher

PHOTO

Tadashi Kai
Section
Center for Innovative Integrated Electronic Systems
Job title
Professor
e-Rad No.
60296746

Research History 6

  • 2025/06 - Present
    Tohoku University　Center for Innovative Integrated Electronic Systems Research and Development Division　Professor

  • 2019/09 - 2025/02
    SAMSUNG ELECTRONICS　Semiconductor R&D Center　Principal Engineer

  • 2017 - 2019/07
    Toshiba Memory Corporation　Institute of Memory Technology Research & Development　Chief Specialist

  • 2000/09 - 2017
    Toshiba Corporation　Corporate R&D Center　Chief Specialist

  • 1998/08 - 2000/07
    University of Alabama　MINT Center　Post Doctoral researcher

  • 1997/04 - 1998/03
    Keio University　Faculty of Science and Technology　Assistant Professor

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Education 2

  • Keio University　Graduate School of Science and Technology

    1992/04 - 1997/03

  • Keio University　Faculty of Science and Technology

    1988/04 - 1992/03

Committee Memberships 1

  • 日本磁気学会　編集委員、論文委員、広報委員

    2001 - 2010

Research Interests 1

  • Spintronics

Research Areas 1

  • Nanotechnology/Materials / Nanomaterials /

Papers 33

  1. World-most energy-efficient MRAM technology for non-volatile RAM applications Peer-reviewed

    T. Y. Lee, J. M. Lee, M. K. Kim, J. S. Oh, J. W. Lee, H. M. Jeong, P. H. Jang, M. K. Joo, K. Suh, S. H. Han, D. -E. Jeong, T. Kai, J. H. Jeong, J. -H. Park, J. H. Lee, Y. H. Park, E. B. Chang, Y. K. Park, H. J. Shin, Y. S. Ji, S. H. Hwang, K. T. Nam, B. S. Kwon, M. K. Cho, B. Y. seo, Y. J. Song, G. H. Koh, K. Lee, J. -H. Lee, G. T. Jeong

    2022 International Electron Device Meeting (IEDM2022)　2022

  2. 28nm CIS-Compatible Embeded STT-MRAM for Frame Buffer Memory Peer-reviewed

    K. Lee, D. S. Kim, J. H. Bak, S. P. Ko, W. C. Lim, H. C. Shin, J. H. Lee, J. H. Park, J. H. Jeong, J. M. Lee, T. Kai, H. Sato, J. W. Lee, K. H. Ryu, Y. J. Kim, S. H. Han, B. Y. Seo, K. S. Suh, H. H. Kim, H. T. Jung, D. H. Jang, N. Y. Ji, M. J. Eom, I. H. Kim, K. Lee, K. H. Hwang, Y. J. Song, H. S. Kim

    2021 International Electron Device Meeting (IEDM2021)　2021

  3. Ab initio calculation of interlayer exchange coupling in Co-based synthetic antiferromagnetic with alloy spacer Peer-reviewed

    R. Takashima, T. Tsukagoshi, T. Ishihara, T. Kai

    AIP Advance　10　015324　2020

  4. Effect of reference layer magnetic properties on storage layer switching properties with STT-MRAM Peer-reviewed

    S. Itai, T. Kai, J. Ozeki, M. Nakayama, J. Ito, T. Ishihara

    2019 Joint MMM- Intermag Conference　2019

  5. High efficient spin transfer torque writing on perpendicular magnetic tunnel junctions for high density MRAMs Peer-reviewed

    H. Yoda, T. Kishi, T. Nagase, M. Yoshikawa, K. Nishiyama, E. Kitagawa, T. Daibou, M. Amano, N. Shimomura, S. Takahashi, T. Kai, M. Nakayama, H. Aikawa, S. Ikegawa, M. Nagamine, J., Ozeki, S. Mizukami, M. Oogane, Y. Ando, S. Yuasa, K. Yakushiji, H. Kubota, Y. Suzuki, Y., Nakatani, T. Miyazaki, K. Ando

    Current Appl. Phys.　10　e87　2010

  6. Reduction of switching current distribution in spin transfer magnetic random access memories Peer-reviewed

    M. Iwayama, T. Kai, M. Nakayama, H. Aikawa, Y. Asao, T. Kajiyama, S. Ikegawa, H. Yoda, A. Nitayama

    Journal of Applied Physics　103　07A720　2008

  7. Spin transfer switching in TbCoFe/CoFeB/MgO/CoFeB/TbCoFe magnetic tunnel junctions with perpendicular magnetic anisotropy Peer-reviewed

