Study of Thermodiffusion in Magnetic Colloids by Forced Rayleigh Scattering (CAT#: STEM-ST-0067-YJL)

Introduction

Magnetic colloids, also called ferrofluids, are divided in two classes, ionic or surfacted, according to the nature of the interparticle repulsion: electrostatic if the particles are coated with ionic ligands, steric if the particles are coated with surfactants. Ferrofluids exhibit very interesting properties under an applied magnetic field and have many technical uses. If a magnetic colloid sample is placed in the interference region of two coherent intersecting laser beams (called here pump beams) having the same polarization directions, the nanoparticle concentration and, therefore, the index of refraction become spatially modulated with the same periodicity as that of the interference pattern.