Pressure and chemical substitution effects in the local atomic structure of BaFe2As2

TL;DR

This study investigates how pressure and chemical substitutions (K and Co) affect the local atomic structure of BaFe2As2 superconductors using EXAFS, revealing slight bond length reductions linked to magnetic and superconducting properties.

Contribution

It provides detailed insights into how pressure and chemical doping influence the local atomic structure and magnetic moments in BaFe2As2, a key superconductor.

Findings

As-Fe bond length decreases slightly with substitutions and pressure.

The As-Fe bond is compressible with a specific bulk modulus.

Bond contraction correlates with reduction in local Fe magnetic moments.

Abstract

The effects of K and Co substitutions and quasi-hydrostatic applied pressure (P<9 GPa) in the local atomic structure of BaFe2As2, Ba(Fe{0.937}Co{0.063})2As2 and Ba{0.85}K{0.15}Fe2As2 superconductors were investigated by extended x-ray absorption fine structure (EXAFS) measurements in the As K absorption edge. The As-Fe bond length is found to be slightly reduced (<~ 0.01 Angstroms) by both Co and K substitutions, without any observable increment in the corresponding Debye Waller factor. Also, this bond is shown to be compressible (k = 3.3(3)x10^{-3} GPa^{-1}). The observed contractions of As-Fe bond under pressure and chemical substitutions are likely related with a reduction of the local Fe magnetic moments, and should be an important tuning parameter in the phase diagrams of the Fe-based superconductors.