Cr3+-doped nanocrystalline nickel–magnesium–cobalt spinel ferrite: microstructural and magnetic

A series of chemical sample with formulae Ni0.2Mg0.2Co0.6Fe2−xCrxO4 (0.00 ≤ x ≤ 0.1; step 0.025) were prepared by sol–gel automatic combustion at 950 °C. X-ray diffraction analysis found that the sample has characteristic peaks belonging to spinel, and Fourier transform infrared (FTIR) analysis found that the sample has a characteristic absorption band indicating the structure of spinel. This above findings can confirm that all samples belong to the single-phase cubic spinel structure. The average crystallite size and the lattice constant increase first and then decrease with the increase of Cr3+ ion content. Surface morphology analysis observed that the shape of the ferrite sample was spherical nanoparticles. The surface morphology of the sample and the stoichiometric ratio of each element contained in it are analyzed by energy-dispersive spectrometer. The sample was subjected to an external magnetic field of 15 KOe at room temperature, and a vibrating sample magnetometer was used to measure the magnetic properties of Ni0.2Mg0.2Co0.6Fe2−xCrxO4 nano-ferrite. Compared with other samples doped Cr3+ ion, the magnetic properties of the sample reach to best when the doping content is x = 0.025, and the Ms, Mr and S* (coercivity squareness) also reach the maximum at the same time.