Effect of obliquely evaporated Au cap layer on the magnetic properties of thin Fe films on Si(111)

Abstract

The influence of Au capping layers on the magnetic properties of thin Fe films grown on Si(111) has been studied by means of room temperature magneto-optic Kerr effect (MOKE). MOKE measurements show a peculiar behavior of the magnetic anisotropy of Fe films grown at normal incidence and covered with obliquely evaporated Au cap layers. The magnetic anisotropy is dependent on the thickness of the deposited Au layer as well as on the growth conditions. First, the initial Fe sixfold in-plane magnetocrystalline anisotropy is replaced by an in-plane uniaxial one for Au thicknesses below 2 ML. Then, for increasing Au film thickness we observe an in-plane switching of the magnetic direction depending of the Au evaporation direction with respect to the substrate. Consider, for example, oblique Au depositions below 2 ML along the [1¯21¯]Si direction. These peculiar deposition conditions lead to a uniaxial anisotropy with easy axis perpendicular to the incidence plane of the Au flux. For thicker Au thicknesses, the uniaxial easy axis undergoes an in-plane switching reorientation of 90° corresponding to the Au evaporation direction. Angular resolved ultraviolet spectroscopy and ion scattering spectroscopy investigations reveal that this complex anisotropy behavior can be attributed partly to Au/Fe interfacial interdiffusion.