Soft Magnetic Nanocrystalline FeSiBCuCa Alloys with High Electric Resistivity

Here, we report a soft magnetic nanocrystalline alloy with high electric resistivity (<i>ρ</i>) up to 221 μΩ·cm. The (Fe₈₂Si₃B₁₄Cu₁)_100−xCa_x (x = 0, 0.12, 0.36, and 0.6) alloys were prepared by melt spinning. The effects of Ca addition and annealing treatment on the microstructure and properties of the alloys have been investigated. It was found that Fe₈₂Si₃B₁₄Cu₁ alloys without Ca doping contain mainly one nanocrystalline phase of α-Fe, but both α-Fe and Fe₃B nanophases coexist in the as-prepared alloys with relatively high Ca contents (x = 0.36 and 0.6) and annealed Ca co-doped alloys. The presence of Fe₃B nano-crystals leads to high resistivity without significantly reducing the soft magnetic properties. The saturated magnetic induction <i>B</i>_s of (Fe₈₂Si₃B₁₄Cu₁)_100−xCa_x (x = 0, 0.12, 0.36, and 0.6) alloys ranges from 1.75 T to 1.80 T, and the coercivity <i>H</i>_c of annealed alloys shows a tendency to increase with an increase in Ca content. Meanwhile, the resistivity of both as-prepared and annealed alloys increases with increasing Ca content. The as-prepared (Fe₈₂Si₃B₁₄Cu₁)_99.4Ca_0.6 alloy exhibits an excellent combination of soft magnetic properties with <i>ρ</i> = 221 μΩ·cm, <i>H_c</i> = 20.3 A/m, and <i>B</i>_s = 1.57 T. After annealing, these values changed to 158 μΩ·cm, 21.6 A/m, and 1.79 T, respectively. We believe that this work is helpful for developing nanocrystalline soft magnetic alloys for high-frequency applications.