Magnetic, electric and thermoelectric properties of the quasi-1D cobalt oxides Ba(1-x)La(x)CoO3 (x=0, 0.2)

The quasi-1D structure-type ferromagnetic (FM) cobalt oxide BaCoO3 was dope d with La to a composition Ba0.8La0.2CoO3 (hexagonal, a = 5.585(1) Angstrom and c = 4.721(1) Angstrom), introducing 0.2 electrons per formula unit. Ma gnetic, electric and thermoelectric properties are compared to those of BaC oO3. The electrical resistivity decreases approximately one order of magnit ude at room temperature (5 X 10(-1) Ohm cm), but remains semiconducting. Th e nearest-neighbor magnetic interaction in chain is FM (J/k(B) similar to 94 K), and no manifest magnetic long-range order was observed above 5 K. Va riable-range hopping behavior in the thermopower was found. Anderson locali zation is most likely to explain the poor electrical conductivity, as was s uggested for the parent material BaCoO3. (C) 2000 Elsevier Science Ltd. All rights reserved.