Resonant magnetic x-ray scattering in a series of uranium compounds

Abstract

We report results of x-ray scattering experiments on the antiferromagnetic uranium compounds ${\mathrm{UO}}_{2}$, USb, and (${\mathrm{U}}_{0.85}$${\mathrm{Th}}_{0.15}$)Sb. The energy dependence of the x-ray scattering cross section is reported in the range 3.5--3.9 keV, which includes the ${\mathit{M}}_{\mathrm{IV}}$ and ${\mathit{M}}_{\mathrm{V}}$ absorption edges. The energy dependencies are very similar and well represented by atomic-resonance methodology. Differences occur in the ratio of intensities (branching ratio) of the two absorption edges, which are larger in ${\mathrm{UO}}_{2}$ than in the other materials. Ab initio calculations based on atomic physics suggest that such differences may arise from differing 5f-electron configurations. Unfortunately, we have not measured accurately the absorption coefficient over the two edges, so that our corrections to the intensities must be regarded as qualitative. This prevents a quantitative comparison between the observed and calculated branching ratios. Consistent with the calculated cross section, the magnetic scattering of the \ensuremath{\sigma}-polarized incident beam is rotated to \ensuremath{\pi} polarization. No unusual effects were found at the ${\mathit{M}}_{\mathrm{IV}}$ edge of Th in the pseudobinary compound.