Synthesis and characterization of superparamagnetic CoxFe3-xO4 nanoparticles

CoxFe3-xO4 nanoparticles having dimensions varying from 6.3 to 10.5 nm have been synthesized by a micelle chemical control method, which is capable of producing large quantities of nanocomposite materials at rather low temperature. The average diameter of cobalt ferrite particles ranged from several nanometers to tens of nanometers, which can be controlled by the value of x. For the fine particle, a diffused electron pattern is observed. The Mossbauer absorption patterns consist of a ferromagnetic component superposed on a superparamagnetic doublet. The intensity of the superparamagnetic doublet is found to be larger for particles having small average diameter. The magnetic hypertine field shows size dependence and is bigger for very fine particle. They decrease with increasing particle size for all the two sublattice sites. For the SPM particles, the quadruple splitting at A sites are generally bigger than those at B sites. Whereas the thing is reversible for isomer shift. The cation distribution and saturation magnetic moment for the obtained powders were presented. (C) 2002 Elsevier Science B.V. All rights reserved.