Issue 10, 2011
From the journal:

Soft Matter

Macroscopic optical effects in low concentration ferronematics

Nina Podoliak,*a   Oleksandr Buchnev,a   Oleksandr Buluy,c   Giampaolo D'Alessandro,b   Malgosia Kaczmarek,a   Yuriy Reznikovc  and  Timothy J. Sluckinb  

* Corresponding authors

a School of Physics and Astronomy, University of Southampton, Southampton, United Kingdom
E-mail: np7g08@soton.ac.uk

b School of Mathematics, University of Southampton, Southampton, United Kingdom

c Institute of Physics, National Academy of Sciences of Ukraine, Prospect Nauky 46, Kyiv, Ukraine

Abstract

We present a detailed experimental and theoretical study of the optical response of suspensions of ferromagnetic nanoparticles (“ferroparticles”) in nematic liquid crystals (“ferronematics”), concentrating on the magnetic field-induced Frederiks transition. Even extremely low ferroparticle concentrations (at a volume fraction between 2 × 10−5 and 2 × 10−4), induce a significant additional ferronematic linear response at low magnetic field (<100 G) and a decrease in the effective magnetic Frederiks threshold. The experimental results demonstrate that our system has weak ferronematic behavior. The proposed theory takes into account the nematic diamagnetism and assumes that the effective magnetic susceptibility, induced by the nanoparticles, no longer dominates the response. The theory is in good agreement with the experimental data for the lowest concentration suspensions and predicts the main features of the more concentrated ones. The deviations observed in these cases hint at extra effects due to particle aggregation, which we have also observed directly in photographs.

Graphical abstract: Macroscopic optical effects in low concentration ferronematics

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Article information

DOI
https://doi.org/10.1039/C1SM05051F
Article type
Paper
Submitted
13 Jan 2011
Accepted
09 Mar 2011
First published
29 Mar 2011

Soft Matter, 2011,7, 4742-4749

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Macroscopic optical effects in low concentration ferronematics

N. Podoliak, O. Buchnev, O. Buluy, G. D'Alessandro, M. Kaczmarek, Y. Reznikov and T. J. Sluckin, Soft Matter, 2011, 7, 4742 DOI: 10.1039/C1SM05051F

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