FERROMAGNETIC CO-FE-ZR-B AMORPHOUS-ALLOYS WITH GLASS-TRANSITION AND GOOD HIGH-FREQUENCY PERMEABILITY

A Co-based amorphous phase with glass transition and supercooled liqui d region before crystallization was formed in Co70-xFexZr10B20 and Co7 2-xFexZr8B20 alloys containing more than 14 at % Fe. The crystallizati on temperature (T-x) is 899 K for the Co-Zr-B alloys and remains uncha nged in the Fe concentration range up to 20%. The glass transition tem perature (T-g) decreases with increasing Fe content, and the Delta T-x (= T-x-T-g) increases from 25 K at 14% Fe to 34 K at 21% Fe. The amorp hous alloys with glass transition crystallize with a single stage prec ipitation of bcc Fe(Co) and Co3ZrB2 phases. The Go-rich amorphous allo ys exhibit good soft magnetic properties, i.e., saturation magnetizati on of 0.58-0.83 T, low coercivity of 4.7-8.3 A/m, and high permeabilit y of 5500-18 300 in the frequency range of 1-10(3) kHz and low magneto striction between - 1.5 x 10(-6) and + 10 x 10(-6) including zero. The success in synthesizing the soft magnetic amorphous alloys with high stability of supercooled liquid is promising for the future developmen t of ferromagnetic Co-based bulk amorphous alloys. (C) 1998 American I nstitute of Physics.