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

The Curie-Weiss behavior of the birefringence, delta, and dichroism, DELTAA, 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 behavior. Moreover, both birefringence and dichroism follow Arrhenius-type behavior with temperature for T > T(m), where T(m) is the temperature at 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 the viscosity of the magnetic fluids plays a major role in the induced optical anisotropy in magnetic fluids.