Investigation of domain pinning fields in ferromagnetic GaMnAs films using angular dependence of the planar Hall effect

The dependence of the planar Hall effect (PHE) in ferromagnetic GaMnAs films on the direction of the applied magnetic field was used to determine domain pinning fields in this material. The investigation was carried out by measuring the effect of reorientation of magnetization from one easy axis to another on the value of PHE as the magnetic field of fixed strength was rotated over 360^{{ring operator}}. This process was repeated at several field strengths, and the PHE results were analyzed using Cowburn's model of magnetic free energy, from which domain pinning fields of Δ E_{[over(1, ̄) 10]} / M = 27.5 ± 0.3 Oe and Δ E_{[over(1, ̄) over(1, ̄) 0]} / M = 38.0 ± 0.7 Oe were obtained for the Ga_0.94Mn_0.06As film used in this study. These values of pinning fields agree with those obtained in earlier studies where the magnetization reversal was investigated by sweeping the magnetic field. We show that the present approach of rotating a fixed field provides a simpler and more elegant way for studying domain pinning fields in a ferromagnetic film.