EFFECTS OF THERMAL ANNEALING ON THE MAGNETIZATION DYNAMICS OF VITROVAC AMORPHOUS RIBBONS

The effects of thermal annealing on the frequency behavior of the initial permeability, mu-0, of Vitrovac(R) 6025 amorphous ribbons have been investigated. For annealing temperatures above the Curie point, T(c), mu-0 shows a significant increase (from 13 760 to 39 600) as compared with the as-quenched sample; for annealing temperatures below T(c) ("aging"), mu-0 decreases (from 13 760 to 7700). The domain wall relaxation frequency exhibited the opposite behavior: a decrease with annealing at T > T(c) (from 69 to 18 kHz) and an increase with aging (from 69 to 127 kHz). The frequency behavior can be modeled by means of a simple, parallel RL circuit, where the inductance value is proportional to the initial permeability, and the equivalent resistance value, which is inversely related to the damping parameter, is the same for all the samples. These results can be interpreted on the basis of a variation of the extent of domain wall pinning, as manifested in changes in the spring constant-alpha, decreasing with annealing and increasing with aging. The relaxation frequency is proportional to the extent of pinning, and initial permeability depends on the inverse.