  Magnetic nanoparticles of cobalt ferrite have been synthesized by wet
chemical method using stable ferric and cobalt salts with oleic acid as the
surfactant. X-ray Diffraction (XRD) and Transmission Electron Microscope (TEM)
confirmed the formation of single phase cobalt ferrite nanoparticles in the
range 15-48nm depending on the annealing temperature and time. The size of the
particles increases with annealing temperature and time while the coercivity
goes through a maximum, peaking at around 28nm. A very large coercivity
(10.5kOe) is observed on cooling down to 77K while typical blocking effects are
observed below about 260K. The high field moment is observed to be small for
smaller particles and approaches the bulk value for large particles.
