INVESTIGATION OF MAGNETIZATION BEHAVIORS OF IONIC FERROFLUIDS BASED ON CoFe2O4 NANOPARTICLES

The average density of CoFe2O4 particles treated by using ferric nitrate is decided from specific saturation magnetization of both untreated and treated particles. Besides, some characteristic parameters, depending on the density of particles, are determined for CoFe2O4 ionic ferrofluids. The magnetization of the ferrofluids exhibits abnormal behaviors and is interpreted in relation to aggregates self-assembled from particles in the ferrofluids. Ringlike aggregates in which particles' moments linked into closed flux cause the saturation magnetization measured to be less than the theoretical value. The aggregates with opposed-parallel moments ordering will break up into isolated particles in the first magnetization process, so that the second magnetization will be easier than the first. For the aggregates with head-to-tail linked moments ordering, the magnetization behavior of the self-assembly structure may be hard to distinguish from fieldinduced aggregates.