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

Giant Magneto-Impedance (MI) effect of CoSiB/SiO2/Cu/SiO2/CoSiB films with line structures have been studied. Easy axes have been induced in perpendicular direction to the driving current, and the insulating SiO2 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 Delta Z/Z(0) = (Z(maximum) - Z(H-ext=0))/Z(H-ext=0) are much higher than that of any other layered film without insulating layers. The Delta Z/Z(0) at 20 MHz is as high as 700% at 11 Oe, and the maximum slope is 300 %/Oe.