Enhancing the microwave absorption properties of Fe-Cu-Nb-Si-B nanocomposite flakes by coating with spinel ferrite NiFe2O4

Fe-based nanocrystalline alloy flakes are believed to have great potential in electromagnetic noise suppression at gigahertz frequency range [1]. However, the high permittivity of Fe-based alloys due to their high conductivity will cause the impedance mismatch. To cope with this problem, people usually coat the alloy particles with high resistive substances which are not ferromagnetic, for instance SiO₂ [2]. However, we believe that the non-ferromagnetic coatings are not a good choice. In this contribution, we intend to coat the Fe-Cu-Nb-Si-B nanocomposite flakes with spinel ferrite (NiFe₂O₄). The ferrimagnetic layer not only can reduce the impedance mismatch, but also can take part in absorbing the electromagnetic noise. Furthermore, the high resistivity layer of spinel ferrites can effectively avoid the oxidation of alloy particles, which will be a headache during the long-time application.