Direct evidence for electron hole depletion in La0.5Sr0.5FeO3-d upon B-site cation doping

TL;DR

This study provides direct evidence that B-site cation doping in La0.5Sr0.5FeO3 reduces electron hole concentration, significantly decreasing electrical conductivity and altering spectral weight distribution in the material.

Contribution

It demonstrates the impact of Ta doping on hole depletion and spectral changes in La0.5Sr0.5FeO3, revealing the link between electronic structure and conductivity.

Findings

Conductivity decreases by up to three orders of magnitude with Ta doping.

Spectral weight shifts from eg to t2g bands near the Fermi level.

Hole states are key to transport properties in the material.

Abstract

Partial substitution of Fe by Ta in the hole-doped La0.5Sr0.5FeO3 decreases the electric conductivity by up to three orders of magnitude. This decrease is in immediate correlation with a decrease of the electron hole concentration and a shift of the spectral weight within the O(1s)-Fe(3d) mixed states from eg bands near the Fermi energy to t2g bands. Corresponding differences in the Fe(2p) and O(1s) X-ray absorption spectra reveals formation of states with increased covalency in the initial state and states which contain O(2p) character, and that hole states are responsible for transport changes in the material. The intensity ratio of eg and t2g bands appears to be a spectral indicator for hole formation.