High-Temperature Metallic State of Room-Temperature Ferromagnet Sr1-xYxCoO3-δ

Resistivity, thermopower, Hall coefficient, and magnetization are measured for a set of polycrystalline samples of the room-temperature ferromagnet Sr 1- x Y x CoO 3-δ up to 800 K. A peculiar metallic state accompanied by a large effective magnetic moment of 3.40 µ B /Co is observed above 600 K, indicating that electrons on the Co 3+ ions are magnetic and itinerant. The magnetic Co 3+ ions survive at low temperatures, which causes the ferromagnetism below 335 K. We attribute this to the large CoO 6 octahedra stabilized in the A-site ordered structure.