Berlin 2008 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 43: Poster Session II - MA 141/144 (Surface Spectroscopy on Kondo Systems; Frontiers of Surface Sensitive Electron Microscopy; Methods: Scanning Probe Techniques+Electronic Structure Theory+Other; Time-Resolved Spectroscopy of Surface Dynamics with EUV and XUV Radiation; joined by SYNF posters)
O 43.46: Poster
Dienstag, 26. Februar 2008, 18:30–19:30, Poster F
Spin-dependent electron lifetimes in 3d ferromagnet thin films — •Andreas Goris1,3, Ilja Panzer1,3, Martin Pickel2, Anke B. Schmidt2, Fabian Giesen1, Jürgen Braun4, Markus Donath2, and Martin Weinelt1,3 — 1Max-Born-Institut, Max-Born-Strasse 2A, 12489 Berlin — 2Physikalisches Institut, Universität Münster, Wilhelm-Klemm-Strasse 10, 48149 Münster — 3Freie Universität Berlin, Arnimallee 14, 14195 Berlin — 4Institut für Mathematik und angewandte Informatik, Universität Hildesheim, Samelsonplatz 1, 31141 Hildesheim
The experimentally found values of the lifetime ratio (τmaj/τmin) of hot electrons in 3d ferromagnetic thin films are by a factor of 4-5 smaller than predicted by values of modern ab initio calculations [1,2].
We have measured the spin-dependent hot-electron lifetime for varying excitation density in a 20 ML Co film on Cu (001) with spin-resolved two-photon photoemission. We identify three contributions to the time resolved spectra: the off-resonant excitation of the image-potential state, the hot electron decay, and the signature of a spin flip exchange-scattering process with an occupied surface-resonance state. In this process a minority hole is filled in the surface-resonance while a majority electron is in turn lifted above the Fermi energy . These results are supported by recent self-consistent LSDA + DMFT calculations of the Co bandstructure. For comparison the lifetime ratio of hot electrons in Ni is discussed.
[1] Aeschlimann et al., Phys. Rev. Lett. 79, 5158 (1997)
[2] Zhukov et al., Phys. Rev. Lett. 93, 096401 (2004)