Structure of ferrofluid nanofilms in homogeneous magnetic fields

Abstract

We report molecular dynamics simulations results for model ferrofluid films subject to an external, homogeneous magnetic field directed parallel or perpendicular to the film surfaces. The interactions between the magnetic nanoparticles are modeled via the Stockmayer potential. In a previous study [J. Jordanovic and S. H. L. Klapp, Phys. Rev. Lett. 101, 038302 (2008)] we have shown that an external field can control the number and internal structure of the layers characterizing the fluid films, in qualitative agreement with experiments. Here we explore the dependence of the layering effects on thermodynamic conditions, and we analyze the results from an energetic (microscopic and macroscopic) perspective. As a special case we investigate a monolayer to bilayer transition induced via a perpendicular field.

The magneto-optical behaviors modulated by unaggregated system for γ-Fe2O3–ZnFe2O4 binary ferrofluids

“…Such a field-induced demixing phase transition could form layers of A particles, similar to the ferrofluid films formed in a homogeneous magnetic field. 37 This proposal is in agreement with experimental studies of the evaporation of ferrofluids in a magnetic field. 38 The demixing phase transition will result in a local increase in the volume fraction of the γ -Fe 2 O 3 particle system, resembling a change in the total density of the binary molecular fluid mixture.…”

Field-induced layering of confined ferromagnetic nanoparticles: the role of attractive interactions

“…Moreover, extending the systems somewhat into the third dimension the lateral structures are supplemented by structure formation in vertical direction such as layering. This has been shown in recent experiments of ferrofluids [10] and related computer simulation studies [11,12].…”

“…Indeed, as we have recently demonstrated via Molecular Dynamics (MD) simulations for confined SM particles [11,12], external (homogeneous) magnetic fields directed parallel or perpendicular to the confining surfaces can "trigger" the formation or destruction of layers present in zero field. The surface separations where this becomes possible can be inferred from the location of maxima and minima of the normal pressure as function of the wall separation [11].…”

Microstructure of bidisperse ferrofluids in a thin layer

“…2, can be thought as the sum of the area of the rectangle with sides (n -1)σ l + mσ s and 2σ l and the area of a circle with radius σ l : (8) One should note that for calculating the excluded area in those mixed chains, the relative positions of large and small particles does not matter.…”

“…In the case of quasi two dimensional systems, despite some works have already shed some light on the microstructure of such systems, [7][8][9] and [14][15][16], those systems are still poorly understood. Previ ous works have disclosed that the microstructure of magnetic fluids in thin layers differs considerably from the three dimensional case.…”