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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 20.102: Poster

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

Structural and Magnetic Properties of Dipolar Nanoparticles — •Stephan Buschmann, Fred Hucht, and Peter Entel — Theoretische Physik, Universität Duisburg-Essen, D-47048 Duisburg

In this work the collective behavior and the structural and magnetic properties of dipolar nanoparticles are investigated. The dynamics of the considered systems are determined by differential equations for the translational and rotational degrees of freedom. Within a molecular dynamics simulation these differential equations are solved using the Verlet algorithm. The interaction potential of the nanoparticles consists of both an anisotropic dipolar interaction and the isotropic hard-sphere potential. Dependent on the temperature and an external magnetic field, the system is found to be in different states. These states can be characterized by their respective structural ordering of the dipolar particles, that is closely related to the magnetic and energetic properties. In the ground state the particles arrange in closed rings due to the anisotropy of the interaction. Beside the ring configuration also the formation of metastable chains and network-like structures consisting of several chain segments can be observed at zero temperature. Thermal excitations lead to a destabilization while the influence of an external magnetic field depends on its relative orientation with respect to the observed structures. In this work the phase diagrams of the various structures are determined as function of temperature and external field by means of molecular dynamic simulations and energetic arguments.