Effect of a near-surface nanolayer formation on the magnetic fluid electrical properties

Abstract

In a magnetic colloid- a magnetic fluid (MF), which is placed in an electrochemical cell (a flat capacitor), a thin near-surface layer is formed in the electric field. This layer is an active medium in which the process of self-organization – autowaves was observed and studied. The layer consists of magnetite particles with a protective coating—oleic acid (HOl). We found a several orders increase of capacitance and a few times increase in the resistance of an electrochemical cell filled with a magnetic fluid by sending a pulsed electric field to the electrodes. Electrodes in the cell are thin transparent conductive ITO (InSnO2) membranes deposited on the glass. The cell reflectivity (reflectance) changes due to the formation of the near-electrode layers of magnetic fluid nanoparticles in the electric field. It can be registered by the interference of the falling light in these layers. The thickness of the near-electrode layer is estimated from the change in the reflectivity of monochromatic light. With increasing voltage on the electrodes, the layer becomes unstable, it periodically arises and collapses. As a result, the intensity of the reflected light fluctuates. When illuminated with white light, brightly colored waves are visible on the surface of the cell