Fabrication of Zn0.25Co0.75(MnZr)xFe2–2xO4 spinel ferrites as broadband microwave absorbers in 26.5–40 GHz frequency range

Abstract

With the advent of 5 G technologies, developing microwave-absorbing materials is an urgent need to address the issues caused by harmful electromagnetic pollution. For this purpose, a novel ferrite series with composition Zn0.25Co0.75(MnZr)xFe2–2xO4 (0.05 ≤ x ≤ 0.25, ∆x = 0.05) was successfully synthesized using the sol-gel citrate route. Also, the effects of the co-substitution of Mn and Zr on the structural, morphological, magnetic, electromagnetic, and microwave absorption characteristics of zinc-cobalt spinel ferrites were studied. The X-ray diffraction patterns indicated the formation of nanoparticles having a cubic spinel lattice structure. Coercivity was found to decrease whereas saturation magnetization increased with the increasing level of substitution from MZ 0.05 to MZ 0.25. In Ka-band, the experimental results showed that MZ 0.15 outperformed all the prepared compositions by exhibiting a minimum reflection loss of −27.99 dB and an efficient absorption bandwidth of 6.5 GHz at a narrow sample thickness of 2.2 mm. The simulation performed by varying the sample thickness revealed that the high values of gross loss tangent and excellent impedance matching lead the composition MZ 0.20 to achieve the optimum value of reflection loss of − 42.71 dB at a matching frequency of 29.20 GHz and a matching thickness of 1.1 mm. These findings suggested that the fabricated materials prove to be efficient absorbers in the 26.5–40 GHz frequency range.