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Deterministic switching of a perpendicularly polarized magnet using unconventional spin–orbit torques in WTe2

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Abstract

Spin–orbit torque (SOT)-driven deterministic control of the magnetic state of a ferromagnet with perpendicular magnetic anisotropy is key to next-generation spintronic applications including non-volatile, ultrafast and energy-efficient data-storage devices. However, field-free deterministic switching of perpendicular magnetization remains a challenge because it requires an out-of-plane antidamping torque, which is not allowed in conventional spin-source materials such as heavy metals and topological insulators due to the system’s symmetry. The exploitation of low-crystal symmetries in emergent quantum materials offers a unique approach to achieve SOTs with unconventional forms. Here we report an experimental realization of field-free deterministic magnetic switching of a perpendicularly polarized van der Waals magnet employing an out-of-plane antidamping SOT generated in layered WTe2, a quantum material with a low-symmetry crystal structure. Our numerical simulations suggest that the out-of-plane antidamping torque in WTe2 is essential to explain the observed magnetization switching.

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Fig. 1: Crystal structure, polarized Raman and electron microscopy of the SOT devices.
Fig. 2: Current-induced AHE loop shift due to out-of-plane antidamping SOT in device A.
Fig. 3: SOT-induced-field-free switching in WTe2/ FGT bilayers (device A).
Fig. 4: Simulation of SOT-induced switching, Joule heating and temperature dependences.

Data availability

All the data supporting the findings of this study are available in the article and its Supplementary Information. Further information is available from the corresponding author on reasonable request.

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Acknowledgements

Funding for this research was provided primarily by the Center for Emergent Materials at The Ohio State University, a National Science Foundation (NSF) MRSEC through award number DMR-2011876. R.M. acknowledges NSF support through an AGEP-GRS supplement to award DMR-1809145. H.Z. and R.C. are supported by the Air Force Office of Scientific Research under grant FA9550-19-1-0307. J.Y. acknowledges support from the US Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division. D.G.M. acknowledges support from the Gordon and Betty Moore Foundation’s EPiQS Initiative through grant number GBMF9069. J.E.G. acknowledges financial support from the Center of Emergent Materials, an NSF MRSEC, under grant number DMR-2011876. D.W. gratefully acknowledges the financial support by the German Science Foundation DFG Research Fellowship (WE6480/1). Support for h-BN crystal growth from the Office of Naval Research from award N00014-20-1-2427 is appreciated. Electron microscopy was performed at the Center for Electron Microscopy and Analysis at The Ohio State University.

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Contributions

S.S. and J.K. designed the experiments and supervised the research. I.-H.K., R.M., S.Y. and J.G. prepared the devices and performed the experiments. H.Z. and R.C. performed the numerical simulations. M.Z and J.H. performed the STEM measurements. R.R. carried out polarized Raman measurements. J.Y. and D.G.M. provided the bulk crystals of WTe2. D.W. and J.E.G. provided the bulk FGT crystals. J.L. and J.H.E. provided the bulk h-BN crystals. All authors contributed to writing the manuscript.

Corresponding author

Correspondence to Simranjeet Singh.

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Nature Materials thanks Saroj Dash and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary information

Supplementary Information

Detailed information on device fabrication, material characterization, measurements on additional devices, and Joule heating analysis.

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Kao, IH., Muzzio, R., Zhang, H. et al. Deterministic switching of a perpendicularly polarized magnet using unconventional spin–orbit torques in WTe2. Nat. Mater. (2022). https://doi.org/10.1038/s41563-022-01275-5

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