Ferrocell and Magnetic Patterns - Illustrations of Concepts, Experiments and Demonstrations (original) (raw)

Magneto-optical properties of a ferronematic colloid

IEEE Transactions on Magnetics, 2014

Fabrication of a thermotropic ferronematic colloid is reported, consisting of a 1% concentration of magnetite nanorods dispersed in a commercially obtained liquid crystal (LC). To produce the nanorods, solvothermal synthesis was utilized by adding Fe(CO) 5 to a reaction solution of hexadecylamine and oleic acid in n-octanol. The procedure allows for tailoring of the size and shape of the nanorods. The magnetic nanorods were functionalized with oleic acid. Magneto-optic (MO) and electro-optic (EO) properties of the colloid were characterized. Specifically, static measurements were performed to determine the birefringence and magnetic and electric Freedericksz thresholds. From the dynamic measurements, the switching time was determined. The nanorods increased the effective magnetic anisotropy of the LC. Depending on nanorod dimensions, the colloid demonstrated faster switching speeds especially in the presence of crossed electric and magnetic fields (MEO).

Magneto-optical effect in ferronematic cell with combined boundary conditions

Eighth International Conference on Nonlinear Optics of Liquid and Photorefractive Crystals, 2001

Magnetic Fredericksz-like transition is theoretically investigated in a homeotropic ferronematic planeparallel cell with different director anchoring (strong and weak) on the cell walls. The optical birefringence of a ferronematic sample and its dependence on the value of applied magnetic field and anchoring energy is studied.

Extinction of light by a Ferrocell and ferrofluid layers: A comparison

Optik

Recently a magneto-optical device called Ferrocell has become commercially available. As per manufacturer data, it mainly consists of a ferrofluid layer sandwiched between two glass plates, somewhat similar to a Hele-Shaw cell. Optical transmission changes with applied magnetic fields are not studied in detail for this device. We investigated transmission changes for one such commercial device and compared it with ferrofluid filled in a thin glass cuvette cell. Results show that the ferrofluid contained in the Ferrocell consists of a mixture of small and large particles.

Horocycles of Light in a Ferrocell

Condensed Matter, 2021

We studied the effects of image formation in a device known as Ferrocell, which consists of a thin film of a ferrofluid solution between two glass plates subjected to an external magnetic field in the presence of a light source. Following suggestions found in the literature, we compared the Ferrocell light scattering for some magnetic field configurations with the conical scattering of light by thin structures found in foams known as Plateau borders, and we discuss this type of scattering with the concept of diffracted rays from the Geometrical Theory of Diffraction. For certain magnetic field configurations, a Ferrocell with a point light source creates images of circles, parabolas, and hyperboles. We interpret the Ferrocell images as analogous to a Möbius transformation by inversion of the magnetic field. The formation of circles through this transformation is known as horocycles, which can be observed directly in the Ferrocell plane.

Optical and magneto-optical properties of Fe nanoparticles

Physical Review B, 2002

The optical and magneto-optical properties of Fe nanoparticles with sizes ranging from 2 to 8 nm, embedded in amorphous Al 2 O 3 , are studied as a function of their size and shape. The optical properties were measured using spectroscopic ellipsometry, whereas the magneto-optical properties were determined in two different Kerr configurations: polar and transverse. A generalization of different effective medium approximations is used to describe and analyze experimental data in nanocomposite media. In this generalization, the shapes of the nanoparticles are considered as an input parameter. The optical and magneto-optical parameters show clearly different values as a function of the nanoparticle size. A reasonable agreement between the theoretical calculations and experimental data is found when the average size of the nanoparticles is larger than 4 nm. On the other hand, the experimental and theoretical curves differ for smaller sizes, implying that below 4 nm the optical and magneto-optical constants of the particles deviate from the bulk behavior.

Observing Dynamical Systems Using Magneto-Controlled Diffraction

Condensed Matter

Observing the light passing through a thin layer of ferrofluid, we can see the occurrence of interesting effects, both in the formation patterns within the ferrofluid layer and in the dispersion of light outside that layer. This leads us to ask what the explanations associated with these effects are. In this paper, we analyze and explain the occurrence of these luminous patterns using a Ferrolens, commercially known as a Ferrocell. We present details of our experimental apparatus, followed by a discussion of some properties of light polarization and its relation to the formation of magnetic contours produced by a Ferrolens. In addition, we present the observation of a magnetochiral effect in this system. Next, we propose an application of this experiment in dynamical systems. The dynamical system is the direct observation of diffracted lines in Ferrolens, a special case of a Hele-Shaw cell containing a transparent ferrofluid subjected to various light sources.

The effect of suspended Fe3O4 nanoparticle size on magneto-optical properties of ferrofluids

Optics Communications, 2015

We investigate the effect of hydrodynamic particle size on the magnetic field induced light transmission and transmitted speckle pattern in water based ferrofluids containing functionalized Fe 3 O 4 nanoparticles of size ranging from 15 to 46 nm. Three water-based magnetic nanofluids, containing Fe 3 O 4 nanoparticles functionalized with poly-acrylic acid (PAA), tetra-methyl ammonium hydroxide (TMAOH) and phosphate, are used in the present study. In all three cases, the transmitted light intensity starts decreasing above a certain magnetic field (called first critical field) and becomes a minimum at another field (second critical field). These two critical fields signify the onset of linear aggregation process and zippering transitions between fully grown chains, respectively. Both these critical fields shift towards a lower magnetic field with increasing hydrodynamic diameter, due to stronger magnetic dipolar interactions. The first and the second critical fields showed a power law dependence on the hydrodynamic diameters. The dipolar resonances occurring at certain values of the scatterer size, leads to the field induced extinction of light. Both the onset of chaining and zippering transitions were clearly evident in the time dependent transmitted light intensity. Above the first critical field, the lobe part of the transmitted intensity and the lobe speckle contrast values increase with increasing external magnetic field due to reduced Brownian motion of the field induced aggregates. The speckle contrast was highest for nanoparticle with the largest hydrodynamic diameter, due to reduced Brownian motion. These results provide better insight into field dependent light control in magnetic colloids, which may find interesting applications in magneto-optical devices.

Controlling light diffraction with nanostructures

TechConnect Briefs, 2019

We are presenting the main results of our research using smart fluids to control the light scattering using some devices based on nanotechnology. We are presenting the Ferrolens or Ferrocell®, which consists of a Hele-Shaw cell with ferrofluid, and the "Polarifluid", which is a Ferrolens placed between two crossed polarizers illuminated with white light, subjected to a magnetic field. We have obtained the equations which represents these systems and solved them analytically and numerically, in order to compare with the patterns obtained using the experiments. We also explore the experiment with the patterns obtained from the atmospheric optics such as the parhelic circle and sundogs, obtaining experimentally the jumping laserdogs and the parlaseric circle.