Intensities of surface spin wave excitations in inelastic electron scattering

The intensity of surface spin wave excitations in inelastic electron scattering is measured as function of electron energy for fcc and hexagonal close packed (hcp) cobalt layers. Intensities are converted into scattering probabilities with the help of a recently established calibration of our spectrometer. The scattering probability as function of energy exhibits a peak around 7 and 3 eV for fcc and hcp cobalt, respectively, and decays to immeasurably small values at energies above 10 to 15 eV in stark contrast to theoretical predictions. By comparison to phonon scattering the peaks in the scattering probabilities at low energies are tentatively attributed to image potential induced resonances.