Advanced, Kerr-microscopy-based MOKE magnetometry for the anisotropy characterisation of magnetic films

摘要

An advanced wide-field Kerr microscopy and magnetometry approach for the investigation of magnetic anisotropy in magnetic films is demonstrated. We have analytically analysed the longitudinal Kerr contrast in a wide-field magneto-optical Kerr microscope, specifically its dependence on the light polarisation direction and the plane of incidence and verified it experimentally. While normally the sensitivity direction (i.e. the direction of maximum contrast for antiparallel domains) of the longitudinal Kerr effect is along the plane of incidence for both, p - and s-polarized light, we found a deviation of the sensitivity direction from the incidence plane for p-polarised light. Based on a multi-component Kerr imaging technique we have developed a fully automated procedure for the measurement of magnetisation reversal loops along arbitrary in-plane field directions for magnetic films with in-plane anisotropy that does not require any mechanical adjustment of the system or sample displacement. The method is applied to the investigation of the magnetic anisotropy of a sputtered iron thin film. Additionally, a sample holder was introduced, which allows for the application of mechanical stress onto magnetic films due to substrate bending, and its applicability to the stress manipulation of the anisotropy direction was demonstrated for a nickel-iron film.