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.