title: Dynamic Assembly of Magnetic Colloidal Vortices.
abstract: Magnetic colloids in external time-dependent fields are subject to complex induced many-body interactions governing their self-assembly into a variety of equilibrium and out-of-equilibrium structures such as chains, networks, suspended membranes, and colloidal foams. Here, we report experiments, simulations, and theory probing the dynamic assembly of superparamagnetic colloids in precessing external magnetic fields. Within a range of field frequencies, we observe dynamic large-scale structures such as ordered phases composed of precessing chains, ribbons, and rotating fluidic vortices. We show that the structure formation is inherently coupled to the buildup of torque, which originates from internal relaxation of induced dipoles and from transient correlations among the particles as a result of short-lived chain formation. We discuss in detail the physical properties of the vortex phase and demonstrate its potential in particle-coating applications.
authors.affiliation: International Research Center for Soft Matter, Beijing University of Chemical Technology , Beijing 100029, P.R. China.|Department of Chemistry, University of Ljubljana , Večna pot 113, 1000 Ljubljana, Slovenia.
authors.forename: Tomaž
authors.initials: T
authors.lastname: Mohorič
authors.affiliation: Jožef Stefan Institute, Jamova cesta 39, 1000 Ljubljana, Slovenia.
authors.forename: Gašper
authors.initials: G
authors.lastname: Kokot
authors.affiliation: Jožef Stefan Institute, Jamova cesta 39, 1000 Ljubljana, Slovenia.
authors.forename: Natan
authors.initials: N
authors.lastname: Osterman
authors.affiliation: Argonne National Laboratory, 9700 Cass Avenue, Lemont, Illinois 60439, United States.
authors.forename: Alexey
authors.initials: A
authors.lastname: Snezhko
authors.affiliation: Jožef Stefan Institute, Jamova cesta 39, 1000 Ljubljana, Slovenia.
authors.forename: Andrej
authors.initials: A
authors.lastname: Vilfan
authors.affiliation: Department of Mathematics and Physics, Jadranska 19, 1000 Ljubljana, Slovenia.
authors.forename: Dušan
authors.initials: D
authors.lastname: Babič
authors.affiliation: International Research Center for Soft Matter, Beijing University of Chemical Technology , Beijing 100029, P.R. China.|Department of Chemistry, University of Cambridge , Cambridge CB2 1TN, United Kingdom.
authors.forename: Jure
authors.initials: J
authors.lastname: Dobnikar