On the Theory of the Dynamic Properties of Dense Magnetic Fluids: Polydisperse Media

The theoretical model was proposed for determining functions of the dynamic response of moderately concentrated ferrofluids on the external magnetic field and their rheological properties. Ferrofluids are considered to be polydisperse colloidal systems with the interacting (albeit individual) particles. The model is based on the regular approximation of virial expansion in powers of the particle concentration and on the well-known effective field method. The effect of system polydispersity and the magnetodipole and hydrodynamic interactions between particles on the macroscopic and dynamic properties of ferrofluids was estimated. Calculations demonstrated that the interparticle interaction results in an increase in the dynamic functions of uniform ferrocolloids up to several tens of percents.