Dresden 2011 – wissenschaftliches Programm

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KR: Fachgruppe Kristallographie

KR 5: Poster Multiferroics (Joint Session of MA, DF, DS, KR, TT)

KR 5.102: Poster

Dienstag, 15. März 2011, 10:45–13:00, P2

Ultrafast demagnetization dynamics of thin Fe/W(110) films: comparison of time and spin-resolved photoemission with time resolved magneto-optic experiments — Alexander Weber^1,2, Federico Pressacco¹, Stefan Günther¹, •Eduardo Mancini¹, and Christian Back¹ — ¹Physics Department, Universität Regensburg, 93040 Regensburg, Germany — ²Institut für Festkörperforschung, Forschungszentrum Jülich, 52425 Jülich, Germany

We use two complementary experimental approaches to probe ultrafast magnetization dynamics. Using a 1.55 eV pump laser pulse we demagnetize 7 monolayer (ML) thin Fe films epitaxially grown on W(110). We probe the temporal evolution of the magnetization using time-resolved magneto-optical Kerr effect (TR-MOKE) at a probe photon energy of 3.1 eV. In addition we use time- and spin- resolved photoemission (TR-SPES) to probe the evolution of the spin polarization of the film (probe photon energy 5.9 eV). With TR-MOKE for all the observed quenching the demagnetization times have the same value (within the error bars) equal to the expected cross-correlation of the pump and probe pulses (about 250 fs). However TR-SPES measurements show demagnetization times limited by the cross-correlation (about 320 fs) only for quenching below 33%. Indeed, for greater quenching we find a significant increase in the demagnetization times to about 500 fs. We explain this behavior as a clear indication of the bandstructure importance in the demagnetization process.