Ferrofluids as thermal ratchets
Materials Science
2009-11-07 v2 Soft Condensed Matter
Abstract
Colloidal suspensions of ferromagnetic nano-particles, so-called ferrofluids, are shown to be suitable systems to demonstrate and investigate thermal ratchet behavior: By rectifying thermal fluctuations, angular momentum is transferred to a resting ferrofluid from an oscillating magnetic field without net rotating component. Via viscous coupling the noise driven rotation of the microscopic ferromagnetic grains is transmitted to the carrier liquid to yield a macroscopic torque. For a simple setup we analyze the rotation of the ferrofluid theoretically and show that the results are compatible with the outcome of a simple demonstration experiment.
Cite
@article{arxiv.cond-mat/0209137,
title = {Ferrofluids as thermal ratchets},
author = {Andreas Engel and Hanns Walter Mueller and Peter Reimann and Achim Jung},
journal= {arXiv preprint arXiv:cond-mat/0209137},
year = {2009}
}
Comments
4 pages, 3 figures, corrected version, improved figures, to be published in Phys. Rev. Lett