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High purity polycrystalline Na0.5La0.5RuO3 was synthesized by a solid state method, and its properties were studied by magnetic susceptibility, heat capacity and resistivity measurements. We find it to be a tetragonal perovskite, in contrast to an earlier report, with random La/Na mixing. With a Curie-Weiss temperature of -231 K and effective moment of 2.74 uB/mol-Ru, there is no magnetic ordering down to 1.8 K. A broad hump at 1.4 K in the heat capacity, however, indicates the presence of a glassy magnetic transition, which we attribute to the influence of the random distribution of Na and La on the perovskite A sites. Comparison to CaRuO3, a structurally ordered ruthenate perovskite with similar properties, is presented. First-principle calculations indicate that the Na-La distribution determines the local magnetic exchange inter-actions between Ru ions, favoring either antiferromagnetic or ferromagnetic coupling when the local environment is Na or La rich. Thus our data and analysis suggest that mixing cations with different charges and sizes on the A site in this perovskite results in magnetic frustration through a balance of local magnetic exchange interactions., 7 figures, 2 tables

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

Ba4NbIr3O12, a previously unreported material with a triangular planar geometry of Ir3O12 trimers, is described. Magnetic susceptibility measurements show no magnetic ordering down to 1.8 K despite the Curie-Weiss temperature of -13 K. The material has a very low effective magnetic moment of 0.80 {\mu}B/f.u. To look at the lower temperature behavior, the specific heat (Cp) was measured down to 0.35 K; it shows no indication of magnetic ordering and fitting a power law to Cp vs. T below 2 K yields the power {\alpha} = 3/4. Comparison to the previously unreported trimer compound made with the 4d element Rh in place of the 5d element Ir, Ba4NbRh3O12, is presented. The analysis suggests that Ba4NbIr3O12 is a candidate spin liquid material., Comment: 19 pages, 7 main figures, 2 SI figures