Structural, morphological, and magnetic properties of sol-gel derived La0.7Ca0.3MnO3 manganite nanoparticles

La0.7Ca0.3MnO3 (LCMO) manganite nanoparticles are synthesized via a sol-gel route at different annealed temperatures. Their structural, morphological, and magnetic properties are investigated. The X-ray diffraction patterns coupled with electron diffraction confirm that all the LCMO samples are single phase and crystallize in the orthorhombic perovskite structure (Pnma space group). The morphology of the samples observed by TEM, reveals a spherical shape with an average grain size lower than 50 nm. The resolved lattice fringes in high-resolution TEM images also reveal the single crystalline nature of the LCMO nanoparticles. Magnetization measurements versus temperature under low magnetic field (0.01 T) show a paramagnetic - ferromagnetic transition for all the samples. The Curie temperature (Tc) is found to be decreased with increasing the annealed temperature. A bifurcation is observed in the zero field-cooled and field-cooled magnetizations, indicating a competition between ferromagnetic and antiferromagnetic interactions in the nanoparticles at low temperatures. Field-cooled hysteresis measurements suggest a cluster glasslike behavior of the nanoparticles. Room temperature and low temperature M - H loops demonstrate that all the samples exhibit ferromagnetic behavior at 5 K, whereas a paramagnetic behavior at room temperature. Resistivity behavior of the LCMO samples shows that they exhibit a metal - insulator transition. Magnetoresistance of ~ 50% at the field up to 8 T was observed at 2 K in the LSCO samples annealed at 600 °C.