MHz cut-off frequency and permeability mechanism of iron-based soft magnetic composites

The lack of soft magnetic composites with high power density in MHz frequency range has become an obstacle in the efficient operation of the electrical and electronic equipments. Here, a promising method to increase the cut-off frequency of iron-based soft magnetic composites to hundreds of MHz is reported. The cut-off frequency is increased from 10 MHz to 1 GHz by modulating the height of the ring, the distribution of particles, and the particle size. The mechanism of cut-off frequency and permeability is the coherent rotation of domain modulated by inhomogeneous field due to the eddy current effect. An empirical formula for the cut-off frequency in a magnetic ring composed of iron-based particles is established from experimental data. This work provides an effective approach to fabricate soft magnetic composites with a cut-off frequency in hundreds of MHz.