Hierarchical Heterogeneous Co‐Based Magnetic Absorbers for Superior Broadband High‐Efficiency Microwave Absorption

Abstract Microwave absorbing materials are crucial for digital industries, communication networks, and stealth technology. However, precise microwave absorption performance control through microstructure design remains challenging. Herein, a strategy based on multiple equilibrium/competitive reactions is developed to fabricate Co‐based microwave absorbers with tunable morphologies. The core–shell spherical cobalt (CS‐SC) exhibits superior microwave absorption performance due to optimized impedance matching and interfacial effects. It achieves an effective absorption bandwidth ( EAB ) of 8.3 GHz (9.7–18.0 GHz) at 2.1 mm thickness, with a minimum reflection loss ( RLmin ) of −51.6 dB. Radar cross‐section (RCS) simulations confirm a low RCS (〈 −20.0 dB m ² ) over incident angles from −90° and 90°. This work provides novel insights into the microstructural engineering of magnetic absorbers via solvothermal methods and the strategic modulation for their microwave absorption performance.