Correlation between magnetic properties and cationic distribution of Zn_0.85−x Ni _x Mg_0.05Cu_0.1Fe₂O₄ nano spinel ferrite: effect of Ni doping

The correlation among magnetic properties and cationic distribution of Ni-doped Zn_0.85−x Ni _x Mg_0.05Cu_0.1Fe₂O₄ (x = 0.00, 0.17, 0.34, 0.51, 0.85) ferrite, synthesized using sol–gel auto-combustion process is studied by X-ray diffraction (XRD), scanning electron microscope (SEM), energy-dispersive X-ray analysis (EDAX), and magnetic measurements. XRD patterns revealed a pure phase spinel ferrite structure for all samples with Scherrer’s grain diameter (D) ranging from 33.55 to 42.07 nm. Experimental, theoretical lattice constant (a _exp. , a _th.), specific surface area (S), and the distances between cations (M_e–M_e) (b, c, d, e, f) of the annealed Zn–Ni–Mg–Cu ferrite decrease with the increase in Ni doping. Elemental analysis, particle diameter, and surface morphology were examined by EDAX and SEM. Coercivity (H _c) and saturation magnetization (M _s) of Zn–Ni–Mg–Cu ferrite ranges between 0.97–167.5 Oe and 47.63–136.93 Am² kg⁻¹, respectively, signifying the soft character of annealed samples. Magnetic parameters such as H _c, magnetocrystalline anisotropy (K ₁), remanence (M _r), and reduced remanent magnetization (M _r/M _s) increase up to x = 0.51 and then reduce thereafter with Ni doping. Particle size dependence of H _c reveals superparamagnetic, single domain, and multi-domain nature of the studied ferrite. Observed similar trend of M _s, Néel/experimental magnetic moment (n _B ^N , n _B ^e ) with Ni content (x) follows the Néel’s two-sublattice model of ferrimagnetism and is accredited to the cationic distribution and B–B exchange interaction. All these results establish a strong connection between magnetic properties and cationic distribution of Zn_0.85−x Ni _x Mg_0.05Cu_0.1Fe₂O₄ ferrite.