An unusual high-spin ground state of Co3+ in octahedral coordination in brownmillerite-type cobalt oxide

S. Ya Istomin, O. A. Tyablikov, S. M. Kazakov, E. V. Antipov, A. I. Kurbakov, A. A. Tsirlin, N. Hollmann, Y. Y. Chin, H. J. Lin, C. T. Chen, A. Tanaka, L. H. Tjeng, Z. Hu

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34 Citations (Scopus)

Abstract

The crystal and magnetic structures of brownmillerite-like Sr2Co1.2Ga0.8O5 with a stable Co3+ oxidation state at both octahedral and tetrahedral sites are refined using neutron powder diffraction data collected at 2 K (S.G. Icmm, a = 5.6148(6) Å, b = 15.702(2) Å, c = 5.4543(6) Å; Rwp = 0.0339, Rp = 0.0443, χ2 = 0.775). The very large tetragonal distortion of CoO6 octahedra (1.9591(4) Å for Co-Oeq and 2.257(6) Å for Co-Oax) could be beneficial for the stabilization of the long-sought intermediate-spin state of Co3+ in perovskite-type oxides. However, the large magnetic moment of octahedral Co3+ (3.82(7)μB) indicates the conventional high-spin state of Co3+ ions, which is further supported by the results of a combined theoretical and experimental soft X-ray absorption spectroscopy study at the Co-L2,3 edges on Sr2Co1.2Ga0.8O5. A high-spin ground state of Co3+ in Sr2Co1.2Ga0.8O5 resulted in much lower in comparison with a LaCoO3 linear thermal expansion coefficient of 13.1 ppm K-1 (298-1073 K) determined from high-temperature X-ray powder diffraction data collected in air.

Original languageEnglish
Pages (from-to)10708-10713
Number of pages6
JournalDalton Transactions
Volume44
Issue number23
DOIs
Publication statusPublished - 21 Jun 2015
Externally publishedYes

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