A new Fe-based nanocrystalline soft magnetic composites with ultra-low core loss and superior DC-bias permeability up to megahertz-frequency

Demands on soft magnetic composites (SMCs) for superior magnetic performance, including low core loss, high permeability, high saturation magnetic flux density, and strong DC-bias stability up to dozes of megahertz, are urgently needed for power electronics, which are crucial in advancing third-generation semiconductors. However, traditional SMCs systems face challenges of high loss and poor DC-bias characteristics. In the present study, high-performance SMCs were fabricated by novel Fe_73.3P₅Si_7.6B_9.5C_1.9Nb₂Cu_0.7 powders with spherical shapes and a fully glassy structure, which were produced via gas atomization. To enhance the magnetic performance at high frequencies, in-situ oxide insulation layers were formed by controlling the varying concentrations of HNO₃. The evolution of the oxidation layer's structure and thickness was systematically clarified. SMCs demonstrated superior magnetic performance, including highly stable permeability (μ′) remained between 30 and 47 up to 20 MHz, excellent DC-bias permeability increase from 57.8 % to 82.7 % under 100 Oe, high cut-off frequency up to 96 MHz, and low core loss (P_cv) that regulated less than 153–173 mW/cm³ (50 mT, 100 kHz), 590–663 mW/cm³ (100 mT, 100 kHz). The magnetic properties of present SMCs are comparable to those of the most prominent SMCs reported so far. The proposed method and alloy composition provide a promising pathway for producing advanced SMCs. These results are meaningful for potentially stimulating the development and application of new low-loss SMCs.