Magnetization of Rotating Ferrofluids: Predictions of Different Theoretical Models

Abstract

Summary We consider a ferrofluid cylinder, that is rotating with constant rotation frequency Ω = Ωe z as a rigid body. A homogeneous magnetic field H 0 = H 0 e x is applied perpendicular to the cylinder axis e z. This causes a nonequilibrium situation. Therein the magnetization M and the internal magnetic field H are constant in time and homogeneous within the ferrofluid. According to the Maxwell equations they are related to each other via H = H 0 − M/2. However, H and M are not parallel to each other and their directions differ from that of the applied field H 0. We have analyzed several different theoretical models that provide equations for the magnetization in such a situation. The magnetization M is determined for each model as a function of Ω and H 0 in a wide range of frequencies and fields. Comparisons are made of the different model results and the differences in particular of the predictions for the perpendicular components H y = −M y/2 of the fields are analyzed.