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

• DOI: 10.1039/c4dt03670k
• Publication Date: 2015-02-02T12:02:29Z
• Authors: 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
• Keywords: Brownmillerite; Spin states; Cobalt oxide

The crystal and magnetic structures of brownmillerite-like Sr(2)Co(1.2)Ga(0.8)O(5) with a stable Co(3+) oxidation state at both octahedral tetrahedral sites are refined using neutron powder diffraction data collected 2 K (S.G. Icmm, = 5.6148(6) Å, b 15.702(2) c 5.4543(6) Å; R(wp) 0.0339, R(p) 0.0443, χ(2) 0.775). very large tetragonal distortion CoO(6) octahedra (1.9591(4) Å for Co-O(eq) 2.257(6) Co-O(ax)) could be beneficial the stabilization long-sought intermediate-spin in perovskite-type oxides. However, moment (3.82(7)μ(B)) indicates conventional high-spin ions, which is further supported by results combined theoretical experimental soft X-ray absorption spectroscopy study Co-L(2,3) edges on Sr(2)Co(1.2)Ga(0.8)O(5). A ground resulted much lower comparison LaCoO(3) linear thermal expansion coefficient 13.1 ppm K(-1) (298-1073 K) determined from high-temperature air.