Magnetization of rotating ferrofluids: the effect of polydispersity

The influence of polydispersity on the magnetization is analysed in a nonequilibrium situation where a cylindrical ferrofluid column is forced to rotate with constant frequency, like a rigid body in a homogeneous magnetic field that is applied perpendicular to the cylinder axis. Then, the magnetization and the internal magnetic field are no longer parallel to each other and their directions differ from that of the applied magnetic field. Experimental results on the transverse magnetization component perpendicular to the applied field are compared and analysed as functions of rotation frequency and field strength with different polydisperse Debye models that take into account the polydispersity in different ways and to a varying degree.