Electronic structure of hole-doped Sr1+xLa1-xFeO4 studied by UPS and XAS.

Abstract

The electronic structure of ${\mathrm{K}}_{2}$${\mathrm{NiF}}_{4}$-type ${\mathrm{Sr}}_{1+\mathit{x}}$${\mathrm{La}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{FeO}}_{4}$ compounds (0\ensuremath{\le}x\ensuremath{\le}0.3) was studied by ultraviolet-photoemission and x-ray-absorption spectroscopies. Resonant photoemission measurements demonstrated that although the satellite feature of ${\mathrm{Sr}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{La}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{FeO}}_{4}$ was attributed to ${\mathit{d}}^{4}$ final states, the whole valence band was constructed from well mixed Fe 3d and O 2p states. It was suggested that the parent ${\mathrm{Sr}}_{1+\mathit{x}}$${\mathrm{La}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{FeO}}_{4}$ compound is intermediate between Mott-Hubbard and charge-transfer insulators. O K-edge and Fe K-edge x-ray-absorption measurements showed that hole bands composed of O 2p and Fe 3d character were formed in the original conduction-band edge upon hole doping, while the valence-band structure obtained by nonresonant photoemission measurements did not change. Changes in the electrical and magnetic properties were correlated with those in electronic structure.