Magnetic after-effect in amorphous FeNiNbCuSiB alloys

An influence of the partial substitution of Fe by Ni on time-temperature st ability of amorphous Fe73.5-xNixNb3Cu1Si13.5Be9 (x = 0,5, 10, 15, 20, 25 at .%) alloys was investigated. Stability of the magnetic properties was obser ved by the magnetic after - effect (MAE) of the reluctivity which is repres ented by its relative change Delta r/r between two fixed times after demagn etization. The relaxation spectra Delta r/r(T) at different Ni content were studied. The heights of peaks Delta r/r(T) are increasing at x = 5, 10 at. % in contrary to Ni concentrations x = 20, 25 at.%. The most probable activ ation energy for MAE was found to be Q = 1.7 eV.