Ultrafast and energy-efficient spin–orbit torque switching in compensated ferrimagnets

Abstract

Spin–orbit torque can be used to manipulate magnetization in spintronic devices. However, conventional ferromagnetic spin–orbit torque systems have intrinsic limitations in terms of operation speed due to their inherent magnetization dynamics. Antiferromagnets and ferrimagnets with antiparallel exchange coupling exhibit faster spin dynamics and could potentially overcome these limitations. Here, we report ultrafast spin–orbit torque-induced magnetization switching in ferrimagnetic cobalt-gadolinium (CoGd) alloy devices. Using a stroboscopic pump–probe technique to perform time-resolved measurements, we show that the switching time in the ferrimagnets can be reduced to the subnanosecond regime and a domain wall velocity of 5.7 km s‒1 can be achieved, which is in agreement with analytical modelling and atomistic spin simulations. We also find that the switching energy efficiency in the ferrimagnets is one to two orders of magnitude higher than that of ferromagnets.

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Fig. 1: Schematic of the time-resolved MOKE set-up and characterization of the CoGd samples.
Fig. 2: Magnetization switching and DW motion in CoGd devices.
Fig. 3: Schematic of angular momentum transfer and calculated DW velocity in a ferrimagnet.
Fig. 4: DW velocity as a function of current density and pulse duration.

Data availability

The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.

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Acknowledgements

This work was supported by the SpOT-LITE programme (A*STAR grant no. A18A6b0057) through RIE2020 funds and the National Research Foundation (NRF), Prime Minister’s Office, Singapore, under its Competitive Research Programme (CRP award no. NRFCRP12-2013-01). We thank K.J. Lee for discussions.

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Contributions

K.C. and H.Y. conceived and designed the experiments. R.M. and K.C. deposited the CoGd films. K.C., L.R., J.M.L., S.D.P. and P.H. performed the characterizations and fabrications. K.C. performed the measurements. Z.Z. and K.C. performed the simulations and analytical calculations. Z.Z., G.L., R.M. and K.L.T. analysed the results and developed the explanation of the experiments. K.C., R.M. and H.Y. wrote the manuscript. H.Y. proposed and supervised the project. All authors discussed the results and revised the manuscript.

Corresponding author

Correspondence to Hyunsoo Yang.

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Supplementary Information

Supplementary Notes 1–9, including Figs. 1–11 and Table 1.

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Cai, K., Zhu, Z., Lee, J.M. et al. Ultrafast and energy-efficient spin–orbit torque switching in compensated ferrimagnets. Nat Electron 3, 37–42 (2020). https://doi.org/10.1038/s41928-019-0345-8

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