Field-Driven Domain-Wall Dynamics in GaMnAs Films with Perpendicular Anisotropy

TL;DR

This study investigates domain wall motion in GaMnAs films with perpendicular magnetic anisotropy using advanced imaging and pulsed magnetic fields, revealing unique dynamic regimes and damping behaviors.

Contribution

It provides the first detailed analysis of domain wall dynamics in GaMnAs with perpendicular anisotropy, including damping mechanisms and resonance phenomena.

Findings

Depinning field is smaller than Walker field, enabling steady and precessional flow observation.

Damping is 30 times larger than ferromagnetic resonance estimates, mainly due to non-conservation of magnetization modulus.

Identification of damping resonance and dissipation regimes linked to Bloch lines.

Abstract

We combine magneto-optical imaging and a magnetic field pulse technique to study domain wall dynamics in a ferromagnetic (Ga,Mn)As layer with perpendicular easy axis. Contrary to ultrathin metallic layers, the depinning field is found to be smaller than the Walker field, thereby allowing for the observation of the steady and precessional flow regimes. The domain wall width and damping parameters are determined self-consistently. The damping, 30 times larger than the one deduced from ferromagnetic resonance, is shown to essentially originate from the non-conservation of the magnetization modulus. An unpredicted damping resonance and a dissipation regime associated with the existence of horizontal Bloch lines are also revealed.