Temperature dependent local structure of NdFeAsO1-xFx system using arsenic K-edge extended x-ray absorption fine structure

TL;DR

This study investigates how local Fe-As bond structures in NdFeAsO$_{1-x}$F$_{x}$ superconductors vary with temperature, revealing differences in lattice dynamics between superconducting and non-superconducting samples.

Contribution

It provides new insights into the local structural dynamics of NdFeAsO$_{1-x}$F$_{x}$ across different doping levels and temperatures using arsenic K-edge EXAFS measurements.

Findings

Fe-As bond length is weakly affected by temperature and F-doping.

Different Einstein-temperatures describe lattice dynamics in superconducting vs. non-superconducting samples.

Distinct local Fe-As lattice dynamics are observed in superconducting and non-superconducting systems.

Abstract

Local structure of NdFeAsO$_{1-x}$F$_{x}$ ($x$=0.0, 0.05, 0.15 and 0.18) high temperature iron pnictide superconductor system is studied using arsenic $K$-edge extended x-ray absorption fine structure measurements as a function of temperature. Fe-As bondlength shows only a weak temperature and F-substitution dependence, consistent with the strong covalent nature of this bond. The temperature dependence of the mean-square relative-displacements of the Fe-As bondlength are well described by the correlated-Einstein model for all the samples, but with different Einstein-temperatures for the superconducting and non-superconducting samples. The results indicate distinct local Fe-As lattice dynamics in the superconducting and non-superconducting iron-pnictide systems.