Valence state of manganese and iron ions in La1−xAxMnO3 (A = Ca, Sr) and Bi1−xSrxFeO3 systems from Mn2p, Mn3s, Fe2p and Fe3s X-ray photoelectron spectra. Effect of delocalization on Fe3s spectra splitting

Abstract

La1−xCaxMnO3 (x = 0.5, 0.7, 0.85, 0.95) ceramic samples are synthesized by solid state reaction method. Mn3s and Mn2p X-ray photoelectron spectra (XPS) of La1−xCaxMnO3, and Fe3s-spectra of Bi1−xSrxFeO3 (0 ≤ x ≤ 1) are measured at room temperature. Both Mn3+ and Mn4+ ions are discovered in La1−xCaxMnO3 similarly to the case of Fe3+ and Fe4+ found earlier in Bi1−xSrxFeO3 ceramics. Relative Mn3+/Mn4+ contents are determined by fitting measured Mn2p spectra with combinations of Mn2p spectra of compounds containing tri- and quadrivalent Mn ions. Relative portion of Mn4+ is shown to increase with the increase of x. Fe3s spectrum splitting in Bi1−xSrxFeO3 increases with x in contrast to the Mn3s-spectrum splitting in La1−xCaxMnO3 and La1−xSrxMnO3. Anomalous behavior of Fe3s splitting is explained in the frame of the model of partly itinerant 3d-electrons by strong effect of 3d electron delocalization on electron correlation interaction in final state of 3s photoabsorption.