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Evidence for a Low-Spin to Intermediate-Spin State Transition in LaCoO3

C. Zobel·M. Kriener·D. Bruns·J. Baier·M. Gr"uninger·T. Lorenz·P. Reutler·A. Revcolevschi
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Abstract

We present measurements of the magnetic susceptibility and of the thermal expansion of a LaCoO$_3$ single crystal. Both quantities show a strongly anomalous temperature dependence. Our data are consistently described in terms of a spin-state transition of the Co$^{3+}$ ions with increasing temperature from a low-spin ground state to an intermediate-spin state without (100K - 500K) and with (>500K) orbital degeneracy. We attribute the lack of orbital degeneracy up to 500K to (probably local) Jahn-Teller distortions of the CoO$_6$ octahedra. A strong reduction or disappearance of the Jahn-Teller distortions seems to arise from the insulator-to-metal transition around 500 K.

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C. Zobel, M. Kriener, D. Bruns, J. Baier, M. Gr"uninger, T. Lorenz, P. Reutler, A. Revcolevschi. 2005-02-10. Evidence for a Low-Spin to Intermediate-Spin State Transition in LaCoO3. https://doi.org/10.1103/physrevb.66.020402

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