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Scaling behavior in thermoelectric misfit cobalt oxides
P Limelette1, S Hébert, V Hardy
1Laboratoire LEMA, UMR 6157 CNRS-CEA, Université F. Rabelais, UFR Sciences, Parc de Grandmont, 37200 Tours, France.
Physical Review Letters
|August 16, 2006
Summary
This study reveals that misfit cobalt oxides exhibit high thermopower due to combined electronic and spin entropy contributions. These thermoelectric properties show universal scaling behavior across different materials.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Solid State Chemistry
Background:
- Misfit cobalt oxides are complex materials with potential thermoelectric applications.
- Understanding the interplay between electronic, magnetic, and thermal properties is crucial for optimizing thermoelectric performance.
Purpose of the Study:
- To investigate the thermoelectric and thermodynamic properties of the misfit cobalt oxide [Bi1.7Co0.3Ca2O4]RS0.6CoO2.
- To elucidate the origin of the enhanced thermopower in these materials.
Main Methods:
- Measurements of magnetothermopower and specific heat.
- Analysis of scaling behavior of thermopower with magnetic field, temperature, and electronic specific heat coefficient (gamma).
Main Results:
- A large negative magnetothermopower was observed, scaling with magnetic field and temperature.
- Significant spin entropy contribution (S0 ≈ 60 microV K-1) to thermoelectric properties was identified.
- Enhanced electronic specific heat (gamma ≈ 50 mJ (mol K2)-1) indicates strong electronic correlations.
- A universal scaling behavior of the thermopower slope as a function of gamma was found across different cobaltites.
Conclusions:
- The high room temperature thermopower in misfit cobalt oxides arises from the synergistic effect of a large spin entropy contribution and an enlarged electronic contribution.
- The observed universal scaling behavior suggests a generic electronic origin for the thermopower in these materials.
