Evaluation of Structural, Magnetic, and Electromagnetic Properties of Co²⁺-Substituted NiCuZn Ferrites

We report citrate gel-assisted autocombusted spinel-type Co²⁺-substituted NiCuZn ferrites and their electromagnetic properties. Several complementary techniques were used to investigate the influence of Co on structural and electromagnetic properties of Ni_0.25-CoCu_0.20Zn_0.55Fe₂O₄ with x = 0.00-0.25 (step of 0.05). XRD analysis confirmed the highly crystalline single-phase cubic spinel structure with a prominent peak of the (311) plane. FE-SEM analysis showed the loss of porous gel structure (colloidal backbone) due to addition of cobalt into the present ferrite system. The EDAX analysis confirmed the presence of Ni, Cu, Zn, Co, and O in accordance with the relative stoichiometry of Co-substituted NiCuZn ferrite. The electrical resistivity of ferrites is observed to decrease when Co²⁺ ions are substituted, regardless of AC and DC. The dielectric properties (ε' and ε″) of ferrites exhibited a consistent decrease as the frequency increased, and this trend persisted even at higher frequencies. VSM analysis showed the normal magnetic hysteresis of the developed ferrite system. At x = 0.05, the saturation magnetization of the ferrite was obtained to be the highest among the other substitution levels of Co. The Curie temperature fell down when there was a higher concentration of cobalt in the ferrite system (x = 0.20). After reaching a specific temperature, the μ_i values decreased abruptly, with an increase in the temperature. The steady state may be deduced from the fact that the constant real component of the initial permeability, μ', remained unchanged. However, with decreasing frequency, the values of μ″ decreased dramatically. The present NiCuZn ferrite series displays the enhanced dielectric properties suggesting the capability of potential candidates for microwave absorption applications with enhanced electromagnetic properties.