Magnetochromatics resulted from optical gratings of magnetic fluid films subjected to perpendicular magnetic fields

A two-dimensional ordered structure can be formed in a thin film of homogen eous magnetic fluids by applying a magnetic field perpendicular to the plan e of the film. The characteristic spacing of the ordered structure can be c ontrolled by several parameters, such as the field strength, the sweep rate , the thickness of the film, and the volume concentration of homogeneous ma gnetic fluids. The length of the characteristic spacing ranges from several micrometers to submicrometers. Depending on the size of the spacing, magne tic fluid films are capable of diffracting an incoming white light. The dif fracted light then interferes resulting in a chromatic effect. This effect is well illustrated by the chromatic rings produced by passing a white ligh t through the magnetic fluid films possessing an ordered structure. Because of the changeability of the characteristic spacing, the magnetochromatic e ffect of magnetic fluid films can be controlled by altering these control p arameters. (C) 2000 American Institute of Physics. [S0021-8979(00)02223-4].