Voltage self-sustained oscillation and phase separation dynamics in a thin layer of a weakly conducting ferromagnetic liquid with periodically emerging electrohydrodynamic flows

Abstract

It is shown that voltage self-sustained oscillations, which are determined by the properties of the near-electrode layer and electrohydrodynamic flows that are periodically formed in the colloid layer, emerge for a preset direct current at the electrodes of a plane-parallel cell filled with a colloid system consisting of stabilized magnetic nanoparticles dispersed in a weakly conducting liquid. The effect of self-sustained oscillations and periodic electrohydrodynamic flows in phase separation in the colloid system is analyzed. It is found that new dynamic formations are generated, which are regions of elevated concentration of magnetite particles having the shape of labyrinths of millimeter size. The emergence of a negative real part of the permittivity of the colloid layer is detected and attributed to the fact that the normal component of the internal electric field produced by volume charges becomes codirectional with the applied field when steady-state electrohydrodynamic flows appear in the system.