Microstructural design of the magnetic composites with ultra-wide microwave absorption bandwidth has been attracting extensive attention in the fields of both electromagnetic shielding and radar stealth, but it still remains a great challenge. Herein, asymmetric Janus nanocomposites of Fe₃O₄/PDA vesicles were successfully prepared, and they exhibited strong absorption intensity (−50.0 dB) and ultra-wide bandwidth (6.4 to 18 GHz) covering 73% of the frequency range of 2–18 GHz with a film thickness of only 2.5 mm. The excellent absorption properties could be due to the asymmetric polarization and magnetic coupling effects, which allow most incident microwaves propagating from the nonmagnetic PDA shell into the magnetic core to be exhausted (−50.0 dB). Electron holography analysis confirmed the intense magnetic coupling of the high-density flux lines within the adjacent Fe₃O₄-derived core@shell network. Our findings suggest that the anisotropic Janus absorber effectively possesses a broad bandwidth, which might be extended to other asymmetric nanomaterials for electromagnetic interference applications.

中文翻译：

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类似于Janus的Fe ₃ O ₄ / PDA囊泡，具有更宽的微波吸收带宽†

具有超宽微波吸收带宽的磁性复合材料的微结构设计已在电磁屏蔽和雷达隐身领域引起了广泛的关注，但仍然是一个巨大的挑战。在此，Fe ₃ O _4的不对称Janus纳米复合材料已成功制备了/ PDA囊泡，它们具有很强的吸收强度（-50.0 dB）和超宽带宽（6.4至18 GHz），覆盖了2-18 GHz频率范围的73％，膜厚仅为2.5 mm。出色的吸收性能可能归因于非对称极化和磁耦合效应，这使从非磁性PDA外壳传播到磁芯的大多数入射微波被耗尽（-50.0 dB）。电子全息分析证实了相邻的Fe ₃ O ₄内高密度磁通线的强磁耦合。派生的core @ shell网络。我们的发现表明，各向异性的Janus吸收器有效地具有较宽的带宽，可以将其扩展到用于电磁干扰应用的其他非对称纳米材料中。