K. Sakthipandi, N. R. Dhineshbabu and V. Rajendran
Centre for Nano Science and Technology, K S Rangasamy College of Technology, Tiruchengode 637 215, Tamil Nadu, India
La1-xSrxMnO3 perovskite magnetic materials with two different compositions namely x = 0.35 and 0.37 both at bulk and nano scale were prepared by solid state reaction and sonochemical reactor method respectively. The evaluation of magnetic phase transition temperature of prepared bulk and nano samples was made through on-line ultrasonic velocity and attenuation measurements. An indigenously designed experimental set-up has been employed for on-line ultrasonic velocities and attenuation measurement over a wide range of temperatures for 300 to 400 K. The observed anomalous lattice softening behaviour in the ultrasonic parameters was used to explore the phase transition temperature (Curie temperature TC) i.e., from paramagnetic (PM) to ferromagnetic (FM) phase transition both in bulk and nanostructured perovskite samples. Further, the ultrasonic measurements confirmed that sharp and broad transitions occur respectively in bulk and nanostructured perovskite manganite materials. The Curie temperature for nanoperovskite sample was lower than corresponding bulk perovskite sample, which was clearly identified by ultrasonic measurement. The variation in the magnitude of the ultrasonic parameter at the transition temperature was used to reveal the role of Sr content on phase transition both in bulk and nano perovskites.