Analysis of steplike change of impedance for thin-film giant magnetoimpedance element with inclined stripe magnetic domain based on magnetic energy

Abstract

The phenomenon of steplike impedance change for thin-film giant magnetoimpedance (GMI) element was reported. The steplike change happens simultaneously with the appearance or the disappearance of stripe magnetic domain. This phenomenon is obtained for amorphous Co85Nb12Zr3 soft magnetic thin film in a rectangle shape with an in-plane uniaxial easy axis in the direction nearly 60° against the short-side axis of the element. The steplike change of impedance appears in a certain magnitude of external magnetic field. A high-sensitive magnetic field sensor can be realized by applying this phenomenon. In this study, a mechanism of the appearance or the disappearance of inclined stripe magnetic domain is discussed based on an analysis of magnetic domain energy, for the purpose of applying to a high-sensitivity magnetic field sensor. We assume these extremely different magnetic domains as (I) stripe domain with closure domain and (II) single domain, based on experimentally observed domain structures. The result of analysis shows that the magnetic energy of these two phases intersects each other in a certain external magnetic field, which means that the basis of steplike GMI of thin-film element is revealed as a structural change of magnetic domain based on magnetic energy.