Spin-Dependent Electron Dynamics in Front of a Ferromagnetic Surface

Exchange splitting and dynamics of image-potential states in front of a 3 monolayer iron film on Cu(100) have been studied with time-, energy-, and spin-resolved bichromatic two-photon photoemission. For the first image-potential state $n=1$ we observe an exchange splitting of $56\pm 10\mathrm{meV}$ and spin-dependent lifetimes of $16\pm 2\mathrm{fs}$ for majority-spin and of $11\pm 2\mathrm{fs}$ for minority-spin electrons, respectively. The time-resolved studies of both the population and the linewidth of image-potential states manifest that at the magnetic surface not only inelastic but also quasielastic scattering processes are spin dependent.