The magnetic properties of a magnetic detector using oxidized amorphous Co95-xFe5(BSi)x alloys

A comparative oxidation study of several amorphous Co7-xFe5(BSi)(20+x) alloys was carried out. Reentrant magnetization behavior and field-induced anisotropy which are of a critical importance for a magnetic detector were obtained after oxidation of the amorphous Go-rich ribbons. During this oxidation, the ribbons develop surface oxides which are primarily nonmagnetic borosilicate or a combination of borosilicate and magnetic oxides such CoO or FeO. Beneath this lies a 100-1000 Angstrom thick Go-rich magnetic alloy which may be either HCP or FCC in its crystal structure. The thickness of the Go-crystallized layer is determined by the type of the surface oxides. The oxidation products such as appear to affect the reentrant magnetization behavior of Go-rich amorphous alloys significantly. We have determined the amount of metalloids (a critical concentration of B and Si) which is necessary to form a continuous layer of the most thermodynamically stable oxide, in our case borosilicate, on the surface. We also observed that there is a good correlation between reentrant magnetization and the thickness of Co layer. The best reentrant M-H loop for the magnetic detector was obtained in ribbons with a surface berate-rich borosilicate since it ensures conditions such as (1) metalloid depletion in the substrate and (2) formation of oxygen impurity faults in Co grains that are required for strong reentrant magnetization behavior. (C) 2000 Elsevier Science B.V. All rights reserved.