THE MAGNETOOPTICAL BIREFRINGENCE AND INITIAL SUSCEPTIBILITY OF VERY DILUTE MAGNETIC FLUIDS

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.