Dresden 2011 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 46: Magnetic Thin Films II
MA 46.3: Vortrag
Mittwoch, 16. März 2011, 17:30–17:45, CHE 184
Magnetic circular dichroism in near-threshold photoemission from an ultrathin Co/Pt(111) film at variable work function — •Kerstin Hild1, Gerd Schönhense1, Hans-Joachim Elmers1, Takeshi Nakagawa2, Toshihiko Yokoyama2, Kartick Tarafder3, and Peter Oppeneer3 — 1Institute of Physics, Johannes Gutenberg University Mainz, Germany — 2Institute for Molecular Science, The Graduate University for Advanced Studies Okazaki, Japan — 3Department of Physics and Materials Science, Uppsala University, Sweden
In order to disentangle the magnetic dichroism effect [1], [2] of the two excitation steps in a two-photon photoemission process (2PPE) we compare measurements at different work function for the same Co/Pt(111) sample. The work function Φ is adjusted by Cs adsorption and the photon energy hν by a tunable Ti:Sa femtosecond laser. For one-photon photoemission (1PPE) at hν = 3 eV we measure an asymmetry of 6.2 %. A 2PPE process at the same photon energy yields a value of 8.3 %. This suggests the first step to be the major asymmetry creating process. A considerably larger asymmetry (17 %) is observed for 2PPE at hν = 1.5 eV. The results are explained by interband transitions deviating from the direction of observation Γ-L. These MCD experiments suggest a paradigm shift from the classical model of photoemission that exclusively considers k|| conserving emission processes.
Funded by Carl-Zeiss-Stiftung and the Graduate School of Excellence MAINZ (Kerstin Hild) [1] T. Nakagawa and T. Yokoyama, PRL 96, 237402 (2006). [2] K. Hild et al., PRL 102, 057207 (2009).