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-x Lax Mn O3 (0≤x≤0.10). Unlike the case of hole-doped ferromagnetic manganites, the magnitude and temperature dependence of the Hall mobility (μH) 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 (α 5.4) with a band effective mass m* ∼4.3 m0 and a polaron mass mp ∼10 m0.