DW dynamics on a topological insulator

Thin-Film Magnetization Dynamics on the Surface of a Topological Insulator.
Yaroslav Tserkovnyak and Daniel Loss
Phys. Rev. Lett. 108, 187201 (2012)

Schematic of a DW in a ferromagnetic strip with an out-of-plane easy (z) axis anisotropy, deposited on the surface of a TI. The DW (of width dw) is parametrized, according to Eq. (2), by two soft dynamic coordinates: its position xdwðtÞ and azimuthal angle dwðtÞ. At the DW position, xdw, the magnetization m lies fully in the xy plane (forming angle dw with the x axis). A chiral electron mode (of width dw) formed in the TI under the DW carries transport current Idw at its exit point, which is governed by the voltage Vy applied to the TI surface at its entrance and the fictitious electromotive force generated by the DW dynamics along its length. An Onsager-reciprocal spin torque affects DW dynamics in the presence of Idw.