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MA: Fachverband Magnetismus
MA 14: Magnetization Dynamics II
MA 14.4: Talk
Monday, March 14, 2011, 17:45–18:00, HSZ 403
Hot electron driven enhancement of spin-lattice coupling — •Marko Wietstruk1,2, Christian Stamm2, Niko Pontius2, Torsten Kachel2, Cornelius Gahl1, Alexey Melnikov3, Muhammad Sultan3, Martin Weinelt1,3, Hermann Dürr2,4, and Uwe Bovensiepen3,5 — 1Max-Born-Institut Berlin — 2Helmholtz-Zentrum Berlin — 3Freie Universität Berlin, Fb. Physik — 4SLAC, California, USA — 5Universität Duisburg-Essen, Fak. für Physik
Laser induced demagnetization of elemental Gd is known to occur on the order of tens of picoseconds [1]. This slow time scale reflects the weak 4f spin-lattice coupling caused by the zero orbital momentum of the half-filled Gd 4f shell.
However, our fs time-resolved x-ray magnetic circular dichroism (TR-XMCD) measurements show that the spin-lattice coupling and thus the demagnetization rate is enhanced by excitation of the sample with an intense fs Laser pulse [2]. We conclude that the additional fast demagnetization process with τ<1 ps is driven by spin-flip scattering of hot electrons, i.e. the demagnetization time corresponds to the equilibration of excited electrons with the lattice.
These findings are supported by measurements on Tb that exhibits much stronger spin-lattice coupling, as well as on Ni, which shows a much shorter demagnetization time scale [3] but nevertheless a similar angular momentum transfer rate.
[1] A. Vaterlaus et al., Phys. Rev. Lett. 67, 3314 (1991)
[2] M. Wietstruk et al., arXiv:1010.1374v1[cond-mat.mtrl-sci] (2010)
[3] C. Stamm et al., Phys Rev. B 81, 104425 (2010)