Hall effect in a layered magnetoresistive cobalt oxide

Hall effect and its change with Pb-doping have been investigated in misfit layered (Bi,Pb)-Sr-Co-O system. The Hall coefficient shows characteristic t emperature dependence, which suggests that not only the density, but also t he scattering time and/or effective mass of carriers are temperature-depend ent. Below 20 K, the anomalous Hall effect is clearly observed and indicate s the existence of the magnetic scattering. These results support the pictu re of small polarons formed by the low spin Co4+ in the nonmagnetic Co3+ ba ckground. (C) 2001 Elsevier Science B.V. All rights reserved.