Scaling Behavior in Thermoelectric Misfit Cobalt Oxides

Abstract : We investigate both thermoelectric and thermodynamic properties of the misfit cobalt oxide [Bi1.7Co0.3Ca2O4]RS0.6CoO2. A large negative magnetothermopower is found to scale with both magnetic field and temperature, revealing a significant spin entropy contribution to thermoelectric properties giving rise to a constant S0 approximately 60 microV K-1. Specific heat measurements allow us to determine an enhanced electronic part with gamma approximately 50 mJ (mol K2)-1 attesting to strong correlations. Thereby, the comparison between cobaltites and other materials reveals a universal behavior of the thermopower slope as a function of gamma, testifying to a purely electronic origin. This potentially generic scaling behavior suggests here that the high room temperature value of the thermopower in misfit cobalt oxides results from the addition of a spin entropy contribution to an enlarged electronic one.
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P. Limelette, S. Hebert, V. Hardy, R. Fresard, Ch. Simon, et al.. Scaling Behavior in Thermoelectric Misfit Cobalt Oxides. Physical Review Letters, American Physical Society, 2006, 97 (4), pp.046601. ⟨10.1103/PhysRevLett.97.046601⟩. ⟨hal-01870063⟩

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