Understanding current-driven dynamics of magnetic domain walls in spin-orbit systems

Mei Li, Jianbo Wang, Jie Lu

Published 2018-03-31, updated 2018-09-28Version 2

In this work, systematic one-dimensional (1D) analyses are performed to understand current-driven domain-wall dynamics in heavy metal/ferromagnetic metal/oxide trilayers with spin-orbit torques (SOTs) originating from various mechanisms. For SOTs induced by Rashba spin-orbit interaction or spin Hall effect, in 1D collective-coordinate-model framework the Walker breakdown suppression is analytically explained in the presence of fieldlike (FL) SOTs with effective fields along $\mathbf{e}_z\times\hat{\mathbf{J}}_e$ ($\mathbf{e}_z$ being the interface normal and $\hat{\mathbf{J}}_e$ being the charge current direction). While the wall mobility (velocity versus current density) change and even motion-direction reversal (from forward to backward of electron flow) as well as its polarity sensitivity can be well explicated only if the anti-damping-like (ADL) SOT is introduced. When bulk inversion asymmetry or strain induced FL-SOTs with effective fields along general transverse orientation are further considered, asymptotic expansions on dynamical equation reveal that the mobility change still can not happen without the help of ADL-SOTs. This also holds for external uniform transverse magnetic fields with general orientations.