Evidence for Spin-Dependent Electron-Hole-Pair Excitations in Spin-Polarized Secondary-Electron Emission from Ni(110)

The energy-resolved spin polarization P of secondary electrons from Ni(110) has been measured with high energy resolution. At the lowest kinetic energy P reaches a maximum of (17±{}2)% which is significantly higher than the mean conduction-band polarization (5.5%). Within about 3 eV towards higher kinetic energy the spin polarization decreases to about 8% and displays pronounced structures at higher energies. Spin-dependent electron-hole-pair excitations are suggested to be responsible for the observed spin polarization.