High-frequency FeSiAl-based soft magnetic composites via simultaneously suppressed eddy and hysteresis losses

Soft magnetic composites present promising solutions for integrated transformers and inductors, but challenges arise at MHz range, where hysteresis and intra-eddy losses result in substantial performance degradation. In this study, we propose a bulk/interface insulation strategy to synthesize FeSiAl:Sn/Al₂O₃ soft magnetic composite by mutual diffusion of metal atoms, where a ~ 3 um-depth Sn-substituted FeSiAl is obtained in the matrix and an insulating Al₂O₃ layer is epitaxially grown on FeSiAl surface. The formation of FeSiAl:Sn can not only suppress intra-eddy loss by enhancing electrical resistivity, but also reduce coercivity by mitigating lattice distortion for reducing hysteresis loss. Meanwhile, the in-situ grown Al₂O₃ layer can reduce inter-eddy loss by electrical isolation between FeSiAl particles. This construction leads to power loss of 47 mW/cm³ at 100 kHz and 1344 mW/cm³ at 1 MHz under 50 mT, as well as effective permeability of 60 up to tens of MHz, associated with cut-off frequency of 250.7 MHz. This approach lays the groundwork for the development of high-frequency soft magnetic composites in engineering applications.