Sequential Architecture Induced Strange Dielectric-Magnetic Behaviors in Ferromagnetic Microwave Absorber

The high filler loading (FL) is a bottleneck in developing lightweight ferromagnetic microwave absorbers (MAs) for the actual applications. Sequential architecture design of MAs can induce strange physical behaviors due to the unique coupling-enhancement effect between functional units, providing a vast potential for achieving high microwave absorption performance. However, the FLs of current sequential MAs fail to be designed on demand because the strange dielectric-magnetic behaviors cannot be fulfilled. The influence of sequential architecture engineering on the macroscopic properties or microscopic loss mechanism still needs more exploration. Herein, based on four mesoscopic models (particles, chains, bundles, and fibers) of ferromagnetic functional units, a series of ferromagnetic MAs with different sequential architectures are prepared via a bottom-up self-assembly method. The fibrous samples exhibit the best microwave absorption performance (-51.3 dB, 4.12 GHz) at a breakthrough FL of 2 wt%, which is one order of magnitude less than other ferromagnetic MAs. Strange dielectric-magnetic behaviors, including negative permittivity and heterodromous chiral vortex, occur due to functional units with lateral and fibrous configurations. Further, four special models are established to reveal the microwave attenuation evolutionary mechanism. This study clarifies the relationship between sequential architecture and strange dielectric-magnetic behaviors, which provides new sight to understand microscopic electromagnetic loss mechanism.