Synthesis of FeNi@kaolin soft magnetic composites with adjustable magnetic properties under different DC bias fields

Constructing the high-quality insulating layer and verifying the effects of DC bias field on magnetic properties is crucial in optimizing magnetic components based on soft magnetic composites. In this paper, a novel APTES-involved insulation technique has been developed to successfully coat kaolin on FeNi particles. Additionally, magnetic properties can be effectively regulated by changing the dosage of kaolin. The results show that anti-magnetization capacity and resistivity are improved by increasing kaolin content. Loss separation model and magnetic field simulation were used to investigate how the coating layer and DC bias field influence core loss for FeNi@kaolin SMCs. It can be found that structural demagnetizing field and eddy current were believed to be the main determinants of core loss variation in ideal sinusoidal waves, while the degree of magnetization state away from saturation plays a leading role in core loss under larger DC bias fields. Therefore, FeNi SMCs insulated with 1 wt% and 7 wt% kaolin exhibit the lowest core loss at DC bias field of 0 Oe and above 100 Oe, respectively. This work not only provides an effective insulating technique, but also supplies deeper insights into optimizing SMC-based magnetic components under larger DC bias fields.