title: Stability of the cationic oxidation states in Pr(0.50)Sr(0.50)CoO₃ across the magnetostructural transition by X-ray absorption spectroscopy.
abstract: The possible hybridization between Pr 4f and O 2p states in Pr(0.50)Sr(0.50)CoO3 at low temperatures was investigated by different techniques. First, using neutron diffraction we observed a strong contraction of some Pr-O bonds across the magnetostructural transition at T(S) ∼ 120 K. In contrast to the Pr-O bond contraction in Pr(0.50)Sr(0.50)CoO3, this transition is not accompanied by the appearance of Pr(4+) at low temperatures, as revealed by X-ray absorption spectroscopy at Pr edges. Despite the fact that a Pr valence change is not the mechanism that drives this transition, we point out an active participation of Pr ions across T(S). Moreover, Co L(2,3)-edge and O K edge X-ray absorption spectra did not reveal any spin-state variation and showed the stability of the average formal valence of cobalt ions. The large density of empty t(2g) symmetry states in the studied thermal range does not suggest the occurrence of Co(3+) in a pure low-spin state. The overall metallic behavior agrees with our findings. We propose a mixture of Co(3+) ions in the intermediate-spin or high-spin configuration together with Co(4+) ions in a low- or intermediate-spin state.
authors.affiliation: Institut de Ciència de Materials de Barcelona, ICMAB-CSIC, Campus universitari de Bellaterra , E-08193 Bellaterra, Barcelona, Spain.
authors.forename: Jessica
authors.initials: J
authors.lastname: Padilla-Pantoja
authors.forename: Javier
authors.initials: J
authors.lastname: Herrero-Martín
authors.forename: Pierluigi
authors.initials: P
authors.lastname: Gargiani
authors.forename: S Manuel
authors.initials: SM
authors.lastname: Valvidares
authors.forename: Vera
authors.initials: V
authors.lastname: Cuartero
authors.forename: Kurt
authors.initials: K
authors.lastname: Kummer
authors.forename: Oliver
authors.initials: O
authors.lastname: Watson
authors.forename: Nicholas B
authors.initials: NB
authors.lastname: Brookes
authors.forename: José Luis
authors.initials: JL
authors.lastname: García-Muñoz