Dependence of giant magnetoresistance on Cu-layer thickness in Co/Cu multilayers: A simple dilution effect.

Abstract

The dependence of the giant magnetoresistance in Co/Cu multilayers on Cu spacer layer thickness is shown to be surprisingly straightforward for multilayers comprised of thin Co layers. At 4.2 K the magnetoresistance decays simply as the inverse Cu spacer layer thickness, which we consider to be a result of dilution of the Co/Cu interfacial regions which give rise to the giant magnetoresistance effect. At 295 K there is an additional exponential decay whose decay length we attribute to volume scattering within the Cu layers. High-resolution cross-section transmission electron micrographs show a high degree of structural ordering within the Cu layers and across the Co/Cu interfaces, perhaps accounting for the long volume scattering lengths (\ensuremath{\simeq}300 \AA{} at 295 K) found within the Cu layers.