Magnetoresistance of interleaved and separated Co/Cu multilayers in the CPP mode

We have measured the field dependence of the magnetoresistance MR(H) in the CPP mode for two types of magnetic multilayers that differ only in the ordering of the magnetic layers: [Co (10 Å)/Cu/Co (60 Å)/Cu]_N and [Co (10 Å)/Cu]_N [Co (60 Å)/Cu]_N, with the Cu layers always being 200 Å. The series resistor model predicts that in the CPP mode, MR(H) is independent of the ordering of the layers. Nevertheless, the MR(H) curves measured were found to be completely different for the two cases. We suggest that the reason for this difference is that the electron mean free path is long enough that the potential that scatters the electrons is due to pairs of neighboring magnetic layers, which differ for the two types of magnetic multilayers.