Pre-edges in oxygen (1s) x-ray absorption spectra: A spectral indicator for electron hole depletion and transport blocking in iron perovskites

The e(g)up arrow/(t(2g)down arrow+e(g)down arrow) band ratio in cation-substituted La-Fe oxides is identified in O (1s) x-ray absorption spectra as a linear spectral indicator for conducting electron holes. The t(2g)down arrow and e(g)down arrow bands act as a conductivity inhibitor by ferromagnetic double exchange coupling on the e(g)up arrow electron. Disorder induced by substitution appears to modulate the hole conduction such that an exponential relation is found between the conductivity and the e(g)up arrow/(t(2g)down arrow+e(g)down arrow) ratio and hole concentration. The quantitative correlation of conductivity and x-ray absorption spectra from heterovalent-substituted LaFeO3 lets substitution-driven metal insulator transitions appear in a new light.