Curvature‐Induced Anisotropy Drives Broadband Magnetic Loss and Ultra‐Strong Microwave Absorption

ABSTRACT Magnetic absorbers are often limited by intrinsic anisotropy and rigid domain configurations, which restrict relaxation pathways and deteriorate bandwidth and efficiency. Here, we introduce a stress‐modulation strategy that harnesses curvature‐induced residual compressive stress in hollow Y 2 Fe 17 to engineer lattice strain, amplify orbital moments, and fragment magnetic domains, thereby enabling broadband and strong microwave absorption. Gas‐atomized hollow particles exhibit localized lattice contraction and atomic‐scale disorder along their inner shell, giving rise to dense, curved domain walls and pronounced gradients in magnetocrystalline anisotropy. The resulting stress‐induced anisotropy coupling significantly enhances the imaginary component of the permeability over 2–18 GHz, thereby promoting impedance matching and enabling multiple internal reflections. As a result, the material achieves an ultralow reflection loss of −72.5 dB and an effective absorption bandwidth of 7.5 GHz at a slim thickness of 2.1 mm. Finite‐element simulations further reveal that electromagnetic dissipation is spatially concentrated at the stressed inner shell, establishing a direct link between geometry, stress, and broadband magnetic attenuation. Our work introduces internal‐stress‐driven domain engineering as a composition‐independent paradigm for designing lightweight, broadband, and high‐efficiency microwave absorbers.