Berlin 2008 – scientific programme

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MA: Fachverband Magnetismus

MA 2: Micro and Nanostructured Magnetic Materials I

MA 2.8: Talk

Monday, February 25, 2008, 12:00–12:15, EB 301

Magnetic ordering in 2 dimensional arrays of polarized particles with higher order multipole moments — •Matthias Schult, Nikolai Mikuszeit, Elena Vedmedenko, and Roland Wiesendanger — Institute of Applied Physics, University of Hamburg, Jungiusstrasse 11, 20355 Hamburg, Germany

In arrays of polarized nanoparticles the stray field couples each particle to all others as stray field interaction is of long range nature. For non-spherical or multidomain polarized particles the stray field deviates from that of a point dipole and in dense arrays higher order moments must be taken into account [1].

Finite arrays of polarized single and two domain particles with spheroidal shape are investigated by means of Monte-Carlo simulation. Typical magnetic self-energy is neglected as the system is regarded as a model for spinor Bose-Einstein condensates. The simulation uses analytical solutions for the higher order moments [2]. For systems with a strong quadrupolar contribution a new ground state, different from the well known dipolar ground state, is found. Lattices of different symmetry are investigated. Lattice-symmetry-induced as well as particle-geometry-induced phase transitions are observed.

[1] E. Y. Vedmedenko, N. Mikuszeit, H. P. Oepen, and R. Wiesendanger, 2005, Phys. Rev. Lett. 95, 207202

[2] M. Schult, N. Mikuszeit, E. Y. Vedmedenko, and R. Wiesendanger, 2007, J. Phys. A, accepted