Regensburg 2010 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 43: Colloids and Complex Liquids II

CPP 43.3: Talk

Thursday, March 25, 2010, 14:30–14:45, H39

Changes of dynamical anisotropy characteristics of ferrofluids in a magnetic field — •Jelena Jordanovic and Sabine H. L. Klapp — Institut für Theoretische Physik, Technische Universität Berlin, Hardenbergstr. 36, 10623 Berlin, Deutschland

We report a Molecular Dynamic study of the dynamical properties of a ferrofluid in equilibrium in the presence of a homogeneous magnetic field. Accordingly, the anisotropic diffusion constant as well as characteristics of the single particle motion are investigated. Experimentally[1] it was observed that diffusion in the directions perpendicular to the field is hindered compared to diffusion in the parallel direction, indicated by a D_⊥<D_∥ relation between the diffusion constants. However, an opposite relation was found in Brownian Dynamic simulations[2]. We found[3] a connection between both anisotropy characteristics, where the field strength as well as the dipole-dipole coupling strength play a key role. The mechanism behind the field-induced inversion of the diffusion constants’ relation is explained from a microscopic point of view by the van Hove correlation function. Moreover, by investigating the single particle motion, we show that the inversion is accompanied by an intermediate deviation from diffusive behavior, which strongly increases with the dipole-dipole coupling strength.

[1] A. Mertelj, L. Cmok, and M. Čopič, Phys. Rev. E 79, 041402 (2009).
[2] P. Ilg, and M. Kröger, Phys. Rev. E 72, 031504 (2005).
[3] J. Jordanovic and S. H. L. Klapp, in preparation.