Asymmetrical giant magnetoimpedance in exchange-biased NiFe

Abstract

Linear asymmetrical magnetoimpedance (MI) has been obtained in thin multilayer strips of exchange-coupled FeNi(5 nm)/IrMn(15 nm)/FeNi(40 nm)/Cu(100 nm)/FeNi(40 nm)/IrMn(15 nm)/FeNi(5 nm), in which the MI response is enhanced by including a Cu layer between the two 40 nm NiFe layers. The antiferromagnetic layer creates an exchange bias that shifts both the hysteresis loop and the MI response. The asymmetrical MI peak positions are shifted to higher magnetic field as the probe frequency increases. Linear MI behavior can be tuned around zero external field without the need for external biasing fields or additional coils, by changing the frequency. The impedance of a planar magnetic conductor was modeled based on a modified Stoner–Wohlfarth energy density.