Infrared absorption from charge-density waves in La0.67−xPrxCa0.33MnO3 (x=0, 0.18, 0.36)

Abstract

The polycrystalline compounds with formula of La0.67−xPrxCa0.33MnO3 (x=0, 0.18, 0.36) were prepared by the standard solid-state reaction method. Infrared-absorption spectra of the three samples have been measured by a WQF-410 Fourier transform spectrophotometer with the wave numbers between 400 and 4400cm−1 in the temperature interval from 20 to 300 K. The stretching mode of the oscillation of the MnO6 octahedron in the samples was observed clearly. From the integration of the optical density Od(ω), we obtained that the carrier numbers decrease with increasing temperature, which can be attributed to the delocalization of charge carriers. The charge-density waveslike band gap has been extracted from the infrared-absorption spectra and its behavior is consistent with the change of the effective carrier numbers.