The giant magnetoresistance and the anomalous Hall effect in molecular-beam-epitaxy grown Co/Cu superlattices

Abstract

We have investigated the dependence of the magnetoresistance (MR) and the Hall effect on both the Cu layer thickness dCu and the Co layer thickness dCo in (111)-oriented epitaxial Co/Cu superlattices. The MR ratio has a single peak near 9 AA as a function of dCu while it shows a broader faint peak near 10 AA as a function of dCo. The maximum MR ratio up to 81% was observed at 4.2 K for dCo=9.0 AA and dCu=9.3 AA. For both dCu and dCo dependence, the saturation field increases monotonically with decreasing layer thickness. As a function of dCo, the anisotropy field changes its sign from in plane for large dCo to perpendicular near dCo=9 AA. The extraordinary part of Hall resistivity shows a single peak against magnetic field for samples with a large MR ratio. The field dependence is explained in terms of the field dependence of both the skew and the side-jump scattering components associated with the giant magnetoresistance. The ratio of the two components is almost unchanged between zero field and saturation field, which suggests that the main scattering mechanisms at both fields are microscopically the same.