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

We report results of x-ray scattering experiments on the antiferromagnetic uranium compounds UO₂, USb, and (U0.85{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 ${M}IV$ and ${M}V$ 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 UO₂ 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 {σ}-polarized incident beam is rotated to {π} polarization. No unusual effects were found at the MIV edge of Th in the pseudobinary compound.