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The European Physical Journal E

, Volume 13, Issue 3, pp 309–319 | Cite as

Physical properties of aqueous suspensions of goethite (\(\alpha\)-FeOOH) nanorods

Part II: In the nematic phase
  • B. J. Lemaire
  • P. DavidsonEmail author
  • D. Petermann
  • P. Panine
  • I. Dozov
  • D. Stoenescu
  • J. P. Jolivet
Article

Abstract.

At volume fractions larger than 8.5%, aqueous suspensions of lath-like goethite (\(\alpha\)-FeOOH) nanorods form a lyotropic nematic phase. In this article, we first discuss the nematic ordering within statistical-physics models of the isotropic/nematic phase transition. We then describe the influence of a magnetic field on the nematic phase. Because the nanorods bear permanent magnetic moments, the nematic suspensions have dipolar order and very low Frederiks thresholds. Moreover, the nematic phase aligns parallel to a small magnetic field but realigns perpendicular to a high field because of a competition between the permanent moments of the nanorods and their negative anisotropy of magnetic susceptibility. This magneto-optical study of the nematic phase is completely consistent with that of the isotropic phase of the same suspensions published in Part I (this issue, p. 291). Besides, we demonstrate the field-induced biaxiality of a nematic single domain aligned perpendicular to the field. We also describe here preliminary experiments where an a.c. electric field is applied to the nematic phase. Both field amplitude and frequency were found to control the alignment direction and homeotropic-to-planar alignment transitions were observed. From this data, simple models were used to estimate some physical constants of the nematic phase.

Keywords

Magnetic Field Phase Transition Goethite Aqueous Suspension Single Domain 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer-Verlag Berlin/Heidelberg 2004

Authors and Affiliations

  • B. J. Lemaire
    • 1
  • P. Davidson
    • 1
    Email author
  • D. Petermann
    • 1
  • P. Panine
    • 2
  • I. Dozov
    • 3
  • D. Stoenescu
    • 3
  • J. P. Jolivet
    • 4
  1. 1.Laboratoire de Physique des Solides, UMR CNRS 8502, Bâtiment 510Université Paris-SudOrsayFrance
  2. 2.European Synchrotron Radiation FacilityGrenobleFrance
  3. 3.NemopticMagny-les-HameauxFrance
  4. 4.Laboratoire de Chimie de la Matiére Condensée, UMR CNRS 7574Université Paris 6ParisFrance

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