Confining Magnetic Response by the Surface Reorganization of Buckling Permalloy Microspheres for Boosting Microwave Absorption

Abstract

Sharp corners and edges with high surface curvature provide low-dimensional nanosized materials with special static magnetic properties. However, the surface engineering of their high-frequency magnetic response remains challenging, and the underlying mechanism requires further clarification. In this study, we propose a template-aided surface reorganization strategy for integrating surfaces with different curvatures into one permalloy architecture. The high-curvature surface demonstrates a dramatic variation in localized magnetic moments and confines the coupling of magnetic flux lines owing to high anisotropy, which helps concentrate magnetic energy absorption and dissipation. In addition, the magnetic resonances of multiple surfaces were superimposed by the spin-wave interaction for enhancing magnetic loss capacity, which cooperates with amorphous/crystalline interfacial polarization to achieve a satisfactory dielectric-magnetic synergistic electromagnetic wave (EMW) absorption performance. The reflectance loss values increased from -13.4 dB for microspheres to -49.7 dB for surface-restructured ones. Remarkably, the effective absorption bandwidth can be extended to 7.68 GHz with a matching thickness of 2.0 mm. This advancement presents new possibilities for an elaborate design of magnetic EMW absorbers and establishes a basis for comprehending a complex magnetic response mechanism.