Evolution from multilayer to granular behavior via Cobalt layers fragmentation in Co/Cu multilayers

We have analyzed the structural evolution of Co(t(Co))/Cu(4t(Co)) multilayers when t(Co) ranges from 12 to 2 Angstrom. The investigation has been performed by studying their magnetization (both at room and low temperatures) and giant magnetoresistance. In the intermediate range of thickness. we observe mixed multilayer granular features yielding an interesting behavior of magnetoresistance curves related to the length scale of the spin-dependent scattering processes. At sufficiently low Co thickness. the samples exhibit non-interacting superparamagnetic behavior (at room temperature). The analysis of the low-temperature data (coercive field and of the ratio between the remnant and saturation magnetization) of the superparamagnetic samples allowed us to address the effects related to particles size distribution on the temperature dependence of coercive field and of the ratio between the remnant and saturation magnetization