Walker breakdown with a twist: Dynamics of multilayer domain walls and skyrmions driven by spin-orbit torque

TL;DR

This paper investigates the current-driven dynamics of multilayer domain walls and skyrmions, revealing a Walker breakdown-like phenomenon caused by spin-orbit torque, with implications for magnetic device performance.

Contribution

It introduces an analytical model and micromagnetic simulations to explain complex precessional dynamics and Walker breakdown in multilayer magnetic systems with spin-orbit torque.

Findings

Walker breakdown-like phenomenon observed at typical velocities of tens of m/s

Precessional frequencies reach gigahertz regime leading to oscillatory motion

Analytical model qualitatively matches micromagnetic simulation results

Abstract

Current-induced dynamics of twisted domain walls and skyrmions in ferromagnetic perpendicularly magnetized multilayers is studied through three-dimensional micromagnetic simulations and analytical modeling. It is shown that such systems generally exhibit a Walker breakdown-like phenomenon in the presence of current-induced damping-like spin-orbit torque. Above a critical current threshold, corresponding to typical velocities of the order tens of m/s, domain walls in some layers start to precess with frequencies in the gigahertz regime, which leads to oscillatory motion and a significant drop in mobility. This phenomenon originates from complex stray field interactions and occurs for a wide range of multilayer materials and structures that include at least three ferromagnetic layers and finite Dzyaloshinskii-Moriya interaction. An analytical model is developed to describe the precessional dynamics in multilayers with surface-volume stray field interactions, yielding qualitative agreement with micromagnetic simulations.