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Ferromagnetism in suspensions of magnetic platelets in liquid crystal

Nature volume 504, pages 237–241 (2013)Cite this article

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Abstract

More than four decades ago, Brochard and de Gennes proposed that colloidal suspensions of ferromagnetic particles in nematic (directionally ordered) liquid crystals could form macroscopic ferromagnetic phases at room temperature. The experimental realization of these predicted phases has hitherto proved elusive, with such systems showing enhanced paramagnetism but no spontaneous magnetization in the absence of an external magnetic field. Here we show that nanometre-sized ferromagnetic platelets suspended in a nematic liquid crystal can order ferromagnetically on quenching from the isotropic phase. Cooling in the absence of a magnetic field produces a polydomain sample exhibiting the two opposing states of magnetization, oriented parallel to the direction of nematic ordering. Cooling in the presence of a magnetic field yields a monodomain sample; magnetization can be switched by domain wall movement on reversal of the applied magnetic field. The ferromagnetic properties of this dipolar fluid are due to the interplay of the nematic elastic interaction (which depends critically on the shape of the particles) and the magnetic dipolar interaction. This ferromagnetic phase responds to very small magnetic fields and may find use in magneto-optic devices.

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Figure 1: Magnetic nanoplatelets.
Figure 2: Switching of ferromagnetic domains in an external magnetic field as seen by polarizing microscopy.
Figure 3: Magnetization curves of monodomain samples show the switching behaviour of magnetic nanoplatelets in ordered nematic suspension.
Figure 4: Time sequence of images showing a complete switching of a monodomain sample.
Figure 5: Dependence of the relaxation rate of director orientational fluctuations on external magnetic field in samples with different concentration of magnetic nanoplatelets.

References

  1. Poulin, P., Stark, H., Lubensky, T. C. & Weitz, D. A. Novel colloidal interactions in anisotropic fluids. Science 275, 1770–1773 (1997)

    Article  CAS  Google Scholar 

  2. Muševič, I., Škarabot, M., Tkalec, U., Ravnik, M. & Žumer, S. Two-dimensional nematic colloidal crystals self-assembled by topological defects. Science 313, 954–958 (2006)

    Article  ADS  Google Scholar 

  3. Lapointe, C. P., Mason, T. G. & Smalyukh, I. I. Shape-controlled colloidal interactions in nematic liquid crystals. Science 326, 1083–1086 (2009)

    Article  ADS  CAS  Google Scholar 

  4. Lavrentovich, O. D. Liquid crystals, photonic crystals, metamaterials, and transformation optics. Proc. Natl Acad. Sci. USA 108, 5143–5144 (2011)

    Article  ADS  CAS  Google Scholar 

  5. Paulson, D. N. & Wheatley, J. C. Evidence for electronic ferromagnetism in superfluid 3He-A. Phys. Rev. Lett. 40, 557–561 (1978)

    Article  ADS  CAS  Google Scholar 

  6. Albrecht, T. et al. First observation of ferromagnetism and ferromagnetic domains in a liquid metal. Appl. Phys. A 65, 215–220 (1997)

    Article  ADS  CAS  Google Scholar 

  7. Brochard, F. & de Gennes, P. G. Theory of magnetic suspensions in liquid crystals. J. Phys. 31, 691–708 (1970)

    Article  CAS  Google Scholar 

  8. Born, M. Über anisotrope Flüssigkeiten. Versuch einer Theorie der flüssigen Kristalle und des elektrischen Kerr-Effekts in Flüssigkeiten. Sitz. Kön. Preuss. Akad. Wiss. 30, 614–650 (1916)

    Google Scholar 

  9. Ilg, P. & Odenbach, S. in Colloidal Magnetic Fluids: Basics, Development and Application of Ferrofluids (ed. Odenbach, S. ) 249–326 (Springer, 2009)

    Google Scholar 

  10. Rosensweig, R. E. Ferrohydrodynamics 237–269 (Dover, 1997)

    Google Scholar 

  11. Senyuk, B. et al. Shape-dependent oriented trapping and scaffolding of plasmonic nanoparticles by topological defects for self-assembly of colloidal dimers in liquid crystals. Nano Lett. 12, 955–963 (2012)

