Dresden 2003 – wissenschaftliches Programm

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MA: Magnetismus

MA 18: Spindynamik / Ummagnetisierungsvorg
änge

MA 18.12: Vortrag

Mittwoch, 26. März 2003, 18:00–18:15, HSZ/401

Coupled Coherent Phonons and Magnons by Resonant Excitation of the Exchange Split Surface State of Gd(0001) — •Ilie Radu, Alexey Melnikov, Uwe Bovensiepen, Oleg Krupin, Kai Starke, Eckart Matthias, and Martin Wolf — Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany

The second harmonic response of ferromagnetic Gd(0001) surfaces following optical excitation at 750-820 nm was studied by pump-probe measurements. As a function of time delay, the electron and spin relaxation processes following the pump pulse lead to a continous change in both the second harmonic (SH) fields, which are even and odd with respect to magnetization reversal. Superimposed on that background, we observed oscillations at a frequency of 3 THz in both the even and odd SH fields. The periodicity in the even field is attributed to a coherent optical phonon, which corresponds to a modulation of the Gd interlayer distance between the surface layer and the bulk. The excitation mechanism of coherent phonons at metal surfaces, which we propose, goes beyond established models and includes the different lifetimes of the two exchange split surface states. To describe the modulation in the odd field, we suggest excitation of a coherent optical magnon and discuss possible mechanisms.