High Temperature Magnetic Properties of Sr-Doped Lanthanum Cobalt Oxide (La_1−xSr_xCoO_3−δ)

A high-temperature, controlled atmosphere Faraday magnetometer has been used to measure the magnetic susceptibility of La 1− x Sr x CoO 3−δ (LSC) as a function of temperature, Sr content ( x ), and oxygen nonstoichiometry ( δ ). Above 800 °C the magnetic susceptibility becomes independent of Co oxidation state and Sr doping, consistent with metallic valance electrons. Under these conditions, conductivity measurements as a function of x, T, and δ exhibit classic metallic behavior, with resistivity scaling linearly with temperature and nonlinearly with defect concentration. However, a large Curie–Weiss susceptibility persists even at high temperatures, suggesting the coexistence of more localized electron configurations. We discuss this behavior in terms of existing theories of electronic and magnetic structure.