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Spin-transfer torque induced by the spin anomalous Hall effect

Abstract

The anomalous Hall effect in ferromagnets is a well-known phenomenon in which electromotive force is generated in the direction perpendicular to both the electric current and the magnetization. With nonmagnetic heavy metals, the generation of spin current by the spin Hall effect, as well as excitation of magnetization dynamics in an adjacent ferromagnet by spin-transfer torque, has been reported. However, the generation of a spin current in ferromagnets by the anomalous Hall effect has so far not been measured. Here we report the observation of spin current generation by the anomalous Hall effect through spin-transfer torque excitation in CoFeB/Cu/NiFe trilayer films. In this spin anomalous Hall effect, a spin current generated in the CoFeB by the anomalous Hall effect is injected into the NiFe and excites spin-transfer torque in the NiFe. This leads to a measurable modulation in the ferromagnetic resonance linewidth of the NiFe. The spin anomalous Hall angle in the CoFeB is estimated to be −0.14 ± 0.05, which is comparable to the spin Hall angle reported in heavy metals.

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Fig. 1: Schematic illustration of the measurements.
Fig. 2: FMR spectrum for the trilayer film.
Fig. 3: Bias DC current dependence of the FMR spectra.
Fig. 4: Field angle dependence of the modulation of the magnetic relaxation.

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Acknowledgements

We would like to thank K. Tanaka and T. Moriyama for valuable discussions. We also thank T. Yorozu, C. Ara and Y. Sato for their support. S.I. would like to thank the Japan Society for the Promotion of Science (JSPS) for a Grant-in-Aid for JSPS Fellows (28-7881).

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T.T., K.Y., A.F.,and H.K. conceived the research idea. K.Y. performed the sample fabrication. H.K. performed microfabrication. S.I., R.H. and H.K. constructed the measurement set-up. S.I. and Y. Suzuki performed data analysis. S.I., T.T., Y. Suzuki and H.K. wrote the manuscript. All authors contributed to discussions of the results.

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Correspondence to Hitoshi Kubota.

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Supplementary Sections A–F.

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Iihama, S., Taniguchi, T., Yakushiji, K. et al. Spin-transfer torque induced by the spin anomalous Hall effect. Nat Electron 1, 120–123 (2018). https://doi.org/10.1038/s41928-018-0026-z

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