Raman scattering in La1-xSrxMnO3 single crystals (x = 0, 0.1, 0.2, 0.3)

We report polarized Raman spectra of La1-xSrxMnO3 crystals (x = 0, 0.1, 0.2 and 0.3) in the temperature range from 5 K to 300 K. The small distortion of the nearly cubic lattice of doped La1-xSrxMnO3 single crystals results in a structured phonon Raman spectrum which is composed of two parts with different contributions depending on the value of doping. The first part is assigned to the distorted non-cubic perovskite lattice and follows the selection rules for a tetragonal structure. This suggests the possible presence of a tetragonal structure in doped La1-xSrxMnO3 single crystals. The second part is mainly due to the density of vibrational states and is attributed to the second-order Raman scattering. The frequency of the A(1g)-like mode was found to be sensitive to doping but the observed shift is opposite to that expected from the difference in the atomic weight of Sr and La. This mode exhibits also an anomalously large shift of similar to 20 cm(-1) in the temperature range from 5 K to 300 K. A possible explanation of this behaviour is suggested. (C) 1998 Elsevier Science Ltd.