LAUSR

A new compound with one-dimensional spin chains, Ba9Co3Se15, was synthesized under high pressure and high temperature conditions and systematically characterized via structural, transport and magnetic measurements. Ba9Co3Se15 crystallizes in a hexagonal structure with the space group P-6c2 (No.188) and lattice constants of a=b=9.6765 Å and c=18.9562 Å. The structure consists of trimeric face-sharing octahedral CoSe6 chains, which are arranged in a triangular lattice in the ab-plane and separated by Ba atoms. The distance of nearest neighbor of CoSe6 chains is very large, given by the lattice constant a=9.6765 Å. The Weiss temperature T θ associated with the intra-chain coupling strength is about -346 K. However, no long-range magnetic order but a spin glass transition at~3 K has been observed. Our results indicate that the spin glass behavior in Ba9Co3Se15 mainly arises from the magnetic frustration due to the geometrically frustrated triangular lattice.