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 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 Å. 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, x=120+/-30 Å, and present a simple model to determine an average column size of 27+/-6 Å and a reduction in the magnetic saturation of ~40%.JRC.E.6-Actinides researc