Giant magnetoresistance and oscillatory exchange coupling in disordered Co/Cu multilayers

We measured the exchange coupling strength and magnetoresistance for multilayers of Co/Cu grown by sputtering. The samples have (111) texture with a grain size of about 140 Å. Their mosaic spread, determined by high-angle x-ray rocking curves in triple-axis geometry, is as large as , suggesting the description disordered . The magnetoresistance oscillates as a function of the Cu thickness and reaches 70% at room temperature with near zero remanence at the first antiferromagnetic peak. These results indicate that a sufficient condition for oscillatory exchange coupling with a period of Å is a well defined separation between the magnetic layers. We also measured the exchange coupling strength as a function of the magnetic layer thickness and found no oscillations. The measured saturating magnetic field is accurately described by the `orange-peel' coupling effect.