Dynamics of Single Chains of Suspended Ferrofluid

Super paramagnetic particles is a new class of magnetic materials that exhibit a susceptibility g near the value of one while most of natural paramagnetic materials have a magnetic susceptibility at least five orders of magnitude lower. Ferrofluid emulsion is one of such systems. A collection of iron oxide nanopanicles (in our case Fe304 with a radius of 6nm) dispersed When the volume fraction is high, bigger aggregates are formed by the lateral coalescence of several chains [3,4,5]. While many studies and applications deal with the rheological properties [6] or the fieldinduced structural changes [3-7], this work is to better understand the chain dynamics. We will show, in the first section, that the kinetics of chain formation is a diffusion-limited aggregation. The second and the in kerosene is called a ferrofluid which has various main part of this work will talk about measurements of properties [1]. The most important is that each nanoparticle has a permanent dipole moment. Due to the small size of the nanoparticles, they only have a single domain magnetization. The thermal agitation randomizes the iron oxide particles so that the total magnetization of the ferrofluid is equal to zero when no magnetic field is applied. Once an external magnetic field is applied, the nanopanicles are oriented slightly in the field direction and the ferrofluid can have a strong magnetization. Particles, having a submicronic size, (in our case 0.23_m as radius) can be made of this ferrofluid. If these ferrofluid droplets are dispersed in water, some surfactant is added to prevent aggregation, the system thus produced is called a ferrofluid emulsion. When ferrofluid particles are suspended in water, they diffuse under Brownian forces. Applying a magnetic field to such a suspension leads to dipole-dipole interactions between particles. The amplitude of this interaction is described by a dimensionless parameter 3., which is the ratio of the magnetic dipolar energy over the thermal energy [2]: