Valence and magnetic state of transition-metal and rare-earth ions in single-crystal multiferroics RMn2O5 (R = Y, Bi, Eu, Gd) from X-ray photoelectron spectroscopy data

Single crystals of orthorhombic multiferroics RMn2O5 (R = Y, Bi, Eu, Gd), and of hexagonal manganite YMnO3 are grown. X-ray photoelectron spectra of the core levels of the Mn, Y, Bi, Eu, Gd, and 0 atoms in multiferroics are obtained at room temperature with the ESCALAB 250 microprobe system with monochromatization of the exciting X-ray radiation. X-ray photoelectron spectra of Mn2p, Mn3s, R4s, and R4d (R = Eu, Gd) levels are assigned based on one-configuration isolated-ion approximation calculations with taking the temperature effect into account. It is shown using the photoelectron spectroscopy methods that both Mn3+ and Mn4+ ions are present in orthorhombic multiferroics, while Eu and Gd are in trivalent state. Paramagnetic moments per structural unit are calculated and compared with those determined from our spectroscopic data and with the data from other authors. (C) 2011 Elsevier B.V. All rights reserved.