Crystal Structure, Magnetic and Transport Properties of New Ruthenate Phase, Ba₂Ru₇O₁₈

Abstract

A new phase of ternary ruthenium oxide, Ba₂Ru₇O₁₈, is discovered. The lattice parameters are: triclinic, a=6.71(4) Å, b=7.10(4) Å, c=7.46(4) Å, α=93.2(2)°, β=94.6(2)°, γ=115.7(2)°. It has a Ba₂Zn₇F₁₈-type structure composed of an egde-shared and corner-shared network of RuO₆ octahedra. The magnetic susceptibility around room temperature exhibits a Pauli paramagnetism with a relatively large value of χ=3.4×10⁻⁴ emu/mol at 300 K, while it exhibits a large temperature dependence in the low temperature range without any evidence of magnetic phase transitions down to 2 K. The resistivity at 300 K is 1.1×10⁻³ Ω cm, larger than that of normal metal. Unlike conventional metals, the resistivity exhibits T^1.2-linear dependence in the low temperature region. These anomalous behaviors of magnetism and resistivity can be interpreted in terms of the non-Fermi liquid state.