Iron rich metallic glasses having high saturation induction and superior soft ferromagnetic properties at high magnetization rates

A method for making a magnetic core useful at magnetization rates greater than about 1 Mt/s, comprising the steps of:

• a. forming a melt of metallic glass having a composition described by the formula Fe.sub.a Co.sub.b B.sub.c Si.sub.d C.sub.e, where "a"-"e" are in atom percent, "a" ranges from about 72 to about 84, "b" ranges from about 2 to about 8, "c" ranges from about 11 to about 16, "d" ranges from about 1 to about 4, and "e" ranges from about 0.5 to about 2, with up to about 1 atom percent of Mn being optionally present in the glass;
• b. rapidly solidifying said glass at a rate of at least about 10.sup.4 .degree. C./sec by directing said melt into contact with a moving quench surface, said glass upon solidification having the form of a ribbon that is at least 80% glassy;
• c. winding said ribbon to form a core having the shape of a toroid;
• and
• d. annealing said core at a temperature ranging from about 573 to 623;
• K for a time ranging from about 900 s to 3600 s under an external field having strength ranging from about 400 to 1600 A/m, said core, after annealing, having saturation induction ranging from about 300 J/m.sup.3 to 400 J/m.sup.3 and a dc swing from negative remanence to positive saturation ranging from about 2.9T to 3.2T.