Magnetoimpedance effect in FeCoB/Cu/FeCoB sandwiched films with Permalloy underlayer

We studied the magnetoimpedance (MI) effect of FeCoB(100 nm)/Cu(100 nm)/FeCoB(100 nm) sandwiched films with different thickness of Permalloy as underlayer for the FeCoB ferromagnetic layer. The maximum MI ratio of sandwiched film is 9.2% when the thickness of the Permalloy underlayer is 2–3 nm. The improvement of MI ratio of sandwiched films with Permalloy underlayer was explained by exchange induced ripple reduction mechanism.