We consider a ferrofluid cylinder, that is rotating with constant rotation frequency Ω = Ωez as a rigid body. A homogeneous magnetic field H0 = H0ex is applied perpendicular to the cylinder axis ez. 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 = H0 − M/2. However, H and M are not parallel to each other and their directions differ from that of the applied field H0. 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 H0 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 Hy = −My/2 of the fields are analyzed.
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