Nanostructured Magnetoimpedance Multilayers

We describe our experience in design, fabrication and advanced characterization of highly sensitive [FeNi/Ti]- and [FeNi/Cu]_n/Cu-based magnetoimpedance multilayers deposited by rf-sputtering onto rigid and flexible substrates. In order to avoid the transition into "transcritical" state and to keep both the low coercivity and magnetic softness for relatively thick films (up to 1 μm), nanostructuring by Ti or Cu layers was successfully used together with an appropriate selection of the thickness and deposition conditions. A maximum sensitivity of the total impedance of 110%/Oe at 30 MHz was obtained for [FeNi/Ti]₃/Cu(500 nm)/[Ti/FeNi]₃ multilayers deposited onto glass substrate (45%/Oe, at 65 MHz for the same multilayers deposited onto a flexible substrate). These values are promising for applications.