Berlin 2008 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 4: Brownian motion and transport

DY 4.9: Vortrag

Montag, 25. Februar 2008, 16:15–16:30, MA 004

Realization of a Brownian ratchet based on a ferrofluid sample — •Thomas John and Ralf Stannarius — Otto-von-Guericke-Universität Magdeburg

We demonstrate an experimental ratchet system where thermal fluctuations plays a necessary role. The system is a suspension of nano-sized ferrite particles (ferrofluid) in a time dependent magnetic field. We use the sensitivity of this suspension to magnetic fields and construct a system where the ratchet is a time periodic, orientational asymmetric magnetic potential. This potential rectifies the stochastic motion of the ferrite particles. Depending on the shape of the potential a macroscopic torque is measured on the sample. Results of our measurements are compared with a microscopic model (Engel et al.).

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

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