BaSn6Co6O19—A novel frustrated antiferromagnet with the magnetoplumbite type structure

Abstract: Single crystals of the novel compound BaSn6Co6O19 with maximum width 1mm and thickness around 0.05mm were grown from a barium chloride flux. The composition was determined from refinements of single crystal X-ray diffraction data and microprobe analysis. BaSn6Co6O19 crystallizes in the magnetoplumbite type structure (hexagonal, space group P63/mmc, a=6.0940(1)Å, c=23.9633(5)Å, V=770.69Å3, Z=2). A significant disorder is generated by random occupation of two octahedrally coordinated crystallographic sites with Co2+ and Sn4+ ions, while further sites are exclusively occupied by either Co2+ (tetrahedrally coordinated) or Sn4+ (octahedrally coordinated). One site with mixed occupation realizes the topology of a kagome net. The temperature dependence of the magnetic susceptibility for a single crystal BaSn6Co6O19 reveals a low temperature antiferromagnetic order at T N =14K. A relatively large value of frustration factor f //= |Θ W//|/T N ≈26 and f ⊥=|Θ W⊥|/T N ≈12 implies a frustrated antiferromagnetism. [Copyright &y& Elsevier]