Gd-doped EuO: Temperature dependence of the4f-photoelectron spin polarization

The spin polarization of the $4f$ electrons photoemitted from ferromagnetic EuO+$x$-at.% Gd ($x=0.1,2.0,4.3\mathrm{}$) has been measured for temperatures $T\lesssim 20$ K. During the photoemission process depolarization of the excited electrons takes place. At low temperatures, the depolarization is nearly constant. It is attributed to spin-flip scattering of the photoelectrons with not ordered ${\mathrm{Eu}}^{2+}$ moments existing at irreqularities of the surface. On approaching $T_c$, the depolarization increases. this is expected because near $T_c$ the magnetization of the ideal, i.e., atomically smooth part of the surface deviates significantly from the one of the bulk, thereby giving rise to additional spin-reversal scattering.