Experiments on negative and positive magnetoviscosity in an alternating magnetic field

Abstract

Recently it has been predicted and shown experimentally that the viscosity of a magnetic fluid flowing through a capillary pipe (Hagen-Poiseuille flow) can be reduced under the influence of an alternating, linearly polarized magnetic field. We present experimental results of the amplitude and frequency dependence of this ``negative viscosity effect.'' Experimental data are quantitatively compared with results we have obtained by numeric integration of a prevailing model.