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Spin currents and spin–orbit torques in ferromagnetic trilayers

Nature Materials volume 17, pages 509–513 (2018)Cite this article

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Abstract

Magnetic torques generated through spin–orbit coupling1,2,3,4,5,6,7,8 promise energy-efficient spintronic devices. For applications, it is important that these torques switch films with perpendicular magnetizations without an external magnetic field9,10,11,12,13,14. One suggested approach15 to enable such switching uses magnetic trilayers in which the torque on the top magnetic layer can be manipulated by changing the magnetization of the bottom layer. Spin currents generated in the bottom magnetic layer or its interfaces transit the spacer layer and exert a torque on the top magnetization. Here we demonstrate field-free switching in such structures and show that its dependence on the bottom-layer magnetization is not consistent with the anticipated bulk effects15. We describe a mechanism for spin-current generation16,17 at the interface between the bottom layer and the spacer layer, which gives torques that are consistent with the measured magnetization dependence. This other-layer-generated spin–orbit torque is relevant to energy-efficient control of spintronic devices.

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Fig. 1: Spin–orbit torque measurement in ferromagnetic trilayers.
Fig. 2: Azimuthal angle-dependent V2ω in the CoFeB/Ti sample.
Fig. 3: The spin z component of spin currents.

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Acknowledgements

The authors acknowledge K.-W. Kim, H.-W. Lee and J. Sinova for discussion. This work was supported by the Creative Materials Discovery Program through the National Research Foundation of Korea (NRF-2015M3D1A1070465). B.-G.P. acknowledges financial support from the NRF (NRF-2017R1A2A2A05069760), K.-J.L. from the NRF (NRF-2017R1A2B2006119) and K.-J.K. from the NRF (NRF-2016R1A5A1008184). V.P.A. acknowledges support under the Cooperative Research Agreement between the University of Maryland and the National Institute of Standards and Technology Center for Nanoscale Science and Technology, Award 70NANB14H209, through the University of Maryland.

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Author notes

  1. These authors contributed equally: Seung-heon C. Baek, Vivek P. Amin.

Authors and Affiliations

  1. Department of Materials Science and Engineering and KI for Nanocentury, KAIST, Daejeon, Korea

    Seung-heon C. Baek, Young-Wan Oh & Byong-Guk Park

  2. School of Electrical Engineering, KAIST, Daejeon, Korea

    Seung-heon C. Baek

  3. Maryland Nanocenter, University of Maryland, College Park, MD, USA

    Vivek P. Amin

  4. Center for Nanoscale Science and Technology, National Institute of Standards and Technology, Gaithersburg, MD, USA

    Vivek P. Amin & M. D. Stiles

  5. Department of Materials Science and Engineering, Korea University, Seoul, Korea

    Gyungchoon Go & Kyung-Jin Lee

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

    Seung-Jae Lee & Kyung-Jin Lee

  7. Department of Physics, KAIST, Daejeon, Korea

    Geun-Hee Lee & Kab-Jin Kim

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  1. Seung-heon C. Baek
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Contributions

B.-G.P. and K.-J.L. planned and supervised the study. S.-h.C.B. and Y.-W.O. fabricated devices and performed spin–orbit torque measurements. G.-H.L. and K.-J.K. performed electrical measurements. V.P.A. and M.D.S. provided a theoretical explanation for the interface-generated spin current. G.G., S.-J.L. and K.-J.L. performed numerical simulations. K.-J.L., B.-G.P., V.P.A. and M.D.S. wrote the manuscript.

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Correspondence to Byong-Guk Park or Kyung-Jin Lee.

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Supplementary Information, 8 figures, 11 references

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Baek, Sh.C., Amin, V.P., Oh, YW. et al. Spin currents and spin–orbit torques in ferromagnetic trilayers. Nature Mater 17, 509–513 (2018). https://doi.org/10.1038/s41563-018-0041-5

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