Scaling behavior of spectral weight changes in perovskite manganites La_0.7-yPr_yCa_0.3MnO₃

Optical conductivity spectra of La_0.7-yPr_yCa_0.3MnO₃ were systematically investigated. For metallic samples, the spectral weight below 0.5 eV, whose magnitude can be represented by an effective carrier number N_eff(0.5eV), increases as temperature becomes lower. Regardless of the Pr doping, all the measured values of N_eff(0.5eV)/T_C fall into one scaling curve. This scaling behavior could be explained by the theoretical model by Röder et al. [Phys. Rev. Lett. 76, 1356 (1996)], which includes spin double exchange and Jahn-Teller lattice coupling to holes.