title: CsCoO(2) featuring a novel polyoxocobaltate(III) anion based on a two-dimensional architecture of interconnected tetrahedra.
abstract: CsCoO2 has been prepared along the azide/nitrate route as a reddish black microcrystalline powder at 833 K. According to single crystal X-ray analysis, the title compound crystallizes as a structure type novel for oxides (Cmca,Z = 8, a = 5.9841(1) Å, b = 12.2458(2) Å, c = 8.2650(1) Å). The prominent features of the structure are pairs of edge-linked CoO4 tetrahedra to form Co2O6 dimers, which are condensed by vertex sharing of the four remaining unshared oxygen atoms to form a two-dimensional architecture of a puckered polyoxyanion spreading along (010). Upon cooling, CsCoO2 undergoes a virtually second order phase transition at ∼100 K leading to a systematic dovetail twin (C2/c). The magnetic susceptibilities show the dominance of antiferromagnetic interactions with a remarkably high Néel temperature of 430 K indicating a very strong antiferromagnetic superexchange between the Co(3+) ions. The spin-exchange for CsCoO2 can be addressed as a set of strongly antiferromagnetically coupled quasi-one-dimensional chains, which are weakly coupled to neighboring chains by ferromagnetic interaction.
authors.affiliation: Max Planck Institute for Solid State Research , Heisenbergstr.1, 70569 Stuttgart, Germany.
authors.forename: Naveed Zafar
authors.initials: NZ
authors.lastname: Ali
authors.forename: Jürgen
authors.initials: J
authors.lastname: Nuss
authors.forename: Reinhard K
authors.initials: RK
authors.lastname: Kremer
authors.forename: Martin
authors.initials: M
authors.lastname: Jansen