【摘要】 通过超声与低频切变模量测量,得到多晶锰氧化物La0.2Ca0.8MnO3材料纵向模量与切变模量随温度变化关系曲线,发现在电荷有序转变温度附近,纵向模量与切变模量都出现最小值.运用合作Jahn-Teller效应理论对实验数据进行了拟合,发现理论与实验曲线符合较好,表明Jahn-Teller效应是发生电荷有序状态转变的主要机制之一.更多还原

【Abstract】 The temperature dependence of the elastic properties of polycrystalline manganites La0.2Ca0.8MnO3 has been studied by means of ultrasonic measurements and low frequency internal friction apparatus. It was found that both the longitudinal modulus and the low frequency shear modulus starts to soften obviously 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 fitted with the cooperative Jahn-Teller theory. 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.更多还原