Electronic structure of double perovskiteA2FeReO6 (A = Ba and Ca): interplay between spin–orbit interaction, electron correlation, and latticedistortion

Abstract

We have investigated the electronic structure of double perovskites,Ba2FeReO6 (metallic)and Ca2FeReO6 (insulating) using optical and x-ray absorption spectroscopy. By comparing the experimentalresults with the density functional theory calculations, we found that the electronic structure ofBa2FeReO6 could bedetermined from the interaction of the electron correlation and spin–orbit coupling. On the other hand,for Ca2FeReO6, the lattice distortion and electron correlation are important indetermining the electronic structure. Additionally, the insulating gap inCa2FeReO6 is realized by the spin–orbit coupling. Our work shows that the subtle interplay of thespin–orbit interaction, electron correlation, and lattice distortion should be taken intoaccount to understand the electronic structure of the 5d transition metal oxides.