A statistical model has been developed describing the magnetostatic properties of dense ferrocolloids and dielectric polar fluids. The is based on relation between magnetization pair correlation function a spatially homogeneous system dipole particles. This approach allows us to calculate ferrofluid (polarization density fluid) in form expansion over both particle concentration potential interparticle dipole-dipole interaction U(d). obtained expressions for ferrocolloid initial magnetic...

Experimental magnetization curves for a polydisperse ferrofluid at various concentrations are examined using analytical theories and computer simulations with the aim of establishing robust method obtaining magnetic-core diameter distribution function $p(x)$. Theoretical expressions fitted to experimental data yield parameters It is shown that majority available results depend strongly on concentration, even though magnetic composition should be fixed. The sole exception second-order...

The theory of particle association in flexible chains dilute ferrofluids is generalized to the case an arbitrarily strengthened magnetic field. chain distribution dynamic equilibrium obtained on basis free energy minimization method under neglect interchain interaction. partition function calculated analytically with help rotation matrix technique condition when interparticle dipole-dipole interaction between nearest neighboring ferroparticles each taken into account. At weak fields, and...

We investigate, via numerical simulations, mean field, and density functional theories, the magnetic response of a dipolar hard sphere fluid at low temperatures densities, in region strong association. The proposed parameter-free theory is able to capture both temperature dependence ring-chain equilibrium contribution susceptibility chain generic length. predicts nonmonotonic initial (zero field) susceptibility, arising from competition between magnetically inert particle rings active...

We investigate, via a modified mean field approach, the dynamic magnetic response of polydisperse dipolar suspension to weak, linearly polarised, AC field. introduce an additional term into Fokker-Planck equation, which takes account dipole-dipole interaction in form first order perturbation, and allows for particle polydispersity. The analytical expressions, obtained real imaginary susceptibilities, predict three measurable effects: increase part low-frequency plateaux; enhanced growth...

The frequency-dependent magnetic susceptibility of a ferrofluid is calculated under the assumption that constituent particles undergo Brownian relaxation only. Brownian-dynamics simulations are carried out in order to test predictions recent theory [A. O. Ivanov, V. S. Zverev, and Kantorovich, Soft Matter 12, 3507 (2016)1744-683X10.1039/C5SM02679B] includes effects interparticle dipole-dipole interactions. based on so-called modified mean-field approach possesses following important...

The theory of particle association in chains dilute ferrofluids and dipole fluids is generalized to the case polydisperse systems. could be formed by ferroparticles different sizes, so various types chain aggregates are considered. probabilities structure appearance calculated, phase diagram, allowing find most probable with only continuous size distribution known, built. Our results demonstrate that spite a very weak dipole-dipole interaction between small fraction particles, their presence...

The dynamic magnetic response of a ferrofluid to weak ac field is studied using statistical mechanical theory and Brownian dynamics simulations, taking account dipole-dipole interactions between the constituent ferromagnetic colloidal particles, presence range particle sizes. effects polydispersity on frequency dispersion are shown be substantial: amplitude can about twice that noninteracting system; for peak power loss reduced by one half; even change qualitative appearance susceptibility spectrum.

A theory for the magnetic properties of interacting immobilized superparamagnetic nanoparticles with various distributions is tested against simulations.

A dynamic mass transfer equation for describing magnetophoresis, sedimentation, and gradient diffusion of colloidal particles in concentrated magnetic fluids has been derived. This takes into account steric, magnetodipole, hydrodynamic interparticle interactions. Steric interactions have investigated using the Carnahan-Starling approximation a hard-sphere system. In order to study effective attraction, free energy dipolar system is represented as virial expansion with accuracy terms...

With the help of a unique combination density functional theory and computer simulations, we discover two possible scenarios, depending on concentration, for hierarchical self-assembly magnetic nanoparticles cooling. We show that typically considered low temperature clusters, i.e. defect-free chains rings, merge into more complex branched structures through only three types defects: four-way X junctions, three-way Y junctions two-way Z junctions. Our accurate calculations reveal predominance...

We study the effects of temperature and concentration on dynamic spectra polydisperse magnetic nanoparticle suspensions.

The dynamic susceptibility of concentrated ferrofluids magnetite-kerosene type is studied experimentally to clarify the effect interparticle interactions on magnetization reversal dynamics and ferrofluid relaxation time spectrum. We synthesize six samples, four which have same wide particle size distribution with a high (more than 2kT) average energy magnetic dipole interactions. These samples differ in concentration viscosity. two remaining lower content large particles moderate For all we...

The magnetization properties of aggregated ferrofluids are calculated by combining the chain formation model developed Zubarev with modified mean-field theory. Using moderate assumptions for inter- and intrachain interactions we obtain expressions initial susceptibility. When comparing results our theory to molecular dynamics simulations same find that at large dipolar couplings $(\ensuremath{\lambda}>3)$ appears give better predictions than other analytical approaches. This supports idea...

The dynamic magnetic susceptibility, $\ensuremath{\chi}(\ensuremath{\omega})$, of a model ferrofluid at very low concentration (volume fraction, approximately $0.05%$), and with range dipolar coupling constants ($1\ensuremath{\le}\ensuremath{\lambda}\ensuremath{\le}8$), is examined using Brownian dynamics simulations. With increasing $\ensuremath{\lambda}$, the structural motifs in system change from unclustered particles, through chains, to rings. This gives rise nonmonotonic dependence...

In this paper we investigate a bidisperse model ferrofluid, where the aggregates are treated as flexible chains, under influence of an arbitrary valued external magnetic field. An extensive comparison theoretical predictions to results computer simulations is provided. Both magnetostatic properties and structural observables investigated with help newly developed approach molecular dynamic simulations. It shown that cluster analysis very sensitive definition. Here use two different criteria...

Anisotropic pair correlations in ferrofluids exposed to magnetic fields are studied using a combination of statistical-mechanical theory and computer simulations. A simple dipolar hard-sphere model the colloidal particles is detail. virial-expansion constructed for distribution function (PDF) which depends not only on length separation vector, but also its orientation with respect field. detailed comparison made between theoretical predictions accurate simulation data, it found that works...

In this contribution, we investigate the low-temperature, low-density behaviour of dipolar hard-sphere (DHS) particles, i.e., hard spheres with dipoles embedded in their centre. We aim at describing DHS fluid terms a network chains and rings (the fundamental clusters) held together by branching points (defects) different nature. first introduce systematic way classifying inter-cluster connections according to topology, then employ classification analyse geometric thermodynamic properties...

Complex fluid–fluid interfaces featuring mesoscale structures with adsorbed particles are key components of newly designed materials which continuously enriching the field soft matter. Simulation tools able to cope different scales characterizing these systems fundamental requirements for efficient theoretical investigations. In this paper we present a novel simulation method, based on approach Ahlrichs and Dünweg [Ahlrichs Dünweg, Int. J. Mod. Phys. C, 1998, 9, 1429], that couples...