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A conductive topological insulator with large spin Hall effect for ultralow power spin–orbit torque switching

Nature Materials volume 17, pages 808–813 (2018)Cite this article

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Abstract

Spin–orbit torque switching using the spin Hall effect in heavy metals and topological insulators has a great potential for ultralow power magnetoresistive random-access memory. To be competitive with conventional spin-transfer torque switching, a pure spin current source with a large spin Hall angle (θSH > 1) and high electrical conductivity (σ > 105 Ω−1 m−1) is required. Here we demonstrate such a pure spin current source: conductive topological insulator BiSb thin films with σ ≈ 2.5 × 105 Ω−1 m−1, θSH ≈ 52 and spin Hall conductivity σSH ≈ 1.3 × 107 \(\frac{\hbar }{{2e}}\)Ω−1 m−1 at room temperature. We show that BiSb thin films can generate a very large spin–orbit field of 2.3 kOe MA–1 cm2 and a critical switching current density as low as 1.5 MA cm–2 in Bi0.9Sb0.1/MnGa bilayers, which underlines the potential of BiSb for industrial applications.

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Fig. 1: Structure, magnetic properties and SOT effect in the Bi0.9Sb0.1(10 nm)/Mn0.6Ga0.4(3 nm) bilayer with perfect PMA.
Fig. 2: Magnetic properties and SOT effect in the Bi0.9Sb0.1(10 nm)/Mn0.45Ga0.55(3 nm) bilayer with tilting magnetization.
Fig. 3: Room-temperature current-induced magnetization switching in the Bi0.9Sb0.1(5 nm)/Mn0.45Ga0.55(3 nm) bilayer.

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Acknowledgements

This work is supported by Grant-in-Aid for Challenging Exploratory Research (no. 16K14228), and Nanotechnology platform 12025014 (F-17-IT-0011) from MEXT. The authors thank H. Iida and R. C. Roca for their help in X-ray diffraction and superconducting quantum interference device measurements. We also thank the Material Analysis Division and Laboratory for Future Interdisciplinary Research of Science and Technology at the Tokyo Institute of Technology, and M. Tanaka Laboratory at the University of Tokyo for their technical supports.

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Authors and Affiliations

  1. Department of Electrical and Electronic Engineering, Tokyo Institute of Technology, Tokyo, Japan

    Nguyen Huynh Duy Khang, Yugo Ueda & Pham Nam Hai

  2. Department of Physics, Ho Chi Minh City University of Pedagogy, Ho Chi Minh City, Vietnam

    Nguyen Huynh Duy Khang

  3. Center for Spintronics Research Network (CSRN), The University of Tokyo, Tokyo, Japan

    Pham Nam Hai

Authors
  1. Nguyen Huynh Duy Khang
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  3. Pham Nam Hai
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Contributions

N.H.D.K. grew the BiSb/MnGa bilayers, fabricated the Hall devices and performed the measurements on the bilayers; Y.U. grew and evaluated the conductivity of various BiSb layers; P.N.H. planned the experiments; N.H.D.K. and P.N.H. analysed the data and wrote the manuscript.

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Correspondence to Pham Nam Hai.

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The authors have filed a patent application for using BiSb as the spin current source in SOT-MRAM.

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Supplementary Figures 1–10, Supplementary Table 1, Supplementary Notes 1–6

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Khang, N.H.D., Ueda, Y. & Hai, P.N. A conductive topological insulator with large spin Hall effect for ultralow power spin–orbit torque switching. Nature Mater 17, 808–813 (2018). https://doi.org/10.1038/s41563-018-0137-y

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