Effect of annealing on the magnetic anisotropy of GaMnAs film with low Mn concentration

The effect of annealing on the magnetic anisotropy of a GaMnAs film with a low Mn composition of 2% has been investigated. Hall measurements have been performed with an external field applied in- and out-of-plane. In as-grown samples, the behavior of the Hall resistance indicates that the out-of-plane magnetic anisotropy dominates over the in-plane anisotropy. The vertical anisotropy, however, gradually decreased with increasing annealing temperatures and changed to in-plane dominant anisotropy in the film annealed at 300 °C. Furthermore, it was found that the direction of the uniaxial anisotropy in the domain with the in-plane easy axes, changed from the [110] direction in as-grown film to the [11̄0] direction in the annealed film. This revealed that annealing altered the magnetic anisotropy of the GaMnAs film between out-of-plane and in-plane directions as well as within the film plane.