Stability of solid phases in the dipolar hard sphere system

The influence of anisotropy on the microstructure and magnetic properties of dipolar nanoplatelet suspensions

In recent years, there has been an increasing interest in magnetic nanoparticles with non-spherical shapes. This is largely due to their broad span of tuneable properties, which allow for tailoring of the colloidal properties by altering the magnetic anisometry or shape anisotropy of the nanoparticle. Although extensive research has gone into novel synthesis methods, the theoretical and analytical treatment of magnetic colloidal suspensions still predominantly focuses on spherical particles. This paper explores the microstructure and initial static magnetic susceptibility of systems of anisometric dipolar magnetic nanoplatelets in order to understand the applicability of dipolar sphere-based theories and models for such systems. We find that the microstructure as characterized by the particle distribution and magnetic clustering of platelets diverges significantly from that of spheres both quantitatively and qualitatively. We find lower initial static magnetic susceptibilities in nanoplatelet systems than in comparable suspensions of dipolar spheres. At lower values of the magnetic coupling constant, this can be accounted for by applying corrections to the volume fraction. However, this approach is less accurate for systems with stronger magnetic interactions. By providing predictions of and explanations for the observed effects, we aim to facilitate the use of magnetic nanoplatelet suspensions in the broad range of applications.

Ground state of dipolar hard spheres confined in channels

We investigate the ground state of a classical two-dimensional system of hard-sphere dipoles confined between two hard walls. Using lattice sum minimization techniques we reveal that at fixed wall separations, a first-order transition from a vacuum to a straight one-dimensional chain of dipoles occurs upon increasing the density. Further increase in the density yields the stability of an undulated chain as well as nontrivial buckling structures. We explore the close-packed configurations of dipoles in detail, and we find that, in general, the densest packings of dipoles possess complex magnetizations along the principal axis of the slit. Our predictions serve as a guideline for experiments with granular dipolar and magnetic colloidal suspensions confined in slitlike channel geometry.

A simulation study of the electrostriction effects in dielectric elastomer composites containing polarizable inclusions with different spatial distributions

Controlled actuation of electroactive polymers with embedded high dielectric nanoparticles is theoretically analyzed.

Size effect and stability of polarized fluid phases

The existence of a ferroelectric fluid phase for systems of 1000-2000 dipolar hard or soft spheres is well established by numerical simulations. Theoretical approaches proposed to determine the stability of such a phase are either in qualitative agreement with the simulation results or disagree with them. Experimental results for systems of molecules or particles with large electric or magnetic dipole moments are also inconclusive. As a contribution to the question of existence and stability of a fluid ferroelectric phase this simulation work considers system sizes of the order of 10 000 particles, thus an order of magnitude larger than those used in previous studies. It shows that although ferroelectricity is not affected by an increase of system size, different spatial arrangements of the dipolar hard spheres in such a phase are possible whose free energies seem to differ only marginally.

Orientation of a dielectric rod near a planar electrode

We present experimental and theoretical results on suspensions of silica rods in DMSO–water, subjected to an applied electric field, in particular on the interaction exhibited between the rods and the electrode used for generating the electric field.