Regensburg 2007 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 15: Poster:ThinFilms(1-33),Transp.(34-49),ExchBias(50-56),
Spindynamics(57-70),Micro-nanostr.Mat.(71-82),
Particles/Clust.(83-88), Mag.Imag./Surface(89-96),
Spinelectronics(97-109), Theory/Micromag.(110-116),
Spinstruct/Phasetr.(117-128),Magn.Mat.(129-139),
Aniso.+Measuring(140-145), MolMag.(146-152),
MSMA(153-156)

MA 15.70: Poster

Dienstag, 27. März 2007, 15:00–19:00, Poster A

Ultrafast Demagnetization Probed by Femtosecond X-Ray Pulses — •Marko Wietstruk, Torsten Kachel, Niko Pontios, Christian Stamm, Hermann A. Dürr, and Wolfgang Eberhardt — BESSY m.b.H., Albert-Einstein-Straße 15, 12489 Berlin, Germany

The energy of an intense fs laser pulse exciting a ferromagnetic sample is absorbed by the electronic system. The subsequent transfer of energy to the lattice and spin systems leads to a demagnetization of the sample within a few 100 fs. However, the total angular momentum previously carried by the ordered spins has to be conserved and consequently transferred to the other reservoirs on the same time scale.

Using X-ray magnetic circular dichroism (XMCD), we observe the evolution of the magnetization as a function of time delay between the laser pump and the x-ray probe pulse. The contribution of the spin and orbital moments can be obtained by XMCD sum rules. Our goal is to get new insight into the energy and angular momentum transfer mechanisms during the ultrafast demagnetization of ferromagnetic thin films.

The experiments were done at the femtosecond slicing source at BESSY have a temporal resolution better than 150fs. It provides circularly polarized synchrotron radiation at energies in the range of absorption edges of 3d transition metals and rare earths (L and M edges, respectively), covering important ferromagnetic elements like Fe, Ni and Gd.