Anomalous expansion and phonon damping due to the Co spin-state transition in RCoO3 (R=La, Pr, Nd, and Eu)

K. Berggold, M. Kriener, P. Becker, M. Benomar, M. Reuther, C. Zobel, and T. Lorenz
Phys. Rev. B 78, 134402 – Published 3 October 2008

Abstract

We present a combined study of the thermal expansion and the thermal conductivity of the perovskite series RCoO3 with R=La, Nd, Pr, and Eu. The well-known spin-state transition in LaCoO3 is strongly affected by the exchange of the R ions due to their different ionic radii, i.e., chemical pressure. This can be monitored in detail by measurements of the thermal expansion, which is a highly sensitive probe for detecting spin-state transitions. The Co ions in the higher spin state act as additional scattering centers for phonons, therefore suppressing the phonon thermal conductivity. Based on the analysis of the interplay between spin-state transition and heat transport, we present a quantitative model of the thermal conductivity for the entire series. In PrCoO3, an additional scattering effect is active at low temperatures. This effect arises from the crystal-field splitting of the 4f multiplet, which allows for resonant scattering of phonons between the various 4f levels.

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  • Received 25 June 2008

DOI:https://doi.org/10.1103/PhysRevB.78.134402

©2008 American Physical Society

Authors & Affiliations

K. Berggold1, M. Kriener1,2, P. Becker3, M. Benomar1, M. Reuther1, C. Zobel1, and T. Lorenz1,*

  • 1II. Physikalisches Institut, Universität zu Köln, Zülpicher Strasse 77, 50937 Köln, Germany
  • 2Department of Physics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
  • 3Institut für Kristallographie, Universität zu Köln, Zülpicher Strasse 49b, 50674 Köln, Germany

  • *lorenz@ph2.uni-koeln.de

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Issue

Vol. 78, Iss. 13 — 1 October 2008

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