Conventional angle-dependent ferromagnetic resonance (FMR) measurements on an epitaxial (001) Fe film grown on a GaAs substrate were performed as a function of the orientation of the external magnetic field Bext for three configurations: One with Bext in the film plane and two with Bext out of plane starting in plane in different crystallographic orientations. From these measurements the magnetization M, the crystalline anisotropy constants K1 and K2, the surface anisotropy Ks and an additional uniaxial anisotropy Ku were deduced self-consistently. The temperature dependence of K1 and M was investigated for the in-plane [110] orientation in the range from 100 to 570 K. In addition, locally resolved photothermally modulated FMR measurements were carried out to study the homogeneity of the magnetization and of the crystalline anisotropy across the film. Disturbances of both magnetic parameters as a function of position were observed which are related to local inhomogeneities in the semiconducting substrate.

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Photothermally modulated ferromagnetic resonance (PM-FMR) was used to investigate the lateral dependence of the magnetic parameters in an epitaxially grown (001) Fe wedge. The wedge thickness varied from 2.2 to 12.8 nm on a length of 10 mm. The PM-FMR measurements, which were carried out with a lateral resolution of 50 μm, permitted to determine the surface anisotropy with a high accuracy. In addition, a small uniaxial in-plane anisotropy was detected which shows an increase with the Fe-film thickness.

The photothermally modulated (PM) ferromagnetic resonance (FMR) combines the high sensitivity of conventional FMR and the spatial resolution of thermal waves. For the first time, this alternative FMR-technique was applied to the magnetic characterization of high-quality thin Fe (001) films epitaxially grown on (001) GaAs substrate : Images of the distribution of crystalline anisotropy constant K1 and the magnetization M were determined from the locally resolved FMR spectra