Melting of chiral order in terbium manganate (TbMnO3) observed with resonant x-ray Bragg diffraction

TL;DR

This study uses resonant x-ray Bragg diffraction to directly observe the temperature-dependent melting of chiral magnetic order in terbium manganate, revealing differences in harmonic behavior and underlying mechanisms.

Contribution

It provides the first direct observation of chiral order melting in TbMnO3 using resonant x-ray diffraction, elucidating the temperature dependence and harmonic differences.

Findings

Chiral order melts with temperature, observed via first and second harmonics.

Differences in temperature dependence explained by harmonic-specific mechanisms.

Extensive azimuthal-angle studies support the observations.

Abstract

Resonant Bragg diffraction of soft, circularly polarized x-rays has been used to observe directly the temperature dependence of chiral-order melting in a motif of Mn ions in terbium manganate. The underlying mechanism uses the b-axis component of a cycloid, which vanishes outside the polar phase. Melting is witnessed by the first and second harmonics of a cycloid, and we explain why the observed temperature dependence is different in the two harmonics. Our direct observation of melting is supported by a solid foundation of evidence, derived from extensive studies of the azimuthal-angle dependence of intensities with both linear and circular polarization.