Abstract
The temperature dependence of the reflectivity spectra of three manganites ceramics with compositions Pr0.7Ca0.3MnO3, Pr0.7Ca0.25Sr0.05MnO3 and Pr0.7Ca0.1Sr0.2MnO3 has been investigated by infrared reflectivity spectroscopy in the wave number range 0.005-1.1 eV. The compound Pr0.7Ca0.25Sr0.05MnO3 which shows the largest conductivity jump at the ferromagnetic-paramagnetic phase transition has been studied in details. The optical conductivity of this compound is deduced from the best fit to reflectivity spectra of a “double-damping Drude” model, itself derived from the factorized form of the dielectric function. Excellent agreement with Kramers-Kronig transformation is reported. The model allows in particular to discriminate the contributions to the optical conductivity of trapped charges (polarons) and mobile charge carriers.
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