Effects of surface coating by sol-gel process on the magnetic properties of a Co-based amorphous alloy

A sol-gel method is employed to coat an insulating layer of magnesium oxide on a Co-based amorphous alloy ribbon and the effects of surface coating are investigated on the core loss and other magnetic properties of the ribbon. The core loss is found to be reduced significantly by the surface coating, the loss reduction becoming more prominent at higher frequencies. In addition, the reliability of measured core losses is better for coated ribbons. Besides the core loss, other ac and dc magnetic properties are also affected; the ac effective permeability is improved and dc hysteresis loops are inclined by the surface coating. The present results are explained by the roles of surface coating in providing an insulation between the layers and in modifying the domain structure.