MEASUREMENT OF MAGNETIC FLUID SURFACE TENSION UNDER THE ACTION OF MAGNETIC FIELD

Direct measurements of surface tension, viscosity, and surface elasticity under the influence of external forces are frequently impossible. Usually, the surface tension of magnetic fluid is considered to be independent of the magnitude of the applied magnetic field; therefore, it is associated with the properties of the base liquid. Because of the jump in the fluid magnetization, the magnetic anisotropy at the interface reflects the dependence of the surface tension tensor on the magnetic field. In this paper, we propose a new experimental method for studying the surface tension of a magnetic fluid in an external uniform magnetic field taking into account the orientation of a magnetic field relative to the liquid-gas interface. A modified version of the capillary wave method was used when the magnetic field was applied orthogonally to the liquid surface, and the ring detachment method−in the case of a longitudinal field. The surface tension of a ferrofluid decreases with the growth of intensity of the magnetic field orthogonal relative to the interface and with increasing frequency of acoustic vibrations. However, an increase in the field strength longitudinally directed to the interface provokes an increase in the surface tension of a magnetic fluid.