Influence of ionic radius on magnetic phase transition in R1-xSrxMnO3 perovskites

R.1-xSrxMnO3 (R-Rare earth elements such as La, Pr, Sm and Nd) perovskite materials were prepared employing solid state reaction technique. On-line measurement of ultrasonic longitudinal velocity was carried out on the prepared perovskites over a wide range of temperature at a fundamental frequency of 5 MHz employing through transmission method. The phase transition temperature is explored based on the variation in observed anomaly in ultrasonic velocity. The obtained transition width and height at Curie temperature (i.e., transition from ferro to para magnetic phase) in the measured ultrasonic velocity were used to explore the physiochemical properties of the perovskites. The transition width and height of anomalous peak in measured ultrasonic velocity are also correlated with the ionic radius of the trivalent element. The results reveal that an increase in ionic radius of the trivalent elements leads to a decrease in double exchange interaction.