Surface studies using spin-polarized electron energy loss spectroscopy

Abstract

Spin-polarized electron energy loss spectroscopy (SPEELS) has been used to investigate several paramagnetic surfaces. In this technique, a low energy beam of spin-polarized electrons from a GaAs source is directed at the surface to be studied and the spin-polarization of the emitted electrons, as well as the kinetic energy distribution, is measured via a micro-Mott polarimeter equipped with a retarding potential energy analyzer. The near-elastic-energy electrons contain information on the inelastic scattering channels available in the solid. The spin-polarization of these same electrons is sensitive to the shape of the final state manifold, i.e., the density of unoccupied states. The low energy and behavior of the spin-polarization spectrum mainly reflects the high number of unpolarized electrons present near zero kinetic energy. Results from Cu(100), polycrystalline Au, GaAs(110), GaAs(100) and Mo(110) surfaces suggest that exchange scattering with spin-flip is ubiquitous for the lowest energy electron beam energies studied ($\sim$14 eV). A simple convolution of the empty and occupied densities of states correctly predicts the shape of the energy dependent spin-flip rate.