Field-free manipulation of magnetization alignments in a Fe/GaAs/GaMnAs multilayer by spin-orbit-induced magnetic fields.

We investigate the process of selectively manipulating the magnetization alignment in magnetic layers in the Fe/GaAs/GaMnAs structure by current-induced spin-orbit (SO) magnetic field. The presence of such fields manifests itself through the hysteretic behavior of planar Hall resistance observed for two opposite currents as the magnetization in the structure switches directions. In the case of the Fe/GaAs/GaMnAs multilayer, hystereses are clearly observed when the magnetization switches direction in the GaMnAs layer, but are negligible when magnetization transitions occur in Fe. This difference in the effect of the SO-field in the two magnetic layers provides an opportunity to control the magnetization in one layer (in the presence case in GaMnAs) by a current, while the magnetization in the other layer (i.e., Fe) remains fixed. Owing to our ability to selectively control the magnetization in the GaMnAs layer, we are able to manipulate the relative spin configurations in our structure between collinear and non-collinear alignments simply by switching the current direction even in the absence of an external magnetic field.