Correlation between the structural phase transition and magnetic properties of sol-gel synthesized nanoparticles

Abstract

The La2CoFeO6 (LCFO) nanoparticles were synthesized using the sol-gel method and calcined at 600°C, 800°C, and 1000°C. The X-ray diffraction data confirm the successful formation of LCFO nanoparticles. The crystallite size was observed to increase from ~13 nm to ~26 nm as the calcination temperature rose. Detailed Rietveld analysis revealed the coexistence of both orthorhombic (Pnma: S.G. 62) and rhombohedral (R3c: S.G. 167) phases in the LCFO samples. A two-phase Rietveld refinement demonstrated a structural phase transition (from Pnma to R3c) as the calcination temperature increased. FESEM micrographs exhibited a granular morphology for the LCFO nanoparticles, and the grain size was observed to increase with the elevated calcination temperature. Magnetization curves illustrated an increase in magnetization with a decrease in crystallite size or a reduction in calcination temperature for LCFO nanoparticles. At higher calcination temperatures, the rhombohedral phase displayed significant antisite disorder, resulting in the disruption of long-range ferromagnetic ordering in the material and a subsequent decrease in maximum magnetization.