Abstract
Spin–orbit torques arising from the spin–orbit coupling of non-magnetic heavy metals allow electrical switching of perpendicular magnetization. However, the switching is not purely electrical in laterally homogeneous structures. An extra in-plane magnetic field is indeed required to achieve deterministic switching, and this is detrimental for device applications. On the other hand, if antiferromagnets can generate spin–orbit torques, they may enable all-electrical deterministic switching because the desired magnetic field may be replaced by their exchange bias. Here we report sizeable spin–orbit torques in IrMn/CoFeB/MgO structures. The antiferromagnetic IrMn layer also supplies an in-plane exchange bias field, which enables all-electrical deterministic switching of perpendicular magnetization without any assistance from an external magnetic field. Together with sizeable spin–orbit torques, these features make antiferromagnets a promising candidate for future spintronic devices. We also show that the signs of the spin–orbit torques in various IrMn-based structures cannot be explained by existing theories and thus significant theoretical progress is required.
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Acknowledgements
The authors acknowledge R. D. McMichael, M. D. Stiles, J. McClelland, and S.-B. Choe for critical reading of the manuscript. This work was supported by Creative Materials Discovery Program through the National Research Foundation of Korea (NRF-2015M3D1A1070465). Further financial support from the NRF was provided to B.-G.P. (NRF-2014R1A2A1A11051344), K.-J.L. (NRF-2013R1A2A2A01013188), H.-W.L. (NRF-2013R1A2A2A05006237) and J-R.J. (NRF-2013R1A2A2A01067144). B.-C.M. was awarded financial support from the KIST institutional programme (2E26380).
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B.-G.P. and K.-J.L. planned and supervised the study. Y.-W.O. and S.-H.C.B. fabricated the devices with help from Y.M.K., H.Y.L. and C.-G.Y. Y.-W.O. and S.-H.C.B. measured spin–orbit torques with help from K.-D.L., E.-S.P., B.-C.M., K.-S.L. and J.-R.J. K.-W.K., G.G., H.-W.L., K.-J.L. and B.-G.P. analysed the results. K.-J.L. and B.-G.P. wrote the manuscript with the help of Y.M.K., K.-W.K. and H.-W.L.
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Oh, YW., Chris Baek, Sh., Kim, Y. et al. Field-free switching of perpendicular magnetization through spin–orbit torque in antiferromagnet/ferromagnet/oxide structures. Nature Nanotech 11, 878–884 (2016). https://doi.org/10.1038/nnano.2016.109
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DOI: https://doi.org/10.1038/nnano.2016.109
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