Optical spin transfer torque driven domain wall motion in ferromagnetic semiconductor

TL;DR

This paper demonstrates optical control of domain wall motion in a ferromagnetic semiconductor using spin transfer torque and localized heating, enabling precise, laser-driven manipulation of magnetic domain walls.

Contribution

It introduces a novel optical method to manipulate domain walls via spin transfer torque and thermal effects in a dilute magnetic semiconductor.

Findings

Laser helicity controls domain wall direction.

Domain walls are attracted to laser hot-spots.

Optical manipulation offers a new way to position domain walls.

Abstract

We demonstrate optical manipulation of the position of a domain wall in a dilute magnetic semiconductor, GaMnAsP. Two main contributions are identified. Firstly, photocarrier spin exerts a spin transfer torque on the magnetization via the exchange interaction. The direction of the domain wall motion can be controlled using the helicity of the laser. Secondly, the domain wall is attracted to the hot-spot generated by the focused laser. Unlike magnetic field driven domain wall depinning, these mechanisms directly drive domain wall motion, providing an optical tweezer like ability to position and locally probe domain walls.