Direct measurement of spin-dependent conduction-electron mean free paths in ferromagnetic metals

Abstract

Using a new giant magnetoresistance structure we measure the spin-up mean free paths of ferromagnetic metals. At room temperature we find for Co ${\ensuremath{\lambda}}^{+}$=55\ifmmode\pm\else\textpm\fi{}4 \AA{}, for Fe ${\ensuremath{\lambda}}^{+}$-15\ifmmode\pm\else\textpm\fi{}2 \AA{}, and for ${\mathrm{Ni}}_{80}$${\mathrm{Fe}}_{20}$ alloy ${\ensuremath{\lambda}}^{+}$=46\ifmmode\pm\else\textpm\fi{}3 \AA{}. Combining these results with the Mott picture of transport we deduce the spin-down mean free paths, and find for Co ${\ensuremath{\lambda}}^{\mathrm{\ensuremath{-}}}$\ensuremath{\lesssim}6 \AA{}, for Fe ${\ensuremath{\lambda}}^{\mathrm{\ensuremath{-}}}$=21\ifmmode\pm\else\textpm\fi{}5 \AA{}, and for ${\mathrm{Ni}}_{80}$${\mathrm{Fe}}_{20}$ ${\ensuremath{\lambda}}^{\mathrm{\ensuremath{-}}}$\ensuremath{\lesssim}6 \AA{}.