title: Self-assembly of smallest magnetic particles.
abstract: The assembly of tiny magnetic particles in external magnetic fields is important for many applications ranging from data storage to medical technologies. The development of ever smaller magnetic structures is restricted by a size limit, where the particles are just barely magnetic. For such particles we report the discovery of a kind of solution assembly hitherto unobserved, to our knowledge. The fact that the assembly occurs in solution is very relevant for applications, where magnetic nanoparticles are either solution-processed or are used in liquid biological environments. Induced by an external magnetic field, nanocubes spontaneously assemble into 1D chains, 2D monolayer sheets, and large 3D cuboids with almost perfect internal ordering. The self-assembly of the nanocubes can be elucidated considering the dipole-dipole interaction of small superparamagnetic particles. Complex 3D geometrical arrangements of the nanodipoles are obtained under the assumption that the orientation of magnetization is freely adjustable within the superlattice and tends to minimize the binding energy. On that basis the magnetic moment of the cuboids can be explained.
authors.affiliation: Physical Chemistry I, University of Bayreuth, 95440 Bayreuth, Germany;
authors.forename: Sara
authors.initials: S
authors.lastname: Mehdizadeh Taheri
authors.affiliation: Physical Chemistry I, University of Bayreuth, 95440 Bayreuth, Germany;
authors.forename: Maria
authors.initials: M
authors.lastname: Michaelis
authors.affiliation: Experimental Physics V, University of Bayreuth, 95440 Bayreuth, Germany;
authors.forename: Thomas
authors.initials: T
authors.lastname: Friedrich
authors.affiliation: Macromolecular Chemistry I, University of Bayreuth, 95440 Bayreuth, Germany;
authors.forename: Beate
authors.initials: B
authors.lastname: Förster
authors.affiliation: Physical Chemistry I, University of Bayreuth, 95440 Bayreuth, Germany;
authors.forename: Markus
authors.initials: M
authors.lastname: Drechsler
authors.affiliation: Fakultät für Physik, University Duisburg-Essen, 47057 Duisburg, Germany;
authors.forename: Florian M
authors.initials: FM
authors.lastname: Römer
authors.affiliation: European Synchrotron Radiation Facility, 38043 Grenoble, France;
authors.forename: Peter
authors.initials: P
authors.lastname: Bösecke
authors.affiliation: European Synchrotron Radiation Facility, 38043 Grenoble, France;
authors.forename: Theyencheri
authors.initials: T
authors.lastname: Narayanan
authors.affiliation: Inorganic Chemistry II, University of Bayreuth, 95440 Bayreuth, Germany.
authors.forename: Birgit
authors.initials: B
authors.lastname: Weber
authors.affiliation: Experimental Physics V, University of Bayreuth, 95440 Bayreuth, Germany; ingo.rehberg@uni-bayreuth.de stephan.foerster@uni-bayreuth.de.
authors.forename: Ingo
authors.initials: I
authors.lastname: Rehberg
authors.affiliation: Physical Chemistry I, University of Bayreuth, 95440 Bayreuth, Germany;
authors.forename: Sabine
authors.initials: S
authors.lastname: Rosenfeldt
authors.affiliation: Physical Chemistry I, University of Bayreuth, 95440 Bayreuth, Germany; ingo.rehberg@uni-bayreuth.de stephan.foerster@uni-bayreuth.de.
authors.forename: Stephan
authors.initials: S
authors.lastname: Förster
keywords: magnetic; nanoparticles; self-assembly