  BaIrO3 is a magnetic insulator driven by the spin-orbit interaction (SOI),
whereas BaRuO3 is a paramagnet and exhibits a crossover from a metallic to an
insulating regime. Our investigation of structural, magnetic, transport and
thermal properties reveals that substitution of Ru4+ (4d4) ions for Ir5+ (5d5)
ions in BaIrO3 reduces the magnitudes of the SOI and a monoclinic structural
distortion, and rebalances the competition between the SOC and the lattice
degrees freedom to generate a rich phase diagram for BaIr1-xRuxO3 (0< x <1).
There are two major effects of Ru additions: (1) Light Ru doping (0 < x < 0.15)
prompts simultaneous, precipitous drops in both the magnetic ordering
temperature TN and the electrical resistivity, which exhibits a crossover
behavior from a metallic to an insulating state near TN. (2) Heavier Ru doping
(0.41< x < 0.9) induces a robust metallic state with a strong spin frustration
generated by competing antiferromagnetic and ferromagnetic interactions.
