Magnetic and transport properties of high-pressure synthesized perovskite cobalt oxide (Sr1–xCax)CoO3 (0⩽x⩽0.8)

Polycrystalline perovskite cobalt oxides (Sr1–xCax)CoO3 (0⩽x⩽0.8) were synthesized under high pressure (6 GPa) and high temperature (1200–1300 °C) conditions. Powder X-ray diffraction data confirmed that they have cubic perovskite structures. The end member of the solid solution, SrCoO3, exhibited a ferromagnetic transition with Curie temperature of image and metallic electric conductivity. With increasing the Ca content image, image increased slightly to 286 K at image then decreased rapidly to 148 K for image. The origin of the ferromagnetism is discussed in relation to the spin state of the Co4+ ions. The present system showed a relatively large (∼5.5%) negative magnetoresistance for image or 0.2 in the vicinity of Tc.