High temperature magnetic properties of Sr-doped lanthanum cobalt oxide (La1-xSrxCoO3-δ)

A high-temperature, controlled atmosphere Faraday magnetometer has been used to measure the magnetic susceptibility of La1-xSrxCoO3-delta (LSC) as a function of temperature, Sr content (x), and oxygen nonstoichiometry (delta). Above 800 degrees 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 delta 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.