Evidence for the excited triplet of Co3+ in LaCoO3 -: art. no. 094404

The state excited from the ground singlet of Co3+ in LaCoO3 was investigated by submillimeter-wave electron spin resonance (ESR) measurements. Clear ESR signals with zero-field splitting were observed above 20 K for the first time. The activation energy is estimated to be Deltaapproximate to140 K, from the temperature dependence of the signal intensity and the resonance-width. The frequency and angular dependence of the signals were successfully analyzed by an effective spin-Hamiltonian with uniaxial anisotropy. The parameters obtained are g(parallel to)=3.35, g(perpendicular to)=3.55, and D=+4.90 cm(-1) for the effective spin S=1. The results reveal that the first excited state is a triplet with a zero-field splitting of Co3+ in LaCoO3.