Saturation magnetization and perpendicular anisotropy of Fe/GaAs(110) epitaxial films studied by the extraordinary hall effect

The magnetic field dependence of the extraordinary Hall effect (EHE) has been used to determine the sum of the perpendicular magnetic anisotropy and the saturation magnetization of thin (5-20 nm) Fe films. The films were grown on (110) surfaces of GaAs by molecular beam epitaxy. The free surface of the films was not protected thereby allowing an iron oxide layer to form upon removal from the MBE apparatus. The relation between the film thickness and the sum of the perpendicular anisotropy energy and the saturation magnetization was compared to that determined in a previous study which relied on ferromagnetic resonance (FMR) to measure the same quantity. The FMR study measured both oxide covered films and also films with a protective overcoating of Al to prevent oxidation. It is found that the data from the EHE are not in agreement with the FMR data taken on the iron oxide covered films but instead are in agreement with the FMR data of the protected or nonoxidized films. In addition a determination of the surface anisotropy energy can be made by subtracting the magnetization data measured on overcoated films from the sum determined by the EHE analysis. In this case there is no indication of a large surface anisotropy energy making the perpendicular direction an easy axis.