Influence of Nanocrystalline Fe-based Powder Particles Size on the Magnetic Performance of Soft Magnetic Composites for High Frequency Applications

The soft magnetic composite (SMC) toroidal cores were prepared by the compaction method from ballmilled Fe-Si-B-Nb-Cu nanocrystalline ribbon with 20 vol% (3.7 wt%) resin addition as a binder. The objective of this work was to study their internal structure and magnetic performance at high excitation frequency. The computed tomography results showed that 70-80 vol% of ferromagnetic phase content was present in all samples, depending on the porosity. These composites exhibited much higher permeability and lower core loss at high frequency than the reference sample made of Somaloy (R) which contained almost 100 vol% of ferromagnetic phase. They exhibited constant level of permeability in the entire measurement range. The influence of the powder size fraction on the magnetic properties was determined as well. It appeared that coarser particles result in higher permeability and it can be increased even further by mixing the coarsest powder size fraction with the finest one. The presented results show that these materials are very attractive for high frequency applications.