Enhancement of giant magneto-impedance in layered film by insulator separation

Giant Magneto-Impedance (MI) effect of CoSiB/SiO/sub 2//Cu/SiO/sub 2//CoSiB films with line structures have been studied. Easy axes have been induced in perpendicular direction to the driving current, and the insulating SiO/sub 2/ layers have prevented the driving current from penetrating into the CoSiB layers. This structure has enabled the effective occurrence of resistance change at a frequency as low as several MHz. As a result, impedance change ratios /spl Delta/Z/Z/sub 0/=(Z/sub maximum/-Z(H/sub ext/=0))/Z(H/sub ext/=0) are much higher than that of any other layered film without insulating layers. The /spl Delta/Z/Z/sub 0/ at 20 MHz is as high as 700% at 11 Oe, and the maximum slope is 300%/Oe.