Synthesis and Magnetic Studies of Ultrafine Cobalt Ferrite Particles

Abstract

Ultrafine monophasic single domain CoFe2O4 particles of 5.80-62.50 nm having surface area 180.50-18.2 m2/g were synthesized by citrate precursor technique. The smaller particles form the chain like clusters due to strong magnetic dipolar interactions. Reduced satuarion magnetization was attributed to superparamagnetic fraction and spin noncollinearlity at the surface. The maximum in magnetization just below Tc (magnetic anomaly) was exhibited by superparamagnetic particles; it was related to the surface/shape anisotropy and well described by the relation, (σmax − σmin)/σmin=±(d/do)-n with 1/n=0.1159±0.013 nm and do=6.26nm corresponds to 6.98nm superparamagnetic particle size.