2009 APS March Meeting
Volume 54, Number 1
Monday–Friday, March 16–20, 2009;
Pittsburgh, Pennsylvania
Session T1: Probes of Nanoscale Magnetism
2:30 PM–5:30 PM,
Wednesday, March 18, 2009
Room: Spirit of Pittsburgh Ballrom A
Sponsoring
Unit:
DCMP
Chair: Chris Hammel, Ohio State University
Abstract ID: BAPS.2009.MAR.T1.4
Abstract: T1.00004 : Ultrafast magnetization dynamics of cobalt nanoparticles and individual ferromagnetic dots
4:18 PM–4:54 PM
Preview Abstract
Abstract
Author:
Jean-Yves Bigot
(Institut de Physique et Chimie des Mat\'eriaux de Strasbourg, UMR7504, CNRS-ULP, Strasbourg 67034)
The ultrafast magnetization dynamics of magnetic materials can be
investigated using femtosecond laser pulses to perform
femtosecond magneto-optical Kerr and Faraday measurements [1]. In
this talk, we will focus on the magnetization dynamics of cobalt
nanoparticles which are either ferromagnetic or
super-paramagnetic at room temperature and on the dynamics of
individual ferromagnetic dots. In the first case (Co
nanoparticles), we will demonstrate that the magnetization
dynamics preceding the fluctuations over the anisotropy energy
barrier is coherent but exhibits a strongly damped precession
[2]. These results, which have been obtained with a three
dimensional analysis of the magnetization vector [3] will be
discussed in the context of the N\'{e}el-Brown models involving
the gyromagnetic character of the magnetization. We will also
examine the dynamics of self-organized supra-crystals of cobalt
nanoparticles [4]. In the second case, we will present the
ultrafast magnetization dynamics of individual ferromagnetic dots
(CoPt$_{3}$, Permalloy, Nickel) made either by e-beam
lithography or induced optically on thin films deposited on
sapphire and glass substrates. The technique employed is the
magneto-optical pump probe imaging (MOPPI) which allows
performing time resolved magneto-optical Kerr images with with
spatial and temporal resolutions of 300 nm and 150 fs [5].
The study of the demagnetization of the dots for different laser
intensities shows that it is possible to write and read ultrafast
monodomains on thin films.
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[1] E. Beaurepaire, J.-C. Merle, A. Daunois, J.-Y. Bigot~ Phys.
Rev. Lett., \textbf{76}, 4250 (1996)
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[2] L.H.F. Andrade, A. Laraoui, M. Vomir, D. Muller, J.-P.
Stoquert, C. Estourn\`{e}s, E.~Beaurepaire, J.-Y. Bigot Phys.
Rev. Lett. \textbf{97}, 127401 (2006).
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[3] M. Vomir, L. H.F. Andrade, L. Guidoni, E. Beaurepaire, J.-Y.
Bigot Phys. Rev. Lett. \textbf{94}, 237601 (2005).
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[4] I.~Lisiecki, V.~Halt\'{e}, C. Petit, M.-P.~Pileni,
J.-Y.~Bigot Adv. Mater., \textbf{20}, 4176 (2008).
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[5] A. Laraoui, M. Albrecht, J.-Y. Bigot Optic. Letters
\textbf{32}, 936 (2007).
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2009.MAR.T1.4