Manipulation of magnetization in GaMnAs films by spin-orbit-induced magnetic fields

We have investigated the effect of spin-orbit-induced (SOI) magnetic fields on magnetization switching in GaMnAs films. The sign of such SOI fields depends on the direction of the current flowing in the film, thus providing a handle for electrically manipulating magnetization in ferromagnetic GaMnAs films. Specifically, when an applied magnetic field is swept along the current direction, magnetization reversal occurs via rotations in opposite sense (i.e., clockwise (CW) or counterclockwise (CCW)) depending on the sign of the current, thus leading to opposite signs of the planar Hall resistance (PHR) measured on the film. The effect of SOI fields also manifests itself through hysteretic behavior of PHR for two opposite currents as a fixed magnetic field is rotated in the film plane. The width of the resulting hysteresis between two current directions then allows us to estimate the magnitude of the SOI field at current density of 1.0 × 10⁵ A/cm² as ∼1.2 Oe in our GaMnAs film. Such switching of magnetization between two magnetic easy axes induced by switching the sign of an applied current provides a means of electronically controlling the value of film resistance (in this case of PHR), a process that can be exploited in spintronic devices.