Tailoring Successive Magnetic‐Dielectric Synergy for Enhancing Electromagnetic Absorption in Ultralong Heterostructure Chains Assisted by High Static Magnetic Field

ABSTRACT The dimensionality and size effects in magnetic‐dielectric composite governs a fundamental trade‐off between the intrinsic functionality and external tunability, which critically constrains the development of high‐performance electromagnetic (EM) materials with efficient magnetic‐dielectric synergy. Herein, we propose a magnetic‐field‐driven dual low‐dimension strategy to fabricate length programmable magnetic‐dielectric heterojunction chains, where one‐dimensional (1D) Fe 3 O 4 chains were tightly encapsulated by the in situ grown two‐dimensional MoS 2 nanosheets. This strategy enables precise control over the chain length across micrometers to millimeters, as well as the surface defects, by deterministic regulation of the applied static magnetic field. Systematical theoretical simulations demonstrate that the high uniaxial anisotropy from 1D structure boosted magnetic response and the abundant Fe 3 O 4 /MoS 2 heterointerfaces induced polarization enhancement jointly contribute to the unique successive synergistic loss mechanism in the 1D magnetic‐dielectric heterojunction chains. Eventually, the optimum 1D Fe 3 O 4 @MoS 2 heterojunction chains with a record length of 2485.15 µm exhibit a broadband EM absorption performance with an effective absorption bandwidth of 5.5 GHz at a thin thickness of 1.8 mm, outperforming conventional counterparts. This study establishes a novel paradigm for crafting low‐dimensional magnetic‐dielectric heterostructure with tailored EM functionality, guiding the design of advanced EM materials for next‐generation flexible electronics.