Comments on diffraction experiments at high-field on uranium dioxide in the ordered state

TL;DR

This paper critically analyzes diffraction data on uranium dioxide, revealing a field-induced rhombohedral distortion and multiple domains, and provides a quantitative explanation based on simple crystallographic arguments.

Contribution

It offers a corrected interpretation of diffraction data, identifying a rhombohedral distortion and domain effects in uranium dioxide under high magnetic fields.

Findings

Identification of rhombohedral distortion in uranium dioxide

Explanation of multiple diffraction peaks and their field dependence

Quantitative analysis based on atomic volume conservation

Abstract

D. J. Antonio et al. report an x-ray diffraction experiment on uranium dioxide at high-magnetic field and low temperature. The authors have apparently not realized that the diffraction data actually shows unambiguously the presence of a rhombohedral distortion induced by the field at low temperature and the presence of more than one domain. Our note correctly analyses their data. The crystallographic analysis we perform is based on simple arguments with respect to plane spacings in slightly distorted cubic materials. Similar studies have been reported in many materials over the last 50 years. Our analysis explains quantitatively the observations, the presence of the two peaks (the appearance of which the authors regard as unexpected) and their different variations with respect to the applied field, which is a simple consequence of the conservation of atomic volume.