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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) angstrom, b = 12.2458(2) angstrom, c = 8.2650(1) angstrom). 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 similar to 100 K leading to a systematic dovetail twin (C2/c). The magnetic susceptibilities show the dominance of antiferromagnetic interactions with a remarkably high Neel temperature of 430 K indicating a very strong antiferromagnetic superexchange between the Co3+ 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.