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2017 Fiscal Year Research-status Report

Fabrication of Weyl semimetals based spintronic heterostructures for future energy-efficient IT devices

Research Project

Project/Area Number 17K14652
Research InstitutionTohoku University

Principal Investigator

温 振超  東北大学, スピントロニクス学術連携研究教育センター, 助教 (40784773)

Project Period (FY) 2017-04-01 – 2019-03-31
KeywordsWeyl semimetals / SMR
Outline of Annual Research Achievements

The investigation of spin orbit effects in exotic materials is of particular importance for developing future spintronic devices. The Weyl semimetal (WS) is a topologically nontrivial phase of matter in which a large spin orbit interaction was theoretically predicted. In this research, we experimentally investigated the spin orbit effect in sputtered WSs, i.e. WTe2 and MoTe2. The films of WTe2 and MoTe2, were fabricated by sputtering for the first time. The structural properties were characterized by x-ray diffraction. A ferromagnetic layer of CoFeB with AlOx capping layer was deposited on the WSs. Furthermore, Hall bar structures were microfabricated for the measurement of spin Hall magnetoresistance (SMR). A SMR ratio of ~0.05% was observed in the sample of WTe2(2 nm)/CoFeB(2.5 nm)/AlOx at room temperature, which is comparable to that in the Pt/YIG system. The temperature and thickness dependence of the SMR was also studied. It is found that the sheet resistances for all the samples with different thicknesses increase with decreasing temperature while the SMR ratio shows an almost constant as the temperature. The spin Hall angle of WTe2 was estimated to be ~-0.04 with a spin diffusion length of 2.5 nm at room temperature for the current conditions. The experimental demonstration of the spin orbit effect in sputtered WSs could contribute the progress of the development of WS-based spintronic devices.

Current Status of Research Progress
Current Status of Research Progress

2: Research has progressed on the whole more than it was originally planned.

Reason

The Weyl semimetals (WSs), i.e. WTe2 and MoTe2, were prepared by a sputtering method. Spin Hall magnetoresistance was investigated in the WS/CoFeB/AlOx heterostructures and the spin Hall angle was achieved. Those experiments were conducted in accordance with our plans. The results are within our expectation. Therefore, the project is progressing smoothly.

Strategy for Future Research Activity

In order to achieve high-quality Weyl semimetals, we plan to use single-crystalline bulk WTe2 or MoTe2 to mechanically exfoliate single or multi layers of the Weyl semimetals. E-beam lithography with lift-off technique will be utilized to pattern the electrodes for transport measurement. The dependence of resistance on magnetic field will be measured by physical properties measurement system (PPMS) in order to characterize the properties of Weyl semimetals. Furthermore, the CoFeB/MgO films will be deposited on the Weyl semimetal layers. Magnetic anisotropy of the heterostructure will be measured by vibrating sample magnetometer (VSM) and magneto-optic Kerr effect. Spin Hall magnetoresistance and spin Hall angles will be investigated and voltage-controlled properties will also be planned to study.

  • Research Products

    (11 results)

All 2018 2017

All Journal Article (5 results) (of which Int'l Joint Research: 5 results,  Peer Reviewed: 5 results) Presentation (6 results) (of which Int'l Joint Research: 3 results)

  • [Journal Article] Epitaxial CuN films with highly tunable lattice constant for lattice-matched magnetic heterostructures with enhanced thermal stability2018

    • Author(s)
      Z. C. Wen, T. Kubota, and K. Takanashi
    • Journal Title

      Adv. Electron. Mater.

