Effects of Mg substitution on the structural and magnetic properties of Coo.sNi0.5xMgxFe2O4 nanoparticle ferrites

In this study, nanocrystalline Co–Ni–Mg ferrite powders with composition Co0.5Ni0.5-xMgxFe2O4 are successfully synthesized by the co-precipitation method. A systematic investigation on the structural, morphological and magnetic properties of un-doped and Mg-doped Co–Ni ferrite nanoparticles is carried out. The prepared samples are characterized using x-ray diffraction（XRD） analysis, Fourier transform infrared spectroscopy（FTIR）, field emission scanning electron microscopy（FESEM）, and vibrating sample magnetometry（VSM）. The XRD analyses of the synthesized samples confirm the formation of single-phase cubic spinel structures with crystallite sizes in a range of 32 nm to 36 nm. The lattice constant increases with increasing Mg content. FESEM images show that the synthesized samples are homogeneous with a uniformly distributed grain. The results of IR spectroscopy analysis indicate the formation of functional groups of spinel ferrite in the co-precipitation process. By increasing Mg2+substitution, room temperature magnetic measurement shows that maximum magnetization and coercivity increase from 57.35 emu/g to 61.49 emu/g and 603.26 Oe to 684.11 Oe（1 Oe = 79.5775 A·m-1）, respectively. The higher values of magnetization Ms and Mr suggest that the optimum composition is Co0.5Ni0.4Mg0.1Fe2O4 that can be applied to high-density recording media and microwave devices.