EPR study of spin-state transition in LaCoO3

Abstract In order to investigate the spin-state transition of cobalt ions in LaCoO 3 , susceptibility and Gd 3+ -EPR were measured for the single-crystals LaCoO 3 and La(1%Gd)CoO 3 , respectively. Below 80 K, the seven lines due to the crystal field of Gd 3+ -EPR can be observed. The crystal field parameter D was calculated as a function of T . Above 40 K, the parameter D and the line width Δ H pp of the main peak increase while the resonance field H r decreases. These results indicate a transition to Co 3+ excited spin-state above about 40 K, which involves local ion-distortion.