Electronic structure of La_1−xSr_xFeO₃

Abstract

We have investigated the electronic structure of well-characterized samples of La_1−xSr_xFeO₃ (x=0.0-0.4) by x-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy, bremsstrahlung isochromat (BI) spectroscopy, and Auger electron spectroscopy. We find systematic behavior in the occupied and unoccupied density of states reflecting changes in the electronic structure on hole doping via Sr substitution as well as providing estimates for different interaction strengths. The spectral features, particularly of the unoccupied states obtained from BI spectra, indicate the probable reason for the absence of an insulator-metal transition in this series. Analysis of the Auger spectra provides the estimates of the on-site effective Coulomb interaction strengths in Fe 3d and O 2p states. The parameter values for the bare charge-transfer energy Δ and the Fe 3d-O 2p hybridization strength t_σ for LaFeO₃ are obtained from an analysis of the Fe 2p core-level XPS in terms of a model many-body calculation. We discuss the character of the ground state in LaFeO₃ as well as the nature of the doped hole states in La_1−xSr_xFeO₃, based on these parameter values.