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Sindt JO, Camp PJ, Kantorovich SS, et al. Influence of dipolar interactions on the magnetic susceptibility spectra of ferrofluids. Phys Rev E. 2016;93(6):063117doi: 10.1103/PhysRevE.93.063117.
Sindt, J. O., Camp, P. J., Kantorovich, S. S., Elfimova, E. A., & Ivanov, A. O. (2016). Influence of dipolar interactions on the magnetic susceptibility spectra of ferrofluids. Physical review. E, 93(6), 063117. https://doi.org/10.1103/PhysRevE.93.063117
Sindt, Julien O, et al. "Influence of dipolar interactions on the magnetic susceptibility spectra of ferrofluids." Physical review. E vol. 93,6 (2016): 063117. doi: https://doi.org/10.1103/PhysRevE.93.063117
Sindt JO, Camp PJ, Kantorovich SS, Elfimova EA, Ivanov AO. Influence of dipolar interactions on the magnetic susceptibility spectra of ferrofluids. Phys Rev E. 2016 Jun;93(6):063117. doi: 10.1103/PhysRevE.93.063117. Epub 2016 Jun 24. PMID: 27415368.
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Phys Rev E. 2016 Jun;93(6):063117. doi: 10.1103/PhysRevE.93.063117. Epub 2016 Jun 24.

Influence of dipolar interactions on the magnetic susceptibility spectra of ferrofluids.

Physical review. E

Julien O Sindt, Philip J Camp, Sofia S Kantorovich, Ekaterina A Elfimova, Alexey O Ivanov

Affiliations

  1. School of Chemistry, University of Edinburgh, David Brewster Road, Edinburgh EH9 3FJ, United Kingdom.
  2. School of Chemistry, University of Edinburgh, David Brewster Road, Edinburgh EH9 3FJ, United Kingdom and Institute of Mathematics and Computer Sciences, Ural Federal University, 51 Lenin Avenue, Ekaterinburg 620000, Russia.
  3. Department of Computational Physics, University of Vienna, Sensengasse 8/9, 1090 Vienna, Austria and Institute of Mathematics and Computer Sciences, Ural Federal University, 51 Lenin Avenue, Ekaterinburg 620000, Russia.
  4. Institute of Mathematics and Computer Sciences, Ural Federal University, 51 Lenin Avenue, Ekaterinburg 620000, Russia.

PMID: 27415368 DOI: 10.1103/PhysRevE.93.063117

Abstract

The frequency-dependent magnetic susceptibility of a ferrofluid is calculated under the assumption that the constituent particles undergo Brownian relaxation only. Brownian-dynamics simulations are carried out in order to test the predictions of a recent theory [A. O. Ivanov, V. S. Zverev, and S. S. Kantorovich, Soft Matter 12, 3507 (2016)1744-683X10.1039/C5SM02679B] that includes the effects of interparticle dipole-dipole interactions. The theory is based on the so-called modified mean-field approach and possesses the following important characteristics: in the low-concentration, noninteracting regime, it gives the correct single-particle Debye-theory results; it yields the exact leading-order results in the zero-frequency limit; it includes particle polydispersity correctly from the outset; and it is based on firm theoretical foundations allowing, in principle, systematic extensions to treat stronger interactions and/or higher concentrations. The theory and simulations are compared in the case of a model monodisperse ferrofluid, where the effects of interactions are predicted to be more pronounced than in a polydisperse ferrofluid. The susceptibility spectra are analyzed in detail in terms of the low-frequency behavior, the position of the peak in the imaginary (out-of-phase) part, and the characteristic decay time of the magnetization autocorrelation function. It is demonstrated that the theory correctly predicts the trends in all of these properties with increasing concentration and dipolar coupling constant, the product of which is proportional to the Langevin susceptibility χ_{L}. The theory is in quantitative agreement with the simulation results as long as χ_{L}≲1.

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