Fe-based soft magnetic amorphous alloys with a wide supercooled liquid region

Amorphous alloys with a wide supercooled liquid region ${\mathrm{(\Delta T}}_x)$ before crystallization were formed in the ${\mathrm{Fe}}_{\mathrm{56}}{\mathrm{Co}}_{\mathrm{7}}{\mathrm{Ni}}_{\mathrm{7}}{\mathrm{Hf}}_{\mathrm{8}}{\mathrm{M}}_{\mathrm{2}}{\mathrm{B}}_{20}$ (M=Nb, Ta) alloys by melt spinning. The ${\mathrm{\Delta T}}_x$ which is a critical factor of glass-forming ability, increases to large values exceeding 90 from 82 K by the addition of 2 at. % M, and the largest ${\mathrm{\Delta T}}_x$ value is larger by about 10 K than the largest value for recently reported (Fe,Co,Ni)–Zr–M–B alloys. By the addition of the M metals, magnetic properties also changed. Good soft magnetic properties were obtained for the alloys annealed for 300 s at 800 K. The saturation magnetization ${\mathrm{(I}}_s\mathrm{),}$ coercive force ${\mathrm{(H}}_c\mathrm{),}$ and effective permeability ${\mathrm{(\mu }}_e)$ at 1 kHz are, respectively, 0.71 T, 1.0 A/m, and 16 700 for the M=Nb alloy and 0.76 T, 1.0 A/m, and 15 600 for the M=Ta alloy. The finding of the Fe-based amorphous alloys exhibiting simultaneously the wide supercooled liquid region before crystallization and the good soft magnetic properties seem to enable the future development of a new ferromagnetic bulk amorphous alloy.