Influence of annealing on spin state of cobalt ions in La_(1-x)Sr_xCoO_3(0≤x≤0.5) system

摘要

Perovskite oxide La1-xSrxCoO3(0≤x≤0.5) series were prepared and effect of oxygen annealing on crystal structure and magnetic susceptibility were studied.High-temperature susceptibility could be well fitted by Curie-Weiss law for all Sr-doped samples.Weiss constant and effective magnetic moment were determined, and their variations with Sr doping and oxygen annealing condition were obtained.The result suggested that by assuming that the Co3+ ions were in the intermediate-spin(IS) state, most of the Co4+ ions in the as-prepared samples might be in the high-spin(HS) state, but both the Co3+ and Co4+ ions might be in the IS state after oxygen annealing, which indicated that annealing in flowing oxygen could cause transition of the spin state of Co4+ ions from the HS state to IS state.