Lattice dynamics and charge ordering in La1-xCaxMnO3 (0.45 <= x <= 0.76)

We study local lattice fluctuations in La1-xCaxMnO3(0.45less than or equal toxless than or equal to0.76)by means of inelastic light scattering. Fluctuation effects are especially strong in the intensity variation of Jahn-Teller mode at 480 cm(-1) around commensurate doping xapproximate to0.5. The linewidth of the Jahn-Teller mode shows a minimum at x=0.50 indicating long-range lattice and charge commensuration at low temperatures. The electron-phonon interaction is fundamentally changed at the transition to the charge-ordered (CO) state as evidenced by sign and magnitude changes in the Fano parameter. Temperature-dependent data show enhanced fluctuations persisting up to temperatures of at least 2 T-co for xapproximate to0.50.