Multiscale assembly of Fe2B porous microspheres for large magnetic losses in the gigahertz range

Highlights: • Multi-scale assembly of Fe₂B porous microspheres were synthesized by a molten salt method. • Microsphere integrates the merits of the magnetic nanoflake and the hierarchical microstructure. • The magnetic loss ability exceeds the dielectric loss capability at 2–18 GHz. • For 1.8 mm and 1.9 mm absorber layer, f_E, in which RL exceeds 10 dB, can achieve 4.4 GHz, respectively. A large magnetic loss is an important factor for microwave absorbers. In this study, we used a molten salt method to synthesize a multiscale assembly of Fe₂B porous microspheres comprising microparticles assembled by Fe₂B nanoflakes. The magnetic loss factor values are larger than those of the dielectric loss factor at 2–18 GHz, which is ascribed to the shape anisotropy and multiple magnetic resonances. The Landau-Lifshitz-Gilbert equations are used to explain the origin of the multiple magnetic resonances, and the fitting curves match well with the permeability values. For 1.8 mm and 1.9 mm thick absorber layers, the effective absorption band, in which the absolute value of the reflection loss exceeds 10 dB, can reach 4.4 GHz, covering 13.6–18 GHz and 12.8–17.2 GHz, respectively. Our study opens up a new way to improve the magnetic loss ability of absorbers with artificial architectures.