FMR measurement of anisotropy dispersion in amorphous GdFe films

Ferromagnetic resonance spectra of a series of evaporated Gd1−xFex amorphous bubble films with x ranging from 67.6 to 81.6 at.% have been measured. From these spectra the g-factor geff was calculated. The experimentally determined values of geff agree well with those expected from Wangness formula. Of particular interest is the comparison of the anisotropy field values HK measured by ferromagnetic resonance and by a vibrating sample magnetometer. Whereas FMR can provide information on the anisotropy distribution in the film, VSM yields at best an average value for HK. In our experiments, several resonance peaks are in general found for a given film indicating the existence of a number of regions having different values of Hk′=HK−4πM. Interface effects on the substrate side and oxidation at the air-film interface may result in layers of different chemical composition.