Elastic behavior of neodymium based manganites

With a view to investigate the elastic behavior of Nd_0.67A_0.33MnO₃ (where A = Ca, Sr, Ba, Pb) manganite system, the samples were prepared by the sol gel method. After characterizing the samples structurally, a systematic investigation of ultrasonic longitudinal and transverse sound velocities of all the samples was undertaken by pulse transmission technique in the temperature range, 100-300 K. It has been found that all the elasticity parameters, including Debye temperature, are found to increase continuously with increasing ionic radii of the dopant ion. All the samples are also found to exhibit anomalies in both the longitudinal and transverse velocities near their ferro to para magnetic transition (T_C) temperatures. Apart from this, Nd_0.67Ca_0.33MnO₃ sample is also found to exhibit, a transition at its charge ordering temperature (T_co). An explanation for the observed elastic anomalies based on a mean field theory has been given.