Effects of Sn4+ and Co2+ Ion Content on the Magnetic and Microwave Absorption Properties of NiCuZn Ferrites

Ni0.5Zn0.5CoxCu0.1SnxFe1.933-2xO4 spinel ferrites x = (0, 0.05, 0.10, 0.15) were synthesized by a conventional solid-state reaction method to investigate the effects of Co2+/Sn4+ co-doping on structural, magnetic, and microwave absorption properties. X-ray diffraction results confirm that all samples possess a single-phase spinel structure without secondary phases. A slight shift of diffraction peaks toward lower angles indicates lattice expansion caused by the substitution of Fe3+ ions with larger Co2+ and Sn4+ ions. Magnetic measurements show typical soft-magnetic behavior for all samples, with coercivity below 30 Oe. The saturation magnetization decreases gradually with increasing doping content due to the reduction of the B-site magnetic moment. Electromagnetic parameter analysis in the 2-18 GHz range reveals that moderate Co/Sn co-doping improves dielectric–magnetic loss synergy and impedance matching. The sample with x = 0.05 exhibits the best microwave absorption performance, achieving a minimum reflection loss of -39.18 dB at 6.72 GHz with a thickness of 5.5 mm and an effective absorption bandwidth of 4.3 GHz. The enhanced absorption performance is mainly attributed to the cooperative regulation of complex permittivity, permeability, and impedance matching induced by Co2+/Sn4+ co-doping. These results demonstrate that Co/Sn co-doping is an effective strategy for tuning the electromagnetic properties of Ni-Zn ferrites for microwave absorption applications.