Structural Disorder and Spin Polarized Electron States in EuS

The electron-spin-polarization (ESP) analysis of the photoemission from ferromagnets is employed for investigating the spin polarized energy levels in EuS. We observe that EuS films, which were evaporated at 4.2 K in uhv, change considerably their magnetophotoelectric properties by annealing: the photothreshold increases by ∼0.8 eV and the tailing into the mobility gap disappears. The 4f7 levels then become the highest occupied energy states and the measured ESP was ∼53% for these electron states. By measuring ESP curves as a function of the external magnetic field for different photon energies we also observed the degree of polarization for the different energy states in disordered EuS.