Temperature-dependent local structure ofNdFeAsO1 − xFx system using arsenic K-edge extended x-ray absorption fine structure

Abstract

Local structure of NdFeAsO1 − xFx (x = 0.0, 0.05, 0.15 and 0.18) high temperature iron-pnictide superconductor system is studiedusing arsenic K-edge extended x-ray absorption fine structure measurements as afunction of temperature. Fe–As bond length shows only a weak temperature andF-substitution dependence, consistent with the strong covalent nature of this bond.The temperature dependence of the mean square relative displacements of theFe–As bond length are well described by the correlated Einstein model for all thesamples, but with different Einstein temperatures for the superconducting andnon-superconducting samples. The results indicate distinct local Fe–As latticedynamics in the superconducting and non-superconducting iron-pnictide systems.