Ultrasonic and elastic moduli evidence for Curie temperature (T_c) in Sm_(1-x)Sr_xMnO_3 perovskite magnetic materials at x = 0.25, 0.30, 0.37, 0.40 and 0.44

摘要

Sm_(1-x)Sr_xMnO_3 perovskite manganite materials with different compositions (x = 0.25,0.30,0.37,0.40 and 0.44) have been prepared using solid state reaction technique. On-line ultrasonic velocities and attenuation have been measured over a wide range of temperatures from 120 to 298 K employing through transmission method operated at a fundamental frequency of 5 MHz. In all compositions, Curie temperature (T_c) and Jahn-Teller temperature (T_(JT)) have been discussed in light of observed interesting results on temperature dependence of ultrasonic parameters. Phase transition from ferromagnetic to canted ferromagnetic state has been observed at T_c. The increase in the magnitude of maximum velocities with change in Sr content at T_c indicates the strength of linear magnetostriction effect. The observed results reveal that Tc value decreases with an increase in Sr content. The existence of Jahn-Teller transition due to electron-phonon interaction and large lattice distortion which is due to the double exchange interactions have been demonstrated from the observed ultrasonic parameters as a function of temperature.