title: Simple rectangular columnar phase of goethite nanorods and its martensitic transition to the centered rectangular columnar phase.
abstract: Using high-resolution small-angle X-ray scattering, we observed a new type of the columnar phase with a simple rectangular (R(S)) structure in colloidal goethite dispersions. Furthermore, it displays a martensitic transition into the usual centered rectangular (R(C)) structure in an external magnetic field. The findings are rationalized in terms of entropic effects within a simple cell model. We interpret the results as an effect of the particle shape and the available degrees of freedom on the delicate balance between the space available for particle translations and rotations within the two structures.
authors.affiliation: Van 't Hoff Laboratory for Physical and Colloid Chemistry, Debye Institute for Nanomaterials Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands. e.vandenpol@uu.nl
authors.forename: Esther
authors.initials: E
authors.lastname: van den Pol
authors.forename: Andrei V
authors.initials: AV
authors.lastname: Petukhov
authors.forename: Dominique M E
authors.initials: DM
authors.lastname: Thies-Weesie
authors.forename: Gert J
authors.initials: GJ
authors.lastname: Vroege