Speed of field driven domain walls in nanowires with large transverse magnetic anisotropy

TL;DR

This paper analyzes how large transverse magnetic anisotropy affects the speed and stability of field-driven domain walls in nanowires, revealing a transition to slower wall profiles at high fields.

Contribution

It provides an asymptotic analysis of the Landau-Lifshitz-Gilbert equation showing the instability of the Walker profile and the emergence of slower domain walls at high applied fields.

Findings

Domain wall speed increases linearly with applied field at low fields.

A critical field causes a transition to slower domain wall profiles.

The transition is explained via a reaction-diffusion front transition.

Abstract

Recent analytical and numerical work on field driven domain wall propagation in nanowires has shown that for large transverse anisotropy and sufficiently large applied fields the Walker profile becomes unstable before the breakdown field, giving way to a slower stationary domain wall. We perform an asymptotic expansion of the Landau Lifshitz Gilbert equation for large transverse magnetic anisotropy and show that the asymptotic dynamics reproduces this behavior. At low applied field the speed increases linearly with the field and the profile is the classic Landau profile. Beyond a critical value of the applied field the domain wall slows down. The appearance of a slower domain wall profile in the asymptotic dynamics is due to a transition from a pushed to a pulled front of a reaction diffusion equation.