Unconventional Hall effect in oriented Ca 3 Co 4 O 9 thin films

International audienceTransport properties of the good thermoelectric misfit oxide Ca 3 Co 4 O 9 are examined. In-plane resistivity and Hall resistance measurements were made on epitaxial thin films which were grown on c-cut sapphire substrates using the pulsed laser deposition technique. Interpretation of the in-plane transport experiments relates the substrate-induced strain in the resulting film to single crystals under very high pressure 5.5 GPa consistent with a key role of strong electronic correlation. They are confirmed by the measured high temperature maxima in both resistivity and Hall resistance. While holelike charge carriers are inferred from the Hall effect measurements over the whole investigated temperature range, the Hall resistance reveals a nonmonotonic behavior at low temperatures that could be interpreted with an anomalous contribution. The resulting unconventional temperature dependence of the Hall resistance seems thus to combine high temperature strongly correlated features above 340 K and an anomalous Hall effect at low temperature, below 100 K