Investigation of the GMI effect in multilayered sensing elements deposited over silicon and glass substrates

The room-temperature longitudinal and in-plane transversal giant magneto-impedance (GMI) effects were investigated in multilayered stripes with composition [Py(100 nm)/Ti(6 nm)]4/Cu(400 nm)/[Py(100 nm)/Ti(6 nm)] ₄ deposited over Si/SiO ₂ and over glass substrates for applied magnetic fields ( H) varying in the range ± 0.4 T and for a broad frequency ( f) range of 0.3–12 MHz. The sensing element was found to couple to the Si/SiO ₂ substrate influencing largely the magneto-impedance ( Z) data. For the sensing element deposited over Si/SiO ₂ (glass) substrate, the maximum variation in the magnetic impedance, Δ Z = Z( H) – Z( H = 0.4 T), was found to be about 18 mΩ (550 mΩ). Moreover, the corresponding maximum sensitivity ( S) for the sample deposited over Si/SiO ₂ (glass) was 36 Ω/T (2500 Ω/T). The significant differences in Δ Z and in S were associated to the leakage of the ac electric current through a capacitive coupling between the Si/SiO ₂ substrate and the sensing element that increases for increasing frequency.