The spin-dependent reflectivity of very-low-energy electrons from ferromagnetic surfaces has recently been utilized in a new type of electron spin detector [1,2]. The underlying effect is a result of electron scattering from a spin-dependent substrate potential as well as from a spin-dependent surface-potential barrier.

 

We present the first spin-polarized very-low-energy electron-diffraction (SPVLEED) measurements on a ferromagnetic system. Our data on Co/Cu(001) reveal a significant spin dependence of the reflected intensities that varies strongly with electron energy, polar and azimuth angle of incidence.

 

In these intensity vs. energy spectra I(V), additionally, fine structures appear [3], which are caused by the surface-potential barrier. Their particular intensities and energy positions are very sensitive to the shape of the surface-potential barrier. On the vacuum side far from the surface, the barrier resembles the well-known Coulomb potential, while, on the crystal side, it converges to the inner potential. In theoretical calculations, the transition region is usually described by a parameterized phenomenological model. Our experiment provides access to exactly this transition region.

 

We could determine the spin-dependent shape of the surface-potential barrier of Co/Cu(001) from the dispersion of the fine structure as a function of polar and azimuth angle.

 

[1] T. Okuda et al., Rev. Sci. Instrum. 79 (2008) 123117 ; [2] A. Winkelmann et al., Rev. Sci. Instrum. 79 (2008) 083303 ; [3] R.O. Jones, P.J. Jennings, Surf. Sci. Reports 9, 165 (1988)