The effect of non-local electron scattering on the current-perpendicular-to-plane-mode magnetoresistance of magnetic multilayers

We have carried out an experimental and theoretical study of non-local elec tron scattering in magnetic multilayers by measuring the magnetoresistance MR(H) in the CPP (current-perpendicular-to-plane) mode for two samples cons isting of different magnetic layers (M1, M2) separated by non-magnetic laye rs (NM). For the two samples, the ordering of the layers was as follows: [M 1/NM/M2/NM](N) and [M1/NM](N)[M2/NM](N). If the non-local character of the electron scattering were unimportant, the two samples would yield identical curves for MR(H) in the CPP mode. However, our measured MR(H) curves are c ompletely different for the two samples. This demonstrates the importance o f non-local electron scattering. For our measurements, M1 = Fe(50 Angstrom) , M2 = Co(20 Angstrom), NM = Cu(200 Angstrom) for Fe-Co samples, and M1 = C o(10 Angstrom), M2 = Co(60 Angstrom), NM = Cu(200 Angstrom), for the Co-Co samples. To confirm our ideas, we calculated MR(H), including the effect of non-local electron scattering, and obtained quantitative agreement with ex periment.