Chemical and magnetic structure of uranium/gadolinium multilayers studied by transmission electron microscopy, neutron scattering, and x-ray reflectivity

We present a multitechnique approach to study the detailed chemical and magnetic structure of uranium/gadolinium multilayers. At low temperature the saturation magnetization is found to be similar to 60% of that of bulk gadolinium. We address this problem, which is found in many other multilayers and suggest a model that may have wider applications. transmission electron microscopy images indicate a microstructure, consistent with a columnar growth of Gd with crystallites of the order 20 -> 100 angstrom. Off-specular neutron scattering is most strongly visible at saturation field, indicating that Gd moments are not aligned with the applied field. X-ray resonant magnetic scattering provides proof of coupled in-plane length scales for both the structural and the magnetic roughness. A detailed x-ray scattering study of both the specular and off-specular reflectivities has been used to investigate the in-plane structure of the multilayers. We calculate the roughness and transverse correlation cut-off length, xi(x) = 120 +/- 30 angstrom, and present a simple model to determine an average column size of 27 +/- 6 angstrom and a reduction in the magnetic saturation of similar to 40%.