Effect of Ru susbstitution on atomic displacements in the layered SmFe_{1-x}Ru_xAsO_{0.85}F_{0.15} superconductor

TL;DR

This study investigates how Ru substitution affects local atomic structures in the layered superconductor SmFe_{1-x}Ru_xAsO_{0.85}F_{0.15} using x-ray absorption spectroscopy, revealing bond length changes and disorder confined mainly to the FeAs layer.

Contribution

It provides new insights into the local structural changes and disorder caused by Ru substitution in layered iron-based superconductors, emphasizing the role of spacer layers.

Findings

Ru substitution causes longer Ru-As bonds compared to Fe-As bonds.

Disorder is mainly confined to the FeAs layer, with the spacer layer remaining ordered.

Coupling between the FeAs and spacer layers influences electronic properties.

Abstract

The effect of Ru substitution on the local structure of layered SmFe$_{1-x}$Ru$_x$AsO$_{0.85}$F$_{0.15}$ superconductor has been studied by As $K$- and Sm $L_3$ - edges x-ray-absorption spectroscopy. The extended x-ray-absorption fine-structure measurements reveal distinct Fe-As and Ru-As bondlengths in the Ru substituted samples with the latter being $\sim$0.03 \AA\ longer. Local disorder induced by the Ru substitution is mainly confined to the FeAs layer while the SmO spacer layer sustains a relative order, consistent with the x-ray-absorption near-edge structure spectra. The results suggest that, in addition to the order/disorder in the active active iron-arsenide layer, its coupling to the rare-earth\textminus oxygen spacer layer needs to be considered for describing the electronic properties of these layered superconductors.