CRUCIAL TESTS OF SPIN FILTERING

The spin polarization P of the photoelectrons emitted at the photothre shold from hcp and fee Co is found to be positive, i.e., the majority of these photoelectrons have their spin magnetic moment directed paral lel to the magnetization. This is in contrast to calculations, which f ind a negative polarization at the Fermi level. Furthermore, P at the photothreshold of very thin fee Co layers is negative. These results a re interpreted as evidence for a spin-filter effect caused by a spin-d ependent inelastic mean free path.