Asymmetric Atomic Diffusion‐Engineered Magnetic Nano‐Interfaces for Enhanced Low‐Frequency Electromagnetic Wave Attenuation

Abstract Heterostructured magnetic nanomaterials, with their multilevel dielectric polarization and synergistic magnetic‐dielectric effects, hold highly promising candidates for low‐frequency electromagnetic (EM) wave absorption. However, fully leveraging these functional advantages requires precise manipulation of interfacial architectures, posing a formidable challenge in nanoscale material design. Here, an asymmetric diffusion‐driven heterointerface regulation strategy is developed to achieve precise control over nanoscale magnetic heterointerfaces within biphase nanoparticles (NPs). This diffusion asymmetry, characterized by the rapid outward migration of Fe atoms compared to the slower inward diffusion of Ni atoms, triggers the nucleation and gradient distribution of the medium‐entropy FeCoNi phase, enabling the rational modulation of FeCoNi/Fe 7 Co 3 nano‐interface distribution along the radial direction. The tailored FeCoNi/Fe 7 Co 3 @C heterostructures possess exceptionally low‐frequency electromagnetic energy conversion capabilities, effectively covering the entire C‐band and extending into the S‐band. This outstanding performance arises from the synergistic effects of i) enhanced local electric field and dipole relaxation polarization induced by the abundant nano‐interfaces and ii) improved magnetic anisotropy, driven by precisely controlled dipole‐dipole interactions dictated by the tunable magnetic nano‐interface distribution. This study provides fresh insights into the design of magnetic heterostructures and fundamental mechanisms governing heterostructure‐driven low‐frequency microwave absorption, paving the way for next‐generation EM wave‐absorbing materials.