Effects of Magnetic Interactions between Ferromagnetic Spherocylinder Particles on Orientational Distributions of a Nondilute Colloidal Dispersion

Abstract

We have analyzed the time-dependent behaviors of the ferromagnetic spherocylinder particles which make a nondilute colloidal dispersion influenced by the external magnetic field. In order to understand the effects of the magnetic interactions between the particles, we have derived a basic equation for the orientational distributions of the particles in steady two dimensional flow by applying the mean-field theory and the perturbation expansion method. An exact solution of the basic equation is obtained theoretically. By using the solution, the mean-field, which is derived from the self-consistent condition, is analytically calculated. The magnetic interactions between the particles restrict the particle directions and make the particle incline to the direction of the chainlike cluster. The strength of the restriction is, by an approximate estimation, inversely proportional to the aspect ratio of the particle. Compared with a dilute system, in the nondilute system, the existence of the particle-particle interactions provides the increased stability of the particle orientation and the swift response to the external magnetic field.