Wideband square spiral metamaterial absorbers based on flaky carbonyl iron/epoxy composites

A broadband and thin microwave absorber composed of metal-base planar metamaterials (MMs) sandwiched between two layers of flaked-shaped carbonyl iron (FCI) composites is presented. FCI powder was prepared by ball milling spherical carbonyl iron powder and then added to epoxy resin to prepare FCI composite (FCIC) samples with different weight fractions. With these electromagnetic characteristics, a broadband, polarization-insensitive and thin metamaterial absorber comprising of arrays of square spirals embedded between two different layers of FCIC is optimally designed through a genetic algorithm. The reflection loss of the measured square spiral MM absorber with a thickness of 3.4 mm can reach –26 dB at matching frequency 4.4 GHz and the absorbing bandwidth below –9.3 dB is covered from 3.6 to 18.0 GHz which almost 4 fourfold bandwidth compared to that of the FCIC without the incorporation of MM layers.