Core loss of ultra-rapidly annealed Fe-rich nanocrystalline soft magnetic alloys

Ultra-rapidly annealed (heating rate >104 K/s, annealing time <1 s) Fe-rich nanocrystalline soft magnetic materials with a nominal composition of Fe100−xBx and Fe87−yB13My where x = 12, 13, 14, y = 1, 2 and M = Cu, Ni (HiB-Nanoperm) have recently been demonstrated with a saturation magnetic polarization (Js) up to 1.92 T and a low coercivity (Hc) of less than 8 A/m. In this study the AC core loss (Pcm) is estimated for HiB-Nanoperm at 50, 400 and 1000 Hz and is compared with existing amorphous, nanocrystalline and conventionally crystalline (Fe-Si) materials. The Pcm of HiB-Nanoperm at 1.5 T, 50 Hz is demonstrated to be 5–15% that of Fe-3 wt% Si. In specific, Fe86B13Cu1 displays losses that are 30% that of Fe-6.5 wt% Si steel while also possessing a 5% larger Js. For maximum magnetic polarization (Jm) values greater than 1.5 T this same composition also exhibits some of the lowest core losses seen from all Fe-based nanocrystalline alloys across the frequencies tested in this study. Core loss separation and an estimation of the anomaly factor (η) for selected HiB-Nanoperm alloys is also undertaken and compared with a Fe-based amorphous alloy. The η of HiB-Nanoperm is seen to be lower than that of Fe-based amorphous alloy and is also observed to be positively correlated with saturation magnetostriction. The low core loss of HiB-Nanoperm is attributed to a reduced anomalous loss which may be brought about by the moderate magnetostriction of this alloy.