Magnetic properties of ruthenium dioxide (RuO2) and charge-magnetic interference in Bragg diffraction of circularly polarized x-rays

TL;DR

This paper investigates the magnetic properties of RuO2 using x-ray Bragg diffraction, exploring magnetic motifs and charge-magnetic interference effects, and analyzing existing diffraction data to understand its antiferromagnetic structure.

Contribution

It introduces specific magnetic motifs compatible with RuO2's symmetry and analyzes charge-magnetic interference effects in x-ray diffraction, providing insights into its antiferromagnetic order.

Findings

Charge-magnetic interference is common in RuO2 diffraction.

Conditions for observed diffraction phenomena are identified.

Existing data analyzed suggests certain magnetic motifs are incompatible.

Abstract

Rutile-type RuO2 likely supports a simple antiferromagnetic structure which can be verified by x-ray Bragg diffraction. Three magnetic motifs that do not break translation symmetry are explored in calculations of amplitudes suitable for diffraction enhanced by tuning the primary x-ray energy to a ruthenium atomic resonance. Coupling to x-ray helicity through a charge-magnetic interference is common to all motifs, together with magnetic and charge intensities in quadrature in the rotated channel of polarization. Necessary conditions for these diffraction phenomena are a centrosymmetric crystal structure, null magnetic propagation vector, and absence of a linear magnetoelectric effect. Published x-ray diffraction data for RuO2 was analysed by the authors against a magnetic motif that does not satisfy the conditions. A polarized neutron study of antiferromagnetic domains can be achieved with a sample that meets the stated crystal and magnetic symmetries.