Fe4N soft magnetic composite with ultra-low eddy current loss and excess loss above megahertz

In this study, Fe4N particles were synthesized from pure iron by gas nitridation and then fabricated into soft magnetic composite through silica-polyurethane insulation combined with warm compaction. The composite exhibits excellent soft magnetic properties in the several-megahertz frequency range. The complex permeability spectra of Fe4N composite show a remarkable frequency stability, with the real part remaining nearly constant below 100 MHz. The resonance frequencies of domain wall motion mechanism and spin rotation mechanism are up to 481 MHz and 2.24 GHz, respectively, which are ten times higher than those of Fe composite. Due to the effective suppression of both eddy current loss and excess loss, the total core loss decreases to 725.6 kw/m3 at 3000 kHz and 10 mT, exhibiting almost a linear growth with frequency. These outstanding properties are mainly due to the relatively large magnetocrystalline anisotropy and high resistivity of Fe4N particles. In addition, Fe4N composite also exhibits an excellent DC bias performance, maintaining over 98 % permeability under a superimposed magnetic field of 100 Oe. This study presents an effective solution for suppressing eddy current and excess losses at high frequencies, offering potential for the application of power inductors in high-frequency scenarios.