arXiv subjects

A. Leschhorn

Publications and source records attributed to A. Leschhorn.

3 recordsLinked to original sources

arXiv2006

Magnetization of rotating ferrofluids: the effect of polydispersity

The influence of polydispersity on the magnetization is analyzed in a nonequilibrium situation where a cylindrical ferrofluid column is enforced 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 not 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 analyzed 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.

physics.flu-dyn↗

arXiv2006

Periodically forced ferrofluid pendulum: effect of polydispersity

We investigate a torsional pendulum containing a ferrofluid that is forced periodically to undergo small-amplitude oscillations. A homogeneous magnetic field is applied perpendicular to the pendulum axis. We give an analytical formula for the ferrofluid-induced ``selfenergy'' in the pendulum's dynamic response function for monodisperse as well as for polydisperse ferrofluids.

physics.flu-dyn↗

arXiv2005

Magnetization of rotating ferrofluids: predictions of different theoretical models

We consider a ferrofluid cylinder, that is rotating with constant rotation frequency Ωe_z as a rigid body. A homogeneous magnetic field 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 Ωand 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.

physics.flu-dyn↗