We investigate spin-orbit torques on magnetization in an insulating ferromagnetic layer that is brought into close proximity to a topological insulator (TI). In addition to the well-known fieldlike spin-orbit torque, we identify an anisotropic anti-damping-like spin-orbit torque that originates in a diffusive motion of conduction electrons. This diffusive torque is vanishing in the limit of zero momentum (i.e., for a spatially homogeneous electric field or current), but it may, nevertheless, have a strong impact on spin-torque resonance at finite frequency provided the external field is neither parallel nor perpendicular to the TI surface. The required electric-field configuration can be created by a grated top gate.
Physical Review B
- Pub Date:
- June 2019
- Condensed Matter - Mesoscale and Nanoscale Physics;
- Condensed Matter - Disordered Systems and Neural Networks;
- Condensed Matter - Materials Science
- 10 page main text, 3 figures