THE EFFECT OF ANNEALING ON MAGNETIC-PROPERTIES OF IRON-BASE AMORPHOUS ALLOY RIBBONS

It is found that there are two minima, for both coercivity and core loss as a function of annealing temperature, when Fe78 B13 Si9 amorphous alloy ribbon is magnetically annealed. The results show that besides stress relaxation and crystallization, alignment of magnetic easy axis also participates in the enhancement of soft magnetic properties, and that the influence of crystallization begins at 623 K. A four-stage model is proposed to interpret the double-minimum behavior. In the first stage, core loss decreases as annealing temperature increases, and magnetic alignment is the dominant mechanism. In the second stage, core loss increases slightly as temperature rises. In this region, the magnetic alignment process is almost completed and surface crystallization begins to occur. In the third stage, the stress relaxation effects overwhelm the crystallization effects and dominate, thus causing the core loss to decrease. In the fourth stage, stress relaxation effects are completed and cannot further reduce the core loss. Meanwhile, crystals have grown up to 200 nm in size, comparable to the size of domain walls, and hence pinning effects dominate the magnetic behavior resulting in the increase of core loss.