Layer-dependent magnetic properties at Fe surfaces using spin-polarized electron emission spectroscopy (SPEES)

We have studied the angle-resolved energy distribution of spin-polarized electrons emitted during ion-surface scattering. At clean Fe surfaces, electron spin polarization values (ESP) of up to 48% are found. Varying the scattering angle of the ions from 1 ° to 45 °, we find that the layer-dependent, average ESP at the topmost surface layer is enhanced by 32% compared to that of the bulk and that the mean free path of electrons with energy 4-10 eV is about 3 atomic distances. The absence of a magnetically dead layer at Fe surfaces covered with one monolayer of O is revealed by the existence of a nonzero surface ESP.