Numerical Study of Current-Induced Domain-Wall Dynamics: Crossover from Spin Transfer to Momentum Transfer

TL;DR

This study investigates how magnetic domain walls move under electric current, revealing a transition from spin transfer to momentum transfer mechanisms depending on anisotropy, through numerical simulations of coupled quantum and classical equations.

Contribution

It introduces a combined quantum-classical simulation approach to analyze current-induced domain-wall dynamics and identifies a crossover between two distinct motion regimes.

Findings

Small anisotropy leads to spin transfer-driven streaming motion.

Large anisotropy results in momentum transfer-driven stick-slip motion.

The origin of motion types is explained via energy level dynamics.

Abstract

We study current-induced dynamics of a magnetic domain wall by solving a time-dependent Schr\"{o}dinger equation combined with Landau-Lifshitz-Gilbert equation in a one-dimensional electron system coupled to localized spins. Two types of domain-wall motions are observed depending on the hard-axis anisotropy, $K_{\perp}$, of the localized spin system. For small values of $K_{\perp}$, the magnetic domain wall shows a streaming motion driven by spin transfer. In contrast, for large values of $K_{\perp}$, a stick-slip motion driven by momentum transfer is obtained. We clarify the origin of these characters of domain-wall motions in terms of the dynamics of one-particle energy levels and distribution functions.