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 ${\lambda }^{+}$=55±4 Å, for Fe ${\lambda }^{+}$-15±2 Å, and for ${\mathrm{Ni}}_{80}$ ${\mathrm{Fe}}_{20}$ alloy ${\lambda }^{+}$=46±3 Å. Combining these results with the Mott picture of transport we deduce the spin-down mean free paths, and find for Co ${\lambda }^{\mathrm{-}}$≲6 Å, for Fe ${\lambda }^{\mathrm{-}}$=21±5 Å, and for ${\mathrm{Ni}}_{80}$ ${\mathrm{Fe}}_{20}$ ${\lambda }^{\mathrm{-}}$≲6 Å.