Charge carriers in optical spectra of electron-doped Ca1−xLaxMnO3 single crystals

Reflection spectra, resistivity, thermopower and the Hall effect of Ca1−xLaxMnO3 (0.03⩽x⩽0.12) single crystals are studied. It is shown that the optical spectra are described by the Drude model. Concentration of the charge carriers is determined to be equal to doping ∼1021 cm−1. In contrast to lightly hole-doped manganites, in Ca1−xLaxMnO3 conductivity has a band character. The optical effective mass m  * of electrons and effective mass of density of states of the conduction band md* are found to be about 2–3m02–3m0 and ∼10m0∼10m0, respectively. The width of the conduction band is estimated as ∼1 eV. The revealed difference between optical effective mass and effective mass of density of states is attributed to the anisotropic dispersion law and multivalley character of the conduction band.