Effect of alloy formation processes in the Co-Cu system on the magnetic and magnetoresistance properties of multilayer Co/Cu films with ultrathin Co layers prepared by DC magnetron sputtering

This paper reports on a study of multilayer Co/Cu films with an effective thickness of the Co layer of ∼3.5 Å, which were prepared by magnetron sputtering. The samples prepared have been found to have a metastable multiphase structure. An analysis of the data obtained by structural and, primarily, by magnetic methods has revealed that the main phases are the Co/Cu supersaturated solid solution (alloy) with a Co concentration of about 30 at %, the superparamagnetic phase, and the paramagnetic phase, which is accounted for by the presence of small (a few atoms at most) Co clusters embedded in the Cu matrix. A clearly pronounced maximum in the temperature dependences of the low-field magnetoresistance has been found, which is associated with the temperature of the magnetic phase transition of the supersaturated Co-Cu alloy.