Spin density at the Fermi level for magnetic surfaces and overlayers

Results of calculations of the spin density at the Fermi energy for several illustrative examples---the clean Fe(110) surface and the O/Fe(110), Fe/Ni(111), and Ru/Ag(001) overlayer systems---using the full potential linearized augmented plane wave method demonstrate that this energy-sliced spin density differs substantially from the total spin density previously given in the literature. The difference of the density of states at EF between the two spin parts is found to play the key role. Its negative sign in the surface-vacuum region for Fe(110) and its sign reversal when oxygen is added as an overlayer explain the experimental results obtained by using spin-polarized metastable atom deexcitation spectroscopy.