Effect of strontium doping level on electrical transport and magnetic properties of La_1-xSr_xMnO₃ perovskite nanoparticles

La_1-xSr_xMnO₃ (x 0.1, 0.2, and 0.3) nanoparticles (LSMO NPs) were successfully synthesized by a simple sonochemical-assisted method. The prepared samples were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The compositions of samples were determined by energy-dispersive spectroscopy (EDS) analysis. The temperature dependence of the resistivity of samples was measured using four-probe technique, and the magnetic measurement was performed in a Magnetic Property Measurement System (MPMS XL 7.0). SEM, TEM, and XRD show that LSMO NPs are 40∼80 nm in diameter with a very clean surface, and exhibit single phase perovskite structure. The ferromagnetic transition temperature (T_c) and metal-insulator transition temperature (T_p) of the NPs increase with the doping level x. The maximum values of T_c (377 K) and T_p (264 K) occur at = x0.3. In this work, the effect of strontium doping level on electrical transport and magnetic properties was systematically studied.