Resonant X-Ray Scattering on the M-Edge Spectra from Triple-k Structure Phase in U_{0.75}Np_{0.25}O_{2} and UO_{2}

TL;DR

This paper develops a theoretical model for resonant x-ray scattering spectra in uranium-neptunium oxides, successfully matching experimental data and revealing the nature of spectral features related to magnetic ordering.

Contribution

The authors derive a spherical symmetry-based expression for the scattering amplitude and demonstrate its effectiveness in explaining experimental spectra of UO₂ and U₀.₇₅Np₀.₂₅O₂.

Findings

Spectra near U and Np M₄ edges match experimental results.

- and -channel spectra show quadrupole and dipole characteristics.

The model confirms the spectral features are consistent with magnetic ordering.

Abstract

We derive an expression for the scattering amplitude of resonant x-ray scattering under the assumption that the Hamiltonian describing the intermediate state preserves spherical symmetry. On the basis of this expression, we demonstrate that the energy profile of the RXS spectra expected near U and Np M_4 edges from the triple-k antiferromagnetic ordering phase in UO_{2} and U_{0.75}Np_{0.25}O_{2} agree well with those from the experiments. We demonstrate that the spectra in the \sigma-\sigma' and \sigma-\pi' channels exhibit quadrupole and dipole natures, respectively.