Ferrofluid nucleus phase transitions in an external uniform magnetic field

Abstract

The phase transition between a massive dense phase and a diluted superparamagnetic phase has been studied by means of a direct molecular dynamics simulation. The equilibrium structures of the ferrofluid aggregate nucleus are obtained for different values of a temperature and an external magnetic field magnitude. An approximate match of experiment and simulation has been shown for the ferrofluid phase diagram coordinates "field-temperature". The provided phase coexistence curve has an opposite trend comparing to some of known theoretical results. This contradiction has been discussed. For given experimental parameters, it has been concluded that the present results describe more precisely the transition from linear chains to a dense globes phase. The theoretical concepts which provide the opposite binodal curve dependency trend match other experimental conditions: a diluted ferrofluid, a high particle coating rate, a high temperature, and/or a less particles coupling constant value.

Magneto-optical extinction trend inversion in ferrofluids

“…In scope of the continuum solvation approximation of not very dense solutions, the Brownian translational and rotational nanoparticle motion is described by the Langevin equations with the hydrodynamic-originated Langevin parameters [27,33]:…”

“…where damping coefficients of translational and rotational motion are given by = 3 and = 6 , where is a carrier liquid dynamic viscosity and is a total hydrodynamic nanoparticle volume. Equations (1) and (2) has been integrated in the scope of the viscous limit approximation [7,27,34].…”

“…However, the literature review indicates that so far no simulation-based investigation have been performed on the role of FF aggregates internal structural changes in the magneto-optical extinction experimental phenomena. We used a molecular dynamics simulation (nanoparticle Brownian motion level) method in this study [25][26][27][28]. The present work is focused on the computational and experimental research.…”

Features of Formation and Transformation of Fe$_{3}$O$_{4}$-Nanoparticle Clusters in a Magnetic Fluid under the Long-Term Magnetic-Field Pulse Action

“…Розрізняють два основні типи МР: високостабілізований колоїд-ний розчин монодоменних частинок з поодинокими «первинними» кластерами -класичну МР [15,16] і МР з «великими» кластерами магнетних наночастинок, які можна побачити навіть в оптичний мікроскоп і які можуть існувати без зовнішнього впливу на таку МР -структуровану МР [17].…”

“…Для пояснення одержаних результатів будемо користуватися мо-дернізованим (із врахуванням одержаних в цій роботі результатів) моделем [16,23] рвинні кластери [16,17,33]. За відсутности зовнішнього магнетно-го поля, такі кластери являють собою окремі структури із замкне-ним магнетним потоком (рис.…”