Spin-dependent scattering is considered to be the origin of giant magnetore
sistance in magnetic multilayers, although the role of bulk or interface de
fects is still under discussion. We present calculations of spin-dependent
impurity scattering potentials as a function of the impurity position in a
Co/Cu-multi-layer. The calculations are performed within spin density funct
ional theory using a Green function method (the tight binding Korringa-Kohn
-Rostoker method). It is shown that the impurity potential depends strongly
on the impurity position, which is reflected in local densities of states
and local impurity moments. Furthermore, calculations of magnetic propertie
s of impurity pairs at the interface are presented and compared with result
s for single impurities.