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2018 Fiscal Year Annual Research Report

Research of pure spin current source using tunable topological insulator

Research Project

Project/Area Number 16K14228
Research InstitutionTokyo Institute of Technology

Principal Investigator

PHAM NAM・HAI  東京工業大学, 工学院, 准教授 (50571717)

Project Period (FY) 2016-04-01 – 2019-03-31
Keywordsトポロジカル絶縁体 / スピン軌道トルク / スピンホール効果
Outline of Annual Research Achievements

本研究では、第3世代のスピン軌道トルク磁気抵抗メモリ(SOT-MRAM)の実現に向けて、高い電気伝導率および大きいなスピンホール角を両立できるトポロジカル絶縁体として、BiSb合金に着目し、そのスピン注入源としての性能評価を行う。
そのために、まず、BiSbの高品質な結晶成長技術を開発し、その電気伝導率がMRAMに使われる磁性金属と同等な高い電気伝導率(σ~2.5x10^5 S/m程度)を有することを確認した。さに、BiSbのスピンホール効果を評価するために、BiSb/垂直磁化膜MnGaのヘテロ接合の結晶成長を試みた。結晶成長条件を最適化し、BiSb(001)/MnGa薄膜ヘテロ接合の作製に成功した。
次にMnGa/BiSb(012)のヘテロ接合を作製し、BiSbのスピンホール効果およびMnGaに作用するスピン軌道トルクによる磁化反転を行った。その結果、常温において超強大なスピンホール効果(θsh~52)を観測し、さらに非常に低い電流密度(1.5 MA/cm^2)で3 nmのMnGa薄膜の磁化反転に成功した。この値は従来に使われた重金属/MnGaの磁化反転に必要な電流密度よりも30~100倍小さい。BiSbのスピンホール伝導率σsh~1.3x10^7 (hbar/2e)S/mに達し、Ptよりも30倍、Bi2Se3などの他のトポロジカル絶縁体よりも100倍大きい。BiSbをナノスケールのSOT-MRAMに適用する場合、STT-MRAMよりも書き込み電流を1桁、書き込みエネルギー2桁以上削減でき、書き込み速度も10倍速くできると分かった。
最後に、BiSbの結晶成長モードを調べるために、様々な面方位のGaAs基板の上に、BiSbの結晶成長を行った。その結果、BiSbの結晶成長が基板の対称性ではなく、表面の終端原子の種類と再構築表面パターンに強く依存したことを明らかにした。

  • Research Products

    (22 results)

All 2019 2018 Other

All Int'l Joint Research (1 results) Journal Article (3 results) (of which Int'l Joint Research: 3 results,  Peer Reviewed: 3 results) Presentation (14 results) (of which Int'l Joint Research: 7 results,  Invited: 6 results) Remarks (3 results) Patent(Industrial Property Rights) (1 results)

  • [Int'l Joint Research] Hochminh city University of Pedagogy(ベトナム)

    • Country Name
      VIET NAM
    • Counterpart Institution
      Hochminh city University of Pedagogy
  • [Journal Article] Influence of crystal orientation and surface termination on the growth of BiSb thin films on GaAs substrates2019

    • Author(s)
      Kenichiro Yao, Nguyen Huynh Duy Khang, Pham Nam Hai
    • Journal Title

      Journal of Crystal Growth

      Volume: 511 Pages: 99~105

    • DOI

      https://doi.org/10.1016/j.jcrysgro.2019.01.041

    • Peer Reviewed / Int'l Joint Research
  • [Journal Article] A conductive topological insulator with large spin Hall effect for ultralow power spin-orbit torque switching2018

    • Author(s)
      Nguyen Huynh Duy Khang, Yugo Ueda, Pham Nam Hai
    • Journal Title

      Nature Materials

      Volume: 17 Pages: 808~813

    • DOI

      http://dx.doi.org/10.1038/s41563-018-0137-y

    • Peer Reviewed / Int'l Joint Research
  • [Journal Article] Conductive BiSb topological insulator with colossal spin Hall effect for ultra-low power spin-orbit-torque switching2018

    • Author(s)
      Pham Nam Hai, Nguyen Huynh Duy Khang , Kenichiro Yao, Yugo Ueda
    • Journal Title

      Proceedings of SPIE

      Volume: 10732 Pages: 107320U

    • DOI

      http://dx.doi.org/10.1117/12.2316612

    • Peer Reviewed / Int'l Joint Research
  • [Presentation] Topological insulator for ultralow power SOT-MRAM2019

    • Author(s)
      Pham Nam Hai
    • Organizer
      International School on Spintronics and Korea-Japan Spintronics Workshop - Topological Phenomena in Magnetism -
    • Int'l Joint Research / Invited
  • [Presentation] Large Unidirectional Magnetoresistance in GaMnAs/BiSb bilayers2019

