a Magnetoresistive Study of Magnetic Anisotropy in Epitaxial Iron Films.

It has been established that ferromagnetic epitaxial thin films display magnetic anisotropy energies differing from bulk single-crystal values. The physical mechanisms contributing most to such changes are the altered atomic and electronic structure near the interfaces, the strains present in the film, and the quality of the interfaces. In order to investigate the origin of these effects in the anisotropy energy, their temperature dependence has been studied in detail in three (110) oriented Fe/GaAs films of varying thicknesses. The anisotropy energies were determined by examining the spin-reorientation phase transition (SRPT) using magnetoresistance measurements. A preliminary magnetoresistive study has also been conducted on two (100) oriented iron films. Discontinuous reorientational transitions have been observed in the latter films similar to those seen in the (110) samples. Values for the room-temperature anisotropy energies of the (100) films were obtained from the magnetoresistance data. The data from the (110) films were analyzed using a model relating the in-plane anisotropy energies to the strain. Given the known properties of these films, the model is found to account well for the observed values and temperature dependence of the anisotropy energies. The data from the (100) films were compared to a model relating the in-plane anisotropy energies to surface roughness via shape anisotropy. It is concluded that a satisfactory account of observed values of the in-plane uniaxial anisotropy energies in (100) films is possible on the basis of the shape anisotropy due to preferentially oriented surface irregularities that are known to exist in samples such as these.