Eur. Phys. J. E 1, 227-235
Magneto-optical study of the orientation confinement of particles in ferrolyotropic systems
D. Spoliansky1,2 - V. Ponsinet1 - J. Ferré2 - J.-P. Jamet2
1 Laboratoire de Physique de la Matière Condensée,
Collège de France, 11 place M. Berthelot, 75231 Paris Cedex 05, France
2 Laboratoire de Physique des Solides, Université Paris-Sud,
Bâtiment 510, 91405 Orsay Cedex, France
vponsine@us.rhodia.com
Received 31 December 1998 and Received in final form 22 September 1999
Abstract
Ferrosmectics and ferrohexagonals are magnetic liquid crystals
which consist of a lamellar and a hexagonal phase in which
magnetic nanoparticles are incorporated. The magnetic field
variation and the relaxation of the linear optical birefringence
of ferrosmectics and ferrohexagonals and its time relaxation are
measured in different geometries and compared with that of a
ferrofluid sample. We interpret our data by the existence of a
mean orientation of the magnetic particles in the lyotropic
structure, which appears to be non-random in zero field. We
conclude that the magnetic moments of the particles are
preferentially aligned in the plane of the ferrosmectic layers and
along the axis of the ferrohexagonal cylinders, respectively. To
account for this preferred alignment, we propose that some of the
particles in the ferrosmectic are adsorbed on the surfactant
layers with their moment aligned in the lamellar plane, while the
orientation of the moments in the ferrohexagonal is restricted to
a cone around the cylinder axis.
PACS
75.50.Mm Magnetic liquids -
78.20.Ls Magnetooptical effects -
61.30.Gd Orientational order
of liquid crystals; electric and magnetic field effects on order
Copyright EDP Sciences, Società Italiana di Fisica, Springer-Verlag
