X-ray absorption spectroscopy measurement on the LaO1-xFxFeAs system

TL;DR

This study uses X-ray absorption spectroscopy to analyze electronic and structural changes in LaO1-xFxFeAs superconductors, revealing charge transfer mechanisms and local atomic environments related to F doping.

Contribution

It provides detailed spectroscopic evidence of charge transfer and local structure modifications in LaO1-xFxFeAs, advancing understanding of its electronic properties.

Findings

F substitution causes electron charge transfer to Fe sites.

Spectral features indicate Fe-d orbital involvement near the Fermi level.

As K-edge remains insensitive to doping, consistent with band structure calculations.

Abstract

Results of Fe K-, As K-, and La L3-edge x-ray absorption near edge structure (XANES) measurements on LaO1-xFxFeAs compounds are presented. The Fe K- edge exhibits a chemical shift to lower energy, near edge feature modifications, and pre-edge feature suppression as a result of F substitution for O. The former two changes provide evidence of electron charge transfer to the Fe sites and the latter directly supports the delivery of this charge into the Fe-3d orbitals. The As K- edge measurements show spectral structures typical of compounds with planes of transition-metal tetrahedrally coordinated to p-block elements as is illustrated by comparison to other such materials. The insensitivity of the As-K edge to doping, along with the strong Fe-K doping response, is consistent with band structure calculations showing essentially pure Fe-d character near the Fermi energy in these materials. The energy of the continuum resonance feature above the La-L3 edge is shown to be quantitatively consistent with the reported La-O inter-atomic separation and with other oxide compounds containing rare earth elements.