title: Field induced phase segregation in ferrofluids.
abstract: We study the phase segregation in magnetite ferrofluids under the influence of an external magnetic field. A phase with lower nanoparticle density and corresponding higher optical transmission is formed in the bottom of a glass cell in the presence of only a very modest magnetic field gradient (smaller than 25 T/m). The flux density in our magnetic configuration is simulated using finite element methods. Upon switching off the external magnetic field, the low-density phase develops into a 'bubble'-like feature. The kinetics of this 'bubble' in the absence and presence of a magnetic field are described and analyzed in terms of a simple model, which takes into account buoyancy and drag forces.
authors.affiliation: Solid State Physics group, MESA(+) Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500AE Enschede, The Netherlands. e.s.kooij@utwente.nl
authors.forename: E S
authors.initials: ES
authors.lastname: Kooij
authors.forename: A C
authors.initials: AC
authors.lastname: Gâlcă
authors.forename: B
authors.initials: B
authors.lastname: Poelsema