A UNIFIED THEORY OF CIP AND CPP GIANT MAGNETORESISTANCE IN MAGNETIC SANDWICHES

A theory of giant magnetoresistance (GMR) in magnetic sandwiches F/P/F for current in plane (CIP) and current perpendicular to plane (CPP) g eometries is developed. We adopted the free electron model described b y four parameters: mean free paths and scattering amplitudes (coherent potentials) at the interfaces for spin-up and spin-down electrons. Fo r both CIP and CPP geometries, we calculated the conductivities and GM R using Kubo formalism and the Green function technique in mixed real space-momentum representation. The final expressions for GMR in both g eometries were obtained using the same microscopic parameters. Main at tention was paid to the relative role of spin-dependent bulk and inter facial scattering. It was shown that increasing of surface scattering for fixed spin asymmetry leads to non-monotonic behaviour of CIP GMR d ue to renormalization of the scattering amplitude, In the case of CPP geometry the dependence of GMR on interfacial scattering amplitude is monotonic.