Spin Polarization of Photoelectrons from Cesiated Fe, Co, and Ni

The electron-spin polarization (ESP) of photoelectrons from cesiated Fe, Co, and Ni films has been measured for photon energies $h\nu <6\mathrm{}$ eV at 4.2°K. The photo-ESP was positive (magnetic moment parallel to the magnetization) independently of Cs coverage and photon energy. For Ni and Co and coverage parameters $\theta$ near to 1 (monoatomic layer) the photo-ESP approaches 0 at photon energies near the photothreshold $\Phi$. However with Fe, the photo-ESP is rather independent of $\theta$, even for $h\nu$ approaching $\Phi$. At higher photon energies a common trend of the spectra is observed: The photo-ESP approaches the average polarization $P=\frac{n_B}{n}$ with photon energies exceeding $\Phi$ only by 2 to 3 eV, which correlates with the $d$ bandwidth observed in recent ultraviolet photoemission and x-ray photoemission spectroscopy.