Determining the properties of magnetic thin films using spectroscopic ellipsometry

Spectroscopic ellipsometry is a non-invasive technique used to determine the permittivity tensor of materials by recording the changes in the polarization state between the incident and reflected beams. In general, this technique determines the permittivity of non magnetic films for both isotropic and anisotropic material because in this case, the permittivity tensor is diagonal. The ability to measure the off-diagonal terms via ellipsometry enables the exploration of magnetic thin films using this optical technique. This is because an external magnetic field that changes the magnetization of the film will in turn change the polarization state of the reflected beam due to the magneto-optical effect produced by the film. In this work, we have performed some preliminary studies on incorporating an external magnet into a spectroscopic ellipsometer with a spectral range between 200 nm and 1700 nm. Several magnetic films, including iron oxide, were investigated using this technique. Initially, standard ellipsometry measurements were performed to determine the permittivity of the films without the presence of the magnetic field. Finally, we performed ellipsometry measurements on the same films with a magnetic field to extract the magnetic properties of the films.