New bulk amorphous Fe–(Co,Ni)–M–B (M=Zr,Hf,Nb,Ta,Mo,W) alloys with good soft magnetic properties

We have found that an amorphous phase with a wide supercooled liquid region reaching 85 K before crystallization is formed in Fe–(Co, Ni)–(Zr, Nb, Ta)–B, Fe–Co–(Zr, Nb)–(Mo, W)–B and Co–Fe–Zr–B systems. The high stability of the supercooled liquid enabled the production of bulk amorphous alloys with diameters up to 5 mm by copper mold casting. These amorphous Fe–(Co, Ni)–M–B alloys exhibit good soft magnetic properties, i.e., saturation magnetization of 0.95 to 1.1 T, low coercivity of 1 to 8 A/m, Curie temperature of 560 to 590 K and low magnetostriction of ${\text{8–14×10}}^{\text{−6}}.$ The effective permeability of the Co–based alloys exceeds 25 000 at 1 kHz and keeps high values above 5000 at the high frequency of 1 MHz. The permeability at 1 MHz is much higher than those for any kinds of soft magnetic materials. The frequency at which the imaginary part of permeability shows a maximum is also about 1 MHz. The success of synthesis of new Fe- and Co-based amorphous alloys with good soft magnetic properties and high glass-forming ability is promising for future development of a new type of soft magnetic material.