      Volume: 4 Pages: 1700367

    • DOI

      10.1002/aelm.201700367

    • Peer Reviewed / Int'l Joint Research
  • [Journal Article] Interface tailoring effect for Heusler based CPP-GMR with an L12-type Ag3Mg spacer2018

    • Author(s)
      T. Kubota, Y. Ina, Z. C. Wen, and K. Takanashi
    • Journal Title

      Materials

      Volume: 11 Pages: 219

    • DOI

      10.3390/ma11020219

    • Peer Reviewed / Int'l Joint Research
  • [Journal Article] Tunable magnetization relaxation of Fe2Cr1-xCoxSi half-metallic Heusler alloys by band structure engineering2017

    • Author(s)
      S. K. He, Y. Liu, Y. Zheng, Q. Qin, Z. C. Wen, Q. Wu, Y. Yang, Y. Wang, Y. Feng, K. L. Teo, and C. Panagopoulos
    • Journal Title

      Phys. Rev. Mater.

      Volume: 1 Pages: 064401

    • DOI

      10.1103/PhysRevMaterials.1.064401

    • Peer Reviewed / Int'l Joint Research
  • [Journal Article] Nonlinear electric field effect on perpendicular magnetic anisotropy in Fe/MgO interfaces2017

    • Author(s)
      Q. Y. Xiang, Z. C. Wen, H. Sukegawa, S. Kasai, T. Seki, T. Kubota, K. Takanashi, and S. Mitani
    • Journal Title

      J. Phys. D: Appl. Phys.

      Volume: 50 Pages: 40LT04

    • DOI

      10.1088/1361-6463/aa87ab

    • Peer Reviewed / Int'l Joint Research
  • [Journal Article] Current perpendicular-to-plane giant magnetoresistance using an L12-Ag3Mg spacer and Co2Fe0.4Mn0.6Si Heusler alloy electrodes: Spacer thickness and annealing temperature dependence2017

    • Author(s)
      T. Kubota, Y. Ina, Z. C. Wen, H. Narisawa, and K. Takanashi
    • Journal Title

      Phys. Rev. Mater.

      Volume: 1 Pages: 044402

    • DOI

      10.1103/PhysRevMaterials.1.044402

    • Peer Reviewed / Int'l Joint Research
  • [Presentation] Epitaxial CuN films with highly tunable lattice constant and resistivity for lattice-matched magnetic heterostructures exhibiting enhanced thermal stability for giant magnetoresistance2017

    • Author(s)
      Z. Wen, T. Kubota, and K. Takanashi
    • Organizer
      62nd Annual Conference on Magnetism and Magnetic Materials
    • Int'l Joint Research
  • [Presentation] Dual-spacer nanojunctions exhibiting large current-perpendicular-to-plane giant magnetoresistance for ultrahigh density magnetic recording2017

    • Author(s)
      Z. Wen, T. Kubota, Y. Ina, and K. Takanashi
    • Organizer
      62nd Annual Conference on Magnetism and Magnetic Materials
    • Int'l Joint Research
  • [Presentation] Layer Thickness Dependence of CPP-GMR in Co2Fe0.4Mn0.6Si | L12-type Ag-Mg | Co2Fe0.4Mn0.6Si Devices2017

    • Author(s)
      T. Kubota, Y. Ina, Z. Wen, and K. Takanashi
    • Organizer
      INTERMAG 2017
    • Int'l Joint Research
  • [Presentation] ホイスラー合金を用いたCPP-GMR効果2017

    • Author(s)
      窪田崇秀, 温振超, 高梨弘毅
    • Organizer
      第79回日本磁気学会ナノマグネティックス研究会
  • [Presentation] Co2Fe0.4Mn0.6Si/L12 型Ag3Mg/Co2Fe0.4Mn0.6Si素子における膜面垂直通電型巨大磁気抵抗効果の強磁性層膜厚依存性2017

    • Author(s)
      窪田崇秀, 伊奈幸佑, 温振超, 高梨弘毅
    • Organizer
      日本磁気学会第41回学術講演会
  • [Presentation] Effects of Interface Layers for the Heusler Based Current-perpendicular-to-plane Giant Magnetoresistance Junctions2017

    • Author(s)
      T. Kubota, Y. Ina, Z. Wen, and K. Takanashi
    • Organizer
      第65回応用物理学会春季学術講演会

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Published: 2019-12-27  

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