Experimental study on the fluctuations of dipolar chains.
Dynamic light scattering is used to study experimentally the dynamics of dipolar chains consisting of ferrofluid particles subjected to a magnetic field (H0). The effective diffusion coefficient shows a pronounced dependence on the scattering wave vector q, reflecting two modes of motion: translational diffusion of the whole chain, and fluctuations of particles within a chain. The characteristic probed frequency of particle displacements is inversely proportional to H0, and exhibits a q(3) dependency. Based on the striking analogy to polymer chain dynamics, we attribute these behaviors to the contribution of hydrodynamic interactions (HI's) that couples particles motion within a chain. This work suggests that chain fluctuations cannot be ignored even for the very strong magnetic field applied (coupling constant<10(6)). HI's can still be important, even at an extremely low particle volume fraction of 10(-5).
Cutillas
S
S
Department of Physics and Astronomy, California State University, Long Beach, California 90840, USA.
Liu
J
J