Spin relaxation effects in the perpendicular magnetoresistance of magnetic multilayers

The spin-diffusion length is the scaling length of the perpendicular giant magnetoresistance in magnetic multilayers and, according to recent experiments, the magnetoresistance ratio can be significantly reduced by enhancing the spin relaxation and thus shortening the spin-diffusion length. We present a theoretical picture of these spin-diffusion-length effects on the magnetoresistance. We also calculate the contribution from several mechanisms (spin-orbit scattering, exchange scattering by paramagnetic impurities, electron-magnon scattering) to the spin relaxation and spin-diffusion length.