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Field-free switching of perpendicular magnetization by two-dimensional PtTe2/WTe2 van der Waals heterostructures with high spin Hall conductivity

Nature Materials (2024)Cite this article

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Abstract

The key challenge of spin–orbit torque applications lies in exploring an excellent spin source capable of generating out-of-plane spins while exhibiting high spin Hall conductivity. Here we combine PtTe2 for high spin conductivity and WTe2 for low crystal symmetry to satisfy the above requirements. The PtTe2/WTe2 bilayers exhibit a high in-plane spin Hall conductivity σs,y ≈ 2.32 × 105 × ħ/2e Ω–1 m–1 and out-of-plane spin Hall conductivity σs,z ≈ 0.25 × 105 × ħ/2e Ω–1 m–1, where ħ is the reduced Planck’s constant and e is the value of the elementary charge. The out-of-plane spins in PtTe2/WTe2 bilayers enable the deterministic switching of perpendicular magnetization at room temperature without magnetic fields, and the power consumption is 67 times smaller than that of the Pt control case. The high out-of-plane spin Hall conductivity is attributed to the conversion from in-plane spin to out-of-plane spin, induced by the crystal asymmetry of WTe2. Our work establishes a low-power perpendicular magnetization manipulation based on wafer-scale two-dimensional van der Waals heterostructures.

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Fig. 1: Crystal symmetry and SOT of the WTe2 layer.
Fig. 2: Crystal symmetry and SOT in PtTe2.
Fig. 3: Deterministic current-induced magnetization switching in PtTe2 (d)/WTe2 (8 – d)/CoFeB heterostructures.
Fig. 4: Spin Hall conductivity of PtTe2/WTe2 bilayers.

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Data availability

The data that support the findings of this study are available from H.Y. (experiment) or K.-J.L. (theory) upon reasonable request.

Code availability

The codes that calculate non-equilibrium spin densities can be accessed from K.-J.L. upon reasonable request.

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Acknowledgements

This research was supported by the SpOT-LITE programme (A*STAR grant, A18A6b0057) through RIE2020 funds (H.Y.); the National Research Foundation (NRF) Singapore Investigatorship (NRFI06-2020-0015; H.Y.); Samsung Electronics’ University R&D programme, Samsung Electronics (IO221024-03172-01; H.Y.); the National Research Foundation of Korea (NRF-2020R1A2C3013302; K.-J.L.); the Nano & Material Technology Development Program through the National Research Foundation of Korea funded by the Ministry of Science and ICT (2022M3H4A1A04098811; K.-J.L.); and the KIST institutional programmes (2E32251 and 2E32252; K.-W.K.).

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Author notes

  1. These authors contributed equally: Fei Wang, Guoyi Shi, Kyoung-Whan Kim.

Authors and Affiliations

  1. Department of Electrical and Computer Engineering, National University of Singapore, Singapore, Singapore

    Fei Wang, Guoyi Shi, Yakun Liu, Taeheon Kim, Dongsheng Yang, Shishun Zhao, Kyusup Lee, Shuhan Yang & Hyunsoo Yang

  2. Integrative Sciences and Engineering Programme, NUS Graduate School, National University of Singapore, Singapore, Singapore

    Guoyi Shi & Hyunsoo Yang

  3. Center of Spintronics, Korea Institute of Science and Technology, Seoul, Korea

    Kyoung-Whan Kim

  4. KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul, Korea

    Hyeon-Jong Park

  5. Department of Physics, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, Korea

    Jae Gwang Jang & Kyung-Jin Lee

  6. Institute of Materials Research & Engineering, Agency for Science Technology & Research (A*STAR), Singapore, Singapore

    Hui Ru Tan, Ming Lin & Anjan Soumyanarayanan

  7. Department of Physics, National University of Singapore, Singapore, Singapore

    Anjan Soumyanarayanan

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Contributions

F.W. and H.Y. conceived and designed the experiments. F.W., G.S. and S.Y. grew the samples. F.W. carried out the reflection high-energy electron diffraction, atomic force microscopy, transport and switching measurements and analysed the data. G.S. performed the ST-FMR measurements. D.Y. performed the Raman and terahertz measurements. K.L. carried out the X-ray diffraction measurements. G.S., Y.L. and S.Z. performed the device fabrications. H.R.T. and M.L. carried out the transmission electron microscopy measurements under the supervision of A.S.; K.-W.K. developed the analytic theories, and H.-J.P. and J.G.J. performed the first-principles calculations under the supervision of K.-J.L.; and T.K. performed the macro-spin simulations. F.W., H.Y., K.-W.K. and K.-J.L. wrote the manuscript with contributions from all authors. H.Y. supervised the experimental aspects, and K.-J.L. supervised the theoretical aspects. All authors discussed the results and commented on the manuscript.

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Correspondence to Kyung-Jin Lee or Hyunsoo Yang.

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Wang, F., Shi, G., Kim, KW. et al. Field-free switching of perpendicular magnetization by two-dimensional PtTe2/WTe2 van der Waals heterostructures with high spin Hall conductivity. Nat. Mater. (2024). https://doi.org/10.1038/s41563-023-01774-z

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