Giant magnetoimpedance of chemically thinned and polished magnetic amorphous ribbons

We have measured the giant magnetoimpedance (GMI) of microstructured Co-bas ed Metglas (R) 2714a amorphous magnetic ribbons. Before micropatterning, th e amorphous ribbons were chemically thinned or polished, to study the influ ence of sample thickness and surface state on the GMI effect. The magnetic domain structure of polished foils near saturation is observed using the bi tter fluid technique. The well-defined geometry of the samples allows a qua ntitative comparison of the GMI effect with a simple skin depth model, from which we obtain the frequency-dependent permeability of the material. We h ave measured the GMI effect for magnetic fields parallel and transverse to the long axis of the sample. We compare the different measurement geometrie s and film preparation methods and, typically, find a room-temperature GMI ratio of about 35%-90% in fields of a few mT and at frequencies of 10-40 MH z. (C) 2001 American Institute of Physics.