Enhancement of magnetic properties of Ni–Mg–Co ferrites by Y3+ ions doping

In this study, yttrium ion-doped nickel–magnesium–cobalt ferrite powder was prepared by the sol–gel auto combustions method. The chemical formula is Ni_0.2Mg_0.1Co_0.7Fe_2–xY_xO₄ (where x = 0.00, 0.02, 0.04, 0.06, and 0.08). The structure and magnetic properties were studied by X-ray diffractometer (XRD), Fourier infrared spectroscopy (FTIR), ultraviolet–visible (UV–Vis), scanning electron microscope (SEM), and vibrating sample magnetometer (VSM). XRD measurements show that Ni–Mg–Co ferrite has a good phase formations, and all samples have single-phase cubic spinel structure. As the doping amount of yttrium ions increases, the lattice constant of the samples increases first and then decreases. FTIR measurements also confirm the formations of the cubic spinel structure of ferrite. The UV–Vis optical analysis shows that the bandgap value of optical energy decreases after doping Y³⁺ ions. SEM confirmed that the sample was spherical spinel with a particle size of 54–60 nm. The saturation magnetizations (M_s) and remanent magnetizations (M_r) increase first and then decrease with the increase of Y³⁺ ions content at room temperature. This shows that the small amount of Y³⁺ ions-doped nickel–magnesium–cobalt nanoferrite can optimize the magnetic properties of the ferrite. The coercivity of the samples also showed a downward trend. The comprehensive measurement data show that the sample has the best magnetic properties when x = 0.02. This is also confirmed that the ferrite can be used as magnetic storage material.