Broadband Tunable Metamaterial Absorber Based on U-shaped Ferrite Structure

A broadband tunable metematerial absorber is proposed and demonstrated. As demonstrated in waveguide, the absorber consists of eight U-shaped ferrite particles and a metallic ground plane. These U-shaped ferrites directly act as resonators, and when the incident electromagnetic wave and applied magnetic field are simultaneously acting on the U-shaped ferrite particles, U-shaped ferrites can produce ferromagnetic resonance (FMR). Absorption frequency of the all-ferrite absorber can be tuned by the applied magnetic field and the saturation magnetization. Simulation results show absorption above 70% in the frequency range from 8.55 GHz to 10 GHz under applied magnetic field with H
₀
= 2700 Oe. By analysis, we find that the magnetic loss and dielectric loss lead to broadband absorption. The experiment test agrees well with the simulation results under different applied magnetic fields. This work provides an alternative route to realize tunable perfect absorbers with all-ferrite structures. With the artificial design of ferrite materials, the broadband tunable absorber can be designed and well serve in high power environment.