Synthesis of CoFe2O4 superparamagnetic nanoparticles using a rapid thermal processing furnace with halogen lamps

Abstract

This work deals with the synthesis of superparamagnetic cobalt ferrite (CoFe2O4) nanoparticles, via a sol-gel method that uses gelatin as an organic precursor and a rapid thermal processing furnace with halogen lamps as a heat source. TEM, HRTEM, XRD, VSM and Mössbauer spectroscopy measurements were performed, at room temperature, to characterize the samples. Nanoparticles with an average size of 5–10 nm and microstrain of the order of 10−4–10−3 were obtained. Magnetic hardening was also observed with increased nanoparticle size, in addition to an increase in the anisotropy constant, which ranged from 1.7 to 4.7·106 erg/cm3. The saturation magnetization decreased with decreasing size due to the formation of a magnetically dead layer on the surface (thickness = 0.6–0.7 nm). The Mössbauer spectra showed an increase in the superparamagnetic phase for samples with smaller nanoparticles and less dispersion.