Studies of anisotropic and giant magnetoresistance in Co/Cu(111) epitaxial multilayers

Co/Cu(111) multilayers, [Co(17 Å)/Cu(8 Å<_Cu<14 Å)]₃₀, have been prepared on Co(70 Å) buffer layers on Al₂O₃(0001) substrates by molecular beam epitaxy. From the longitudinal and transverse magnetoresistance (MR) measurements, it is observed that MRs consist of two components with a small anisotropic MR (<2%) component at low field sitting on top of the giant MR (up to 22%) component at higher field. The AMR effect strongly correlates with the abundance of hep stacking of Co, which tends to decrease with the increasing of Cu spacer thickness. The AMR saturation fields (1-3 kOe) coincides with those of the magnetization. It is suggested that the observed AMR effect is due to scattering from the hep-phase Co layers in the multilayers. This together with the large saturation field (30-40 kOe) obtained from the entire MR curves indicate that the observed GMR effect may result from the Co-Cu interfacial spin-dependent scattering.