Tetragonal to Orthorhombic Transition of GdFeAsO Studied by Single-Crystal Synchrotron X-Ray Diffraction

TL;DR

This study investigates the structural phase transition of GdFeAsO from tetragonal to orthorhombic using single-crystal synchrotron X-ray diffraction, revealing twin domains, lattice distortions, and fluctuations above the transition temperature.

Contribution

It introduces a detailed analysis of the phase transition in GdFeAsO, including a model for lattice distortion and detection of fluctuations above the transition temperature.

Findings

Identification of twin domain orientations below transition

Quantification of lattice distortion from diffraction data

Detection of structural fluctuations above transition temperature

Abstract

A study of the tetragonal to orthorhombic phase transition of GdFeAsO is presented. Planes of the reciprocal space were reconstructed form single-crystal synchrotron X-ray diffraction data. By cooling below the structural transition temperature splitting of the Bragg reflections was observed corresponding to four different twin domain orientations. A model was developed to quantify the distortion of the lattice from the position of the splitted reflections relative to each other. Constrained 2D-Cauchy fits of several splitted reflections provided positions of the reflections. The influence of the structural distortion was detectable already above the structural transition temperature hinting at fluctuations in the tetragonal phase.