Interface microstructure and electromagnetic properties of phosphorylated FeSiB@Fe3O4 amorphous soft magnetic composites via thermal decomposition

Herein, the phosphorylated FeSiB@Fe 3 O 4 amorphous soft magnetic composites (ASMCs) were designed and fabricated via powder metallurgy technology using high-temperature thermal decomposition. The influence of Fe 3 O 4 content on the microstructure, interface, and electromagnetic properties of phosphorylated FeSiB ASMCs was systematically investigated. Uniformly distributed Fe 3 O 4 magnetic nanoparticles (17.9 nm average size) with high saturation magnetization and low coercivity were synthesized, effectively filling powder gaps and enhancing resistivity from 0.585 Ω m to 1.187 Ω m, which mitigates magnetic dilution and reduces eddy current losses. Three-dimensional loss separation analysis confirms optimal Fe 3 O 4 addition decreases hysteresis, eddy current, and excess losses. However, excessive Fe 3 O 4 causes severe agglomeration, significantly increasing hysteresis loss. As a result, the phosphorylated FeSiB@Fe 3 O 4 ASMCs with 0.2 wt% Fe 3 O 4 nanoparticles achieve the lowest core loss of 118 kW/m 3 (at 100 kHz/50 mT) and high effective permeability of 65. This work provides a novel approach for designing high performance and ultralow loss SMCs for high frequency applications.