Dresden 2009 – scientific programme
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MA: Fachverband Magnetismus
MA 25: Micro- and Nanostructured Magnetic Materials II
MA 25.17: Talk
Wednesday, March 25, 2009, 19:00–19:15, HSZ 403
Quasi-Antiferromagnetic 120∘ Néel-State in 2D Clusters of Dipole-Quadrupole-Interacting Particles Arranged on a Hexagonal Lattice — •Nikolai Mikuszeit1, Larysa Baraban2, Elena Y. Vedmedenko1, Artur Erbe2, Paul Leiderer2, and Roland Wiesendanger1 — 1Institute of Applied Physics, University of Hamburg Jungiusstr. 11, 20355 Hamburg, Germany — 2Department of Physics, University of Konstanz, Universitätsstr. 10, Konstanz, 78457, Germany
Recent experiments on colloidal particles, capped with Co/Pt multilayers, have shown a 120∘ Néel-state [1], which was unexpected for particles interacting via stray field. The state, where all particles are reversed, is not observed. In the framework of multipole expansion [2] this asymmetry requires not only odd but also even parity moments (e.g. a quadrupole (q)). The even parity moments significantly alter the dipolar ordering of the presumably dominant dipole (d).
We performed Monte Carlo simulations of particle clusters taking into account a d- and a
q-moment.
Although the symmetries of the pure dipolar (vortex) or pure quadrupolar (pinwheel) ground states strongly differ from the
observed Néel-state, the latter one can be established by competing d and q interactions.
The relative strength of d-d- and
q-q-interaction as well as the cluster size was varied. A small region was found, where the
120∘ Néel-state is formed.
L. Baraban, et al. Phys. Rev. E 77, 031407 (2008)
E. Y. Vedmedenko and N. Mikuszeit, ChemPhysChem, 9, 1222 (2008)