High-performance core-shell-type FeSiCr@MnZn soft magnetic composites for high-frequency applications

Abstract Soft magnetic composites (SMCs) are widespread utilized in modern electronic components such as inductors, transformers, and electrical motors. They have attracted much attention for use in high- and ultra-high-frequency applications for their advantages over conventional ferrite core materials. However, to make SMCs meet the requirements of high-frequency, miniature and lightweight electrical systems, it is necessary to suppress core losses Pcv and obtain excellent frequency characteristics, which is a tremendous challenge. Herein, we improve the high-frequency characteristics of core losses Pcv by coating FeSiCr powders with different concentrations of MnZn ferrites (0.0–10.0 wt%). The microstructure, magnetic, electric and core losses characteristics of the FeSiCr@MnZn soft magnetic composites are analysed in detail. A remarkable coating quality is revealed by energy-dispersive X-ray spectroscopy mapping. The core losses Pcv (at 25–800 kHz, 10 mT and 25 °C) are separated into hysteresis losses Ph and eddy current losses Pe. With increasing MnZn ferrite concentration, Pcv, Ph and Pe present an initial decrease and subsequent increase. SMCs with 4.0 wt% MnZn ferrites exhibit the best electromagnetic properties in terms of saturated magnetization Ms (149 emu/g), effective permeability μe (48 at 10 kHz–1 MHz), resistivity ρ (8.46 × 103 Ω∙m), and core losses Pcv (45 mW/cm3 at 800 kHz, 10 mT and 25°C). These FeSiCr@MnZn SMCs have outstanding electromagnetic performance, giving them great potential for application to power devices and components.