Regensburg 2007 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 30: Poster II

DY 30.61: Poster

Donnerstag, 29. März 2007, 16:00–18:00, Poster D

Quantitative measurement of directed fluctuations in a ferrofluid ratchet — •Christian Müller, Thomas John, and Ralf Stannarius — Universität Magdeburg, ANP, Universitätsplatz 2, 39106 Magdeburg

Ferrofluids as many particle systems stabilized by thermal fluctuations are well suited to compare theoretical model predictions for a nanoscale thermal ratchet [1] with experimental results. We study the influence of the field frequency and wave form on the time-averaged macroscopic torque generated in a ferrofluid volume. Two pairs of Helmholtz coils are used to generate an oscillating (non-rotation) magnetic field. This field induces a ratchet potential for the ferrofluid particles. In combination with thermal fluctuations, this symmetry breaking potential leads to a net rotation of the particles, which is transferred to the sample liquid by viscous forces. The total macroscopic torque is measured and compared with predictions based on a microscopic model [2].

[1] A. Engel et al., PRL 91, 060602 (2003).

[2] A. Engel and Peter Reimann, PRE 70, 051107 (2004).