We have patterned multilayers of amorphous magnetic foils of Metglas/sup /spl reg// 2714a (cobalt-based) and Cu foil into microstructures of different sizes. We have studied the GM effect in these structures, and we have characterized the behavior of the relative permeability as a function of frequency and magnetic field. We obtain GMI ratios [Z/sub max/-Z(B/sub sat/)]/Z(B/sub sat/) up to 800% and GMR ratios [R/sub max/-R(B/sub sat/)]/R(B/sub sat/) up to 2400% at frequencies of 100 kHz-10 MHz, with B/sub sat/ the magnetic field where impedance and resistance saturate (typically a few mT).