Charge ordering correlated elastic anomalies in La_1−<i>x</i>Ca_<i>x</i>MnO₃perovskite

Abstract

The temperature dependence of the elastic properties of polycrystalline manganite La1−xCaxMnO3 (0.5 ⩽ x ⩽ 0.85) has been studied systematically by means of ultrasonic measurements. It was found that the longitudinal modulus starts to soften with decreasing temperature from higher temperature to the charge ordering transition temperature, TCO, and stiffens dramatically just below TCO. The abnormal temperature dependence of the elastic modulus around TCO is described by the mean-field theory, which describes the coupling of Jahn–Teller ions to distortions of lattice of the cooperative Jahn–Teller system. The good fit of the theory to the data indicates that the Jahn–Teller effect is the dominant mechanism responsible for the charge ordering state of the system.