High-frequency giant magneto-impedance in multilayered magnetic films

We present the results of experimental and theoretical investigations of giant magneto-impedance (GMI) in the thin-film multilayer structure of F/SiO2/Ti/Cu/Ti/SiO2/F, where F stands for the ferromagnetic alloy having a composition of Fe73.5Cu1Nb3Si16.5B6. The layers were deposited under a transversemagnetic field Hp = 200 Oe applied in the plane of the sample perpendicular to its long side and were annealed at 280°C under Hp = 420 Oe for 2h. The GMI effect was measured at frequencies ranging from 0.5 to 1250 MHz using a waveguide methhod. An external magnetic field with a strength of up to 130 Oe was applied along the direction of the alternating current. The GMI is shown to exist in the multilayer structure even if the skin depth in the ferromagnetic layers is of the order of their thickness. Both real and imaginary parts of the impedance vary significantly under external magnetic field. A maximum GMI sensitivity of 10–35%/Oe was achieved at high frequencies