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Spin–orbit torque switching without an external field using interlayer exchange coupling

Nature Nanotechnology volume 11, pages 758–762 (2016)Cite this article

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Abstract

Manipulation of the magnetization of a perpendicular ferromagnetic free layer by spin–orbit torque (SOT)1,2,3,4 is an attractive alternative to spin-transfer torque (STT) in oscillators and switches such as magnetic random-access memory (MRAM) where a high current is passed across an ultrathin tunnel barrier5. A small symmetry-breaking bias field is usually needed for deterministic SOT switching but it is impractical to generate the field externally for spintronic applications. Here, we demonstrate robust zero-field SOT switching of a perpendicular CoFe free layer where the symmetry is broken by magnetic coupling to a second in-plane exchange-biased CoFe layer via a nonmagnetic Ru or Pt spacer6. The preferred magnetic state of the free layer is determined by the current polarity and the sign of the interlayer exchange coupling (IEC). Our strategy offers a potentially scalable solution to realize bias-field-free switching that can lead to a generation of SOT devices, combining a high storage density and endurance with a low power consumption.

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Figure 1: The thin film device structure, with pinned and free ferromagnetic layers.
Figure 2: Free layer switching, with and without an external field.
Figure 3: Spin Hall magnetoresistance.

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Acknowledgements

This work was supported by Science Foundation Ireland through AMBER and by grant no. 13/ERC/I2561. KR acknowledges financial support from the European Community's Seventh Framework Programme IFOX, NMP3-LA-2010-246102. D.B. acknowledges financial support from IRCSET. The authors thank G.Q. Yu, N. Thiyagarajah and J.Y. Chen for fruitful discussions, Q. Chevigny for the assistance in lithography and K. Borisov for some of the magnetometry.

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Author notes

  1. Yong-Chang Lau & Davide Betto

    Present address: Present address: National Institute for Materials Science, Tsukuba 305-0047, Japan (Y.-C.L.); European Synchrotron Radiation Facility, B.P. 220, 38043 Grenoble, France (D.B.),

  2. Yong-Chang Lau and Davide Betto: These authors contributed equally to this work

Authors and Affiliations

  1. CRANN, AMBER and School of Physics, Trinity College Dublin, Dublin 2, Ireland

    Yong-Chang Lau, Davide Betto, Karsten Rode, J. M. D. Coey & Plamen Stamenov

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  1. Yong-Chang Lau
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Contributions

Y.C.L. and D.B. contributed equally to this work. Y.C.L. and D.B. designed the experiment and planned the study with the input from K.R. D.B. grew the samples and fabricated the devices. Y.C.L. and D.B. measured the devices. D.B. performed data analysis. Y.C.L. and D.B. wrote the manuscript with advice from J.M.D.C. and P.S.

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Correspondence to Davide Betto.

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Lau, YC., Betto, D., Rode, K. et al. Spin–orbit torque switching without an external field using interlayer exchange coupling. Nature Nanotech 11, 758–762 (2016). https://doi.org/10.1038/nnano.2016.84

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