Structural and magnetic properties of high-pressure/high-temperature synthesized (Sr1-xRx)CoO3 (R=Y and Ho) perovskites

Polycrystalline perovskite cobalt oxides Sr_1-xR_xCoO₃ (R=Y and Ho; 0?x?1) were prepared by high-pressure/high-temperature technique. X-ray powder patterns of the Y-system indicated cubic perovskite form for 0?x?0.5, and orthorhombic perovskite form for x=0.8 and 1.0, while coexisting of the two phases for x=0.6. The cubic perovskite samples had metallic electric resistivities while the orthorhombic ones with semiconducting or insulating nature. The parent compound SrCoO₃ showed a ferromagnetic transition at 266 K. With the Y substitution, the transition temperature increased slightly to ∼275 K at x=0.1, then decreased rapidly to ∼60 K for x=0.6. The YCoO₃ (x=1) sample showed non-magnetic behavior. The Ho-substituted system showed quite similar structural, transport and magnetic properties to those of the Y-system.