GIANT MAGNETORESISTANCE - COMPARISON OF BAND-STRUCTURE AND INTERFACIAL-ROUGHNESS CONTRIBUTIONS

A real-space Green-function technique, in which the scattering is trea ted exactly, is used in a single-band tight-binding model to evaluate the Ohmic resistivities and the giant magnetoresistance in trilayer sy stems. The model includes (i) spin dependence of the density of states and Fermi velocity in the magnetic material, giving a qualitative rep resentation of Co/Cu and Fe/Cr systems; (ii) spin-independent bulk dis order, representing intrinsic defects in real systems; (iii) chemicall y sharp interfacial roughness. It is found that for parameters that pr oduce 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 int erfacial roughness enhances the effect. Its contribution becomes signi ficant in the limit of sufficiently dense roughness steps, sufficientl y weak bulk disorder, and sufficiently thin magnetic layers.