Unusual high-spin ground state of Co3+ in octahedral coordination in brownmillerite-type cobalt oxideстатья
Статья опубликована в высокорейтинговом журнале
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Статья опубликована в журнале из списка Web of Science и/или Scopus
Дата последнего поиска статьи во внешних источниках: 19 сентября 2015 г.
Аннотация:The crystal and magnetic structures of brownmillerite-like Sr2Co1.2Ga0.8O5 with a stable Co3+ oxidation state at both octahedral and tetrahedral sites were 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) Ǻ for Co-Oeq and 2.257(6) Ǻ 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 combined theoretical and experimental soft x-ray absorption spectroscopy study at the Co-L2,3 edges on Sr2Co1.2Ga0.8O5. High-spin ground state of Co3+ in Sr2Co1.2Ga0.8O5 resulted in much lower in comparison with LaCoO3 linear thermal expansion coefficient of 13.1 ppm K-1 (298-1073K) determined from high-temperature X-ray powder diffraction data collected in air.