Uniaxial in-plane magnetic anisotropy of Ga1-xMnxAs

The anisotropic magnetic properties of a series of epitaxial Ga1-xMnxAs films with thicknesses ranging from 0.2 to 6.8 mum were investigated using magnetometry and x-ray diffraction. The films all show a distinct uniaxial contribution to the magnetic anisotropy along the in-plane [110] direction, whose relative importance increases with the temperature. The uniaxial anisotropy field is found to be essentially thickness independent, ruling out the possibility that this is an effect produced by a single surface or interface due to well-known surface reconstruction. Furthermore, even the very thick samples are found to be tetragonal and coherently strained to the GaAs substrate. Our results suggest that the uniaxial anisotropy arises from surface reconstruction induced preferential Mn incorporation occurring at every step of layer-by-layer growth and thus uniformly penetrates the entire sample. (C) 2004, American Institute of Physics.