Giant magnetoresistance: Comparison of band-structure and interfacial-roughness contributions

A real-space Green-function technique, in which the scattering is treated exactly, is used in a single-band tight-binding model to evaluate the Ohmic resistivities and the giant magnetoresistance in trilayer systems. The model includes (i) spin dependence of the density of states and Fermi velocity in the magnetic material, giving a qualitative representation of Co/Cu and Fe/Cr systems; (ii) spin-independent bulk disorder, representing intrinsic defects in real systems; (iii) chemically sharp interfacial roughness. It is found that for parameters that produce realistic total resistivities, the spin-polarized band structure in conjunction with the spin-independent bulk disorder gives the main contribution to the giant magnetoresistance. The chemically sharp interfacial roughness enhances the effect. Its contribution becomes significant in the limit of sufficiently dense roughness steps, sufficiently weak bulk disorder, and sufficiently thin magnetic layers.