    M. Nakayama, T. Kai, N. Shimomura, M. Amano, E. Kitagawa, T. Nagase, M. Yoshikawa, T. Kishi, S. Ikegawa, H. Yoda

    J. Appl. Phys.　103　07A710　2008

  8. Estimation of spin transfer torque effect and thermal activation effect on magnetization reversal in CoFeB∕MgO∕CoFeB Peer-reviewed

    M. Yoshikawa, E. Kitagawa, S. Takahashi, T. Kai, M. Amano, N. Shimomura, T. Kishi, S., Ikegawa, Y. Asao, H. Yoda, K. Nagahara, H. Numata, N. Ishiwata, H. Hada, S. Tahara

    Journal of Applied Physics　99　08R702　2007

  9. Reduction of switching field distributions by edge oxidization of submicron magnetoresistive tunneling junction cells for high-density magnetoresistive random access memories Peer-reviewed

    M. Yoshikawa, E. Kitagawa, S. Takahashi, T. Kai, M. Amano, N. Shimomura, T. Kishi, S., Ikegawa, Y. Asao, H. Yoda, K. Nagahara, H. Numata, N. Ishiwata, H. Hada, S. Tahara

    Journal of Applied Physics　99　08R702　2006

  10. Ion-beam-etched profile control of MTJ cells for improving the switching characteristics of high-density MRAM Peer-reviewed

    S. Takahashi, T. Kai, N. Shimomura, T. Ueda, M. Amano, M. Yoshikawa, E. Kitagawa, Y. Asao, S. Ikegawa, T. Kishi, H. Yoda, K. Nagahara, T. Mukai, H. Hada

    IEEE Transactions on Magnetics,　42　2745　2006

  11. 1.8 V power supply 16Mb-MRAMs with 42.3% array efficiency Peer-reviewed

    H. Yoda, T. Kai, T. Inaba, Y. Iwata, N. Shimomura, S. Ikegawa, K. Tsuchida, Y. Asao, T. Kishi, T. Ueda, S. Takahashi, M. Nagamine, T. Kajiyama, M. Yoshikawa, M. Amano, T. Nagase, K. Hosotani, M. Nakayama, Y. Shimizu, H. Aikawa, K. Nishiyama, E. Kitagawa, R. Takizawa, Y. Ueda, M. Iwayama, K. Itagaki

    IEEE Transactions on Magnetics,　42　2724　2006

  12. Disturb robust switching astroid curve od C-shape cell with weakly coupled synthetic antiferromagnetic layer Peer-reviewed

    M. Nakayama, T. Kai, S. Ikegawa, H. Yoda, T. Kishi, E. Kitagawa, T. Nagase, M. Yoshikawa, Y. Asao, K. Tsuchida

    IEEE Transactions on Magnetics,　42　2733　2006

  13. Switching current fluctuation and repeatability for MRAM with propeller-shape MTJ Peer-reviewed

    N. Shimomura, H. Yoda, S. Ikegawa, T. Kai, M. Amano, T. Ueda, M. Nakayama, Y. Asao, K. Hosotani, Y. Shimizu, K. Tsuchida

    IEEE Transactions on Magnetics,　42　2757　2006

  14. A concept of exchange-coupled recording medium for heat-assisted magnetic recording Peer-reviewed

    A. Kikitsu, T. Kai, T. Nagase, J. Akiyama

    Journal of Applied Physics　97　10P701　2005

  15. Bit yield improvement by precise control of stray fields from SAF pinned layers for high-density MRAMs Peer-reviewed

    M. Yoshikawa, T. Kai, M. Amano, E. Kitagawa, T. Nagase, M. Nakayama, S. Takahashi, T. Ueda, T. Kishi, K. Tsuchida, S. Ikegawa, Y. Asao, H. Yoda, Y. Fukuzumi, K. Nagahara, H. Numata, H. Hada, N. Ishiwata, S. Tahara

