Ferromagnetic–paramagnetic transition temperature in bulk and nanostructured La0.7Sr x Ca0.3−x MnO3 (x = 0.10, 0.15, and 0.20) manganite materials

Abstract

Series of bulk and nanostructured La 0.7 Sr x Ca 0.3-x MnO 3 (x = 0.10, 0.15, and 0.20) manganites were synthesized and characterized using different techniques. In the series, both the bulk and nanostructured La 0.7 Sr 0.10 Ca 0.20 MnO 3 and La 0.7 Sr 0.20 Ca 0.10 MnO 3 manganites have orthorhombic and rhombohedral structures, whereas La 0.7 Sr 0.15 Ca 0.15 MnO 3 manganite has rhombohedral and orthorhombic structures, respectively. Online ultrasonic velocity and attenuation measurements were taken through an indigenously designed ultrasonic setup, and the analysis was done from 300 to 400 K during the aging of the samples to explore the structural/phase transitions. The bulk and nanocrystalline La 0.7 Sr x Ca 0.3-x MnO 3 perovskite samples show the particle size distribution in the range of 197-943 and 24-93 nm, respectively. The addition of Sr 2? alters the size of particles, which decrease in size. The observed anomaly in ultrasonic velocities, attenuations, and elastic moduli is correlated with the ferromagnetic-paramagnetic (FM-PM) transition temperature (T C ) in both bulk and nanocrystalline perovskites. In addition, the shift in T C and the magnitude and width of observed anomaly are correlated with the value of x to study the behavior of T C .