Soft X-ray Resonant Magnetic Reflectivity: a probe for complex magnetization distribution in thin films

This thesis deals with depth resolved magnetic profile of ultrathin Fe layers studied by soft X-ray Resonant Magnetic Reflectivity (SXRMR). This SXRMR technique combines magneto-optic effects to X-ray scattering, allowing the sensitivity to depth resolved magnetic properties. The derived magnetic profile allows to probe the homogeneity of magnetic properties and to reveal interfacial effect. First, we present the study of a thin Fe film grown on a Ag(116) vicinal substrate and covered by Au. This study reveals a magnetization enhancement of 20 to 30% in the two to three monolayers near both interfaces, whatever the Fe thickness. We have also evidence an inhomogeneity of the out of plane magnetic component at low temperature for sample where the easy magnetization axis is perpendicular to the steps: the out of plane magnetic component is decreased with Fe layer away from the vicinal substrate of Ag. Second, we present the study of a six monolayers thin film of Fe grown on a Cu(100) substrate and covered by Au. Using a new approach to constrain the magnetic parameters, we have highlighted that the temperature dependence of the magnetization is not the same depending on the position of the monolayer inside the Fe thin film. (author)