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Asynchronous current-induced switching of rare-earth and transition-metal sublattices in ferrimagnetic alloys

Abstract

Ferrimagnetic alloys are model systems for understanding the ultrafast magnetization switching in materials with antiferromagnetically coupled sublattices. Here we investigate the dynamics of the rare-earth and transition-metal sublattices in ferrimagnetic GdFeCo and TbCo dots excited by spin–orbit torques with combined temporal, spatial and elemental resolution. We observe distinct switching regimes in which the magnetizations of the two sublattices either remain synchronized throughout the reversal process or switch following different trajectories in time and space. In the latter case, we observe a transient ferromagnetic state that lasts up to 2 ns. The asynchronous switching of the two magnetizations is ascribed to the master–agent dynamics induced by the spin–orbit torques on the transition-metal and rare-earth sublattices and their weak antiferromagnetic coupling, which depends sensitively on the alloy microstructure. Larger antiferromagnetic exchange leads to faster switching and shorter recovery of the magnetization after a current pulse. Our findings provide insight into the dynamics of ferrimagnets and the design of spintronic devices with fast and uniform switching.

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Fig. 1: Time-, space- and element-resolved current-induced switching of GdFeCo.
Fig. 2: Switching dynamics of GdFeCo.
Fig. 3: Switching dynamics of TbCo.
Fig. 4: Micromagnetic simulations of the asynchronous dynamics.
Fig. 5: Microstructure of fresh and aged GdFeCo films.

Data availability

The datasets presented in this study are available from the corresponding authors upon reasonable request and in the ETH Research Collection at https://doi.org/10.3929/ethz-b-000482072.

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Acknowledgements

We thank M. Baumgartner and C. Murer for fruitful discussions and help with the STXM measurements, and F. Binda for the assistance with the measurements at the vibrating sample magnetometer. We thank R. Erni for collaborating in the analysis of the diffraction measurements. We thank C. Vockenhuber for performing Rutherford backscattering measurements on GdFeCo and TbCo. This research was supported by the Swiss National Science Foundation (grant nos 200020_200465 and PZ00P2-179944) and the Swiss Government Excellence Scholarship (ESKAS no. 2018.0056). The PolLux end station was financed by the German Ministerium für Bildung und Forschung (BMBF) through contracts 05K16WED and 05K19WE2. The work by E.M. and V.R. was supported by the Ministerio de Economía y Competitividad of the Spanish Government (project no. MAT2017-87072-C4-1-P) and by the Consejería de Educación of the Junta de Castilla y Leon (project nos SA299P18 and SA0114P20). We acknowledge the Paul Scherrer Institut, Villigen, Switzerland for provision of synchrotron radiation beamtime at beamline X07DA-PolLux of the Swiss Light Source. We also thank the Helmholtz-Zentrum Berlin for the allocation of synchrotron radiation beamtime at the UE-46 Maxymus beamline.

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P.G., G.S. and C.-H.L. planned the experiment. G.S., C.-H.L., V.K. and G.K. performed the STXM measurements with the support of S.F., M.W. and J.R.; G.S. characterized the magnetic properties of the full films and devices. E.M. and V.R. developed the micromagnetic code and performed the simulations. M.R. performed the STEM characterization and the nanobeam diffraction measurements. M.R and G.S. analysed the STEM–EDX maps. G.S. and P.G. analysed the data and wrote the manuscript with input from E.M. All authors discussed the data and commented on the manuscript.

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Correspondence to Giacomo Sala or Pietro Gambardella.

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Nature Materials thanks Olena Gomonay, Xuepeng Qiu and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary information

Supplementary Information

Supplementary Notes 1–13 and Figs. 1–22.

Supplementary Video 1

Dynamics of type I.

Supplementary Video 2

Dynamics of type II.

Supplementary Video 3

Dynamics of type III.

Supplementary Video 4

Simulation of the dynamics of type I.

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Sala, G., Lambert, CH., Finizio, S. et al. Asynchronous current-induced switching of rare-earth and transition-metal sublattices in ferrimagnetic alloys. Nat. Mater. 21, 640–646 (2022). https://doi.org/10.1038/s41563-022-01248-8

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