Optical anisotropy induced by external magnetic fields on magnetic fluid films

We examined the optical anisotropy of a magnetic fluid film under magnetic fields parallel to the plane of the film by detecting its birefringence effect. It was found that the transmission axis of the transmitted light was rotated significantly by an angle Delta eta, with respect to the axis of the linearly polarized incident light when an external magnetic field is applied. The angled Delta eta increases with an increase of the field strength and then becomes saturated for higher fields. By comparing the detected Delta eta 's with the corresponding structures formed in the magnetic fluid film under various magnetic fields, the angle Delta eta was found to be proportional to the ratio of the chain area to the liquid area in the film. (C) 2001 Elsevier Science B.V. All rights reserved.