Abstract
Some experimental results by X-ray diffraction and Mössbauer spectroscopy are presented as to the annealing temperature dependence of AC magnetic properties in Fe78.5B13Si8.5 amorphous alloy.
The best values of the iron loss, W13⁄50, and the magnetic flux density at 100 A/m, B1 have been obtained after annealing at 673 K, which is below the Curie temperature 685 K of the amorphous alloy. Surface crystallization into α-Fe has been found to take place on the roll-side surface during annealing at temperatures above 698 K for 3.6 ks. Structural relaxation by annealing makes some peaks in radial distribution function (RDF) sharp and increases monotonously their peak heights with the rise of annealing temperature up to 723 K. The change in the in-plane magnetic anisotropy by annealing corresponds well with the change in the AC magnetic properties, and the biggest in-plane magnetic anisotropy is formed after annealing at 648-673 K.
It is suggested that the improvement of the magnetic properties by annealing at temperatures below 673 K is due to the stress relaxation, and that the deterioration above 673 K is due to the decreases in the in-plane magnetic anisotropy by annealing in a paramagnetic state and by compressive stress from the crystalline α-Fe surface layer formed during annealing.
