Chiral properties of hematite ({\alpha}-Fe2O3) inferred from resonant Bragg diffraction using circularly polarized x-rays

TL;DR

This study reveals the chiral magnetic properties of hematite ({e2O3) in different phases using resonant Bragg diffraction with circularly polarized x-rays, identifying distinct multipole contributions and orbital angular momentum behaviors.

Contribution

It demonstrates the use of circularly polarized x-ray diffraction to characterize chiral magnetic multipoles in hematite across the Morin transition, providing new insights into its magnetic structure.

Findings

High-temperature canted phase characterized by magneto-electric multipoles including an anapole.

Low-temperature collinear phase supports both parity-odd and parity-even multipoles, with orbital angular momentum present.

Experimental intensities match atomic model predictions based on known chemical and magnetic structures.

Abstract

Chiral properties of the two phases - collinear motif (below Morin transition temperature, TM=250 K) and canted motif (above TM) - of magnetically ordered hematite ({\alpha}-Fe2O3) have been identified in single crystal resonant x-ray Bragg diffraction, using circular polarized incident x-rays tuned near the iron K-edge. Magneto-electric multipoles, including an anapole, fully characterize the high-temperature canted phase, whereas the low-temperature collinear phase supports both parity-odd and parity-even multipoles that are time-odd. Orbital angular momentum accompanies the collinear motif, while it is conspicuously absent with the canted motif. Intensities have been successfully confronted with analytic expressions derived from an atomic model fully compliant with chemical and magnetic structures. Values of Fe atomic multipoles previously derived from independent experimental data, are shown to be completely trustworthy.