    Journal of Applied Physics　97　10P508　2005

  16. Magnetic and electronic structures of FePtCu ternary ordered alloy Peer-reviewed

    T. Kai, T. Maeda, A. Kikitsu, J. Akiyama, T. Nagase, T. Kishi

    Journal of Applied Physics　95　609　2004

  17. Reduction of ordering temperature of an FePt-ordered alloy by addition of Cu Peer-reviewed

    T. Maeda, T. Kai, A. Kikitsu, T. Nagase, J. Akiyama

    Appl. Phys. Lett.　80　2147　2002

  18. Effect of direct exchange coupling between antiferromagnetic grains on magnetic behavior of ferro/antiferromagnetic exchange coupled polycrystalline layer systems Peer-reviewed

    H. Fujiwara, K. Zhang, T. Kai, T. Zhao

    Journal of Magnetism and Magnetic Materials　235　319　2001

  19. Rotational hysteresis of torque curves in polycrystalline ferro/antiferromagnetic systems Peer-reviewed

    K. Zhang, T. Kai, T. Zhao, H. Fujiwara, C. Hou, M. T. Kief

    Journal of Applied Physics　89　7546　2001

  20. Biquadratic coupling effect on magnetoresistance response curves of spin valves with a synthetic antiferromagnet

    K. Zhang, T. Kai, T. Zhao, H. Fujiwara, G. J. Mankey

    Journal of Applied Physics　89　6814　2001

  21. First principles study of direct exchange coupling between the grains in NiMn antiferromagnets Peer-reviewed

    T. Kai, H. Fujiwara, T. C. Schulthess, W. H. Butler

    Journal of Applied Physics　89　7940　2001

  22. First-principle band calculation of ruthenium for various phases Peer-reviewed

    S. Watanabe, T. Komine, T. Kai, K. Shiiki

    Journal of Magnetism and Magnetic Materials　220　277　2000

  23. Interlayer exchange coupling and electronic structure of Co/Mn multilayers Peer-reviewed

    T. Kai

    Journal of Magnetism and Magnetic Materials　214　167　2000

  24. Influence of spin-dependent scattering at rough interface on the giant magnetoresistance in magnetic multilayers Peer-reviewed

    T. Kai, K. Shiiki

    Journal of Magnetism and Magnetic Materials　195　537　1999

  25. Study of Giant MagnetoResistance in Co/X superlattices (X=Cu, Ru, Rh and Pd) by first principle band calculation Peer-reviewed

    T. Kai, Y. Ohashi, K. Shiiki

    Journal of Magnetism and Magnetic Materials　183　292　1998

  26. Effect of 4d-transition metal on the electronic structure and magnetic properties of a-Fe Peer-reviewed

    T. Kai, M. Nakamura, N. Takano, Y. Ohashi, K. Shiiki

    J. Phys.: Condens. Mater.　10　371　1998

  27. Electronic Structure and Giant MagnetoResistance of Co/X Superlattices Peer-reviewed

    T. Kai, K. Shiiki

    J. Magn. Soc. Jpn.　22　529　1998

  28. Effect of Nb addition to Ni and Fe on electronic structure and magnetic properties Peer-reviewed

    M. Kobayashi, T. Kai, N. Takano, Y. Ohashi, K. Shiiki

    Journal of Magnetism and Magnetic Materials　166　329　1997

  29. EFFECT OF COPICIOUS VACANCIES ON MAGNETISM OF Pd Peer-reviewed

    N. Takano, T. Kai, K. Shiiki, F. Terasaki

    Solid State Communications　97　153　1996

  30. Effect of Ru addition to Ni on electronic structure and magnetic property Peer-reviewed

    M. Kobayashi, T. Kai, N. Takano, Y. Ohashi, K. Shiiki

    J. Phys. : Condens. Matter.　8　7863　1996

  31. The possibility of ferromagnetic BCC ruthenium Peer-reviewed

    M. Kobayashi, T. Kai, N. Takano, K. Shiiki

    J. Phys. : Condens. Matter.　7　1835　1995

  32. The effect of addition of Ru to Fe on the electronic structure and magnetic properties Peer-reviewed

    M. Kobayashi, N. Ando, T. Kai, N. Takano, K. Shiiki

    J. Phys. : Condens. Matter.　7　9607　1995

  33. EFFECT OF CHARGE NEUTRALITY CONDITION IN KKR-CPA METHOD Peer-reviewed

    T. Kai, N. Takano, K. Shiiki, M. Fukuchi

    Solid State Communications　96　971　1995

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Presentations 25

  1. Spin Hall conductivity in 5d elemental metals and high-entropy alloys: Influence of lattice structures and atomic arrangements

