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Low temperature mixed spin state of Co3+ in LaCoO3 evidenced from Jahn-Teller lattice distortions

V. Gnezdilov·K. -Y. Choi·Yu. Pashkevich·P. Lemmens·S. Shiryaev·G. Bychkov·S. Barilo·V. Fomin·A. V. Yeremenko
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Abstract

One- and multi-phonon excitations of the single crystalline LaCoO3 were studied using Raman spectroscopy in the temperature region of 5 K - 300 K. First-order Raman spectra show a larger number of phonon modes than allowed for the rhombohedral structure. Additional phonon modes are interpreted in terms of activated modes due to lattice distortions, arising from the Jahn-Teller (JT) activity of the intermediate-spin (IS) state of Co3+ ions. In particular, the 608-cm-1 stretching-type mode shows anomalous behavior in peak energy and scattering intensity as a function of temperature. The anomalous temperature dependence of the second-order phonon excitations spectra is in accordance with the Franck-Condon mechanism that is characteristic for a JT orbital order.

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V. Gnezdilov, K. -Y. Choi, Yu. Pashkevich, P. Lemmens, S. Shiryaev, G. Bychkov, S. Barilo, V. Fomin, A. V. Yeremenko. 2006-01-06. Low temperature mixed spin state of Co3+ in LaCoO3 evidenced from Jahn-Teller lattice distortions. https://doi.org/10.1063/1.2171521

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