Factors controlling magnetic properties of CoFe۲O۴ nanoparticles synthesizedby chemical co-pericipitation

Chemical co-precipitation method is proposed for the synthesis of CoFe۲O۴ nanoparticles with highcoercivity (HC) and moderate saturation magnetization (MS). Cobalt ferrite nanoparticles possessunique properties such as strong magneto-crystalline anisotropy, moderate magnetization, highcoercivity and good mechanical hardness, which made this ferrite a promising candidate for highdensity recording media. The applications of cobalt ferrite are limited due to the lack of synthesistechnique to produce nanoparticles with high crystallinity and controlling particle size at the singledomain range. It is well known that the degree of crystallinity and particle size can be controlledby adjusting the supersaturation condition during the nucleation and crystal growth processes.Based on this premise, the effect of reaction temperature, reaction time, pH value, and feeding rateof reactant solutions were evaluated. X-ray diffraction analysis (XRD), scanning electronmicroscope (SEM), and Vibrating Sample Magnetometer (VSM) were carried out at roomtemperature to study the structural and magnetic properties of nanoparticles. X-ray patternsrevealed the production of single cubic phase with the average particle sizes of ۴ to ۲۵ nm for pHchange from ۸ to ۱۳, respectively. M–H measurements verified the strong influence of synthesisconditions and crystal size on the magnetic properties of ferrite nanoparticles. The coercivity valuesincreased from ۰ up to ۶۵۰ Oe under optimum synthesis conditions.

Keywords:

Coercivity , CoFe۲O۴ , ferrites , nanoparticles