Article

# Anomalous expansion and phonon damping due to the Co spin-state transition in RCoO_ {3}(R= La, Pr, Nd, and Eu)

Phys. Rev. B 10/2008; 78(13). DOI:10.1103/PhysRevB.78.134402
Source: arXiv

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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### Keywords

combined study

detecting spin-state transitions

phonon thermal conductivity

quantitative model

thermal expansion

various 4f levels

well-known spin-state transition