Abstract

In the first part of the talk, I will give a brief overview of the Hitachi Cambridge Laboratory. Then I will present unpublished results demonstrating control of magnetic domain wall position using a train of ultrafast laser pulses in a thin film of GaMnAsP, a dilute magnetic semiconductor. The laser generates two main forces acting on the domain wall. The first polarization independent force is proportional to the laser induced temperature gradient and attracts the domain wall to the laser hot-spot. The direction of the second force depends on the helicity of the laser, and is identified as the optical spin transfer torque, where the spin of the photo-carriers exerts a torque on the magnetization via the exchange interaction. The experiments provide strong insights into the physics of laser induced magnetization reversal, and tools for local measurements of domain wall dynamics.