title: Ferrofluids as thermal ratchets.
abstract: Colloidal suspensions of ferromagnetic nanoparticles, 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.
authors.affiliation: Universität Magdeburg, Institut für Theoretische Physik, PSF 4120, 39106 Magdeburg, Germany. andreas.engel@physik.uni-magdeburg.de
authors.forename: Andreas
authors.initials: A
authors.lastname: Engel
authors.forename: Hanns Walter
authors.initials: HW
authors.lastname: Müller
authors.forename: Peter
authors.initials: P
authors.lastname: Reimann
authors.forename: Achim
authors.initials: A
authors.lastname: Jung