Rotational Brownian dynamics simulations of non-interacting magnetized ellipsoidal particles in d.c. and a.c. magnetic fields

Jorge H. Sánchez, Carlos Rinaldi

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    29 Scopus citations

    Abstract

    The rotational Brownian motion of magnetized tri-axial ellipsoidal particles (orthotropic particles) suspended in a Newtonian fluid, in the dilute suspension limit, under applied d.c. and a.c. magnetic fields was studied using rotational Brownian dynamics simulations. The algorithm describing the change in the suspension magnetization was obtained from the stochastic angular momentum equation using the fluctuation-dissipation theorem and a quaternion formulation of orientation space. Simulation results are in agreement with the Langevin function for equilibrium magnetization and with single-exponential relaxation from equilibrium at small fields using Perrin's effective relaxation time. Dynamic susceptibilities for ellipsoidal particles of different aspect ratios were obtained from the response to oscillating magnetic fields of different frequencies and described by Debye's model for the complex susceptibility using Perrin's effective relaxation time. Simulations at high equilibrium and probe fields indicate that Perrin's effective relaxation time continues to describe relaxation from equilibrium and response to oscillating fields even beyond the small field limit.

    Original languageEnglish
    Pages (from-to)2985-2991
    Number of pages7
    JournalJournal of Magnetism and Magnetic Materials
    Volume321
    Issue number19
    DOIs
    StatePublished - Oct 2009

    Bibliographical note

    Funding Information:
    The authors thank Juan J. de Pablo and Juan Pablo Hernandez from the Department of Chemical and Biological Engineering, University of Wisconsin. The work was supported by the National Science Foundation (NSF) CAREER Program under Grant no. CBET-0547150.

    Keywords

    • Ellipsoidal particle
    • Magnetic susceptibility
    • Relaxation time
    • Rotational Brownian motion
    • Strong probe magnetic field

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