The infrared absorption spectra in perovskite manganite La0.27Pr0.4Ca0.33MnO3

Abstract The polycrystalline compound of perovskite manganite La 0.27 Pr 0.4 Ca 0.33 MnO 3 was prepared by the standard solid-state reaction method. The magnetic moment vs temperature was measured in the field H =0.2 T to obtain T c . The result indicates that the ferromagnetic–paramagnetic (FM–PM) transitions occur near 115 K and a peak due to the charge ordering (CO) near 210 K appears in the sample. Infrared absorption spectra of the sample were measured by a Fourier transform infrared spectrophotometer with the wave numbers between 400 and 4400 cm −1 in the temperature interval from 20 to 300 K. The infrared absorption intensity, which related with the effective carrier numbers obtained from the optical conductivity, decreased with increasing temperature. From the integration of the absorption intensity, it can be seen that the effective carrier numbers also decrease with increasing temperature, which can be attributed to the localization of the polarons. The absorption peak of stretching mode, rising from the vibration of Mn–O bond, was also observed clearly in the sample.