NMR study of the spin-state transitions in LaCoO3

A study of Co-59-NMR on single crystals of LaCoO3 is presented in order to investigate the spin-state transition through the nuclear-spin relaxation. The spin-lattice and spin-spin relaxation rates exhibit a thermal activatio n-type temperature dependence at low temperatures, suggesting the spin-sing let ground state with a spin gap. The magnitude of the gap energy similar t o 180 K is close to the values predicted by the two-stage spin-state model including the intermediate spin state, supporting the propriety of the mode l. (C) 2000 Elsevier Science B.V. All rights reserved.