Broadband ultra-thin millimeter wave absorber designed using multilayered ε-Ga_δFe_2−δO₃ nanomagnets in the V-band

A broadband millimeter wave absorber is designed using multilayered ultra-thin ε-Ga_δFe_2−δO₃ nanomagnets in the V-band, where δ is the doping level of the gallium into the host ε-Fe₂O₃ material. Four different doping levels are considered to build four kinds of ε-Ga_δFe_2−δO₃ nanomagnets, which are further stacked as a four-layer broadband absorber. Its absorption properties are theoretically studied using the lossy transmission line theory. Results show that the four-layer nanomagnets can absorb over 90% of perpendicularly incident power from 50.7 to 74.9 GHz in the V-band. The proposed multilayered absorber is ultra-thin with the total thickness of 351 μm. It is only 0.059λ_L, where λ_L is the wavelength at the lowest frequency 50.7 GHz. The robustness of the absorbing performance is also studied by slightly varying the four-layer nanomagnets’ doping levels and layer thickness from the default setting.