The new nickel tellurite chloride compound Ni15Te12O34Cl10 - synthesis, crystal structure and magnetic properties

A new nickel tellurite oxohalide, Ni15Te12O34Cl10, has been prepared by chemical vapour transport reactions and the crystal structure was determined by single-crystal X-ray diffraction. The compound crystallizes in the triclinic space group P (1) over bar with the pseudomonoclinic cell parameters a = 10.3248(6) angstrom, b = 10.3249(6) angstrom, c = 11.6460(8) angstrom, alpha = 73.782(6)degrees, beta = 73.782(6)degrees, gamma = 63.51(2)degrees, Z = 1, R-1 = 0.0264. The Ni2+ ions have octahedral [NiO6] and [NiO4Cl2] coordinations, the Te4+ ions have one-sided [TeO3] and [TeO4] coordinations. The crystal structure can be described as consisting of nickel oxide ribbons extending along (001) that are connected by corner sharing [TeO3] and [TeO4] groups to build the open framework structure. The chlorine atoms and the Te-lone pairs are facing voids in the oxide framework. The new compound undergoes two successive antiferromagnetic ordering transitions at similar to 50 K and similar to 10 K. The Curie-Weiss temperature obtained from detailed evaluation of the high-temperature magnetic susceptibilities is positive indicating predominant ferromagnetic superexchange interactions between the Ni magnetic moments.