The construction of 3D porous structures and metamaterials (MMs) is the most promising approaches to achieve broadband electromagnetic wave (EMW) absorption. However, it is still a huge challenge to achieve multispectral ultra-broadband EMW absorption properties compatible with low-frequency band (L- and S-band) due to its ultralong wavelength and strong bypass capability. Herein, magnetic-dielectric synergistic gradient MMs (MDSGM) consisting of oriented flaky carbonyl iron (FCI) film and periodical RGO/CNT/CNF aerogel (GTFA) array are demonstrated. Benefiting from the synergistic effect of strong magnetic-dielectric loss, structural loss, and excellent impedance matching, MDSGM harvests an exciting multispectral ultra-broadband EMW absorption performance with a remarkable effective absorption bandwidth covering the whole measured frequency of 1-40, 50-110 GHz, and 0.1-2.0 THz for the first time. The minimum RL (RLmin) reaches -40.24 dB and average RL is up to -19.3 dB (98.8% EMW being absorbed) in microwave band. Moreover, this multispectral ultra-broadband EMW absorption property is less affected by the incident angle. This work pioneered realization of multispectral ultra-broadband EMW absorption compatible with low-frequency, which provides a great thrust for the development of stealth technology in the upcoming smart era.

The novel strong magnetic-dielectric synergistic gradient metamaterials (MDSGM) consists of oriented flake carbonyl iron film and periodical unit of RGO/CNT/CNF aerogel are successfully assembled. Accordingly, MDSGM provide excellent impedance matching and strong magnetic-dielectric loss capability in all measured frequencies and thus demonstrate a remarkable multispectral ultra-broadband (1-40, 50-110 GHz, and 0.1-2 THz) absorption performance for the first time.