Arsenic K-edge XANES study of REFeAsO oxypnictides

Abstract

PACS 74.70.Xa -Pnictides and chalcogenides PACS 78.70.Dm -X-ray absorption spectra PACS 71.20.-b -Electron density of states and band structure of crystalline solids Abstract -Arsenic K-edge X-ray absorption near-edge structure (XANES) spectroscopy has been used to investigate the local geometry around the pnictogen site in the REFeAsO (RE = La, Pr, Nd and Sm) oxypnictides, combined with full multiple-scattering calculations to understand different XANES features. The As K-edge XANES spectrum for the LaFeAsO is found to be significantly different from the other oxypnictides. The results suggest that interlayer order/disorder has a significant effect on the XANES features with the coupling between the FeAs and the REO spacers being important in the electronic and magnetic properties of the oxypnictides.

Effect of Ru substitution on atomic displacements in the layered SmFe1−xRuxAsOIadecola1, Joseph2, Simonelli3 et al. 2012Phys. Rev. BSelf Cite2015390View full textAdd to dashboardCite

“…The feature B ′ in the spectra of SmFe 1−x Ru x AsO 0.85 F 0.15 gets intense with increasing Ru substitution that is an indication of reduced disorder in the SmO spacer layer. In this respect, it appears that the effect of the Ru substitution in the FeAs layer is similar to the one with increasing rare-earth size [7,8] To address the question of order/disorder in the spacer layer, we have directly measured the atomic correlations by Sm L 3 -edge absorption spectroscopy. Figure 3 shows FT magnitudes of the Sm at a distance ∼ 2.3Å (main peak at ∼ 1.8Å).…”

Nanoscale structure and atomic disorder in the iron-based chalcogenides

“…Indeed, 1111-type structures have a well-defined spacer layer and the structure is less susceptible to external fields such as the strain effects due to chemical pressure or the charge density introduced through substitutions or defects. In fact, local structure studies on the 1111-type materials [22–25, 31] have shown that the interlayer atomic correlations play an important role in local structural displacements controlling the stability of the structure, unlike the 11-type and 122-type chalcogenides. The local structure studies discussed here underline the importance of the structural topology and local chemistry with the glassy nature of these complex phases being key to the exotic properties of these new superconductors.…”

Potassium doping effect on the lattice softening and electronic structure of Ba1–xKxFe2As2probed by X-ray absorption spectroscopy

“…In the doped samples the shoulder peak at 11875.7 eV of the As edge is higher with respect to that of the parent sample, and the change of the main peak probes the potassium doping effect on the 4p orbital of the As atom, in agreement with the hypothesis that holes are shared by iron and arsenic in the BaFe 2 As 2 -based system. The discrepancy in resonance peaks (11900 eV) versus doping may be due to different multiple-scattering contributions (Xu et al, 2010) describing the changed medium-range shell around the arsenic atom.…”