Hall effect measurements on thermoelectric Ca{sub 3}Co{sub 4}O{sub 9}: On how to determine the charge carrier concentration in strongly correlated misfit cobaltites
- Department of Physics, Centre for Materials Science and Nanotechnology, University of Oslo, Sem Sælandsvei 26, 0371 Oslo (Norway)
- Department of Chemistry, Centre for Materials Science and Nanotechnology, University of Oslo, Sem Sælandsvei 26, 0371 Oslo (Norway)
The Hall coefficient R{sub H} and electrical conductivity of misfit calcium cobalt oxide (Ca{sub 2}CoO{sub 3−δ}){sub q}(CoO{sub 2}) (CCO) were measured at room temperature for different oxygen vacancy concentrations δ. Based on these and numerous previous results, it is shown that the charge carrier concentrations n obtained by the classical formula R{sub H} = 1/ne are between 3 and 6 × 10{sup 20} cm{sup −3} and thereby much lower than those derived by other experimental techniques and fail to explain the observed electric properties of CCO. We show that the experimental results are well described using an earlier proposed t–J-model for strongly correlated electrons on a triangular lattice. The hopping parameter t for CCO was found to be ≈ −20 K and the charge carrier concentration of fully oxidized CCO to be 5.7 × 10{sup 21} cm{sup −3} (0.41 hole type carriers per formula unit), in agreement with other experimental techniques.
- OSTI ID:
- 22410257
- Journal Information:
- Journal of Applied Physics, Vol. 117, Issue 20; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
- Country of Publication:
- United States
- Language:
- English
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