title: Direction dependent diffusion of aligned magnetic rods by means of x-ray photon correlation spectroscopy.
abstract: Rodlike hematite particles in suspension align perpendicular to an external magnetic field due to a negative anisotropy of their magnetic susceptibility Δχ. The diffusion tensor consists of two principal constants D(∥) and D(⊥) for the diffusion parallel and perpendicular to the long particle axis. X-ray photon correlation spectroscopy is capable of probing the diffusive motion in optically opaque suspensions of rodlike hematite particles parallel to the direction of the scattering vector Q. Choosing Q parallel or perpendicular to the direction of an external magnetic field H the direction dependent intermediate scattering function is measured by means of x-ray photon correlation spectroscopy. From the intermediate scattering function in both directions the principal diffusion constants D(∥) and D(⊥) are determined. The ratio D(∥)/D(⊥) increases with increasing aspect ratio of the particles and can be described via a rescaled theoretical approach for prolate ellipsoids of revolution.
authors.affiliation: Institut für Chemie, Universität Rostock, Albert-Einstein-Straße 3a, 18059 Rostock, Germany.
authors.forename: Joachim
authors.initials: J
authors.lastname: Wagner
authors.affiliation: Physikalische Chemie, Universität des Saarlandes, Campus B22, 66123 Saarbrücken, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Märkert
authors.affiliation: Deutsches Elektronensynchrotron, Notkestraße 85, 22607 Hamburg, Germany.
authors.forename: Birgit
authors.initials: B
authors.lastname: Fischer
authors.affiliation: Deutsches Elektronensynchrotron, Notkestraße 85, 22607 Hamburg, Germany.
authors.forename: Leonard
authors.initials: L
authors.lastname: Müller
mesh_terms: D005290:Ferric Compounds / Q000737:chemistry*; D008280:Magnetics; D008956:Models, Chemical; D056951:Photoelectron Spectroscopy / Q000379:methods*
chemical_list: D005290:Ferric Compounds; C000499:ferric oxide