Influence of NiZn-Ferrite Spacers on Giant Magnetoimpedance Effect in FeNi/Cu/FeNi Nano Films

FeNi/Cu/FeNi sandwich films without and with one or two NiZn-ferrite spacers were prepared by radio frequency magnetron sputtering. The microstructures and magnetic properties of these multilayer films are presented, and the influence of NiZn-ferrite spacers on the giant magnetoimpedance effect has also been studied. An enhanced giant magnetoimpedance effect is observed in the multilayer film with one 65 nm NiZn-ferrite spacer. The highest giant magnetoimpedance ratio in the FeNi/NiZn-ferrite/Cu/FeNi multilayer film reaches up to 36% at 10 MHz, which is a relatively high value for a nanometer thick film. This ratio is about 1.25 times larger than that of the FeNi/Cu/FeNi sandwich film (similar to 16% at 30 MHz), while the giant magnetoimpedance effect is not evidently enhanced in the FeNi/NiZn-ferrite/Cu/NiZn-ferrite/FeNi multilayer film. These results indicate that inserting one NiZn-ferrite spacer to a sandwich film is a simple and effective way to improve the giant magnetoimpedance effect in the nano film system.