Remarkable Magnetic Exchange Coupling via Constructing Bi-Magnetic Interface for Broadband Lower-Frequency Microwave Absorption

摘要

Severe lower-frequency (2–8 GHz) microwave pollution caused by the rapiddevelopment of 5th generation (5G) communication posts significance on cutting-edge microwave absorbers. However, the intensely coupled wave-impedanceand microwave dissipating ability dramatically hinder their performancein the exact lower-frequency range. The rationally designed heterostructure ofhard/soft ferrite composite provides an efficient solution to address the issue.In this context, core-shell structured hard/soft BaFe(12-x)Co_xO_(19)@Fe_3O_4 withabundant heterointerface is created using facile spray-drying and subsequentsolvothermal approach, where hard magnetic BaFe(12-x)CoxO19 serves as thecore and soft magnetic Fe3O4 serves as the shell, respectively. The unique coreshellintegration contributes sufficient magnetic exchange coupling interactionfor strong magnetic loss beyond Snoek’s limitation, which considerably boostsa lower-frequency microwave absorption. Accordingly, the minimum reflectionloss (Rlmin) of typical BaFe_(11.6)Co_(0.4)O_(19)@Fe_3O_4 microcomposite reaches?48.9 dB at the thickness of 3.5 mm, its bandwidth of reflection loss < ?10 dBcan cover almost all the S and C bands (2.6–8 GHz). Generally, an easy andcontrollable pathway is conveyed in this work to encourage improved magneticloss ability as well as decouple the wave-impedance and microwave dissipatingability in magnetic composites, which widens the road to the development ofadvanced lower-frequency magnetic absorbers.