The role of inelastic exchange scattering in spin polarization experiments (invited) (abstract)

Abstract

Inelastic exchange scattering of electrons can result in spin-dependent mean free paths (MFP) for electrons in ferromagnetic transition metals and glasses. The MFP of electrons with spin in the majority-spin direction will be greater than those with spin in the minority direction due to the larger number of empty minority-spin d states into which minority-spin electrons can scatter. This difference in MFP can explain the increase in the spin polarization of secondary electrons in transition metals and glasses that is observed at low energies. In addition, it will be shown that the ratio of the majority to minority spin MFP as a function of energy can be determined directly from measurements of the energy dependence of the secondary electron-spin polarization. A different type of experiment in which exchange is important is the production of Ni Auger electrons by the scattering of metastable He atoms from a Ni surface. The number of Auger electrons produced is found to depend on the relative spin of the He and Ni, parallel or antiparallel. The normalized difference of these two cases is found to increase with increasing energy of the Auger electrons. It is found that this effect is directly related to exchange scattering of the Ni electrons that neutralize the He atoms and that the experimental results can be accounted for by a simple model.