Magnetic and Structural Studies of CoFe2 O4 Nanoparticles Suspended in an Organic Liquid

We present a study of magnetic and structural properties of CoFe sub(2) O sub(4) nanoparticles suspended in an organic liquid. Transmission electron microscopy shows that the nanoparticles have a narrow size distribution of average particle size 5.9 plus or minus 1.0 nm. X-ray diffraction shows that the particles are of cubic spinel crystal structure. Dynamic light scattering measurements reveal the existence of an organic shell around the CoFe sub(2) O sub(4) nanoparticles with an average hydrodynamic diameter of 14.4 nm. Coercive magnetic field at T=5 K is found to be 11.8 kOe. Disappearance of the coercive field and remanent magnetization at about 170 K suggests that the CoFe sub(2) O sub(4) nanoparticles are superparamagnetic at higher temperatures which is confirmed by the room temperature Mossbauer spectrum analysis. Saturation magnetization of the nanoparticles of 80.8 emu/g(CoFe sub(2) O sub(4) ) at 5 K reaches the value detected in the bulk material and remains very high also at room temperature. The cobalt ferrite nanoparticle system synthesized in this work exhibits magnetic properties which are very suitable for various biomedical applications.