    Article  ADS  CAS  Google Scholar 

  12. Senyuk, B. & Smalyukh, I. I. Elastic interactions between colloidal microspheres and elongated convex and concave nanoprisms in nematic liquid crystals. Soft Matter 8, 8729–8734 (2012)

    Article  ADS  CAS  Google Scholar 

  13. Eskandari, Z., Silvestre, N. M., Tasinkevych, M. & da Gama, M. M. T. Interactions of distinct quadrupolar nematic colloids. Soft Matter 8, 10100–10106 (2012)

    Article  ADS  CAS  Google Scholar 

  14. Rault, J., Cladis, P. E. & Burger, J. P. Ferronematics. Phys. Lett. A 32, 199–200 (1970)

    Article  ADS  CAS  Google Scholar 

  15. Chen, S.-H. & Amer, N. M. Observation of macroscopic collective behavior and new texture in magnetically doped liquid crystals. Phys. Rev. Lett. 51, 2298–2301 (1983)

    Article  ADS  CAS  Google Scholar 

  16. Kopčanský, P. et al. Structural changes in the 6CHBT liquid crystal doped with spherical, rodlike, and chainlike magnetic particles. Phys. Rev. E 78, 011702 (2008)

    Article  ADS  Google Scholar 

  17. Buluy, O. et al. Magnetic sensitivity of a dispersion of aggregated ferromagnetic carbon nanotubes in liquid crystals. Soft Matter 7, 644–649 (2011)

    Article  ADS  CAS  Google Scholar 

  18. Podoliak, N. et al. Macroscopic optical effects in low concentration ferronematics. Soft Matter 7, 4742–4749 (2011)

    Article  ADS  CAS  Google Scholar 

  19. Podoliak, N. et al. Magnetite nanorod thermotropic liquid crystal colloids: synthesis, optics and theory. J. Colloid Interf. Sci. 386, 158–166 (2012)

    Article  ADS  CAS  Google Scholar 

  20. Lev, B. I., Chernyshuk, S. B., Tomchuk, P. M. & Yokoyama, H. Symmetry breaking and interaction of colloidal particles in nematic liquid crystals. Phys. Rev. E 65, 021709 (2002)

    Article  ADS  CAS  Google Scholar 

  21. Ovtar, S., Lisjak, D. & Drofenik, M. Barium hexaferrite suspensions for electrophoretic deposition. J. Colloid Interface Sci. 337, 456–463 (2009)

    Article  ADS  CAS  Google Scholar 

  22. Lisjak, D. & Drofenik, M. Chemical substitution—an alternative strategy for controlling the particle size of barium ferrite. Cryst. Growth Des. 12, 5174–5179 (2012)

    Article  CAS  Google Scholar 

  23. Moreno-Razo, J. A. et al. Effects of anchoring strength on the diffusivity of nanoparticles in model liquid-crystalline fluids. Soft Matter 7, 6828–6835 (2011)

    Article  ADS  CAS  Google Scholar 

  24. Evans, J. S., Beier, C. N. & Smalyukh, I. I. Alignment of high-aspect ratio colloidal gold nanoplatelets in nematic liquid crystals. J. Appl. Phys. 110, 033535 (2011)

    Article  ADS  Google Scholar 

  25. Mahle, S., Ilg, P. & Liu, M. Hydrodynamic theory of polydisperse chain-forming ferrofluids. Phys. Rev. E 77, 016305 (2008)

    Article  ADS  Google Scholar 

  26. López-López, M. T., Zubarev, A. Y. & Bossis, G. Repulsive force between two attractive dipoles, mediated by nanoparticles inside a ferrofluid. Soft Matter 6, 4346–4349 (2010)

    Article  ADS  Google Scholar 

  27. Dalton, L. R., Harper, A. W. & Robinson, B. H. The role of London forces in defining noncentrosymmetric order of high dipole moment–high hyperpolarizability chromophores in electrically poled polymeric thin films. Proc. Natl Acad. Sci. USA 94, 4842–4847 (1997)

