Structural and Interfacial Effects on Magnetoresistance in Ultra-Thin Co/Cu Multilayers

This study theoretically analyzes the magnetoresistance (MR) of Co/Cu multilayers as a function of the mean free path (MFP) in the Co layer ( λ Co ), under varying geometric and interfacial conditions. Different correlation lengths (L s = 2 Å, 7 Å, and 20 Å) of geometric roughness at the outer surface are examined, with interfacial and surface roughness both fixed at 2 Å, and the MFP in the Cu layer set to 1000 Å. The results reveal that MR strongly depends on λ Co , with a more pronounced effect at higher L s values, where decreased roughness leads to weaker scattering. For L s = 20 Å, the dependence of MR on λ Co is further examined for various Co layer thicknesses (d Co = 5 Å, 10 Å, and 100 Å). The findings show that the sensitivity of MR to λ Co increases with Co layer thickness, reflecting the growing influence of bulk scattering in thicker layers and boundary effects in thinner ones. Moreover, changes in the asymmetry of interfacial scattering significantly affect MR, highlighting the intricate interplay between electronic transport and structural parameters. These results contribute to a better understanding of MR behaviour in metallic multilayers and may guide the optimization of spintronic devices and magnetic sensors.