Structure, magnetic, and microwave absorption properties of (MnNiCu)0.9−xCoxZn0.1Fe2O4/graphene composite powders

Highlights: • Single phase (MnNiCu)_0.9−xCo_xZn_0.1Fe₂O₄ powders were prepared by solution combustion synthesis method. • The coercivity of powders increased from 100 to 300 Oe with the Co substitution. • The 70 wt% (MnNiCuZn)_0.7Co_0.3Fe₂O₄/paraffin composite sample exhibited a high RL of −30 dB in Ku band. • The lower RL of -16 dB and wider effective bandwidth were achieved at the lower mass fraction by adding graphene. -- Abstract: (MnNiCu)_0.9−xCo_xZn_0.1Fe₂O₄/graphene composite powders (x=0.05, 0.1, 0.2, and 0.3) were prepared by one-pot solution combustion synthesis method. Structure, microstructure, and magnetic and microwave absorption properties were analyzed by modern characterization methods. The X-ray diffraction patterns showed that single phase (MnNiCu)_0.9−xCo_xZn_0.1Fe₂O₄ powders were obtained following combustion reaction without further heat treatment. The saturation magnetization was independent of Co substitution (~65 emu/g), while the coercivity increased from 100 to 300 Oe. The (MnNiCu)_0.6Co_0.3Zn_0.1Fe₂O₄/paraffin composite sample at the mass fraction of f=70 wt. % showed the maximum reflection loss of −30 dB with the effective bandwidth of 1.1 GHz at the matching thickness of 5.8 mm in Ku band. Although the maximum reflection loss decreased to −15 dB in X band with the addition of graphene, but the effective bandwidth increased to 2 GHz at the smaller matching thickness of 2.2 mm. Furthermore, the microwave absorption performance was obtained at lower mass fraction of (MnNiCu)_0.6Co_0.3Zn_0.1Fe₂O₄/graphene powders.