Ferrosmectics are magnetic liquid crystals which consist of a lyotropic lam
ellar phase in which colloidal particles of maghemite are incorporated. The
rotational dynamics of the colloidal particles is studied by measuring the
linear birefringence relaxation of an oriented ferrosmectic sample submitt
ed to a pulse of magnetic field. Two characteristic time scales are found f
or the relaxation rate. The shorter ( similar to 5 mu s) is the characteris
tic Brou'nian relaxation time of the particles in the isotropic colloidal s
uspension (ferrofluid), The slow evolution ( similar to 15 ms), due to the
presence of the lyotropic matrix, can be interpreted as due to the adsorpti
on of some particles on the surfactant layers, (C) 1999 Published by Elsevi
er Science B.V. All rights reserved.