The effect of disorder on transverse domain wall dynamics in magnetic nanostrips

TL;DR

This study investigates how disorder affects the dynamics of transverse domain walls in ferromagnetic nanostrips, revealing different pinning mechanisms and velocity behaviors under magnetic field and current driving forces through extensive micromagnetic simulations.

Contribution

It provides new insights into the influence of disorder on domain wall motion, including pinning mechanisms and the effective damping parameter, using GPU-accelerated simulations.

Findings

Disorder causes different pinning mechanisms below and above Walker breakdown.

Increasing disorder raises the Walker breakdown field and current.

Disorder suppresses intrinsic pinning in adiabatic spin transfer torque.

Abstract

We study the effect of disorder on the dynamics of a transverse domain wall in ferromagnetic nanostrips, driven either by magnetic fields or spin-polarized currents, by performing a large ensemble of GPU-accelerated micromagnetic simulations. Disorder is modeled by including small, randomly distributed non-magnetic voids in the system. Studying the domain wall velocity as a function of the applied field and current density reveals fundamental differences in the domain wall dynamics induced by these two modes of driving: For the field-driven case, we identify two different domain wall pinning mechanisms, operating below and above the Walker breakdown, respectively, whereas for the current-driven case pinning is absent above the Walker breakdown. Increasing the disorder strength induces a larger Walker breakdown field and current, and leads to decreased and increased domain wall velocities at the breakdown field and current, respectively. Furthermore, for adiabatic spin transfer torque, the intrinsic pinning mechanism is found to be suppressed by disorder. We explain these findings within the one-dimensional model in terms of an effective damping parameter $\alpha^*$ increasing with the disorder strength.