    Yuki Ohnishi, Yosephine Novita Apriati, Tadashi Kai, Kohji Nakamura

    ISAMMA2026　2026/06

  2. Effective switching for field-free sub-ns write speed SOT-MRAM cell with canted SOT structure

    T. Kai, T. V. A. Nguyen, H. Honjo, Y. Sato, T. Tanigawa, S. Ikeda, T. Endoh

    17th MRAM Global Innovation Forum 2025　2025/12

  3. World-most energy-efficient MRAM technology for non-volatile RAM applications

    T. Y. Lee, J. M. Lee, M. K. Kim, J. S. Oh, J. W. Lee, H. M. Jeong, P. H. Jang, M. K. Joo, K. Suh, S. H. Han, D. -E. Jeong, T. Kai, J. H. Jeong, J. -H. Park, J. H. Lee, Y. H. Park, E. B. Chang, Y. K. Park, H. J. Shin, Y. S. Ji, S. H. Hwang, K. T. Nam, B. S. Kwon, M. K. Cho, B. Y. seo, Y. J. Song, G. H. Koh, K. Lee, J. -H. Lee, G. T. Jeong

    IEDM 2022　2022/12

  4. 28nm CIS-Compatible Embeded STT-MRAM for Frame Buffer Memory

    K. Lee, D. S. Kim, J. H. Bak, S. P. Ko, W. C. Lim, H. C. Shin, J. H. Lee, J. H. Park, J. H. Jeong, J. M. Lee, T. Kai, H. Sato, J. W. Lee, K. H. Ryu, Y. J. Kim, S. H. Han, B. Y. Seo, K. S. Suh, H. H. Kim, H. T. Jung, D. H. Jang, N. Y. Ji, M. J. Eom, I. H. Kim, K. Lee, K. H. Hwang, Y. J. Song, H. S. Kim

    IEDM 2021　2021/12

  5. Investigation of Transport Property of MgO-based Magnetic Tunnel Junction with Vacancies and Grain Boundaries by First Principles Calculations

    H. Kawai, Y. Nakasaki, T. Daibou, T. Ishihara, T. Kai, J. Ito

    2019 Joint MMM- Intermag Conference　2019

  6. Effect of reference layer magnetic properties on storage layer switching properties with STT-MRAM

    S. Itai, T. Kai, J. Ozeki, M. Nakayama, J. Ito, T. Ishihara

    2019 Joint MMM- Intermag Conference　2019/01

  7. Effect of stray field from adjacent bits of high-density STT-MRAM on switching current

    S. Itai, T. Kai, M. Nakayama, T. Daibou, J. Ito

    in Intermag 2018　2018/05

  8. Large tunnel magnetoresistance of over 200% in MgO-based magnetic tunnel junction with perpendicular magnetic anisotropy

    K. Nishiyama, T. Nagase, M. Nakayama, M. Yoshikawa, E. Kitagawa, T. Daibou, M. Nagamine, T. Kai, H. Yoda

    11th Joint MMM/Intermag Conference　2010

  9. Spin Transfer torque switching in perpendicular magnetic tunnel junctions using L10-ordered FePd electrodes

    T. Daibou, M. Yoshikawa, E. Kitagawa, T. Nagase, K. Nishiyama, M. Nagamine, M. Amano, M. Nakayama, T. Kai, T.Kishi, H. Yoda

    11th Joint MMM/Intermag Conference　2010

  10. Lower- current and fast switching of a perpendicular TMR for high speed and high density spin-transfer- torque MRAM

    T. Kishi, H. Yoda, T. Kai, T. Nagase, E. Kitagawa, M. Yoshikawa, K. Nishiyama, T. Daibou, M. Nagamine, M. Amano, S. Takahashi, M. Nakayama, N. Shimomura, H. Aikawa, S. Ikegawa, S. Yuasa, K. Yakushiji, H. Kubota, A. Fukushima, M. Oogane, T. Miyazaki, K. Ando

