Field-induced structural anisotropy in magnetic fluids

Under parallel magnetic fields, a periodic long-chain structure pattern will form in the magnetic fluid film when the field strength exceeds some critical value H-c. The distance d between the chains and the chain width a are inversely proportional to the field strength and the sweep rate. Due to the structural formation inside the film, the degree of anisotropy of the magnetic fluid film and the intensity of the transmitted polarized light passing through the film will increase as the distance between chains and chain width decrease. The curves of the normalized light intensity and the ratio a/(d-a) exhibit a similar behavior. Moreover, the normalized transmitted intensity is a function of the angle between the direction of H and of the polarization of the incident light and is observed as a universal law sin(2)2 theta. Thus the field-induced structural anisotropy in the magnetic fluid film under parallel magnetic fields was established. (C) 1999 American Institute of Physics. [S0021-8979(99)22908-8].