High-Pressure Synthesis Of Ba2rho4, A Rhodate Analog Of The Layered Perovskite Sr-Ruthenate

A layered perovskite-type oxide Ba2RhO4 was synthesized by a high-pressure technique with the support of convex-hull calculations. The crystal and electronic structure were studied by both experimental and computational tools. Structural refinements for powder x-ray diffraction data showed that Ba2RhO4 crystallizes in a K2NiF4-type structure, isostructural to Sr2RuO4 and Ba2IrO4. Magnetic, resistivity, and specific-heat measurements for polycrystalline samples of Ba2RhO4 indicate that the system can be characterized as a correlated metal. Despite the close similarity to its Sr2RuO4 counterpart in the electronic specific-heat coefficient and the Wilson ratio, Ba 2 Rh0 4 shows no signature of superconductivity down to 0.16 K. Whereas the Fermi surface topology has reminiscent pieces of Sr2RuO4, an electronlike e(g)-(d(x2-y2)) band descends below the Fermi level, making this compound unique also as a metallic counterpart of the spin-orbit coupled Mott insulator Sr2IrO4.