    • Author(s)
      Nguyen Huynh Duy Khang, Pham Nam Hai
    • Organizer
      第66回応用物理学会春季学術講演会
  • [Presentation] Giant spin Hall effect in BiSb topological insulator2018

    • Author(s)
      Pham Nam Hai
    • Organizer
      The 50th Reimei workshop: Universal Physics in Many-Body Quantum Systems -From Atoms to Quarks-
    • Int'l Joint Research / Invited
  • [Presentation] Influence of crystalorientation and surface terminationon the growth of BiSb topological insulator thin films on GaAs substrates2018

    • Author(s)
      Kenichiro Yao, Nguyen Huynh Duy Khang, Pham Nam Hai
    • Organizer
      20th International Conference on Molecular Beam Epitaxy (ICMBE 2018)
    • Int'l Joint Research
  • [Presentation] Colossal spin Hall effect in a conductive topological insulator Bi0.9Sb0.1 for ultra-low-power spin-orbit-torque switching2018

    • Author(s)
      Nguyen Huynh Duy Khang, Yugo Ueda, Pham Nam Hai
    • Organizer
      The 11th Vietnam-Japan Scientific Exchange Meeting
    • Int'l Joint Research / Invited
  • [Presentation] Conductive BiSb topological insulator with colossal spin Hall effect for ultra-low power spin-orbit-torque switching2018

    • Author(s)
      Pham Nam Hai, Nguyen Huynh Duy Khang, Kenichiro Yao, Yugo Ueda
    • Organizer
      SPIE Spintronics XI
    • Int'l Joint Research / Invited
  • [Presentation] Role of surface states in the generation of the colossal spin Hal effect in BiSb topological insulator2018

    • Author(s)
      Kenichiro Yao, Takanori Shirokura, Pham Nam Hai
    • Organizer
      Intermag 2018
    • Int'l Joint Research
  • [Presentation] Ultra-low-power spin-orbit-torque switching using the colossal spin Hal effect in BiSb topological insulator2018

    • Author(s)
      Nguyen Huynh Duy Khang, Yugo Ueda, Pham Nam Hai
    • Organizer
      Intermag 2018
    • Int'l Joint Research
  • [Presentation] Topological insulator for ultra-low power magnetic memories2018

    • Author(s)
      Pham Nam Hai, Nguyen Huynh Duy Khang, Kenichiro Yao, Takanori Shirokura
    • Organizer
      第23回 半導体におけるスピン工学の基礎と応用(PASPS-23)
    • Invited
  • [Presentation] Origin of the giant spin Hall effect in BiSb topological insulator2018

    • Author(s)
      K. Yao, T. Shirokura, P. N. Hai
    • Organizer
      第23回 半導体におけるスピン工学の基礎と応用(PASPS-23)
  • [Presentation] Field-free ground-state skyrmions in BiSb/MnGa bi-layers at room temperature revealed by topological Hall effect2018

    • Author(s)
      Nguyen Huynh Duy Khang, Tuo Fan, Pham Nam Hai
    • Organizer
      第23回 半導体におけるスピン工学の基礎と応用(PASPS-23)
  • [Presentation] 超高性能純スピン注入源としての BiSb トポロジカル絶縁体2018

    • Author(s)
      Pham Nam Hai, Nguyen Huynh Duy Khang, 八尾 健一郎, 白倉 孝典
    • Organizer
      ISSPワークショップ「スピン軌道強結合伝導系におけるサイエンスの新展開」
    • Invited
  • [Presentation] Room-temperature field-free formation of stable skyrmions in BiSb/MnGa bi-layers2018

    • Author(s)
      Nguyen Huynh Duy Khang, Tuo Fan, Pham Nam Hai
    • Organizer
      第79回応用物理学会秋季学術講演会
  • [Presentation] Crystal Growth of BiSb topological insulator on GaAs(001), (111)A and (111)B substrates2018

    • Author(s)
      Kenichiro Yao, Nguyen Huynh Duy Khang, Masataka Ichimura, Pham Nam Hai
    • Organizer
      第79回応用物理学会秋季学術講演会
  • [Remarks] Colossal breakthrough for topological spintronics

    • URL

      https://www.titech.ac.jp/english/news/2018/042001.html

  • [Remarks] トポロジカル絶縁体で高性能純スピン注入源開発

    • URL

      http://eetimes.jp/ee/articles/1808/02/news051.html

  • [Remarks] BiSb films feature a colossal spin hall effect

    • URL

      https://www.spintronics-info.com/bisb-films-feature-colossal-spin-hall-effect-and-high-electrical-conductivity

  • [Patent(Industrial Property Rights)] スピンホール発振器および磁気記録デバイス2019

    • Inventor(s)
      ファム ナムハイ, 白倉 孝典
    • Industrial Property Rights Holder
      ファム ナムハイ, 白倉 孝典
    • Industrial Property Rights Type
      特許
    • Industrial Property Number
      特願2019- 37682

URL: 

Published: 2019-12-27  

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