2004/05/18 by A. Engel, Andreas Engel, Peter Reimann
Engineering · Physics and Astronomy · #Advanced Thermodynamics and Statistical Mechanics #Brownian motion #Characterization and Applications of Magnetic Nanoparticles #Classical mechanics #Condensed matter physics #Coupling (piping) #Ferrofluid #Ferromagnetism #Magnetic field #Magnetic nanoparticles #Materials science #Mechanics #Nanoparticle #Physics #Quantum mechanics #Ratchet #Ratchet effect #Rectification #Rotating magnetic field #Rotation (mathematics) #Thermal #Thermodynamics #cond-mat.mtrl-sci #cond-mat.stat-mech #stochastic dynamics and bifurcation
paper · pdf · doi:10.1103/physreve.70.051107
18 pages, 6 figures
arxiv created 2004/05/18 · openalex publication_date 2004/11/22 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
Rotational Brownian motion of colloidal magnetic particles in ferrofluids under the influence of an oscillating external magnetic field is investigated. It is shown that for a suitable time dependence of the magnetic field, a noise-induced rotation of the ferromagnetic particles due to rectification of thermal fluctuations takes place. Via viscous coupling, the associated angular momentum is transferred from the magnetic nanoparticles to the carrier liquid and can then be measured as macroscopic torque on the fluid sample. A thorough theoretical analysis of the effect in terms of symmetry considerations, analytical approximations, and numerical solutions is given which is in accordance with recent experimental findings.