Magnetoimpedance in narrow NiFe/Au/NiFe multilayer film systems

Abstract

Magnetoimpedance (MI) in RF sputtered magnetic/metallic multilayers of composition NiFe/Au/NiFe has been investigated with the purpose of clarifying the effect of in-plane size. The film width was varied between 20 /spl mu/m and 200 /spl mu/m, the length was 2 or 5 mm and the layer thickness was 0.5 /spl mu/m. The films of 50 /spl mu/m wide demonstrated the highest MI ratio of more than 140% for frequencies of 200-400 MHz. We believe this is one of the best obtained results regarding the film dimensions and sensitivity. However, when the width is further decreased, the MI ratio drops considerably due to flux leakage through the inner conductor. This effect was analyzed within a 2-D model of a three-layer symmetrical film system, having magnetically open-loop structure, giving a reasonable agreement with the experimental results in 50 and 20 /spl mu/m wide films.