Giant magnetoresistance, antiferromagnetic volume fraction and saturation field in Co/Cu multilayers

A series of Co/Cu multilayers is prepared exhibiting giant magnetoresistance in the first maximum of the oscillatory exchange coupling regime. The size of the magnetoresistance strongly depends on the thickness of the layers involved, the substrate material, the buffer layer and the sputtering conditions. The analysis of resistive and magnetic data reveals that to a first approximation the magnetoresistance linearly depends on the volume fraction of Co coupled antiferromagnetically. This volume fraction can be derived from the extrapolated remanent magnetization. The authors investigate under which conditions and to what extent the linearity applies. A maximum of the magnetoresistivity of 72% at room temperature is reached under optimized conditions