Lattice anomalies in the FeAs$_{\rm 4}$ tetrahedra of the NdFeAsO$_{\rm 0.85}$ superconductor that disappear at T$_{\rm c}$

TL;DR

This study reveals temperature-dependent lattice anomalies in NdFeAsO$_{0.85}$ superconductors, especially in FeAs$_4$ tetrahedra, which correlate with the superconducting transition at T$_c$.

Contribution

It uncovers structural modifications in FeAs$_4$ tetrahedra linked to superconductivity, observed through high-resolution synchrotron X-ray diffraction.

Findings

Structural anomalies start around 180K.

Anomalies in FeAs$_4$ tetrahedra disappear at T$_c$.

Minor changes in Nd-O charge reservoir layer.

Abstract

High resolution synchrotron X-ray powder diffraction (SXRPD) was used to study the temperature dependence of the oxygen deficient NdFeAsO$_{0.85}$ superconducting compound. By employing a dense temperature sampling we have managed to reveal unnoticed structural modifications that start around $\sim$180K, and disappear at the transition temperature. The data show minor changes of the structural characteristics in the Nd-O charge reservoir layer while in the superconducting Fe-As layer the FeAs$_{4}$ tetrahedron shows gradual modifications below $\sim$180K, which suddenly disappear at T$_{\rm c}$ strongly indicating a connection with superconductivity.