Molten salt route of La1 − xCaxMnO3 nanoparticles: Microstructural characterization, magnetic and electrical transport properties

Single-crystalline La1 − xCaxMnO3 (LCMO, x = 0.3 and 0.5) nanoparticles synthesized by molten salt method, have been studied based on their microstructural characterization, magnetic and electrical transport property measurements. X-ray diffraction patterns and electron diffraction patterns reveal that all the LCMO nanoparticles crystallize in the orthorhombic perovskite structure (Pnma space group). TEM images show that the LCMO nanoparticles exhibit irregular shapes and their particle sizes are increased with increasing the annealed temperatures. The resolved (200) lattice fringes in high-resolution TEM images confirm the single crystalline nature of the LCMO nanoparticles. Magnetization measurements versus temperature show a paramagnetic - ferromagnetic transition for all the nanoparticles. Room temperature and low temperature M - H loops demonstrate that the LCMO nanoparticles exhibit ferromagnetic behavior at 5 K, whereas a paramagnetic behavior at 300 K. Resistivity behavior of the LCMO nanoparticles demonstrate that they exhibit a broad metal - insulator (M − I) transition, and the transition temperature shifts towards a high temperature under an external magnetic field. The magnetoresistance (MR) values of the LCMO nanoparticles were increased monotonically with decreasing the temperature below 300 K, and finally reached constant values at temperatures below 100 K. The MR value of the La0.5Ca0.5MnO3 nanoparticles annealed at 650 °C for 3 h, was found to be 77% at 50 K in 5 T, and 57% for the La0.7Ca0.3MnO3 nanoparticles annealed at 650 °C for 3 h. Such large MR values of the present LCMO nanoparticles make them ideal candidates for the spintronic devices.