title: Magnetic-field-induced nematic-columnar phase transition in aqueous suspensions of goethite (alpha-FeOOH) nanorods.
abstract: Colloidal aqueous suspensions of goethite lath-shaped nanorods form nematic and isotropic phases. We show that they also display a 2D rectangular (c2mm) columnar phase at volume fractions phi larger than 15%. Interestingly, the nematic-columnar first-order transition can also be triggered by applying to the nematic phase a magnetic field of intensity decreasing with phi (1 T at 8.5%; 0.5 T at 12%). Single domains of the columnar phase were thus produced and their structure investigated by synchrotron x-ray scattering. This magnetic-field-induced transition is fully reversible and reproducible.
authors.affiliation: Laboratoire de Physique des Solides, UMR CNRS 8502, Bâtiment 510, Université Paris-Sud, 91405 Orsay, France.
authors.forename: B J
authors.initials: BJ
authors.lastname: Lemaire
authors.forename: P
authors.initials: P
authors.lastname: Davidson
authors.forename: P
authors.initials: P
authors.lastname: Panine
authors.forename: J P
authors.initials: JP
authors.lastname: Jolivet