Structure, Dynamics, and Thermodynamics of Ferrofluids

Camp, Philip J.

doi:10.1007/978-3-319-61109-9_9

Cited by 2 publications

(2 citation statements)

References 106 publications

(128 reference statements)

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“…where ρ is the magnetic particle number concentration and α = mH/k B T is the Langevin parameter (the relation of the Zeeman interaction energy of the particle magnetic moment m with the external magnetic field H to the thermal energy k B T = β −1 ). Since then ferrofluids have been the subject of intense scrutiny, with regard to their structure, phase behavior, and dynamics [6][7][8][9][10][11][12]. It became clear that a theory based on a single-particle approximation, like expressions (1), is only valid for an infinitely diluted suspension, when the interparticle magnetic interactions can be neglected.…”

Section: Introductionmentioning

confidence: 99%

Interparticle Correlations in the Simple Cubic Lattice of Ferroparticles: Theory and Computer Simulations

Solovyova,

Kuznetsov,

Elfimova

2020

Preprint

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Anisotropic interparticle correlations in the simple cubic lattice of single-domain ferroparticles (SCLF) are studied using both theory and computer simulation. The theory is based on the Helmholtz free energy expansion like classical virial series up to the second virial coefficient. The analytical formula for the Helmholtz free energy is incorporated in a logarithmic form to minimize the effects of series truncation. The new theoretical approach, including discrete summation over lattice nodes coordinates, is compared critically against the classical virial expansion of the Helmholtz free energy for the dipolar hard sphere fluid; the main differences between the Helmholtz free energy of SCLF and dipolar hard sphere fluid are discussed. The theoretical results for the Helmholtz free energy, the magnetization, and the initial magnetic susceptibility of the SCLF are compared against Molecular Dynamic simulation data. In all cases, theoretical predictions using logarithmic form of the Helmholtz free energy are seen to be superior, but they only have an applicability range of the effective dipolar coupling constant λe < 1.5. For highest values of λe, the structural transition of the magnetic dipoles in SCLF is observed in Molecular Dynamic simulation. It has been shown that for λe 2, an antiferromagnetic order appears in the system.

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Section: Introductionmentioning

confidence: 99%

Interparticle Correlations in the Simple Cubic Lattice of Ferroparticles: Theory and Computer Simulations

Solovyova,

Kuznetsov,

Elfimova

2020

Preprint

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“…Consequently, the dipolar interactions between magnetic moments play a critical role in magnetic fluids, unlike in other colloidal suspensions, where their typical magnitude is given in terms of the interparticle distance L . In theoretical simulations, the magnetic fluid has been modeled as a dipolar hard-sphere fluid considering dipolar interactions, a dipolar soft sphere fluid additionally considering electrostatic repulsion forces, or by van der Waals interactions as in the case of the Stockmayer fluid . The instabilities attributed to the above forces have been discussed as phase separation owing to condensation into a liquidlike dense phase, − sedimentation of solidlike clusters, − or gelation caused by three-dimensional chain networking, − analogous to those of molecular gases, liquids, crystals, or gels.…”

mentioning

confidence: 99%

Macroscopic and Microscopic Structural Analyses of Needle-Shaped Condensed Phases in Magnetic Fluids under External Magnetic Fields

et al. 2020

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Hierarchal structures in magnetic fluids have been studied to ensure the optimal utilization of these fluids, which exhibit both magnetism and fluidity, in various engineering devices and biomedical applications. In this study, magnetic fluids were prepared by dispersing monodispersed magnetite particles with sizes of 10.0, 11.7, and 17.4 nm in kerosene. Dark-field optical microscopy and small-angle X-ray scattering (SAXS) experiments showed no results indicating destabilization of colloidal dispersion in the absence of magnetic fields. Under magnetic fields, the formation of a needle-shaped micrometer-scale condensed phase was observed on the macroscopic level, irrespective of the differences in the average diameter of the particles. Analyses of SAXS profiles under magnetic fields revealed that loosely bundled chains of nanoparticles were formed in the magnetic fluid containing particles with a size of 17.4 nm, whereas other magnetic fluids lacked local spatial ordering of nanoparticles. Thus, the results indicate that the microscopic arrangements of nanoparticles inside a macroscopic structure vary with size, despite the similarity exhibited in their outward form. The results are discussed based on magnetostatic energy and interparticle dipolar interactions. These different hierarchal structuring conditions are key to fully exploiting the properties for each application; for instance, an excellent design for magnetic fluid hyperthermia treatments involves both the individual delivery of well-dispersed nanoparticles as thermal seeds and cooperative magnetic heat generation of chained nanoparticles under exposure to magnetic fields.

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Structure, Dynamics, and Thermodynamics of Ferrofluids

Cited by 2 publications

References 106 publications

Interparticle Correlations in the Simple Cubic Lattice of Ferroparticles: Theory and Computer Simulations

Interparticle Correlations in the Simple Cubic Lattice of Ferroparticles: Theory and Computer Simulations

Macroscopic and Microscopic Structural Analyses of Needle-Shaped Condensed Phases in Magnetic Fluids under External Magnetic Fields

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