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Berlin 2008 – scientific programme

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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

Tuesday, February 26, 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 Weinelt1,31Max-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 (τmajmin) 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)

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