Nanocrystalline soft magnetic materials with a saturation magnetization greater than 2 T

The effect of Co on the magnetic properties of ultra-rapidly annealed (heating rate > 10⁴ K/s, annealing time < 1 s) nanocrystalline (Fe_1−xCo_x)₈₇B₁₃ with x = 0–0.5 has been investigated. A saturation magnetic polarization of 2.02 T is observed for x = 0.2 while maintaining a coercivity of 9.3 A/m. This represents a 0.1 T increase over existing Co-free HiB-Nanoperm alloys with a B content of 13 at.% and is directly comparable to conventional crystalline Fe-3 wt%Si. Ultra-rapid annealing is shown to be a requirement for producing magnetically soft materials in this alloy system. The effect of Cu on ultra-rapidly annealed nanocrystalline (Fe_0.8Co_0.2)_87−yB₁₃Cu_y where y = 0–1.5 is also investigated. It is found that Cu is effective at improving the magnetic softness of Co-containing HiB-Nanoperm, with y = 1 displaying a H_c of 7 A/m and a saturation magnetic polarization of 2.0 T.