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Field-free switching of a perpendicular magnetic tunnel junction through the interplay of spin–orbit and spin-transfer torques

Abstract

Magnetization switching in magnetic tunnel junctions using spin-transfer torque and spin–orbit torque is key to the development of future spintronic memories. However, both switching mechanisms suffer from intrinsic limitations. In particular, the switching current in spin-transfer torque devices needs to be lowered, whereas an external magnetic field is required for spin–orbit torque devices to achieve deterministic switching in perpendicular magnetic tunnel junctions. Here, we experimentally demonstrate field-free switching of three-terminal perpendicular-anisotropy magnetic tunnel junction devices through the interaction between spin–orbit and spin-transfer torques. We show that the threshold current density of spin–orbit torque switching can be reduced by increasing the spin-transfer torque current density, and thus an optimal point for low-power perpendicular magnetic tunnel junction switching can be found by tuning the two current densities. Furthermore, and due to this interplay, low-power switching in two-terminal perpendicular magnetic tunnel junctions without an external magnetic field is also achieved.

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Fig. 1: Device geometry and magnetic properties.
Fig. 2: Current-induced magnetization switching for a device with r = 75 nm and w = 1.95 μm at room temperature.
Fig. 3: Magnetization switching through the interaction between ISOT and ISTT for three-terminal devices.
Fig. 4: Two-terminal device measurements at room temperature.
Fig. 5: Results of macrospin simulation and finite element simulation.

Data availability

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

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Acknowledgements

The authors gratefully acknowledge the National Natural Science Foundation of China (Grant Nos 61571023, 61627813), the International Collaboration Project B16001, and the National Key Technology Program of China 2017ZX01032101 for their financial support of this work. The device fabrication was carried out at the University of Minnesota Nanofabrication Centre, which receives partial support from the NSF through the NNIN program. J.-P.W. is acknowledges the Robert F. Hartmann Endowed Chair Professorship.

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W.Z. initialized, conceived and supervised the project. M.W., W.C., D.Z. and Z.W. contributed equally to this work. M.W. and Z.Z fabricated the devices under J.-P.W.’s supervision. W.C., M.W. and T.Z. performed the measurements. J.K. and C.P. developed, grew and optimized the films. D.Z. performed the spin dynamics and finite element calculations, and A.F. analysed the results. M.W., W.C., D.Z., Z.W. and W.Z. wrote the manuscript. All authors discussed the results and implications.

Corresponding author

Correspondence to Weisheng Zhao.

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Wang, M., Cai, W., Zhu, D. et al. Field-free switching of a perpendicular magnetic tunnel junction through the interplay of spin–orbit and spin-transfer torques. Nat Electron 1, 582–588 (2018). https://doi.org/10.1038/s41928-018-0160-7

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