X-ray photoelectron study of temperature effect on the valence state of Mn in single crystal YMnO3

Temperature effect on the valence state of Mn in single crystal YMnO3 is studied using Y3d-, Mn2p-, and O1s-spectra. Mn2p- spectra of Mn3+ and Mn4+ ions at various temperatures are calculated in an isolated ion approximation. Original crystal at room temperature was found to contain only Mn3+ ions, whereas after the temperature treatment (heating in vacuum up to 593 K, cooling down back to room temperature and consecutive heating to a given temperature), Mn4+ ions were detected in the crystal. Relative Mn4+/Mn3+ abundances at various final temperatures are determined by fitting the experimental Mn2p spectra with the superposition of theoretical spectra from Mn3+ and Mn4+ ions, and from relative intensities of O1s-spectrum components. Concentration of Mn4+ ions correlates with the distortion of the crystal structure reflected in overstoichiometry of manganese and understoichiometry of oxygen.