8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

Wed 711:10-14:00P5.51Influence of interparticle correlations on thethermodynamic properties of concentrated ferrocolloidsEkaterina Elfimova 1 and Alexey Ivanov 11 Urals State University, Lenin av. 51, 620000, