CARRIER AND CHAIN FORMATION DEPENDENCE OF BIREFRINGENCE IN MAGNETIC FLUIDS

Measurements of the birefringence in Fe3O4 magnetic fluids were undertaken in the temperature range 190-313 K in magnetic fields up to 0.7 kOe. Our results show that the birefringence increases with temperature exhibiting a maximum near the melting point, T(m), of the liquid carrier (kerosene, decalin and Isopar M). For T > T(m) the birefringence follows a generalized Curie-Weiss law yielding positive ordering temperatures for the three samples. Moreover, our results show that the birefringence behaves irreversibly with temperature, in the decalin based sample. The results also show that the magnitude of the birefringence and the shape of the maximum change with the applied magnetic fields.