Tetragonal to orthorhombic phase transition in SmFeAsO: a synchrotron powder diffraction investigation

TL;DR

This study investigates the structural phase transition in SmFeAsO from tetragonal to orthorhombic using synchrotron powder diffraction, revealing the transition occurs around 140 K with detailed structural insights.

Contribution

It provides detailed high-resolution diffraction data showing the phase transition and clarifies the low-temperature structure of SmFeAsO.

Findings

Tetragonal to orthorhombic transition at ~140 K

High-resolution synchrotron diffraction confirms structural change

Refinement indicates orthorhombic symmetry at low temperature

Abstract

The crystal structure of SmFeAsO has been investigated by means of Rietveld refinement of high resolution synchrotron powder diffraction data collected at 300 K and 100 K. The compound crystallizes in the tetragonal P4/nmm space group at 300 K and in the orthorhombic Cmma space group at 100 K; attempts to refine the low temperature data in the monoclinic P112/n space group diverged. On the basis of both resistive and magnetic analyses the tetragonal to orthorhombic phase transition can be located at T about 140 K.