Spin-Polarized Photoelectrons from Nickel Single Crystals

Photoelectrons emitted from nickel single-crystal surfaces defined by low-energy-electron diffraction and Auger-electron-spectroscopy analysis exhibit negative electron-spin polarization at threshold. The abrupt change from negative to positive polarization occurs at $h\omega \simeq \Phi +0.05\mathrm{}$ eV, where $\Phi$ is the work function. This excludes an interpretation based on a simple band theory of magnetism and also explains why the negative electron-spin polarization has not been observed in earlier experiments on polycrystalline films.