Separation of α-Fe phase from Nd2Fe17N3， dramatically broadening microwave absorption bandwidth at low frequency

The low-frequency microwave absorption (MA) problem urgently needs to be solved, although very difficult, to address the electromagnetic interference (EMI) issues caused by modern communication systems and devices. In this paper, magnetic nano-composites of Nd ₂ Fe ₁₇ N ₃ /α-Fe with controllable phase proportion, oxidized surface, high permeability, large magnetic loss, and low permittivity at microwave frequency band, were prepared only by controlling the purity of N ₂ used for doping. As a result, strong MA below − 10 dB is achieved at the low frequency C band and S band, when the absorber thickness is 2.8 mm and 5.0 mm respectively, obviously better than the low frequency microwave absorbers reported and thus showing great application prospects. More importantly, it is demonstrated that the design concept proposed by us is feasible, that is combination of easy-plane anisotropic materials like the Nd ₂ Fe ₁₇ N ₃ and axis anisotropic materials like the α-Fe, capable of helping broaden the MA bandwidth, significantly. Additionally, a kind of particular magnetic loss mechanism on moments from one side to the other side of heterogeneous interfaces of two-phase magnetic nano-composites is proposed and discussed. In short, this paper has presented a novel method of experiment and some unique ideas of design, practical to solve the low-frequency MA problem.