Effect of chemical etching on magnetic anisotropy of ferromagnetic GaMnAs films studied by planar Hall effect

We have investigated the effect of chemical etching on magnetic anisotropy of ferromagnetic GaMnAs film using the planar Hall effect (PHE). Different thicknesses were obtained on a single GaMnAs specimen by using different etching times on selected areas, and the PHE was then measured using the Hall bar configurations patterned on the area. Cubic and uniaxial anisotropy fields were obtained for the films by fitting the angular dependence of the PHE data to the Stoner-Wohlfarth model. The results exhibited a very systematic dependence on the etched thickness, demonstrating that the chemical etching process significantly affects the magnetic anisotropy of ferromagnetic GaMnAs films.