Tailoring the Magnetic Properties of Giant Magnetoresistance Multilayers via Modification of Ultrathin Non-Magnetic Spacer Thickness

We present a detailed theoretical analysis of the magnetoresistance (MR) of Co/Cu magnetic metallic multilayers (MLs) and spin-valves (SVs) with spacer layer thickness ranging from 2.5 Å to 140 Å. The magnetoresistive properties of the systems under consideration are calculated using the Boltzmann equation. The MR exhibits a continuous monotonic decrease and a maximum triggered when Cu layer thickness is equal to 10 Å and its mean free path (MFP) exceeds 300 Å. An initial increase in the MR to achieve its maximum followed by a decrease is observed by varying the geometric roughness magnitude. The optimal MR is obtained at a Cu layer thickness equal to 20 Å for smooth interfaces. The MR also presents the same behaviour by modifying the top Co layer thickness, and the MR maximum is absent when the thickness of the bottom ferromagnetic (FM) layer has a value equal to or half that of the top FM layer. These magnetic behaviours can be explained by interfacial electronic scattering. The effects of characteristic and geometric parameters of the SV on the electrical conductivity of the spacer layer are also investigated. The results on [Co/Cu]₁₀ MLs suggest a decrease in MR without any sign of oscillatory behaviour when the interlayer thickness increases.