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DY: Dynamik und Statistische Physik

DY 33: Ferrofluids and Liquid Crystals

DY 33.4: Vortrag

Montag, 7. März 2005, 14:45–15:00, TU H2032

Influence of a magnetic field on the Soret effect in ferrofluids — •Thomas Voelker and Stefan Odenbach — ZARM, University of Bremen

Investigations were made to determine the influence of a magnetic field on the Soret coefficient of magnetic particles in a ferrofluid. This so called magnetic Soret effect was theoretically predicted to be two to three orders of magnitude smaller than the conventional Soret effect. In contrast, former experiments have qualitatively shown that the magnetic Soret effect is much higher than the theoretical predictions. However in those experiments the influence of buoyancy and magnetically driven convection disturbed the measurement significantly. Thus it is still an open question how strong the magnetic Soret effect can be. Therefore an experimental setup was developed which minimizes parasitic effects, simplifying the analysis of the experimental results. These results provide quantitative measures of the magnetic field dependence of the Soret effect in suspensions of magnetic nanoparticles. It is shown, that the magnetic Soret effect can even be higher than the conventional one and that its strength as well as its direction depend on the magnetic field strength and its relative alignment to the temperature gradient in the fluid.