Anomalous magneto-optical behavior of uniaxial Co/CoO bilayer films

We study the magneto-optical properties of thin epitaxially grown Co/CoO bilayer films with in-plane uniaxial anisotropy by means of Magneto-Optical Kerr Effect (MOKE) measurements. The magneto-optical response obtained from these samples exhibits a surprising and atypical behavior, in that the polarizer setting, at which signal inversion occurs, is a function of the sample orientation. This behavior even occurs for identical orientations of the magnetization with respect to the plane-of-incidence. Using Generalized Magneto-Optical Ellipsometry, we show that the origin of this behavior is the presence of optical anisotropy, which we attribute to the strained epitaxial CoO overlayer in our samples.

► We study the MO response of epitaxial Co/CoO bilayers with high crystalline order. ► The MO response studied by means of GME shows an unusual behavior. ► Optical anisotropy arises as the origin of such a large change in the MO response. ► This anomaly might occur in many experiments, leading to wrong magnetic properties. ► GME ellipsometry can distinguish in between these two different effects.