The two-band model of the LaCoO₃semiconductor-metal transition: a spectroscopic evaluation

Abstract

Co K-edge near-edge X-ray absorption spectra are reported for RECoO3 (RE=Y, Ho, Gd, Nd) at 300 K and for LaCoO3 in the temperature range (140<or=T<or=830 K). The pre-edge structure associated with Co 1s to 3d excitation is found to be comparable for all the cobaltates at room temperature, consistent with the proposed similarity of their electronic structure. For LaCoO3, temperature-dependent changes are observed in the pre-edge structure. These data, when compared with previously published UV photoelectron spectra and calculated density of states, are found to be consistent with a proposed model for the higher-order semiconductor-to-metal transition of LaCoO3 which involves increased sigma *- pi * band overlap with temperature.