Influence of cobalt substitution on the magnetic properties of zinc nanocrystals synthesized via micro-emulsion route

A series of nanocrystalline spinel ferrites with chemical formula CoxZn1−xFe2O4 (x=0, 0.2, 0.4, 0.6, 0.8, and 1.0) were synthesized by the micro-emulsion technique. The samples were annealed at 700 °C for 7 h at the rate of 15 °C/min. The cubic spinel structure was systematically examined by X-ray diffraction and Fourier transform infrared spectroscopy. The lattice constant decreased from 8.39 to 8.34 Å as the Co concentration increased from x=0 to x=1 because of the smaller ionic radii of Co as compared to Zn. The dielectric properties of the synthesized nanomaterials were studied in the frequency range 1-3 GHz. The dielectric properties were influenced by Co substitution and were explained by the electron hopping mechanism between Fe2+ and Fe3+ ions. Vibrating sample magnetometry was used to study the magnetic parameters of these nanoferrites. M-H loops of the materials show CoxZn1−xFe2O4 nanocrystals to exhibit ferrimagnetic behavior at room temperature. The magnetic properties are explained in terms of cation distribution and grain size effect. Thus high Ms (21.29 emu/g) and Hc (1382.4 Oe) exhibited by the CoFe2O4 nanocrystals are favorable for their potential use in high density recording media applications.