Structural and physical properties of the 6M BaIrO(3): a new metallic iridate synthesized under high pressure.

The 6M BaIrO(3) with the distorted hexagonal BaTiO(3) structure was synthesized by high-pressure sintering. Through Rietveld refinement of the powder X-ray diffraction data, the lattice parameters of a = 5.7459(1) A, b = 9.9289(2) A, c = 14.3433(2) A, and beta = 91.340(1) degrees were obtained. In the Ir(2)O(9) dioctahedron, the average Ir-O distance and direct Ir-Ir distance were equal to 2.067(19) and 2.719(1) A, respectively. The temperature dependence of electrical resistivity shows that the 6M BaIrO(3) is a new metallic iridate. It is an abnormal metal, being deviated from the Fermi liquid behavior, following a linear relationship of rho versus T below 20 K. Both magnetic susceptibility and specific heat data indicate that it is an exchange-enhanced Pauli paramagnet, because of the electron-electron correlation effect.