Magnetic Birefringence and Dichroism in Magnetic Fluid

Abstract

Magnetooptical effect of magnetic fluids is investigated. The phase difference θ between the ordinary ray and the extraordinary ray which are transmitted through the magnetic fluid thin film was found to be described in the functional form θ1f(H)/[T-T1+f(H)], where H is the magnetic field applied to the magnetic fluid thin film, T is the absolute temperature of the film, f(H) is a certain increasing function of H and T1, θ1 are the positive constants. The field dependence of light transmissivity of magnetic fluid thin films is well described by the cluster model of ferrous colloidal particles in the applied field direction when the aggregation is small. The field dependence of transmissivity is, however, interpreted neither by the electric absorption of the clusters nor by the Rayleigh scattering when the cluster becomes larger. The diffraction effect by the linear clusters directed to the applied field must be taken into account in interpreting the light extinction.