Research on microwave absorption properties of FeCoGe composites and achieving ultra-broad bandwidth via metamaterial design

FeCo-based soft magnetic alloys have been widely used as high-temperature-resistant microwave absorbents. However, the high hardness of pure FeCo alloy limits the formation of flaky morphology. Here, the brittleness of the alloy is improved by doping Ge. Excellent flaky morphology of Fe_6.5Co_3.5Ge_x powders is, thus, achieved while the Curie temperature maintains 850.8 ℃. The absorption performance of corresponding composites is significantly improved when being used in traditional continuous form. The bandwidth of Fe_6.5Co_3.5Ge_0.2 composite reaches 2.71 GHz (4.53–7.24 GHz) at thickness of 2 mm. To further extend the bandwidth by designing full-scale microwave absorbers, microscopic-scale and mesoscopic-scale regulations of Fe_6.5Co_3.5Ge_0.4 composite are combined with macroscopic-scale regulation of metamaterial design. The simulation results show that ultra-broadband absorption can be realized from 6.8 to 60 GHz at total thickness of only 2 mm. The performance is attributed to standing wave resonance and diffraction effects. This work provides an effective approach to obtain flaky FeCo-based absorbents and significantly extends absorption bandwidth by introducing metamaterial design, which has important application value.