Charge-ordering correlated elastic anomalies in Pr1-xCaMnO3 perovskite

The temperature dependence of the elastic properties of polycrystalline manganite Pr1-xCaxMnO3 (0.5 less than or equal to x less than or equal to 0.85) has been studied systematically by means of ultrasonic measurements. It was found that the longitudinal modulus starts to soften obviously with decreasing temperature from higher temperature to the charge-ordering transition temperature T-co, and stiffens dramatically just below T-co. The elastic anomalies observed near T-co cannot be explained based on a conventional antiferromagnetic transition. The electron-phonon coupling originating from the Jahn-Teller effect may play an important role in the system. The good fit of the theory to the temperature dependence of the elastic modulus data indicates that the mean-field theory, which describes the coupling of Jahn-Teller ions to lattice distortions of the Jahn-Teller system, adequately characterizes the behavior. (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.