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Nat Nanotechnol. 2014 Mar;9(3):211-7. doi: 10.1038/nnano.2014.15. Epub 2014 Mar 2.

An antidamping spin-orbit torque originating from the Berry curvature.

Author information

1
1] Microelectronics Group, Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, UK [2] PRESTO, Japan Science and Technology Agency, Kawaguchi 332-0012, Japan [3].
2
1] Institut für Physik, Johannes Gutenberg-Universität Mainz, 55128 Mainz, Germany [2] Department of Physics, Texas A&M University, College Station, Texas 77843-4242, USA [3] Institute of Physics ASCR, v.v.i., Cukrovarnická 10, 162 53 Praha 6, Czech Republic.
3
Microelectronics Group, Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, UK.
4
1] Institute of Physics ASCR, v.v.i., Cukrovarnická 10, 162 53 Praha 6, Czech Republic [2] Hitachi Cambridge Laboratory, Cambridge CB3 0HE, UK.
5
Institute of Physics ASCR, v.v.i., Cukrovarnická 10, 162 53 Praha 6, Czech Republic.
6
School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD, UK.
7
1] Department of Physics, Texas A&M University, College Station, Texas 77843-4242, USA [2] Institute of Physics ASCR, v.v.i., Cukrovarnická 10, 162 53 Praha 6, Czech Republic.
8
1] Institute of Physics ASCR, v.v.i., Cukrovarnická 10, 162 53 Praha 6, Czech Republic [2] School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD, UK.

Abstract

Magnetization switching at the interface between ferromagnetic and paramagnetic metals, controlled by current-induced torques, could be exploited in magnetic memory technologies. Compelling questions arise regarding the role played in the switching by the spin Hall effect in the paramagnet and by the spin-orbit torque originating from the broken inversion symmetry at the interface. Of particular importance are the antidamping components of these current-induced torques acting against the equilibrium-restoring Gilbert damping of the magnetization dynamics. Here, we report the observation of an antidamping spin-orbit torque that stems from the Berry curvature, in analogy to the origin of the intrinsic spin Hall effect. We chose the ferromagnetic semiconductor (Ga,Mn)As as a material system because its crystal inversion asymmetry allows us to measure bare ferromagnetic films, rather than ferromagnetic-paramagnetic heterostructures, eliminating by design any spin Hall effect contribution. We provide an intuitive picture of the Berry curvature origin of this antidamping spin-orbit torque as well as its microscopic modelling. We expect the Berry curvature spin-orbit torque to be of comparable strength to the spin-Hall-effect-driven antidamping torque in ferromagnets interfaced with paramagnets with strong intrinsic spin Hall effect.

PMID:
24584275
DOI:
10.1038/nnano.2014.15

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