Influence of demagnetization effect on giant magneto-impedance of soft ferromagnetic metal

The magneto-impedance (MI) of an amorphous ferromagnetic ribbon with nominal composition Fe40Ni40B20 and of different lengths is measured using non-contact method at 1 MHz frequency. In the presence of static magnetic field around 30 Oe, the MI of the ribbon of long length is reduced by nearly 90%. With decreasing sample dimension the extent of reduction in MI becomes smaller. The MI of a ferromagnetic metallic system results from the e.m field’s screening which in turn depends on the magnetic response of the sample. The demagnetization field of smaller sample size reduces the magnetic response which in turn decreases the field sensitivity of MI. The phenomenology based on the Landau–Gilbert equation predicts similar qualitative behaviour of MI.