Domain wall motion in ferromagnetic nanowires driven by a localized Gaussian thermal gradient

Abstract

We investigate magnetic domain wall (DW) dynamics in a uniaxial ferromagnetic nanowire under the localized Gaussian temperature profile of a laser spot using the stochastic Landau-Lifshitz-Gilbert equation. The DW velocity increases linearly with peak laser temperature and decreases with increasing laser to DW distance. The velocity varies nonlinearly with Gilbert damping because damping strengthens thermal magnon excitation but shortens the magnon propagation length. The DW initially lies away from the laser-heated region, so the temperature gradient at its position is effectively zero and the entropic torque is negligible. The DW motion is therefore mainly driven by magnonic spin-transfer torque. We analyze laser temperature, laser to DW distance, damping, uniaxial anisotropy, and laser width. The analysis shows that laser width and laser to DW distance independently control the DW response. These findings may clarify the mechanism of localized thermally driven DW motion and guide thermal control strategies in spintronic racetrack-memory devices.