Ferromagnetism in suspensions of magnetic platelets in liquid crystal
- 11 December 2013
- journal article
- Published by Springer Science and Business Media LLC in Nature
- Vol. 504 (7479), 237-241
- https://doi.org/10.1038/nature12863
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.Keywords
This publication has 28 references indexed in Scilit:
- Magnetite nanorod thermotropic liquid crystal colloids: Synthesis, optics and theoryJournal of Colloid and Interface Science, 2012
- Shape-Dependent Oriented Trapping and Scaffolding of Plasmonic Nanoparticles by Topological Defects for Self-Assembly of Colloidal Dimers in Liquid CrystalsNano Letters, 2012
- Macroscopic optical effects in low concentration ferronematicsSoft Matter, 2011
- Liquid crystals, photonic crystals, metamaterials, and transformation opticsProceedings of the National Academy of Sciences of the United States of America, 2011
- Effects of anchoring strength on the diffusivity of nanoparticles in model liquid-crystalline fluidsSoft Matter, 2011
- Magnetic sensitivity of a dispersion of aggregated ferromagnetic carbon nanotubes in liquid crystalsSoft Matter, 2010
- Structural changes in the 6CHBT liquid crystal doped with spherical, rodlike, and chainlike magnetic particlesPhysical Review E, 2008
- Hydrodynamic theory of polydisperse chain-forming ferrofluidsPhysical Review E, 2008
- Observation of Macroscopic Collective Behavior and New Texture in Magnetically Doped Liquid CrystalsPhysical Review Letters, 1983
- Evidence for Electronic Ferromagnetism in Superfluid-Physical Review Letters, 1978