Magnetic-field-induced optical anisotropy in ferrofluids: A time-dependent light-scattering investigation

Abstract

We report an experimental investigation of time dependent anisotropic light scattering by an aqueous suspension of tetramethyl ammonium hydroxide coated Fe3O4 nanoparticles (approximately 6 nm) under the ON-OFF transient of an external dc magnetic field. The study employs the synchronized recording and measurement of the two magnetic-field-induced light-scattering patterns produced by two identical orthogonal He-Ne laser beams passing through the ferrofluid sample and propagating parallel and perpendicular to the applied field, respectively. From these patterns, we extract the time dependence of the induced optical anisotropy, which provides a measure of the characteristic time scale and kinematic response for field-induced structure formation in the sample. We propose that the time evolution of the scattering patterns, which is very fast at short times and significantly slower at long times, can be explained using a model based on a two-stage chain formation and coarsening processes.

Magneto-controlled illumination with opto-fluidics

“…To interpret the experimental results, the authors proposed to take into account the light retardation caused by standing waves in the nanoparticles. However, the effect of chain formation in the suspension, which depends on time and magnetic field, has shown to be important [14]. An elegant study on time dependent anisotropic scattering induced by magnetic field in chemically stabilized Fe 3 O 4 nanoparticles were analyzed in detail in Ref.…”

“…An elegant study on time dependent anisotropic scattering induced by magnetic field in chemically stabilized Fe 3 O 4 nanoparticles were analyzed in detail in Ref. [14]. Light scattering patterns were simultaneously recorded for light beams oriented along and across magnetic field.…”

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

“…6, в), довжина яких L в нашому випадку обмежена то-вщиною контейнера з МР. Подальше трансформування таких стру-ктур у зовнішньому полі приводить до латеральної аґреґації цих ланцюжків і утворення товстіших стовпчастих кластерів [16,31,36] (рис. 6, г), товщина D яких збільшується при подальшій дії маг-нетного поля (рис.…”

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

“…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]. The authors reported time dependent changes in the transmitted light intensity for both beam orientations but only polarization parallel to the magnetic field was considered.…”