DIRECT MEASUREMENT OF SPIN-DEPENDENT CONDUCTION-ELECTRON MEAN FREE PATHS IN FERROMAGNETIC METALS

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 angstrom, for Fe lambda+ = 15+/-2 angstrom, and for Ni80Fe20 alloy lambda+ = 46+/-3 angstrom. Combining these results with the Mott picture of transport we deduce the spin-down mean free paths, and find for Co lambda- less than or similar to 6 angstrom, for Fe lambda- = 21+/-5 angstrom, and for Ni80Fe20 lambda- less than or similar to 6 angstrom.