Widely Spaced Planes of Magnetic Dimers in the Ba6Y2Rh2Ti2O17-�� Hexagonal Perovskite

We report the synthesis and initial characterization of Ba6Y2Rh2Ti2O17-��, a previously unreported material with a hexagonal symmetry structure. Face-sharing RhO6 octahedra form triangular planes of Rh2O9 dimers that are widely separated in the perpendicular direction. The material displays a small effective magnetic moment, due to the Rh ions present, and a negative Curie-Weiss temperature. The charge transport and optical band gaps are very similar, near 0.16 eV. A large upturn in the heat capacity at temperatures below 1 K, suppressed by applied magnetic fields larger than {��0H = 2 Tesla, is observed. A large T-linear term in the specific heat (��=166 mJ/mol f.u-K2) is seen, although the material is insulating at low temperatures. These results suggest the possibility of a spin liquid ground state in this material.
5 figures, 2 tables