Mechanical and magnetic properties of nanodispersed systems
The magnetic particles, responsible for the magnetisation process in the magnetic fluid, are in the superparamagnetic state, i.e., their magnetic moment carries out Brownian motion. In the quasistatic approximation the magnetisation vector of the magnetic fluid M and the vector of the strength of the magnetic field in the medium H are assumed to be parallel. The thermal fluctuations determine the stochastic rotation of the magnetic moment in relation to the direction of the field. The efficiency of the rotational influence of the fluid flow on the aggregates in comparison with the effect of the thermal Brownian motion and the magnetic field is relatively small. The magnetisation of the real magnetic fluids and ferrosuspensions may be characterised by the rearrangement of the structure in which the microscopic homogeneity of the system is disrupted. The energy of magnetic interaction decreases with increasing distance at a considerably lower rate than the energy of the van-der- Waals interaction.