High-frequency permeability characteristics of Fe- and Co-based amorphous alloys with high B concentrations

New Fe-based and Go-based amorphous alloys with a high B concentration of 30at% were formed in (Fe,Co,Ni)(62)Nb8B30 system. The amorphous alloys exhibit a wide supercooled liquid region (Delta T-x) above 80K before crystallization in the range of 5 to 40%Co and 0 to 10%Ni and the largest Delta T-x is 87K for Fe52Co10Nb8B30. The Fe62-xCoxNb8B30 alloys exhibit good soft magnetic properties i.e., low coercive force (H-c) of 2-3 Am high effective permeability (mu(c)) of 20000-30000 at 1kHz and low saturated magnetostriction (lambda(s)) of 2-8 x 10(-6), The high Il characteristics are maintained in a higher frequency range and the highest mu(e) at 1kHz is 7500 for Co40Fe22Nb8B30 with a high resistivity of 237 mu Omega cm. The finding of the (Fe,Co)(62)Nb8B30 amorphous alloys exhibiting large Delta T-x, good high-frequency permeability and high resistivity is encouraging the future development as a new soft magnetic materials.