Frustration-induced magic number clusters of colloidal magnetic particles

Abstract

We report the formation of stable two-dimensional clusters consisting of long-range-interacting colloidal particles with predefined magnetic moments. The symmetry and arrangement of the particles within the cluster are imposed by the magnetic frustration. By satisfying the criteria of stability, a series of magic number clusters is formed. The magic clusters are close packed and have compensating magnetic moments and chirality. Thus, the system can be regarded as a classical mesoscopic model for spin arrangements in two-dimensional triangular antiferromagnets, although the exact nature of the interactions between the macroscopic magnetic moments is different.

Colloidal ribbons and rings from Janus magnetic rods

“…Second, variations of the coating thickness allow precise control of the dipole strength. Third, variations of the shape anisotropy, as in our case, or incorporation of special magnetic films 41 , allow precise control of the dipole orientation.…”

“…To implement the goal of monodisperse size and homogeneous magnetic response, we take the approach of directionally depositing thin magnetic coatings onto monodisperse colloids [27][28][29]40,41 . To realize shape anisotropy, we first prepare silica rods that are 2.4 ± 0.1 mm long and 0.81 ± 0.04 mm wide (that is, an aspect ratio of 3), using a known method 42 .…”

Quasiantiferromagnetic120°Néel state in two-dimensional clusters of dipole-quadrupole-interacting particles on a hexagonal lattice

“…The coordinate system is chosen in such a way that the z direction is the symmetry axis of the cap, which is assumed to have rotational symmetry. Although the spheres are magnetic the moments are defined via charge, i.e., we define a magnetic surface charge 0-, (1) where n is the outward surface normal of the cap. Hence, we are not using vector spherical harmonics; all steps are equivalent to electric charge--except that .the total charge must be zero.…”

“…When comparing the strength of dipole and quadrupole, we refer to the energy of the dipole-dipole and the quadrupole-quadrupole interactions in the above mentioned n configuration. To combine the moments we use the continuous parameter SE [0,1] and construct the dipole and quadrupole moments as…”

Microstructure and magnetic properties of magnetic fluids consisting of shifted dipole particles under the influence of an external magnetic field

“…71 Recently, we proposed an alternative way for creating a system with "unusual" properties. [72][73][74] These works were inspired by a study of particles with magnetic caps 68 but also show a strong similarity to particles with embedded magnetic cubes. 71 In our model, the particles are spherical but the dipole moment is not located at their centres.…”