Magnetization of rotating ferrofluids:: Predictions of different theoretical models

We consider a ferrofluid cylinder, that is rotating with constant rotation frequency Omega = Omega e(z) as a rigid body. A homogeneous magnetic field Ho = 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 Omega 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.