Dimensional Self‐Assembled Magnetic Coupling via Embedding Ferromagnetic Nanoparticles in Multi‐Channel Fibers for Microwave Absorption.

1D magnetic fibers with significant morphological diversity and magnetic anisotropy are highly desirable for optimizing magnetic properties and electromagnetic responsiveness. However, it remains challenging for the precise control over internal magnetic interactions within each fiber. Herein, a strategy for self‐assembled magnetic coupling is taken to achieve the controllable reconstruction of continuous multiple coupling networks within a single fiber. High‐density ultrafine cobalt nanoparticles are uniformly embedded inside a carbon framework with a 1D multi‐channel structure (Co@MCF). This structure establishes a complex magnetic response system characterized by inherent inter‐fiber interactions and refined intra‐fiber self‐assembling coupling. The distinctive distribution of magnetic flux lines demonstrates enhanced magnetic sensitivity. This results in a minimum reflection loss of −57.65 dB and a broadband absorption frequency range of 7.28 GHz at 1.9 mm, effectively covers the entire Ku band and a substantial portion of the X band. The multi‐channel structure enhances the understanding of the relationship between microstructure and performance in magnetic fibers. Additionally, it positions Co@MCF as a highly competitive candidate for microwave absorption applications. [ABSTRACT FROM AUTHOR]