Dual-function structure design of CNT/Bi@Fe3O4 magnetic metacomposites towards tunable ε′-Negative response

Metacomposites have shown promising prospects in the application fields of radio frequency bands such as electromagnetic (EM) shielding/absorbing, meta-antennas, and stealth. However, the realization of their negative parameters is not due to the periodic array structure, which leads to the complex and ambiguous structure-property relationship. Therefore, we have created a bifunctional structure design strategy based on the three-dimensional network structure of carbon nanotubes (CNT) and the matrix phase of Bi and Fe 3 O 4 synergy. This strategy is based on the percolation concept of conductor/insulator and achieves dual-functional responses of magnetism/dielectric. We achieved a ε′ -negative response in the range of 100 MHz to 1 GHz by utilizing the plasma oscillation effect in the CNT network. The ε′ -negative value was regulated within the 1000 order of magnitude by the CNT content and the electric field frequency. Owing to the competition of multi-level interface polarization mechanisms, the effective carrier concentration of metacomposites is diluted, resulting in a significantly lower ε′ order compared to pure conductors. The maximum saturation magnetization of the CNT/Bi@Fe 3 O 4 metacomposites after percolation reaches 15–25 emu/g. The effectiveness of this structure can be further analyzed by using the equivalent circuit model and radar cross-section EM simulation technology, thereby clarifying the capacitance/inductance characteristics and EM shielding effect of ε′ -negative materials. Our work offers a novel structural design concept which broadens the scope of EM metacomposites and pave the way to practical applications.