Giant magnetoimpedance strip and coil sensors

We present noticeable values of giant magnetoimpedance on a cobalt-rich amorphous alloy, together with a new approach to giant magnetoimpedance devices of reduced size. Values as high as 260% of impedance variation as a function of the applied magnetic field are obtained with the samples in the usual form of long ribbons. The benefits of specific thermal treatments in reaching these high values are studied through the magnetic domain structure. In order to reduce the size of the system and therefore extending the practical use of giant magnetoimpedance devices, we present the results obtained in wound ribbons in the form of coils. Though the magnetoimpedance is considerably reduced, it is still large enough to be applicable in sensor devices. (C) 2001 Elsevier Science B.V. All rights reserved.