Simultaneously improving the permeability, core loss and frequency stability of Fe-based soft magnetic composite by optimizing the aspect ratio of reduced Fe powders

• The reduced Fe powders with various aspect ratios were prepared by ball-milling. • A large aspect ratio lowers the demagnetizing field and eddy current loss in SMC. • Increased aspect ratio of powder is beneficial for the magnetic properties of SMC. • Permeability, core loss and frequency stability can be simultaneously enhanced. Aiming at developing Fe-based soft magnetic composites (SMCs) with good high-frequency performance, the aspect ratio of reduced Fe powders was modified by ball-milling. The SMCs were prepared by phosphating treatment and resin binding followed by pressing forming. It is found that a large aspect ratio of the powder can effectively reduce the demagnetizing field and suppress the intra-particle eddy loss in the SMC by forming a lamellar structure. As a result, the effective permeability μ e , core loss P s , and frequency stability of the SMC can be simultaneously improved. The excellent magnetic properties with high μ e of 84, low core loss P s of 552 kW/m 3 at 50 mT and 100 kHz, and high-quality factor Q of 62, together with a high frequency stability up to 2.5 MHz, were obtained by using the reduced Fe powders with the aspect ratio of 30:1. Electromagnetic simulation further verified that the increased aspect ratio contributes to the reduced eddy current loss. This work provides a possibility for the application of reduced Fe powder in SMCs for high performance power inductors or other electronic components.