Magnetic torques generated through spin–orbit coupling1,2,3,4,5,6,7,8 promise energy-efficient spintronic devices. For applications, it is important that these torques switch films with perpendicular magnetizations without an external magnetic field9,10,11,12,13,14. One suggested approach15 to enable such switching uses magnetic trilayers in which the torque on the top magnetic layer can be manipulated by changing the magnetization of the bottom layer. Spin currents generated in the bottom magnetic layer or its interfaces transit the spacer layer and exert a torque on the top magnetization. Here we demonstrate field-free switching in such structures and show that its dependence on the bottom-layer magnetization is not consistent with the anticipated bulk effects15. We describe a mechanism for spin-current generation16,17 at the interface between the bottom layer and the spacer layer, which gives torques that are consistent with the measured magnetization dependence. This other-layer-generated spin–orbit torque is relevant to energy-efficient control of spintronic devices.
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Miron, I. M. et al. Perpendicular switching of a single ferromagnetic layer induced by in-plane current injection. Nature 476, 189–193 (2011).
Liu, L. et al. Spin torque switching with the giant spin Hall effect of tantalum. Science 336, 555–558 (2012).
Pai, C.-F. et al. Spin transfer torque devices utilizing the giant spin Hall effect of tungsten. Appl. Phys. Lett. 101, 122404 (2012).
Kim, J. et al. Layer thickness dependence of the current-induced effective field vector in Ta|CoFeB|MgO. Nat. Mater. 12, 240–245 (2013).
Garello, K. et al. Symmetry and magnitude of spin-orbit torques in ferromagnetic heterostructures. Nat. Nanotech. 8, 587–593 (2013).
Fan, X. et al. Quantifying interface and bulk contributions to spin-orbit torque in magnetic bilayers. Nat. Commun. 5, 3042 (2014).
Qiu, X. et al. Spin-orbit-torque engineering via oxygen manipulation. Nat. Nanotech. 10, 333–338 (2015).
Demasius, K.-U. et al. Enhanced spin–orbit torques by oxygen incorporation in tungsten films. Nat. Commun. 7, 10644 (2016).
Yu, G. et al. Switching of perpendicular magnetization by spin-orbit torques in the absence of external magnetic fields. Nat. Nanotech. 9, 548–554 (2014).
Fukami, S. et al. Magnetization switching by spin-orbit torque in an antiferromagnet/ferromagnet bilayer system. Nat. Mater. 15, 535–541 (2016).
Oh, Y.-W. et al. Field-free switching of perpendicular magnetization through spin-orbit torque in antiferromagnet/ferromagnet/oxide structures. Nat. Nanotech. 11, 878–884 (2016).
van den Brink, A. et al. Field-free magnetization reversal by spin-Hall effect and exchange bias. Nat. Commun. 7, 10854 (2016).
Lau, Y.-C., Betto, D., Rode, K., Coey, J. M. D. & Stamenov, P. Spin-orbit torque switching without an external field using interlayer exchange coupling. Nat. Nanotech. 11, 758–762 (2016).
Cai, K. et al. Electric field control of deterministic current-induced magnetization switching in a hybrid ferromagnetic/ferroelectric structure. Nat. Mater. 16, 712–716 (2017).
Taniguchi, T., Grollier, J. & Stiles, M. D. Spin-transfer torque generated by the anomalous Hall effect and anisotropic magnetoresistance. Phys. Rev. Appl. 3, 044001 (2015).
Amin, V. & Stiles, M. D. Spin transport at interfaces with spin–orbit coupling: formalism. Phys. Rev. B 94, 104419 (2016).
Amin, V. & Stiles, M. D. Spin transport at interfaces with spin–orbit coupling: phenomenology. Phys. Rev. B 94, 104420 (2016).
Sinova, J., Valenzuela, S. O., Wunderlich, J., Back, C. H. & Jungwirth, T. Spin Hall effects. Rev. Mod. Phys. 87, 1213 (2015).
D’yakonov, M. I. & Perel, V. I. Possibility of orienting electron spins with current. J. Exp. Theor. Phys. Lett. 13, 467–469 (1971).
Hirsch, J. E. Spin Hall effect. Phys. Rev. Lett. 83, 1834–1837 (1999).
Magin, S. et al. Current-induced magnetization reversal in nanopillars with perpendicular anisotropy. Nat. Mater. 5, 210–215 (2006).
Ikeda, S. et al. A perpendicular-anisotropy CoFeB-MgO magnetic tunnel junction. Nat. Mater. 9, 721–724 (2010).
Franken, J. H., Swagten, H. J. M. & Koopmans, B. Shift register based on magnetic domain wall ratchets with perpendicular anisotropy. Nat. Nanotech. 7, 499–503 (2012).
MacNeill, D. et al. Control of spin-orbit torques through crystal symmetry in WTe2/ferromagnet bilayers. Nat. Phys. 13, 300–305 (2016).
Humphries, A. M. et al. Observation of spin–orbit effects with spin rotation symmetry. Nat. Commun. 8, 911 (2017).
Wang, X., Vanderbilt, D., Yates, J. R. & Souza, I. Fermi-surface calculation of the anomalous Hall conductivity. Phys. Rev. B 76, 195109 (2007).
Bass, J. CPP magnetoresistance of magnetic multilayers: A critical review. J. Magn. Magn. Mater. 408, 244–320 (2016).
Lee, K. J. et al. Spin transfer effect in spin-valve pillars for current-perpendicular-to-plane magnetoresistive heads. J. Appl. Phys. 95, 7423 (2004).
Freimuth, F., Blügel, S. & Mokrousov, Y. Direct and inverse spin–orbit torques. Phys. Rev. B 92, 064415 (2015).
Wang, L. et al. Giant room temperature interface spin Hall and inverse spin Hall effects. Phys. Rev. Lett. 116, 196602 (2016).
The authors acknowledge K.-W. Kim, H.-W. Lee and J. Sinova for discussion. This work was supported by the Creative Materials Discovery Program through the National Research Foundation of Korea (NRF-2015M3D1A1070465). B.-G.P. acknowledges financial support from the NRF (NRF-2017R1A2A2A05069760), K.-J.L. from the NRF (NRF-2017R1A2B2006119) and K.-J.K. from the NRF (NRF-2016R1A5A1008184). V.P.A. acknowledges support under the Cooperative Research Agreement between the University of Maryland and the National Institute of Standards and Technology Center for Nanoscale Science and Technology, Award 70NANB14H209, through the University of Maryland.
The authors declare no competing interests.
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Baek, S.C., Amin, V.P., Oh, Y. et al. Spin currents and spin–orbit torques in ferromagnetic trilayers. Nature Mater 17, 509–513 (2018). https://doi.org/10.1038/s41563-018-0041-5
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