THE TEMPERATURE-DEPENDENCE OF THE OPTICAL ANISOTROPY IN MAGNETIC FLUIDS - BIREFRINGENCE AND DICHROISM

The temperature dependence of birefringence, delta, and dichroism, DEL TA A, in Fe3O4 Isopar-M based magnetic fluids have been investigated i n the temperature range 100 < T < 320 K and in magnetic fields up to 3 kOe. The results show that birefringence and dichroism for a given co ncentration and at a given field are zero below a certain temperature T(s), and then both increase with temperature until they reach a maxim um at a temperature T(m), and then decrease with temperature for T > T (m). The values of T(m) and T(s) are found to vary with concentration and the applied field. The results also show that delta-H2 and DELTA A -H2 curves deviate from linearity. This deviation is attributed to int erparticle interactions, the orientation of pre-existing clusters, and the field-induced chain formation.