X-ray scattering from magnetic metallic multilayers

Abstract

Study of structure and interface morphology of magnetic thin films is crucial in obtaining a better understanding of the coupling mechanisms in such systems. In this thesis various x-ray scattering techniques are applied to a series of Co/Cr trilayers, Cu/Co multilayers and spin valve structures. It is demonstrated that modifications to the distorted wave Born approximation allow the modelling of grazing incidence diffuse scatter originating from graded systems such as Co/Cr. Grazing incidence scattering techniques are also employed to investigate the out of plane correlations of lateral roughness in Cu/Co multilayers, as well as in miscible trilayer structures. The use of soft x-rays in the investigation of 3d transition metal multilayers is also presented. Such experiments are sensitive to the component of magnetisation aligned with the direction of the incident beam. In a series of magnetisation experiments, the dependence of the x-ray scatter sensitive to this component of magnetisation are analysed. For the first time evidenced is found for correlated magnetic roughness, which has lateral correlation lengths far greater than the structural roughness length scales. This magnetic roughness is measured in detail, and the correlation length is found to vary with applied field direction. Grazing incidence x-ray fluorescence is applied to two spin valve structures. These experiments provide a direct measure of buried layer thicknesses which is not possible by other x-ray scattering techniques. This novel method for the determination of the copper layer thickness in spin valves shows the versatility of non-destructive x-ray methods for the characterisation of magnetic metallic multilayers.