Spin Reorientation of Fe Films Studied by the Magneto-Optical Kerr Effect

The ability to alter magnetic anisotropy values is of technological importance in the application of magnetic ultrahigh-density recording. By capping some other atoms onto the surface of a magnetic thin film or inserting a thin layer between the magnetic film and the substrate, we can change the surface or interface perpendicular magnetic anisotropy and then alter the magnetic properties of the film, such as the spin reorientation transition (SRT), in ultrathin ferromagnetic films. The SRT of face-centered-tetragonal (fct) Fe films grown on Cu(001) substrate is determined by the magneto-optical Kerr effect. We find that the out-of-plane magnetization changes to in-plane induced by a Ni-capping or a Co-inserting layer at 110 K. From the linear relation of the critical thickness of a fct-Fe film with Ni or Co covering when SRT occurs, the "true" critical thickness of the pure fct-Fe film without coverage or buffer in the absence of structural transformation is obtained by setting the coverage to zero value. The estimated true critical thickness is approximately 4.3 ML for the Ni-capping method and 4.6 ML for the Co-inserting experiment, which are very close to the reported result for the Co-capping experiment.