Spin state and metal-insulator transition in LaCoO3 and RCoO3 (R = Nd, Sm and Eu)

We made Co-59 NMR measurements up to 800 K to clarify the spin state and the metal-insulator (MI) transition in LaCoO3 and RCoO3 (R = Nd. Sm and Eu). The Co-59 Knight shift K-59 in LaCoO3 has a peak due to the spin state transition From the low-spin to intermediate-spin states at similar to 100 K. However. K-59 in RCoO3 is almost independent of temperature up to the temperature T-M1 similar to 600 K where the MI transition takes place. This means that the spin state in RCoO3 remains the low-spin state up to T-M1. (C) 2000 Elsevier Science B.V. All rights reserved.