Dresden 2006 – wissenschaftliches Programm

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MA: Magnetismus

MA 20: Poster: Films(1-36) Transp(37-56) Ex.Bias(57-67) Spindyn(68-80) Micromag(81-95) Particle(96-109) Imag.+Surface(110-113) Spinelectr(114-122) Theory+Micromag(123-131) Spinstr+Aniso(132-142) MagMat(143-156) Meas(157,158) MolMag+Kondo(159-162) Postdead(163-)

MA 20.129: Poster

Dienstag, 28. März 2006, 15:15–19:15, P1

Monte-Carlo simulations of magnetic nanospheres with angular dependent hysteresis loops — •Jörg Neder and Peter Nielaba — University of Konstanz, Department of Physics, 78457 Konstanz, Germany

A Co/Pd multilayer evaporated onto a monolayer of self-assembled polystyrene nanoparticles has shown an angular dependence of its magnetic behaviour on an external magnetic field [1]. We investigate these structures in the diameter range of 20 to 100 nm via Monte-Carlo simulations. The magnetic system is described using a model of classical moments [2] which are localized on a spherical cap. The energy contains contributions from exchange and dipole-dipole interaction, the external magnetic field and crystalline anisotropies. To match the perpendicular anisotropy of the evaporated Co/Pd film the easy axis due to interface anisotropy is pointing radially away from the center of the nanosphere. The size of the cells constituting the system varies from 10 to 25 Å. In our simplified model for the single magnetic cap the coercitive field decreases with increasing field angle for the diameters investigated which is in agreement with experimental results.

[1] M. Albrecht et al., Nature Materials 4, 203-206 (2005)

[2] U. Nowak, Annual Reviews of Comp. Phys. IX, 105-151 (2001)