Spin wave resonance study in a series of etched GaMnAsP films

Although ferromagnetic semiconductor films have already been investigated for the last two decades, some fundamental issues still puzzle the researchers in this field. One of these issues is how the magnetic anisotropy field distributes along the growth direction. In order to resolve this issue in a 108-nm GaMnAsP film, a series of etched samples formed by wet-etching this GaMnAsP film were studied by XRD, SQUID and FMR. The thicknesses of the etched GaMnAsP films were determined by XRD measurements, using the oscillations observed in ω-2θ scans. The XRD peaks from GaMnAsP films are also used for determine the Mn and P contents along the growth direction. Magnetizations of the films are measured by SQUID as a function of field and temperature. FMR measurements were carried out at 4K as function of field orientation, using both out-of-plane and in-plane geometries. A series of spin wave modes are observed when field is applied in the plane of film, as well a critical angle phenomenon is found in specific resonance configurations. The angular dependence of spin wave modes will be analyzed using newly reported spherical surface pinning model in order to map the surface free energy. The results will be summarized as a function of film thickness for all etched samples.