Phase transitions of bulk and nanocrystalline La1-xSrxMnO3 (x=0.35 and 0.37) perovskite manganite materials using in situ ultrasonic studies

La1-xSrxMnO3 perovskite manganite materials with two compositions, namely x = 0.35 and 0.37, both at bulk and nanoscale, were prepared by solid-state reaction and sonochemical reactor methods, respectively. The magnetic phase transition temperature of the prepared bulk and nanosamples was evaluated by in situ ultrasonic velocity and attenuation measurements. A home-made experimental setup was used for in situ measurement of ultrasonic velocities and attenuation over a wide range of temperatures (from 300 to 400 K). The observed anomalous lattice-softening behavior in the ultrasonic parameters was used to study the phase transition temperature (Curie temperature, T-C), i.e., from paramagnetic to ferromagnetic phase, both in bulk and nanostructured perovskite samples. Further, the ultrasonic measurements confirmed that sharp and broad transitions occur in bulk and nanostructured perovskite manganite materials, respectively. The Curie temperature for nanostructured perovskite samples was lower than that for the corresponding bulk perovskite sample, which was clearly identified by ultrasonic measurements. (C) 2013 Elsevier Ltd. All rights reserved.