CoFeB/Cu layered film with crossed anisotropy for asymmetrical magneto-impedance

This paper reports experimental results on sensitive (up to 25%/Oe) asymmetric magnetoimpedance (AMI) in magnetic/metallic multilayers with crossed anisotropy, excited by a sinusoidal current (1-100 MHz) biased with a dc current. The film structure having two outer magnetic layers Co/sub 70.2/Fe/sub 7.8/B/sub 22/ and Cu inner lead is made on a glass substrate using dc sputtering. Each layer thickness is 0.5/spl mu/m. The magnetic anisotropy in the upper film is crossed with respect to that in the lower one, which is achieved by current annealing in a longitudinal magnetic field. The AMI characteristics are found by measuring the S/sub 11/ microwave parameter using a HP8753 spectrum analyzer. The asymmetric behavior of the impedance is more pronounced at relatively low frequencies of about a few megahertz where the impedance-field characteristics are caused by domain-wall dynamics. The obtained results present a very good compromise on size, sensitivity, and linearity.