Spin-Dependent Hot Electron Transport inCo/CuThin Films

Hot-electron transport in Co/Cu/Co trilayer films has been studied in the energy range from 1.0 to 2.0 eV using ballistic electron magnetic microscopy. Both the spin-dependent attenuation lengths of Co and the cumulative polarizing effects of spin-dependent tunneling and transmission across a Co/Cu interface have been determined. For very thin (a few Å) Co layers, the latter effects result in a weakly majority-spin polarized electron beam above $\sim 1.3\mathrm{eV}$ and a minority-spin polarized beam below $\sim 1.2\mathrm{eV}$. For thicker Co layers the transmitted beam is always majority-spin polarized.