Berlin 2015 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 27: Magnetization / Demagnetization Dynamics I
MA 27.4: Vortrag
Mittwoch, 18. März 2015, 10:15–10:30, EB 301
Constant spin polarization of the Gd(0001) surface state during laser-induced ultrafast demagnetization — •Beatrice Andres1, Marko Wietstruk1, Cornelius Gahl1, Jürgen Kirschner2, and Martin Weinelt1 — 1Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin — 2Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, 06120 Halle
Yet, there is no theory that is capable to completely describe the dynamics in the electronic structure during laser-induced ultrafast demagnetization. However, recent approaches can reproduce the observed electronic binding energies on Gd [1] by assuming a disordering either of the 4f [2] or the 5d spin orientation [3] after laser irradiation.
To test the validity of these models, we perform spin- and time-resolved photoemission spectroscopy on Gd/W(110) with our amplified Ti:Sa laser system. Using 4 mJ/cm2 of the fundamental (1.5 eV) as pump and the 4th harmonic (6 eV) as probe pulse, we directly measure the spin polarization and binding energy of the majority surface-state.
We observe a shift in binding energy that is in accordance with the decreasing exchange splitting of the 5d bands in Ref. [1]. In parallel, the spin polarization remains constant before spins and lattice equilibrate after several tens of picoseconds. This is in clear contrast to thermal heating where the surface state’s spin polarization decreases, while the exchange splitting remains finite even above the Curie temperature.
[1] Robert Carley et al., Phys. Rev. Lett. 109, 057401 (2012)
[2] Leonid M. Sandratskii, Phys. Rev. B 90, 184406 (2014)
[3] Björn Frietsch et al., submitted, (2014)