Magnetic transformation of Ni–Mg–Zn ferrite substituted by the Co 2+ ions from soft magnetic to hard magnetic

Co2+ ions substituted Ni0.2Mg0.2CoxZn0.6−xFe2O4 (x = 0, 0.15, 0.3, 0.45 and 0.6) nanoferrite was prepared by sol–gel method. The spinel structure of the material was characterized by X-ray diffraction (XRD) and fourier transform infrared spectroscopy (FTIR). Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were used to observe the morphology and shape of the prepared nanoferrite particles. The diffraction ring of the sample was observed by selected area electron diffraction (SAED), which is similar with the diffraction ring of spinel structure. The chemical element composition of the sample was analyzed by EDS, which confirmed the presence of Ni, Mg, Zn, Co, Fe, and O elements in the sample. Vibrating sample magnetometer (VSM) was used to measure the magnetic properties of prepared samples. It found that the magnetism of Ni0.2Mg0.2CoxZn0.6−xFe2O4 (x = 0, 0.15, 0.3, 0.45 and 0.6) nanoferrite substituted by Co2+ ions changed from soft magnetic to hard magnetic. The coercivity increased from 4.87 to 523.25 (Oe). Moreover, the Ni0.2Mg0.2CoxZn0.6−xFe2O4 nanoferrite sample has the characteristics of ferromagnetism when x increase to 0.6.