Surface crystallized Co66Fe4B15Si15 amorphous ribbons studied using magneto-optical magnetometry

Abstract

Amorphous Co66Fe4B15Si15 ribbons field-annealed in air atmosphere exhibit the asymmetric giant magnetoimpedance effect which is promising for sensor applications (GMI valve). The desired effect originates from the exchange between the magnetically harder surface crystalline phase and the soft amorphous magnetic bulk. In this paper, the magneto-optic Kerr effect (MOKE) is used to investigate the surface magnetic properties of field-annealed ribbons. Inhomogeneity of magnetic properties in the near-surface region is studied using the complex longitudinal magneto-optical Kerr effect and a method for investigation of depth profiles is proposed. A hard magnetic film with the saturation field is detected at the surface followed by a layer with coercivity field . The proposed model is in good agreement with measurements at field-annealed amorphous ribbons with a surface gradually removed by polishing.