Magnetic, electric and thermoelectric properties of the quasi-1D cobalt oxides Ba1−xLaxCoO3 (x=0, 0.2)

The quasi-1D structure-type ferromagnetic (FM) cobalt oxide BaCoO3 was doped with La to a composition Ba0.8La0.2CoO3 (hexagonal, a=5.585(1) Å and c=4.721(1) Å), introducing 0.2 electrons per formula unit. Magnetic, electric and thermoelectric properties are compared to those of BaCoO3. The electrical resistivity decreases approximately one order of magnitude at room temperature (5×10−1 Ω cm), but remains semiconducting. The nearest-neighbor magnetic interaction in chain is FM (J/kB∼+94 K), and no manifest magnetic long-range order was observed above 5 K. Variable-range hopping behavior in the thermopower was found. Anderson localization is most likely to explain the poor electrical conductivity, as was suggested for the parent material BaCoO3.