Diffraction effects in ferrofluids

Abstract

Diffraction effects have been observed in ferrofluids in the presence of a magnetic field. The diffraction pattern from a laser beam normal to a thin layer of ferrofluid and normal to a magnetic field is confined to a plane also normal to the layer and normal to the field, indicating alignment of ferrofluid particles.

Magneto-controlled illumination with opto-fluidics

“…1A), was observed in magnetic fluids [5,[13][14][15]. When a laser beam passes through a magnetic fluid placed in a magnetic field it undergoes diffraction producing a characteristic pattern, such as that shown in Fig.…”

“…Since their discovery, numerous interesting optical phenomena have been observed [4][5][6] and there has been a growing interest in applications of optical effects in magnetic fluids over the last decade. The promising applications include magnetic dichroism, magnetically induced birefringence, Faraday rotation and ellipticity, as well as field-affected light scattering [4,[7][8][9][10][11].…”

Time dependent magnetically induced variations in optical transmission of magnetite nanoparticle aqueous suspension

“…As light travels through the magnetite colloid it suffers multiple scattering and diffraction on the chains. This multiple diffraction leads to an emerging of a diffraction pattern observed on a screen placed orthogonal to the light beam [15,21]. For the transverse geometry the pattern appears as a condensation of speckles within bright narrow line oriented orthogonal to the magnetic field.…”

“…Suspended magnetic nanoparticles subjected to the external magnetic field form linear structures resembling thin columns, chains and filaments oriented along the field [12][13][14]. Another evidence of chains formation in magnetized ferrofluid follows from emerging of a diffraction pattern, which can be visualized on an opaque or translucent screen placed at a certain distance from a sample [15]. Rablau et al presented gracious experiment where diffraction patterns were simultaneously recorded for the light beams oriented parallel and orthogonal to the applied magnetic field using CCD cameras [16].…”

Retarded response of the optical transmittance through a magnetic fluid film under switching-on/off external magnetic fields

“…When a magnetic fluid thin film is subjected to an external-pulsed magnetic field, the particles in the film rotate to align their magnetic moment to the field direction but are prevented from agglomerating through external control of the duration of the pulsed field within hundreds of microseconds. Because of the anisotropy in the magnetic particle shape [1,2] or the interaction between particles [3,4], the magnetic fluids become optically anisotropic [5][6][7][8], and dichroism or birefringence may occur as a linearly polarized light passed normally through the thin film. By aligning the transmission axes of the linear polarizer and the analyzer so that they are perpendicular to each other, the intensity of the transmitted light increases during the application of the pulsed field.…”