Potassium doping effect on the lattice softening and electronic structure of Ba_1-xK_xFe₂As₂ probed by X-ray absorption spectroscopy

Ba_1-xK_xFe₂As₂ superconducting samples (x = 0, 0.2, 0.4, 0.5) were synthesized by the solid-state reaction method. In this contribution the doping effect of potassium on the lattice dynamics in this newly discovered Ba_1-xK_xFe₂As₂ superconductor has been investigated by extended X-ray absorption fine-structure spectroscopy. The analysis shows that with potassium doping an increased disorder in the iron layers is mainly related to the softening of the Fe-Fe bond. Information about the electronic structure of these materials has also been obtained by looking at the X-ray absorption near-edge structure spectra that point out the presence of holes in the Fe-3d/As-4p hybridized orbital of the BaFe₂As₂-based system.