Electronic structures and spin states of BaFe2As2 and SrFe2As2 probed by x-ray emission spectroscopy at Fe and As K -absorption edges

Abstract

Electronic structures of electron- and hole-doped ${\mathrm{BaFe}}_{2}{\mathrm{As}}_{2}$ and nondoped ${\mathrm{SrFe}}_{2}{\mathrm{As}}_{2}$ have been studied systematically by x-ray emission spectroscopy at Fe and As $K$-absorption edges. The electron and hole doping causes slight increase of the integrated absolute difference (IAD) values of the Fe $K\ensuremath{\beta}$ x-ray emission spectra which correlate to the local magnetic moment. Pressure decreases the IAD values and local magnetic moment, and induces the lower-spin states in these compounds. The pre-edge peak intensity of the XAS spectra at the Fe $K$-absorption edge increases with pressure in both compounds. This indicates an increase of the Fe $3d$--As $4p$ hybridization. It was found that pressure induced a discontinuous increase of the prepeak intensity of the PFY-XAS spectra at the As $K$-absorption edge at low pressures in the ${\mathrm{BaFe}}_{2}{\mathrm{As}}_{2}$ systems. Our results may suggest that the Fe $3d$--As $4p$ hybridization plays a key role in suppressing the AFM order by the doping or pressure and fluctuation of the local magnetic moment and the electron-electron correlation may also play a role on the physical properties of the iron superconductors.