Control parameters for the tunable refractive index of magnetic fluid films

In this work, we systematically investigate the influence of control parameters, including the concentration of magnetic particles, film thickness, external field direction, and field sweep rate, on the magnetically tunable refractive index of magnetic fluid films. We find that the variation in the refractive index of the magnetic fluid film with rising field strength is enhanced by increasing either the concentration or the film thickness, or by applying the field along the film surface, whereas it is independent of the sweep rate of the field. The results clearly reveal how to control the tunable refractive index of magnetic fluid films. Furthermore, they provide valuable information that may assist in the development of magnetic-fluid-based index-tunable devices.