Regensburg 2004 – wissenschaftliches Programm
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MA: Magnetismus
MA 14: Hauptvortr
äge Eisenmenger / Münzenberg
MA 14.2: Hauptvortrag
Mittwoch, 10. März 2004, 14:30–15:00, H10
Ultrafast magnetization dynamics in pump probe experiments — •M. Münzenberg1, M. Lüttich1, P. Moschkau1, M. Djordjevic1, G. Eilers1, S. Bretschneider1, A. Parge1, P. Guderian1, T. Kampfrath1, R. G. Ulbrich1, B. Sass2, F. Leuenberger2, W. Felsch2, T. H. Kim3, and J. S. Moodera3 — 1IV. Phys. Inst., Universität Göttingen — 2I. Phys. Inst., Universität Göttingen — 3Francis Bitter Magnet Laboratory, MIT, USA
Ultrafast magnetization dynamics is a new evolving field having tools at hand to reach new frontiers in ultrafast spin dynamics: all optical pump experiments with Ti:Sapphire oscillators can explore electron excitations on a timescale of 50 fs to >100 ps. They are accompanied by a change in the reflectivity due to the nonequlibrium distribution of the excited electrons. In ferromagnetic systems the spin system is almost instantaneously demagnetized. Origin is a coupling of the electron, spin and lattice temperatures (three temperature model). Changing optical properties lead to a change in the Kerr rotation and ellipticity with non magnetic origin but can be separated by a variation of the probe beam wave length as proposed by Kampfrath. This is even more important on a longer time scale where phonon shock waves and magnetic excitations dominate the dynamics. For this regime we simulate the demagnetization effect in the order of 5-10% using the oommf code: the magnetic Eigen states of nanostructured rectangular structures are strongly dominated by the dipolar stray fields of the curling magnetization of the S state. Ultrafast dynamics is also accessible by the use of photoconductive switches that allow to excite the spin system directly.