Dielectric shell regulation in synergy FeCoNi@ZnIn<sub>2</sub>S<sub>4</sub> microspheres with broadband electromagnetic wave absorption

Core-shell structure and magnetic-dielectric coupling in functional composites are important factors for obtaining excellent electromagnetic (EM) wave absorption performance, but they also face challenges. In this study, magnetic FeCoNi and dielectric ZnIn₂S₄ were combined to form unique core-shell structured microspheres. The morphology characteristics, EM parameters, and absorption performance of FeCoNi@ZnIn₂S₄ composites with different annealing temperatures were investigated to reveal impedance matching and synergistic absorption mechanisms. Those results show that FeCoNi@ZnIn₂S₄-600 (FCNZ-600) has excellent EM wave absorption properties, with the minimum reflection loss (RL_min) of -52.4 dB at 1.9 mm and the efficient absorption bandwidth of 6.08 GHz at 1.53 mm, which achieves broadband absorption. Core-shell magnetic-dielectric design provides a new perspective in efficient EM wave absorption systems.