X-ray absorption spectroscopic study on A2FeReO6 double perovskites

The electronic and geometrical local structures of Re-based double perovskites, A2FeReO6 (A = Ba, Sr, Ca), have been probed by using x-ray absorption spectroscopy at the Fe K- and Re L1,2,3-edges. The measurements have shown a significant sensitivity of the Fe K- and Re L1-edges to the Fe and Re valences, respectively. EXAFS and XANES spectra are consistent with the presence of nominal Fe3+ and Re5+ except for the Ba-based compounds. Ba strongly affects the charge distribution on the Fe-O-Re sublattice, leading to mixed valence Fe3-δ ions. We have explained our results in the frame of recent band models. In this way, pre-peak features at the Re L1-edge can be used as an indicator of the degree of pd hybridization existing in these systems