Design and preparation of new Fe-based bulk amorphous alloys toroids

We investigate dc and ac magnetic properties of Fe/sub 56/Co/sub 7/Ni/sub 7/Zr/sub 6/M/sub 1.5/Nb/sub 2.5/B/sub 20/ (M = Zr, Ti, Ta, Mo) amorphous alloys toroids prepared by mold casting. Electrical resistivities of 180-230 /spl times/ 10/sup -8/ /spl Omega//spl middot/m, coercive fields up to 10 A/m, dc-magnetic permeabilities of about 1 /spl times/ 10/sup 5/ and ac-magnetic permeabilities up to 3 /spl times/ 10/sup 4/, saturation magnetizations of 0.9-1.2 T, and Curie temperatures between 550 and 600 K are measured in the as-cast state. We discuss the influence of the preparation conditions, composition, frequency (5 Hz-10 MHz), and treatments on the electrical and magnetic characteristics and present the advantages of using bulk amorphous alloys with soft magnetic properties in new physical and engineering applications.