Spin State Transition in LaCoO3 with Temperature or Strontium Doping as Seen by XAS

An X-ray absorption spectroscopy study of the polycrystalline La1-xSrxCoO3 (x=0, 0.25, 0.5) series at O K-edge was performed above and below the various magnetic transition temperatures. A crystal field analysis is proposed to explain the observed fine structure changes. Temperature-dependent O K-edge of LaCoO3 shows evidence of smooth and continuous spin transition of Co3+ from low to intermediate spin states. This result is confirmed by cobalt K-edge measurements. Upon strontium doping, O K-edges of the La1-xSrxCoO3 (x=0, 0.25, 0.5) series suggested a mixed (LS–IS) Co3+/IS Co4+ cobalt ion configuration. The fundamental mechanism governing the magnetotransport properties shown by the compounds is then discussed.