Regensburg 2007 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 33: Spindynamics / Switching III

MA 33.2: Vortrag

Freitag, 30. März 2007, 11:15–11:30, H23

Spin Dynamics Probed by Femtosecond X-ray Pulses — •Christian Stamm, Niko Pontius, Torsten Kachel, Marko Wietstruk, Hermann A. Dürr, and Wolfgang Eberhardt — BESSY, Albert-Einstein-Str. 15, 12489 Berlin

When a ferromagnetic sample is highly excited by an intense fs laser pulse, the energy is first absorbed by the electronic system. Subsequently, energy is transferred to the lattice and spin subsystems on the fs time scale. This leads to a disordered spin system: ferromagnetic order is lost within several 100 fs. As the total angular momentum is conserved, the moment previously carried by the spins has to be transferred to other reservoirs on the same time scale.

Utilizing x-ray magnetic circular dichroism (XMCD), we observe the evolution of the magnetic moments as a function of time delay between laser pump and x-ray probe pulses. XMCD sum rules allow determining the contribution of spin and orbital moments separately. Our goal is to get new insight into the transfer mechanisms of energy and angular momentum during ultrafast demagnetization of thin ferromagnetic films.

The experiments were performed at the BESSY slicing source having a time resolution better than 150 fs. The available x-ray energies give access to x-ray absorption edges of the 3d transition elements and rare-earth elements (L and M edges, respectively), covering the important ferromagnetic elements Fe, Co, Ni, and Gd.