Thickness dependence of magnetic domain pinning energy in GaMnAs ferromagnetic semiconductor films

Magnetotransport measurements were performed on GaMnAs films with four different thicknesses. The process of magnetization reorientation was investigated by planar Hall effect, from which the magnetization switching fields were determined for each film thickness. Domain pinning energies were then obtained for the films by fitting the angular dependence of the switching fields using the model developed by Cowburn [J. Appl. Phys. 78, 7210 (1995)]. The results show a systematic increase of domain pinning energies as the thickness of the film decreases. Such dependence of domain pinning can be understood in terms of the carrier dependence of magnetic anisotropy in GaMnAs films on the concentration of carriers.