    IEDM2008　2008/12

  11. Spin Torque Transfer Switching of Perpendicular Magnetoresistive elements for High Density MRAMs

    H. Yoda, T. Kishi, T. Kai, T. Nagase, M. Yoshikawa, M. Nakayama, E. Kitagawa, M. Amano, H. Aikawa, N. Shimomura, K. Nishiyama, T. Daibou, S. Takahashi, S. Ikegawa, K. Yakushiji, T. Nagahama, H. Kubota, A. Fukushima, S. Yuasa, Y. Nakatani, M. Oogane, Y. Ando, Y. Suzuki, K. Ando, T. Miyazaki

    Intermag 2008　2008

  12. Stable Spin transfer switching in magnetic tunnel junctions with perpendicular magnetic anisotropy

    M. Nakayama, T. Kai, H. Yoda, S. Ikegawa, T. Nagase, H. Aikawa, N. Shimomura

    53rd MMM Conference　2008

  13. Advantage of Perpendicular MRAM using Spin Transfer Torque Switching for a high density non-volatile memory

    T. Kai, M. Nakayama, J. Ozeki, H. Aikawa, S. Ikegawa, H. Yoda

    53rd MMM Conference　2008

  14. Pulse duration dependence and effective energy barrier for current- induced magnetization switching in MgO-based tunnel junctions

    S. Ikegawa, H. Aikawa, N. Shimomura, T. Ueda, T. Kai, M. Nakayama, M. Iwayama, H. Yoda, M. Yoshikawa, Y. Asao

    6th International Symposium on Metallic Multilayers (IEEE MML 2007)　2007

  15. Thermal stability of MRAM with propeller shape

    T. Kai, T. Nagase, M. Yoshikawa, T. Kishi, S. Ikegawa, H. Yoda

    MORIS2006　2006

  16. Enlargement of Operating Window and Reduction of Switching Current in MRAM with Yoke Wire

    H. Aikawa, T. Ueda, T. Kai, N. Shimomura, S. Ikegawa, Y. Asao, H. Yoda

    Inetrmag 2006　2006

  17. Effect of magnetic domain on thermal stability for MRAM cells with propeller shape

    T. Kai, N. Shimomura, Y. Shimizu, S. Ikegawa, Y. Asao, K. Tsuchida, H. Yoda

    Inetrmag 2006　2006

  18. Improvement in Thermal Stability of MRAM with novel MTJ cell

    T. Kai, Y. Shimizu, R. Takizawa, Y. Ueda, N. Shimomura, S. Ikegawa, Y. Asao, K. Tsuchida, H. Yoda, N. Ishiwata, H. Hada, S. Tahara

    MMM 2005　2005

  19. Improvement of robustness against write disturbance by novel cell design for high density MRAM

    T. Kai, M. Yoshikawa, M. Nakayama, Y. Fukuzumi, T. Nagase, E. Kitagawa, T. Ueda, T. Kishi, S. Ikegawa, Y. Asao, K. Tsuchida, H. Yoda, N. Ishiwata, H. Hada, S. Tahara

    IEDM2004　2004

  20. Influence of oxygen content on the reduction of the ordering temperature of L10 FePtCu alloy

    A. Kikitsu, T. Maeda, T. Kai, T. Nagase, J. Akiyama, N. Fujioka, T. Ishigami

    2003Intermag　2003

  21. Ordering of FePt alloy at low temperature by addition of Cu

    T. Maeda, A. Kikitsu, T. Kai, T. Nagase, H. Aikawa, J. Akiyama

    2002Intermag,　2002

  22. Magnetic and electronic structures of FePtCu ternary ordered alloy Invited

    T. Kai, T. Maeda, A. Kikitsu, J. Akiyama, T. Nagase, T. Kishi

    MMM2001　2001

  23. Magnetization process of polycrystalline NiFe/NiO bilayers with enhanced coercivity

    T. Zhao, H. Fujiwara, K. Zhang, T. Kai, C. Hou

    2000Intrermag　2000

  24. Effect of direct interaction between antiferromagnet grains on rotational hysteresis of torque curves in F/AF system

    T. Kai, C. Hou, T. Zhao, H. Fujiwara

    2000Intermag　2000

  25. Prediction of Giant MagnetoResistance in Co/X Superlattice from First Principle Calculation

    T. Kai, Y. Ohashi, K. Shiiki

    PMRC ’97　1997

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