    Article  ADS  CAS  Google Scholar 

  28. de Gennes, P. G. & Prost, J. The Physics of Liquid Crystals 41–162 (Clarendon, 1995)

    Google Scholar 

  29. Pleiner, H., Jarkova, E., Muler, H. W. & Brand, H. R. Landau description of ferrofluid to ferronematic phase transition. Magnetohydrodynamics 37, 254–260 (2001)

    ADS  Google Scholar 

  30. Jarkova, E., Pleiner, H., Müller, H.-W. & Brand, H. R. Macroscopic dynamics of ferronematics. J. Chem. Phys. 118, 2422–2430 (2003)

    Article  ADS  CAS  Google Scholar 

  31. Liechtenstein, A. I., Katsnelson, M. I. & Gubanov, V. A. Exchange interactions and spin-wave stiffness in ferromagnetic metals. J. Phys. F 14, L125–L128 (1984)

    Article  ADS  CAS  Google Scholar 

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Acknowledgements

This work was supported by the Slovenian Research Agency (A.M. and M.Č., grant no. P1-0192; D.L. and M.D., grant no. P2-0089-4). We thank the CENN Nanocenter for use of the LakeShore 7400 Series vibrating-sample magnetometer.

Author information

Authors and Affiliations

  1. J. Stefan Institute, SI-1000 Ljubljana, Slovenia

    Alenka Mertelj, Darja Lisjak, Miha Drofenik & Martin Čopič

  2. Faculty of Chemistry and Chemical Engineering, University of Maribor, SI-2000 Maribor, Slovenia,

    Miha Drofenik

  3. Faculty of Mathematics and Physics, University of Ljubljana, SI-1000 Ljubljana, Slovenia,

    Martin Čopič

Authors
  1. Alenka Mertelj
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  2. Darja Lisjak
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  3. Miha Drofenik
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  4. Martin Čopič
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Contributions

A.M. designed the study and performed the experiments; A.M. and M.Č. interpreted results and wrote the paper; and D.L. and M.D. designed and synthesized nanoplatelets, and prepared the suspension of nanoplatelets in isotropic solvent.

Corresponding author

Correspondence to Alenka Mertelj.

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The authors declare no competing financial interests.

Extended data figures and tables

Extended Data Figure 1 Images of polydomain samples with different concentrations of magnetic nanoplatelets in an external magnetic field.

The director lies in the plane of the sample either parallel or perpendicular to the external magnetic field, B. P and A show directions of polarizer and analyser, respectively. The scale bar in the first image is 40 µm.

Extended Data Figure 2 Images of monodomain samples with different concentrations of magnetic nanoplatelets in an external magnetic field.

The director lies in the plane of the sample either parallel or perpendicular to the external magnetic field. The scale bar in the first image is 40 µm.

Extended Data Figure 3 Sequence of images showing domain growth.

The external magnetic field is slowly increased in a sample that was quenched in the absence of an external magnetic field. The direction of the external field is perpendicular to n. If the field is switched off, the initial dark field is obtained. However, if the field is switched on immediately or within a few hours, the formed domains are still visible. The concentration of the platelets in 5CB was 0.16 wt%. The scale bar in the first image is 40 µm.

Extended Data Figure 4 Sequence of images showing transition from a polydomain to a monodomain sample.

The external field is parallel to n. The white lines are the edges of domain walls. The concentration of the platelets in 5CB was 0.3 wt%. The scale bar in the first image is 40 µm.

Extended Data Figure 5 Sequence of images showing the complete switching of a monodomain sample.

The field is applied parallel to n and in reverse direction to the field that was used during the quench to nematic phase and then switched off. Travelling white lines are the surface domain walls, where the director rotates by π. The concentration of the platelets in 5CB was 0.16 wt%. The scale bar in the first image is 40 µm.

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Mertelj, A., Lisjak, D., Drofenik, M. et al. Ferromagnetism in suspensions of magnetic platelets in liquid crystal. Nature 504, 237–241 (2013). https://doi.org/10.1038/nature12863

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