Deutsche Tagung f ¨ur Forschung mit ... - SNI-Portal

Magnetismus Poster: Do., 13:00–15:30 D-P232
Approach to the Neutron Scattering Analysis of Magnetic Nanostructures.
Wolfgang Kreuzpaintner 1 , Helena Tartakovskaya 1 , Andreas Schreyer 1
1 GKSS Forschungszentrum Geesthacht, Max-Planck-Straße 1, 21502 Geesthacht
Elastic and inelastic Small Angle Neutron scattering on magnetic nanostructures, such
as nanowires, nanodots or nanomatrices, is a most promising technique for obtaining
information on structural and dynamical magnetic properties, which are essential
for the further development of higher density magnetic data storage devices and new
technologies like magnetic random access memory devices.
The main problem nowadays still lies in producing specimens of large enough area or
volume with sufficient filling fraction for achieving sufficient scattered neutron intensities.
For multilayer systems these difficulties have already successfully been overcome
and results on inelastic neutron scattering on e.g. Dy/Y superlattices have been reported
[1].
We show approaches for also overcoming these difficulties in laterally nanostructured
samples. Most promising are the use of holographic methods in combination with
etching continous epitaxially grown layers (for nanowires and nanodots with an equal
minimal lateral dimension and distance of 180 nm), the use of substrate shading by
self organised periodic substrate surface structures during deposition (for nanowires
with a basically infinite one dimensional expansion) as described in [2] and the use of
self-assembly of CoPt3 Nanocrystals [3] for high volume filling fractions.
Also we present the expectations for inelastic neutron scattering experiments which
follow from the last theoretical results on inelastic neutron scattering in ordered systems
of nanowires [4]. We show that a similar approach could be used in the case
of three-dimensional ordered structures of CoPt3 nanospheres presented elsewhere [5].
In such systems two different types of spin wave excitations could be interesting for
neutron experimental investigation. The first is the lowest uniform mode, which energy
is about 0.07 meV, and the second is the set of non-uniform modes with much larger
energy scale. The corresponding dispersion and dynamic structure factor of inelastic
neutron scattering are calculated and presented here, showing that these modes are
indeed accessible for inelastic neutron scattering experiments.
[1] A. Schreyer et al., J. Appl. Phys. 87 (2000) 5443
[2] M. Huth et al., Adv. Funct. Mater. 12 (2002) 333
[3] P. Beecher, A. J.Quinn, E. V. Shevchenko, H. Weller and G. Redmond,
J. Phys. Chem. B 108 (2004) 9564
[4] E. V. Tartakovskaya, Phys. Rev. B 73 (2006) 092415
[5] F. Wiekhost, E. Shevchenko, H. Weller and J. Kötzler, Phys. Rev. B 67, (2003) 224416