Fabrication of soft magnetic cores composed of amorphous Fe–B particles for next generation magnetic passive components

This paper reports the core loss of soft magnetic composite toroidal cores consisting of submicron-sized amorphous Fe–B particles with spherical shape synthesized by an aqueous reduction reaction method. The core loss of Fe–B composite cores was as low as 0.0015 J/m3 in the frequency range of 10 kHz to 4 MHz at a maximum magnetic flux density Bm of 1 mT, meaning that the eddy current loss can be suppressed. This result can be derived from a combination of the reduction of the particle size, amorphous structure and their relatively higher resistivity. In contrast to Fe–B particles, the toroidal core consisting of the commercial carbonyl iron particles showed the increase of core loss at the frequency more than 200 kHz, which may be attributed to the increment of eddy current loss originating from their relatively larger particle size and decrement of resistivity induced by particle coarse after compaction. Therefore, these results suggest that submicron-sized amorphous Fe–B particles is one of the candidate materials for the next-generation magnetic passive components in the frequency range of MHz.