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

Amorphous alloys with a wide supercooled liquid region (Delta T-x) before c rystallization were formed in the (FeCoNiHfMB20)-Co-56-Ni-7-Hf-7-M-8-B-2 (M =Nb, Ta) alloys by melt spinning. The 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 Delta T-x value is larger by a bout 10 K than the largest value for recently reported (Fe,Co,Ni)-Zr-M-B al loys. By the addition of the M metals, magnetic properties also changed. Go od soft magnetic properties were obtained for the alloys annealed for 300 s at 800 K. The saturation magnetization (I-s), coercive force (H-c), and ef fective permeability (mu e) at 1 kHz are, respectively, 0.71 T, 1.0 A/m, an d 16700 for the M=Nb alloy and 0.76 T, 1.0 A/m, and 15600 for the M=Ta allo y. The finding of the Fe-based amorphous alloys exhibiting simultaneously t he wide supercooled liquid region before crystallization and the good soft magnetic properties seem to enable the future development of a new ferromag netic bulk amorphous alloy. (C) 1999 American Institute of Physics. [S0021- 8979(99)15308-8].