Valence state of the manganese ions in mixed-valence La1-αBiβMn1+δO3±γ ceramics by Mn 2p and Mn 3s X-ray photoelectron spectra

Valence state of Mn in La1-alpha Bi beta Mn1+delta O3 +/-gamma (LBMO) ceramic samples and in orthorhombic manganates RMn2O5 (R = Y, Bi, Eu, Gd), is studied using Mn 2p- and Mn 3s-spectra. Both Mn3+ and Mn4+ ions are shown to be present in those compounds. Relative Mn3+/Mn4+ ions contents are determined by fitting experimental Mn 2p-spectra with weighted superpositions of theoretical spectra of Mn3+ and Mn4+ ions calculated in one-configuration Pauli-Fock approximation considering thermal excitations in initial state. Content of the Mn4+ ions correlates with the deviation delta in La1-alpha Bi beta Mn1+delta O3 +/- y from stoichiometry, La1-xBixMnO3. Separation of low-spin and high-spin components of Mn 3s-spectrum can be sensible to the relative content of Mn3+ and Mn4+ ions. Mn3+/Mn4+ ratios derived from Mn 2p- and from Mn 3s-spectra compare well in the case of the RMn2O5 manganates, while in the case of the LBMO ceramics the results obtained from the Mn 3s spectra are physically meaningless. Due to a complex interplay between 3d-electrons delocalization and strong many-electron effects the 3s spectra of 3d-elements may be misleading. (c) 2012 Elsevier B.V. All rights reserved.