Crossover between the ballistic and diffusive regime of the spin-conductance and giant magnetoresistance in magnetic multilayered nanostructures

We analyze the interplay between disorder and band structure in current per pendicular to the planes giant magnetoresistance (GMR). We consider finite magnetic multilayers attached to pure crystalline leads, described by a tig ht-binding simple cubic two-band model (s-d). Several models of disorder ar e considered, including random on-site potentials, lattice distortions, imp urities, vacancies, and cross-section fluctuations. Magnetotransport proper ties are calculated in the zero-temperature zero-bias limit, within the Lan dauer-Buttiker formalism. Using a very efficient numerical scattering techn ique, we are able to perform simulations, over large length scales, and to investigate spin transport in the ballistic, diffusive, and localized regim es, as well as the crossover between them. The competition between disorder -induced mean-free-path reduction and disorder-induced spin asymmetry enhan cement of the conductance highlights several different regimes of GMR. [S01 63-1829(99)01534-9].