Emerging Materials and Designs for Low- and Multi-Band Electromagnetic Wave Absorbers: The Search for Dielectric and Magnetic Synergy?

Vigorous development of 5G communication technologies can boost mobile networks yet bring in electromagnetic interferences and safety concerns in utilizing electronic devices. Particularly, 5G network can not only involve a low-frequency band of n78 (3.3–3.8 GHz) but also cover multi-frequency bands of n77 (3.3–4.2 GHz) and n79 (4.4–5.0 GHz), displaying multiple electromagnetic radiations. Countless efforts have been devoted to investigating electromagnetic wave (EMW) absorbers with low- and multi-band absorption properties. However, in terms of emerging materials and designs, few reports propose the mechanisms related to those properties. This perspective briefly reviews the impressive achievements of low- and multi-frequency EMW absorbers and analyzes the design strategies that may enable low- and multi-frequency absorption. Furthermore, the cutting-edge mechanisms of corresponding electromagnetic responses, such as Snoek limit, quarter wavelength, and dielectric-magnetic synergy effects are elaborated. Thus, this perspective can shed light on the new trends and ongoing challenges for EMW absorbers and further promote their practical application.