Temperature dependence of infrared conductivity of manganites Pr0.7Ca0.3-xSrxMnO3 (x=0, 0.05 and 0.2)

The temperature dependence of the reflectivity spectra of three manganites ceramics with compositions Pr0.7Ca0.3MnO3; Pr0.7Ca0.25Sr0.05MnO3 and Pr0.7C a0.1Sr0.2MnO3 has been investigated by infrared reflectivity spectroscopy i n the wave number range 0.005-1.1 eV. The compound Pr0.7Ca0.25Sr0.05MnO3 wh ich shows the largest conductivity jump at the ferromagnetic-paramagnetic p hase transition has been studied in details. The optical conductivity of th is compound is deduced from the best fit to reflectivity spectra of a "doub le-damping Drude" model, itself derived from the factorized form of the die lectric 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 charg e carriers.