MHz low loss approach of Fe-Si soft magnetic composite

Soft magnetic materials (SMMs) play a key role in the conversion of electric energy throughout the world. Developing MHz SMMs is a strategy for modern power systems supported by wide bandgap semiconductor devices. However, significant loss above hundreds of kHz in SMMs become a bottleneck for efficient energy conversion. Here, we report an effective approach to achieve a 250 kW/m³ low loss of Fe-Si composites at 3 MHz with 1.5 T saturation magnetization. By decreasing the particle size to 1 μm in a core-shell structure or increasing the particle ratio of diameter/thickness to 100 in a layered structure, low loss particles with mechanism of coherent rotation modulated by the eddy current is formed in dense composites. Study shows that the decrease of loss primary comes from the collaborative decreasing of eddy current and excess loss. This approach opens a way to find MHz efficient SMMs for next-generation high-efficiency power systems.