Polaron transport in the paramagnetic phase of electron-doped manganites

The electrical resistivity, Hall coefficient, and thermopower as functions of temperature are reported for lightly electron-doped Ca1-xLaxMnO3 (0 <= x <= 0.10). Unlike the case of hole-doped ferromagnetic manganites, the magnitude and temperature dependence of the Hall mobility (mu(H)) for these compounds is found to be inconsistent with small-polaron theory. The transport data are better described by the Feynman polaron theory and imply intermediate coupling (alpha similar or equal to 5.4) with a band effective mass m(*)similar to 4.3m(0) and a polaron mass m(p)similar to 10m(0).