Dimensional Engineering of Hierarchical Nanopagodas for Customizing Cross-Scale Magnetic Coupling Networks to Enhance Electromagnetic Wave Absorption

Dimensional engineering of appropriate structure is an effective approach to achieve high-performance electromagnetic (EM) wave absorption for magnetic materials. However, controllable modulation of the material configuration and a comprehensive understanding of the relationship between structure and loss mechanism remain challenging. Herein, magnetic CoNi pentagonal nanopagodas (PNPs) are ingeniously tailored using a competition orientation strategy, in which high-density PNPs with sharp corners/edges and hierarchical structure are rooted in situ on the surface of CoNi alloy microsphere. This unique configuration of PNPs originates from the orientation growth of CoNi fivefold twins, which can be effectively regulated by manipulating metal ratio and evolves into flake-, serrated thorn-, prismoid-, and blocks-like morphologies. Optimized CoNi microspheres with high-density PNPs exhibit a broad absorption bandwidth of 6.82 GHz at only 1.8 mm thickness. Cross-scale magnetic coupling networks strengthen magnetic loss ability, magnetocrystalline defects induce dielectric polarization enhancement, which are intuitively confirmed by Lorentz off-axis electron holography and geometric phase analysis. The underlying mechanism of enhanced magnetic interaction in sharp structure is clearly deciphered by micromagnetic simulation. This study provides methodological guidance for dimensional engineering in fabricating hierarchical magnetic structure and significant insights into the morphology-dependent loss mechanism for magnetic EM absorption materials.