THE PERMINVAR EFFECT IN BINARY AMORPHOUS COB ALLOYS

The time-temperature dependent Perminvar effect in amorphous Co100-xBx (x = 17-30 at%) alloys was investigated in the temperature region of 150 to 450 K for stabilization times of up to 12 hours. After stabiliz ation of the demagnetized domain structure the AC susceptibility (perm eability) dependent on the driving magnetic field H shows a constant v alue up to the Perminvar critical field H(CR). The fact that H(CR) in CoB alloys can be higher than coercive field H(C) is rather curious. I n the Co75B25 alloy H(CR) reaches values of 1.5 to 56 A/m dependent on the time and temperature of the stabilization. From the relative diff erence between two values of H(CR) Measured at two times t1 and t2 a m agnetic relaxation spectrum similar to that obtained from reluctivity have been constructed. The kinetics of the H(CR) increase measured at different temperatures indicates that relaxation parameters are equal to those obtained from the magnetic reluctivity aftereffect and that b oth effects have the same inherent nature.