Engineering Structural Anisotropy for Visualizing and Controlling Nanomagnetic Interactions with High‐Frequency Electromagnetic Wave

Abstract Structural anisotropy in micro‐ and nanoscale magnetic materials is critical for their magnetic response to high‐frequency electromagnetic (EM) fields. However, controlling and visualizing these magnetic properties at the nanoscale remains a significant challenge. In this study, it proposes a strategy for the directional regulation of anisotropy in iron‐based magnetic materials. By manipulating particle structures, preferential orientation designs are achieved, resulting in spherical, spindle‐shaped, symmetrical hexagonal cone‐shaped, and disc‐shaped morphologies. Utilizing off‐axis electron holography and micromagnetic simulations, it observes that the material's response to high‐frequency EM waves intensifies with increasing structural anisotropy. This enhanced anisotropy directly influences high‐frequency magnetic permeability, enabling effective modulation of EM waves. Building on these insights, spindle‐shaped magnetic structures are developed with strong uniaxial anisotropy, achieving enhanced microwave absorption and surpassing the Snoek limit. These structures exhibit an initial permeability of up to 2.03, a 35% improvement over isotropic structures. They cover the 4.58–7.88 GHz range, providing absorption across more than 50% of the wireless communication band with a thin coating of just 3.0 mm, outperforming existing absorbers. Notably, the absorption bands predominantly lie within civilian frequency ranges (2–8 GHz), offering electromagnetic pollution protection for 5G and future 6G communication technologies.