Synergistic Dielectric–Magnetic Enhancement via Phase‐Evolution Engineering and Dynamic Magnetic Resonance

Abstract Dielectric polarization and magnetic resonance associated with intrinsic constituent and extrinsic structure are two kinds of fundamental attenuation mechanisms for microwave absorbers, but remain extremely challenging in revealing the composition‐morphology‐performance correlation. Herein, hierarchical MXene/metal‐organic framework derivatives with coherent boundaries and magnetic units below critical grain size are constructed to realize synergistic dielectric–magnetic enhancement by phase‐evolution engineering and dynamic magnetic resonance. Specifically, phase‐evolution induced inseparable interfaces, diverse incompatible phases, and defects/vacancies contribute to dielectric polarization, while closely distributed magnetic units simultaneously realize nanoscale multi‐domain coupling and long‐range magnetic interaction. As results, the hierarchical derivatives promise an exceptional reflection loss of −59.5 dB and an effective absorption bandwidth of 6.1 GHz. Both experimental results and theoretical calculations indicate that phase‐evolution engineering and dynamic magnetic resonance maximize the absorption capability and demonstrate a versatile methodology for manipulating microwave attenuation. More importantly, the proposed multi‐domain coupling and long‐range magnetic interaction theories innovatively offer dynamic magnetic resonance mechanism for magnetic loss within critical grain size.