DOES CURIE-WEISS BEHAVIOR EXIST IN THE BIREFRINGENCE AND DICHROISM INMAGNETIC FLUIDS

The Curie-Weiss behavior of the birefringence, delta, and dichroism, D ELTAA, in magnetic fluids have been investigated. The analysis of our experimental data on both delta and DELTAA in Fe3O4 particle magnetic fluids in the temperature range 100 < T < 320 K and in magnetic fields up to 3 kOe shows appreciable deviations from Curie-Weiss-type behavi or. Moreover, both birefringence and dichroism follow Arrhenius-type b ehavior with temperature for T > T(m), where T(m) is the temperature a t which the maxima in delta and DELTAA take place, and a Vogel-Fulcher type behavior type behavior for T < T(m). This behavior of delta and DELTAA with temperature is similar to the behavior of the viscosity of a magnetic fluid with temperature. Therefore, it is suggested that th e viscosity of the magnetic fluids plays a major role in the induced o ptical anisotropy in magnetic fluids.