Abstract
CoFe(2)O(4) (CFO) nanoparticles (NPs) were synthesized by co-precipitation technique and annealed up to 1273K under air and vacuum atmospheres. X-ray diffraction (XRD) analysis of pristine, vacuum and air - annealed samples confirms the spinel structure without any secondary phases. Transmission electron microscopy (TEM) of pristine CFO NPs confirms a wider distribution with an average particle size of 26 ± 7 nm. Further, the estimated activation energy for the growth of CFO NPs under vacuum and air atmosphere is 14.5 kJ/mol and 20.4 kJ/mol respectively. A relative decrease in activation energy for the vacuum - annealed samples suggest part of the thermal energy is utilized for cation migration between the interstitial sites of the spinel structure. Further, the cation migration is unambiguously confirmed by Raman spectroscopy. This study further reveals that the improved saturation magnetization upon vacuum annealing (from 47 emu/g to 80 emu/g) compared to air annealing (76 emu/g) is mainly due to the cation migration and the creation of oxygen vacancies.