Phosphating-enhanced Fe-based amorphous soft magnetic composites with ultra-low power loss for efficient electrical energy conversion

Soft magnetic composites (SMCs) play an indispensable role in electromagnetic conversion, transmission, and storage. However, achieving high-frequency, low-loss soft magnetic materials compatible with third-generation wide bandgap semiconductor devices remains a significant challenge. In this study, we report a novel strategy to fabricate Fe-based amorphous SMCs through a precisely controlled phosphating process. As the phosphoric acid content increases, the thickness of the insulating layer increases, resulting in higher resistivity. At the same time, the contribution of spin rotation to magnetization increases gradually and dominates throughout the magnetization. Compared with the untreated SMCs, the core loss (P_cv) of the SMCs treated with 1.0 wt.% phosphoric acid at 0.1 T/1 MHz was reduced by 11.6%, primarily due to the reduction of excess losses resulting from the different magnetization mechanisms. The optimized SMCs demonstrate outstanding overall magnetic performance, including ultra-low P_cv of 14.35 W/cm³ at 0.1 T/1 MHz, excellent DC-bias stability (69.4% at 100 Oe), relatively high saturation magnetic flux density (B_s = 0.84 T), and ultra-stable permeability (μ_e = 32.7) up to 20 MHz. These findings offer a promising pathway for designing high-performance SMCs tailored for high-frequency and high-power electronic applications.