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Synopsis

Spin-orbit torques (SOTs) are relativistic quantum mechanical effects that allow electrical manipulation of magnetization. Systems displaying giant spin-orbit torque are attractive for fundamental spin dynamics studies and have potential for use in energy-efficient memory, wireless communication, and novel computation such as neuromorphic computing. Giant SOTs can be generated in bilayers of ferromagnetic (FM) and non-magnetic (NM) materials with broken inversion symmetry. The earliest and most well-known SOTs originate from Rashba effect at the NM/FM interface and from spin Hall effect in the NM layer. We recently discovered that the planar Hall current in a FM can lead to a giant SOT applied to the same FM – an example of a new class of self-generated SOTs. In this talk, I will report the discovery of a giant self-generated SOT associated with the anomalous Hall effect (AHE) in the FM. This new SOT displays an unusual angular symmetry that is distinct from the previously studied spin Hall, Rashba, and planar Hall torques. Together the spin Hall, planar Hall, and anomalous Hall torques form a triad of universal Hall-type SOTs active in FM|NM systems. I will also report recent advances in how electrically generated orbital angular momentum currents can be used to increase the efficiency of spin-orbit torque devices.