High performance soft magnetic composites with optimized Fe3O4 coating layer using rotary reactor-based sputtering

Abstract

Soft magnetic composites with low power loss and high magnetic permeability are essential for energy-efficient and high-performance devices, as their applications have rapidly expanded. In this study, we propose a rotary reactor-based sputtering for powder coating technique employing a rotary reactor to achieve a uniform Fe3O4 coating layer with a precisely controlled thickness on FeSiBCr amorphous magnetic powder. By varying the Fe3O4 thickness from 15 to 50 nm, we optimized the microstructure to minimize power loss as well as enhance magnetic properties at high frequencies. As a result, the 15 nm-thick Fe3O4 coated powders exhibited a 73.5 % reduction in power loss compared to that of uncoated samples, with an improvement in effective permeability as much as 133.8 % of bare powders. The microstructural analysis also reveals that introduction of an amorphous Fe3O4 layer serves as an oxygen source leading to the formation of interfacial SiO2 layer, which plays an important role in reducing eddy current losses. This innovative sputtering technique on powder surfaces demonstrates a significant improvement over traditional coating methods, providing a scalable solution for high-performance soft magnetic composites in electronic and industrial applications. © 2025 The Author(s)