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Magnetization switching by spin–orbit torque in an antiferromagnet–ferromagnet bilayer system

Nature Materials volume 15, pages 535–541 (2016)Cite this article

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Abstract

Spin–orbit torque (SOT)-induced magnetization switching shows promise for realizing ultrafast and reliable spintronics devices. Bipolar switching of the perpendicular magnetization by the SOT is achieved under an in-plane magnetic field collinear with an applied current. Typical structures studied so far comprise a nonmagnet/ferromagnet (NM/FM) bilayer, where the spin Hall effect in the NM is responsible for the switching. Here we show that an antiferromagnet/ferromagnet (AFM/FM) bilayer system also exhibits a SOT large enough to switch the magnetization of the FM. In this material system, thanks to the exchange bias of the AFM, we observe the switching in the absence of an applied field by using an antiferromagnetic PtMn and ferromagnetic Co/Ni multilayer with a perpendicular easy axis. Furthermore, tailoring the stack achieves a memristor-like behaviour where a portion of the reversed magnetization can be controlled in an analogue manner. The AFM/FM system is thus a promising building block for SOT devices as well as providing an attractive pathway towards neuromorphic computing.

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Figure 1: Sample structure and magnetic properties.
Figure 2: RH–HZ loops measured with various ICH for non-exchange-biased and exchange-biased structures.
Figure 3: RH–ICH loops at zero field.
Figure 4: RH–ICH loops under various HX.
Figure 5: tPtMn dependence of the bias field and critical current (density).

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Acknowledgements

The authors thank C. Igarashi, T. Hirata, Y. Kawato, H. Iwanuma and K. Goto for their technical support. A portion of this work was supported by the R&D Project for ICT Key Technology to Realize Future Society of MEXT, R&D Subsidiary Program for Promotion of Academia-Industry Cooperation of METI, ImPACT Program of CSTI, and JSPS KAKENHI 15J04691.

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Authors and Affiliations

  1. Center for Spintronics Integrated Systems, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan

    Shunsuke Fukami & Hideo Ohno

  2. Center for Innovative Integrated Electronic Systems, Tohoku University, 468-1 Aramaki Aza Aoba, Aoba-ku, Sendai 980-0845, Japan

    Shunsuke Fukami & Hideo Ohno

  3. Laboratory for Nanoelectronics and Spintronics, Research Institute of Electrical Communication, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan

    Chaoliang Zhang, Samik DuttaGupta, Aleksandr Kurenkov & Hideo Ohno

  4. WPI Advanced Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan

    Hideo Ohno

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  1. Shunsuke Fukami
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Contributions

S.F. and H.O. planned the study. S.F. deposited the film. S.F. and C.Z. fabricated the samples. S.F. and A.K. performed the measurements and analysed the data. S.D. and S.F. performed the MOKE microscopy observation. S.F. wrote the manuscript with input from H.O., C.Z. and S.D. All authors discussed the results.

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Correspondence to Shunsuke Fukami or Hideo Ohno.

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The authors declare no competing financial interests.

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Fukami, S., Zhang, C., DuttaGupta, S. et al. Magnetization switching by spin–orbit torque in an antiferromagnet–ferromagnet bilayer system. Nature Mater 15, 535–541 (2016). https://doi.org/10.1038/nmat4566

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