Anisotropic magnetoelastic coupling in single-crystalline CeFeAsO as seen via high-resolution x-ray diffraction

TL;DR

This study uses high-resolution x-ray diffraction to reveal anisotropic magnetoelastic coupling in CeFeAsO, showing how magnetic order influences lattice correlations and suggesting significant fluctuations above the structural transition.

Contribution

First direct observation of anisotropic charge correlation lengths linked to magnetoelastic coupling in CeFeAsO using synchrotron x-ray diffraction.

Findings

Anisotropic in-plane charge correlations below the AFM transition.

Shorter in-plane correlations above the orthorhombic-to-tetragonal transition.

Evidence of strong O-T fluctuations possibly driven by spin fluctuations.

Abstract

Single-crystal synchrotron x-ray diffraction studies of CeFeAsO reveal strong anisotropy in the charge correlation lengths along or perpendicular to the in-plane antiferromagnetic (AFM) wave-vector at low temperatures, indicating an anisotropic two-dimensional magnetoelastic coupling. The high-resolution setup allows to distinctly monitor each of the twin domains by virtue of a finite misfit angle between them that follows the order parameter. In addition, we find that the in-plane correlations, above the orthorhombic (O)-to-tetragonal (T) transition, are shorter than those in each of the domains in the AFM phase, indicating a distribution of the in-plane lattice constants. This strongly suggests that the phase above the structural O-to-T transition is virtually T with strong O-T fluctuations that are probably induced by spin fluctuations.