Strain-engineered magnetic anisotropy of GaMnAs ferromagnetic semiconductors

A series of GaMnAs epilayers grown on GaInAs buffer layers have been investigated. The concentrations of Mn in the GaMnAs layer and In in the GaInAs layer were varied in the series, for which the tensile strain condition for the GaMnAs layer are systematically changed. The X-ray measurement provided the lattice constants of the layers, from which the stain of the GaMnAs layer was determined. The magneto-transport data revealed in-plane anisotropy in the GaMnAs sample grown on a GaInAs buffer with a low concentration of In. Such in-plan magnetic anisotropy of the GaMnAs layer continuously changed to a vertical magnetic anisotropy when the tensile strain was increased in the sample grown on the GaInAs buffer with a higher In concentration. This experiment clearly demonstrated that the magnetic anisotropy of GaMnAs could be continuously engineered by using the strain introduced by the GaInAs buffer layers.