Synthesis, structure and properties of the (Bi_0.5Sr _0.5)(Co_0.5Ru_0.5)O₃ perovskite

The new perovskite (Bi_0.5Sr_0.5)(Co _0.5Ru_0.5)O₃ has been prepared under high pressure (10 GPa) and temperature (900 °C). The room-temperature crystal structure is described by the space group Pnma (a = 5.5702(3), b = 7.8793(5) and c = 5.5599(4) Å) with no observed order between Bi and Sr or between Co and Ru cations. This material shows antiferromagnetic spin ordering or freezing below 50 K and a paramagnetic moment of 4.07 μ_B per formula unit at high temperatures, consistent with the presence of high-spin Co²⁺ or Co³⁺ ions. (Bi_0.5Sr_0.5HCo _0.5Ru_0.5)O₃ is a variable range hopping semiconductor between 40 and 300 K with a small negative magnetoresistance.