L. Sakhnini et J. Popplewell, THE MAGNETOOPTICAL BIREFRINGENCE AND INITIAL SUSCEPTIBILITY OF VERY DILUTE MAGNETIC FLUIDS, Journal of magnetism and magnetic materials, 122(1-3), 1993, pp. 146-149
In this paper the behaviour of birefringence and the initial susceptib
ility in the low concentration range (epsilon = 1.34 x 10(-5) to 0.01)
have been examined for magnetite ferrofluids. Our measurements show t
hat the initial degree of clustering does not change appreciably by di
luting the sample. In low fields the birefringence results from the sh
ape anisotropy of single particles. In the case where particle interac
tions are pronounced the birefringence results from the interactions w
ithin the pre-existing clusters in the sample.