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2020 年度 実施状況報告書

Deciphering spin-orbit torque in magnetic single layers: Towards spin-torque devices with extended scalability

研究課題

研究課題/領域番号 20K15156
研究機関東北大学

研究代表者

LAU Yongchang  東北大学, 金属材料研究所, 特任助教 (60795764)

研究期間 (年度) 2020-04-01 – 2022-03-31
キーワードCompensated ferrimagnet / Spin-orbit torque / Spin-orbitronics / Spin caloritronics / Anomalous Nernst effect
研究実績の概要

Epitaxial Mn2RuxGa (MRG) films of varying Ru composition were grown on single-crystal MgO(001) substrates by magnetron co-sputtering. Magnetic compensation was achieved at 300K for sample with x ~ 0.6 and preliminary single-layer spin-orbit torque (SOT) measurements were performed on these samples. In addition, anomalous Nernst effect (ANE) was discovered in MRG. The ANE, the Seebeck effect and the transverse thermoelectric conductivity of MRG were found to switch sign across the magnetic compensation. These results suggest instead of the net moment, the direction of one magnetic sublattice moment governs the magneto-caloric properties of this compound. This work leads to 2 oral presentations (JSAP spring meeting 2021 and INTERMAG 2021) and a related manuscript is in preparation.

現在までの達成度 (区分)
現在までの達成度 (区分)

2: おおむね順調に進展している

理由

The originally planned research for FY2020 includes:
1) Optimize the growth of MRG on single-crystal substrates
2) Develop an experimental protocol for quantifying the SOT
3) Investigate the correlation between the SOT and different properties
MRG films of varying strain, magnetic compensation temperature, and ordering were successfully grown by varying the film thickness, Ru concentration, and growth temperature. SOT was quantified by harmonic Hall technique in a PPMS equipped with a home-made measurement platform. Correlation between magnetic compensation, domain twinning and SOT was the main focus. Similar comparison was extended to between magnetic compensation and anomalous Nernst effect. All initially planned research aims were achieved. The project has progressed smoothly.

今後の研究の推進方策

Based on the knowledge acquired in FY2020, two main research activities/strategies were planned:
1) Domain twinning of MRG grown on centrosymmetric substrates (e.g. MgO) is a main technical obstacle that hinders the observation of single-layer SOT. The growth of MRG on non-centrosymmetric substrates (e.g. GaAs) will be optimized, which is expected to reduce the domain twinning.
2) The growth of a new inverse Heusler compound Mn2RuAl will be optimized. Replacing Ga by Al is expected to reduce the lattice constant, providing a better lattice match with GaAs than MRG.
These strategies will improve our understanding on single-layer SOT and eventually will guide us towards SOT switching of a magnetic single layer.

次年度使用額が生じた理由

Partly due to COVID-19, part of the budget, including that originally planned for the travel expenses will be transferred to the next fiscal year. In FY2021, I plan to use the research budget for the purchase of new instruments (e.g. lock-in amplifier and a.c. current sourcemeter), sputtering targets (e.g. Mn-Al alloy target for exploring new materials), and single-crystal substrates (e.g.MgO, SrTiO3, semi-insulating GaAs, etc.). If the situation improves, part of the budget will be used for attending domestic and international conferences held in late2021/early2022.

  • 研究成果

    (7件)

すべて 2021 2020

すべて 雑誌論文 (1件) (うち査読あり 1件) 学会発表 (6件) (うち国際学会 2件)

  • [雑誌論文] Magnetization switching induced by spin?orbit torque from Co2MnGa magnetic Weyl semimetal thin films2021

    • 著者名/発表者名
      Tang Ke、Wen Zhenchao、Lau Yong-Chang、Sukegawa Hiroaki、Seki Takeshi、Mitani Seiji
    • 雑誌名

      Applied Physics Letters

      巻: 118 ページ: 062402~062402

    • DOI

      10.1063/5.0037178

    • 査読あり
  • [学会発表] Anomalous Nernst effect in compensated ferrimagnetic Mn2RuxGa2021

    • 著者名/発表者名
      Y.-C. Lau, J. Wang, T. Kubota, K. Takanashi
    • 学会等名
      第68回応用物理学会春季学術講演会
  • [学会発表] Anomalous Hall and spin Hall effect in kagome-lattice cobalt shandite films2021

    • 著者名/発表者名
      Y.-C. Lau, J. Ikeda, K. Fujiwara, A. Ozawa, T. Seki, K. Nomura, A. Tsukazaki, and K. Takanashi
    • 学会等名
      令和3年東北大学電気通信研究所共同プロジェクト研究会「固体中のスピン・軌道ダイナミクスとその制御」
  • [学会発表] Spin Hall effect in paramagnetic kagome-lattice semimetal Co3Sn2S2(CSS)2020

    • 著者名/発表者名
      Y.-C. Lau, J. Ikeda, K. Fujiwara, T. Seki, A. Tsukazaki, K. Takanashi
    • 学会等名
      65th Annual Conference on Magnetism and Magnetic Materials (MMM) 2020
    • 国際学会
  • [学会発表] Spin Hall effect in paramagnetic kagome-lattice topological semimetal Co3Sn2S22020

    • 著者名/発表者名
      Y.-C. Lau, J. Ikeda, K. Fujiwara, T. Seki, A. Tsukazaki, K. Takanashi
    • 学会等名
      第81回応用物理学会秋季学術講演会
  • [学会発表] Perpendicular magnetic anisotropy and spin Hall effect in X/Co/Y (X, Y = Pt, Pd) metallic trilayers2020

    • 著者名/発表者名
      Y.-C. Lau, Z. Wen, K. Ito, J. Ieda, T. Sasaki, T. Seki and K. Takanashi
    • 学会等名
      Spin-RNJ若手オンライン研究発表会
  • [学会発表] Origin of field-like torque enhancement with decreasing Co thickness in X/Co/Y (X, Y = Pt, Pd) metallic trilayers2020

    • 著者名/発表者名
      Y.-C. Lau, Z. Wen, K. Ito, J. Ieda, T. Taniguchi, T. Sasaki, T. Seki and K. Takanashi
    • 学会等名
      IEEE International Magnetics Conference (INTERMAG) 2020 - Canceled
    • 国際学会

URL: 

公開日: 2021-12-27  

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