The magnetic properties of Fe-based amorphous ribbons coated with various oxides using the sol–gel process

Abstract

The metal oxides MgO, BaO, Al2O3, SiO2, MgO–Al2O3, CaO–Al2O3, SrO–Al2O3, BaO–Al2O3 and MgO–SiO2 have been coated onto ribbons of the Fe-based amorphous alloy Metglas 2605S3A using a sol–gel process. The effects of the surface coating on the magnetic properties of the alloy are investigated. The d.c. hysteresis loop for ribbons coated with MgO and MgO–Al2O3 is more square shaped than that for the uncoated ribbon. For ribbons coated with BaO, SrO–Al2O3 and BaO–Al2O3 it is more inclined than for the uncoated ribbon. Significant differences in the frequency dependence of the effective permeability are observed that depend on the nature of the coated oxides. The core loss is also affected by the coating. These results may be explained in terms of a stress induced by the coating and the modification of the domain structure via elastic and/or magnetoelastic interactions. It is thought from the magnetoelastic interactions that the MgO and MgO–Al2O3 coatings induce tensile stresses whilst those of BaO, SrO–Al2O3 and BaO–Al2O3 induce compressive stresses.