Study of GMI-valve characteristics in the Co-based amorphous ribbon by ferromagnetic resonance

The mechanism of the drastic increase of the giant magneto impedance (GMI) sensitivity which is enhanced to over 1000%/Oe, which shows the GMI-valve characteristic, has been studied using ferromagnetic resonance (FMR). The FMR linewidth of the annealed sample increased with the increasing annealing time in parallel and perpendicular to it. From the FMR results, it can be concluded that the GMI-valve characteristic is attributed to the surface anisotropy due to the exchanging coupling arising from the interaction between the ferromagnetic amorphous core and the antiferromagnetic oxidation layer.