title: Anisotropic magnetic particles in a magnetic field.
abstract: We characterize the structural properties of magnetic ellipsoidal hematite colloids with an aspect ratio ρ ≈ 2.3 using a combination of small-angle X-ray scattering and computer simulations. The evolution of the phase diagram with packing fraction ϕ and the strength of an applied magnetic field B is described, and the coupling between orientational order of magnetic ellipsoids and the bulk magnetic behavior of their suspension addressed. We establish quantitative structural criteria for the different phase and arrest transitions and map distinct isotropic, polarized non-nematic, and nematic phases over an extended range in the ϕ-B coordinates. We show that upon a rotational arrest of the ellipsoids around ϕ = 0.59, the bulk magnetic behavior of their suspension switches from superparamagnetic to ordered weakly ferromagnetic. If densely packed and arrested, these magnetic particles thus provide persisting remanent magnetization of the suspension. By exploring structural and magnetic properties together, we extend the often used colloid-atom analogy to the case of magnetic spins.
authors.affiliation: Division of Physical Chemistry, Department of Chemistry, Lund University, Lund, Sweden. jerome.crassous@fkem1.lu.se peter.schurtenberger@fkem1.lu.se and Adolphe Merkle Institute and Fribourg Center for Nanomaterials, University of Fribourg, Fribourg, Switzerland.
authors.forename: Ilya
authors.initials: I
authors.lastname: Martchenko
authors.affiliation: Division of Physical Chemistry, Department of Chemistry, Lund University, Lund, Sweden. jerome.crassous@fkem1.lu.se peter.schurtenberger@fkem1.lu.se.
authors.forename: Jérôme J
authors.initials: JJ
authors.lastname: Crassous
authors.affiliation: Division of Physical Chemistry, Department of Chemistry, Lund University, Lund, Sweden. jerome.crassous@fkem1.lu.se peter.schurtenberger@fkem1.lu.se.
authors.forename: Adriana M
authors.initials: AM
authors.lastname: Mihut
authors.affiliation: Division of Physical Chemistry, Department of Chemistry, Lund University, Lund, Sweden. jerome.crassous@fkem1.lu.se peter.schurtenberger@fkem1.lu.se.
authors.forename: Erik
authors.initials: E
authors.lastname: Bialik
authors.affiliation: Institut fur Geophysik, ETH Zurich, Zurich, Switzerland.
authors.forename: Ann M
authors.initials: AM
authors.lastname: Hirt
authors.affiliation: Adolphe Merkle Institute and Fribourg Center for Nanomaterials, University of Fribourg, Fribourg, Switzerland.
authors.forename: Chantal
authors.initials: C
authors.lastname: Rufier
authors.affiliation: Swiss Light Source, Paul Scherrer Institute, Villigen, Switzerland.
authors.forename: Andreas
authors.initials: A
authors.lastname: Menzel
authors.affiliation: Adolphe Merkle Institute and Fribourg Center for Nanomaterials, University of Fribourg, Fribourg, Switzerland.
authors.forename: Hervé
authors.initials: H
authors.lastname: Dietsch
authors.affiliation: Division of Physical Chemistry, Department of Chemistry, Lund University, Lund, Sweden. jerome.crassous@fkem1.lu.se peter.schurtenberger@fkem1.lu.se.
authors.forename: Per
authors.initials: P
authors.lastname: Linse
authors.affiliation: Division of Physical Chemistry, Department of Chemistry, Lund University, Lund, Sweden. jerome.crassous@fkem1.lu.se peter.schurtenberger@fkem1.lu.se.
authors.forename: Peter
authors.identifier: http://orcid.org/0000-0002-2790-8831
authors.initials: P
authors.lastname: Schurtenberger