Abstract
Planar spin transport in disordered ultrathin magnetic bilayers comprising a ferromagnet and a normal metal (typically used for spin pumping, spin Seebeck and spin-orbit torque experiments) is investigated theoretically. Using a tight-binding model that puts the extrinsic spin Hall effect and spin swapping on equal footing, we show that the nature of spin-orbit coupled transport dramatically depends on the ratio between the layer thickness and the mean free path . While the spin Hall effect dominates in the diffusive limit (), spin swapping dominates in the Knudsen regime (). A remarkable consequence is that spin swapping induces a substantial fieldlike torque in the Knudsen regime.
- Received 11 November 2015
DOI:https://doi.org/10.1103/PhysRevLett.117.036601
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