Regensburg 2000 – scientific programme

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AM: Magnetismus

AM 16: Dünne Schichten III: Magnetooptik, Nanostrukturen

AM 16.5: Talk

Wednesday, March 29, 2000, 17:45–18:00, H10

Femtosecond spin dynamics on Cu(111)/Ni/Cu wedges — •Maarten van Kampen, Bert Koopmans, Jürgen Kohlhepp, and Wim de Jonge — Department of Applied Physics, Eindhoven University of Technology, The Netherlands

The spin dynamics in ferromagnetic metals is studied on a femtosecond timescale using time-resolved magneto-optics on an epitaxial Ni-wedge. A significant difference is observed between the Kerr rotation and ellipticity during the first ∼ 500 fs after excitation by a laser pulse. This clearly proofs the absence of a direct relation between the observed magneto-optical signal and the magnetization shortly after excitation. Furthermore, the results indicate that after 1–2 ps the spin system has come into equilibrium with the electrons and the lattice. A systematic study of the spin dynamics as a function of Ni-thickness (1–4 nm) showed little variation, indicating that interface scattering, magnetic anisotropy and the morphology seem to have a small influence on the observed dynamics in this thickness regime. Currently theoretical models are being developed to explain the different behavior of Kerr rotation and ellipticity by changes in the occupied density of states during the thermalization of the hot electron gas.