# Synchrotron x-ray scattering of UN and U2N3 epitaxial films

## TL;DR

This study uses synchrotron x-ray scattering to investigate the magnetic ordering and lattice interactions in epitaxial films of UN and U2N3, revealing new insights into their magnetic structures and electron charge contributions.

## Contribution

The paper provides the first determination of antiferromagnetic ordering in U2N3 and identifies quadrupolar charge contributions involving 5f electrons, challenging previous assumptions about UN's magnetic distortion.

## Key findings

- Confirmed AF ordering of UN without expected lattice distortion.
- Determined AF wave-vector of cubic U2N3 for the first time.
- Identified quadrupolar charge contributions in U2N3 involving 5f electrons.

## Abstract

We examine the magnetic ordering of UN and of a closely related nitride, U2N3, by preparing thin epitaxial films and using synchrotron x-ray techniques. The magnetic configuration and subsequent coupling to the lattice are key features of the electronic structure. The well-known antiferromagnetic (AF) ordering of UN is confirmed, but the expected accompanying distortion at Tn is not observed. Instead, we propose that the strong magneto-elastic interaction at low temperature involves changes in the strain of the material. These strains vary as a function of the sample form. As a consequence, the accepted AF configuration of UN may be incorrect. In the case of cubic a-U2N3, no single crystals have been previously prepared, and we have determined the AF ordering wave-vector. The AF Tn is close to that previously reported. In addition, resonant diffraction methods have identified an aspherical quadrupolar charge contribution in U2N3 involving the 5f electrons; the first time this has been observed in an actinide compound.