USE OF SPIN-POLARIZED ELECTRON-ENERGY-LOSS SPECTROSCOPY TO INVESTIGATE DIPOLE AND IMPACT SCATTERING FROM TRANSITION-METAL SURFACES

Spin polarized electron-energy-loss spectra have been obtained from Ag (100), Cu(100), Mo(110) and unmagnetized Co(110) and Fe(100) surfaces, in both specular and off-specular scattering geometries, by use of a low-energy polarized incident beam coupled with energy- and angle-reso lved spin analysis of the scattered electrons. The data ars: interpret ed in terms of a model that takes account of both dipole and impact sc attering. Dipole scattering preserves the full polarization of the inc ident beam, whereas the scattered electron polarization is degraded by electron exchange in impact-scattering events that produce electron-h ole pair excitation in the target. It is found that dipole scattering dominates at noble-metal surfaces but that the impact- and dipole-scat tering rates are comparable for targets with incompletely filled d she lls. The data also suggest that impact scattering, Like dipole scatter ing, tends to be concentrated in the specular direction.