Ground-state tuning of metal-insulator transition by compositional variations in BaIr1-xRuxO3 (0 <= x <= 1)

Hexagonal BaIrO3 is a magnetic insulator driven by the spin-orbit interaction (SOI), whereas BaRuO3 is an enhanced paramagnetic metal. Our investigation of structural, magnetic, transport, and thermal properties reveals that substitution of Ru4+ (4d(4)) ions for Ir4+ (5d(5)) ions in BaIrO3 reduces the magnitudes of the SOI and a monoclinic structural distortion and rebalances the competition between the SOI and the lattice degrees of freedom to render an evolution from a magnetic insulting state to a robust metallic state. The central findings of this paper are as follows: (1) light Ru doping (0 < x <= 0.15) prompts simultaneous, precipitous drops in both the magnetic ordering temperature T-N and the electrical resistivity, and (2) heavier Ru doping (0.41 <= x <= 0.9) induces a robust metallic state without any long-range magnetic order. All results suggest a critical role of the lattice degrees of freedom in determining the ground state in the heavy transition-metal oxides.