On the concentration dependence of Faraday rotation in magnetic fluids

Faraday rotation and magnetization measurements at room temperature were undertaken on Fe₃O₄ particle magnetic fluids with different concentrations. The results show that Faraday rotation follows a Langevin-type behavior with the applied magnetic field. The results also show that Faraday rotation increases with the concentration of the sample and tends to saturate at higher fields for higher concentration. By comparing the optical and magnetic data the role of chain formation in Faraday rotation is discussed. From these measurements, the chain length at given field is found to be linear with the concentration of the sample, a result that is in agreement with recent studies on the concentration dependence of chain formation