Tuning the magnetic and dielectric properties of Fe₃O₄ nanoparticles for EMI shielding applications by doping a small amount of Ni²⁺/Zn²⁺

Magnetite (Fe₃O₄) nanoparticles have been considered as a promising microwave absorption materials. To further tune their electromagnetic interference shielding efficiency, different compositions of doped Ni_0.01−xZn_xFe_2.99O₄ (x = 0.0, 0.005, 0.01) nanoparticles were synthesized by the co-precipitation technique. The prepared nanoparticles structure was characterized by X-ray diffraction, transmission electron microscopy, and Mössbauer spectroscopy. Impedance spectroscopy and magnetic measurements showed a dramatic enhancement in the dielectric and magnetic properties of Ni²⁺ doped Fe₃O₄ among the prepared samples, respectively. This is ascribed to the homogeneous distributed microstructure and considerable Fe²⁺/Fe³⁺ ratio at the octahedral sites due to unusual cation redistribution in the Ni_0.01Fe_2.99O₄ nanoparticles. Moreover, the measurements of total shielding efficiency exhibited an improvement of 83% in the shielding effectiveness of Ni_0.01Fe_2.99O₄ (∼22 dB) with the absorption dominant mechanism compared to pure Fe₃O₄ (∼12 dB) in the X-band frequency range. This is probably the result of a better impedance matching between the permittivity/permeability and dielectric/magnetic losses.