Buffer effect on GMR in thin Co/Cu multilayers

[Co(1.1 nm)/Cu(0.9 nm)]_×25 multilayers (MLs) with different textures and interfacial Co-Cu roughness have been obtained by depositing them on different buffer layers (Fe, Cr, Cu, Co, Ta or Al) 8 nm thick using an unusual RF sputtering method. An attempt has been made to understand the correlation between the interfacial roughness and giant magnetoresistance (GMR) from the magnetic properties of Co/Cu MLs. It has been observed that high GMR is weakly dependent on the texture of MLs. High GMR has been observed in either in weakly textured (2 0 0) Co/Cu MLs (GMR ∼ 45%) or strongly oriented (1 1 1) Co/Cu MLs (GMR ∼ 30%). However, a strong correlation between interfacial roughness and magneto-transport properties of sputtered Co/Cu(0.9 nm) MLs (corresponding to the first maximum of antiferromagnetic exchange coupling) has been determined. Contribution to GMR from superparamagnetic (SPM) interfacial region has been analyzed in terms of the Langevin function and also the expected standard linear dependence of GMR versus (M/M_s)² for magnetoresistive granular-type Co-Cu system.