Quantitative aspects of spin-polarized scanning tunneling spectroscopy of Gd(0001)

The Gd(0001) surface is ideally suited in order to demonstrate spin-polariz ed: vacuum tunneling since it exhibits a d(z)2-like surface state that is e xchange split into two parts with opposite spin: polarization. Both, the ma jority as well as the minority spin parts appear as:peaks in the tunneling spectra. The use of ferromagnetic probe tips leads to magnetic field depend ent asymmetries in the differential tunneling conductivity at bias voltages which correspond to the energies of the spin components. By mapping the as ymmetry parameter we can image the magnetic domain structure of the sample. The spin polarization of the differential tunneling conductivity is found to be in excellent agreement with (inverse) photoemission data. Prolonged e xpos;re to the residual gas being present in the vacuum system leads to a s ignificant decrease of spin polarization. (C) 1999 American Vacuum Society. [S0734-2101(99)09404-X].