Crossover from polaron to band conduction upon doping CaMnO$_3$ with La ions

In studying the specular reflection IR spectra of manganite polycrystals with electron doping Ca_1−x La _x MnO₃ (0 ≤ x ≤ 0.050) at room temperature, a crossover from polaron to band conduction is observed at x = 0.030. It has been shown that the observed changes in the electronic subsystem is associated with the crossover in the behavior of the magnetization and magnetoresistance in the magnetically ordered and paramagnetic phases that occurs at the same concentration and is described in [C. Chiorescu et al., Phys. Rev. B 73, 014406 (2006)].