Temperature dependence of infrared conductivity of manganites Pr_(0.7)Ca_(0.3 - x)Sr_xMnO_3 (x = 0, 0.05 and 0.2)

摘要

The temperature dependence of the reflectivity spectra of three manganites ceramics with compositions Pr_(0.7)Ca_(0.3)MnO_3, Pr_(0.7)Ca_(0.25)Sr_(0.05)MnO_3 and Pr_(0.7)Ca_(0.1)MnO_3 has been investigated by infrared reflectivity spectroscopy in the wave number range 0.005-1.1 eV. The compound Pr_(0.7)Ca_(0.25)Sr_(0.05)MnO_3 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.