Effects of Li+ and Mg2+ Dopants on the Magnetic Properties of Ni–Zn Ferrites

Ni_0.5-0.5xZn_0.5-0.5xMg_xFe₂O₄ and Ni_0.4Zn_0.6-2xLi_xFe_2+xO₄ ferrites (x = 0.05, 0.10, and 0.15) were prepared and examined. Both systems after sintering showed a pure spinel phase and a uniform grain size and the lattice constants declined slightly as the amount of the Mg²⁺ and Li⁺ dopants increased. The average grain sizes of the Ni_0.5-0.5xZn_0.5-0.5xMg_xFe₂O₄ ferrites appeared to show little variation (ranging from 4.22 to 4.55 gm), while those of the Li⁺-doped Ni-Zn ferrites were dramatically reduced from 5.95 to 1.40 gm corresponding to the escalation in the x values from 0 to 0.15. In terms of the magnetic properties evaluated, the Ni_0.475Zn_0.475Mg_0.05Fe₂O₄ and Ni_0.4Zn_0.4Li_0.10Fe_2.10O₄ ferrites demonstrated the best performance. The Ni_0.475Zn_0.475Mg_0.05Fe₂O₄ ferrite reported a saturation magnetization of 76.9 emu/g, an initial permeability of 611.3, and a quality factor of 16.3, while the Ni_0.4Zn_0.4Li_0.10Fe_2.10O₄ ferrite presented a saturation magnetization of 82.3 emu/g, an initial permeability of 191.3, and a quality factor of 64.3. The former is marked with a high permeability and the latter a high quality factor. These properties make them exceptionally promising for high-frequency applications.