Magnetoresistance study of Ni 80Fe 20/Co1/CuAgAu/Co2 asymmetric sandwiches

Abstract

The (Ni 80Fe 20/Co1)/CuAgAu/Co2 asymmetric sandwiches have been examined for different sublayer thicknesses. Magnetoresistance, magnetooptical Kerr effect and alternating gradient magnetometry measurements showed that for 1.2 nm⩽ d CuAgAu⩽1.6 nm our trilayers are antiferromagnetically coupled whereas for d CuAgAu⩾1.9 nm the coupling between Ni 80Fe 20/Co1 and Co2 is ferromagnetic. The ferromagnetic coupling strength oscillates with CuAgAu thickness with a period of 1 nm. The appearance of the ferromagnetic interlayer coupling for d CuAgAu⩾1.9 nm and its oscillatory character result from the interplay between RKKY-like exchange coupling and the magnetostatic orange-peel coupling. The values of the ferromagnetic coupling field between Ni 80Fe 20/Co1 and Co2 for a constant CuAgAu thickness can be either enhanced or reduced depending on the ratio between Co1, Co2 and Ni 80Fe 20 thicknesses. In spite of oscillatory ferromagnetic coupling strength for d CuAgAu⩾1.9 nm our trilayers show the GMR amplitude of about 10% and the GMR field sensitivity of about 5%/Oe at room temperature being very promising from the application point of view.