Berlin 2012 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe

MA: Fachverband Magnetismus

MA 34: Magnetization / Demagnetization Dynamics III

MA 34.7: Vortrag

Mittwoch, 28. März 2012, 16:30–16:45, H 1012

Laser induced heating of thin nickel films investigated by time-resolved electron diffraction — •Carla Streubühr, Thorsten Brazda, Ping Zhou, Dietrich von der Linde, and Uwe Bovensiepen — Universtität Duisburg-Essen, Germany

Recently phonon excitation was reported to play an essential role in the ultrafast demagnetization of ferromagnetic materials [1]. Therefore information on the dynamics of lattice heating in magnetic materials is desired. Here we report on ultrafast lattice heating of thin crystalline nickel films at room temperature which were analyzed by time-resolved electron diffraction after femtosecond laser excitation.

Similar to the experiments on polycrystalline Ni [2], Au, Ag and Cu films [3] we observed an intensity decrease of the various diffraction spots after laser excitation. The relation of the intensity changes of different orders is interpreted as a rise in lattice temperature according to the Debye-Waller Effect. The heat capacity of nickel can no longer be treated as constant because of its high Debye temperature which leads to differences to the experiments on noble metals. We obtained a lattice temperature increase of about 160 K with a time constant of (1.5±0.4) ps after exciting the sample by a fluence of about 5 mJ/cm² at a wavelength of 800 nm. In contrast to this the demagnetization of nickel on a silicon substrate is reported to have a time constant of 0.16 ps [1].

[1] B. Koopmans et al, Nature Materials 9, 259 (2010)

[2] X. Wang et al, PRB 81, 220301 (2010)

[3] M. Ligges et al, APL 94, 1019410 (2009)