Structural and Magnetic Properties Evolution of Li-Substituted Co0.5Ni0.5Fe2O4 Ferrite

Four types of Co-Ni based ferrites materials with the general formula Li-x Co0.5Ni0.5-xFe2O4 (0.0 <= x <= 0.3) were successfully synthesized by thermal decomposition of oxalates in air. The effect of substitution of diamagnetic Li+ ions for partial Ni2+ ions in a spinel lattice on the crystalline structure and the magnetic properties of Co-Ni ferrites was studied. X-ray diffraction examination confirms that a high-crystallized LixCo0.5Ni0.5-xFe2O4 with cubic spinel structure is obtained when the precursor is calcined at 900 degrees C in air for 3 h. The substitution of Li+ ions for partial Ni2+ ions does not change the spinel crystalline structure of MFe2O4, but crystallinity of LixCo0.5Ni0.5-xFe2O4 can be improved. The incorporation of Li+ ions in place of Ni2+ ions in Co-Ni ferrites decreases the average crystallite size and results in higher specific saturation magnetization as compared to un-substituted Co-Ni ferrites. In this study, Li0.1Co0.5Ni0.4Fe2O4, obtained at 900 degrees C, exhibits the highest specific saturation magnetization of 88 emu/g +/- 2 emu/g and magnetic moment (3.60 mu(B) +/- 0.05 mu(B)).