Measurement of magnetization of Ga1−xMnxAs by ferromagnetic resonance

In this paper, we extend ferromagnetic resonance (FMR) studies of thin layers of the ferromagnetic semiconductor Ga1−xMnxAs to the analysis of the integrated intensity of the resonance in order to obtain information on the total spin in the sample directly involved in ferromagnetically-ordered magnetization. A theoretical model is proposed for the dependences of the FMR integrated intensity and linewidth on the orientation of the applied magnetic field as the field direction is varied from in-plane to normal-to-the-plane of the Ga1−xMnxAs layer. The strain-induced magnetic anisotropy of Ga1−xMnxAs presents a significant challenge to conventional FMR linewidth and integrated intensity models. The new model predicts that the integrated FMR intensity is proportional to the saturation magnetization MS of the sample, with the constant of proportionality varying as a function of the polar and azimuthal angles of the applied magnetic field. The angular and temperature behaviors of the integrated intensity and linewidth of the FMR predicted by the proposed model are in good qualitative agreement with measurements.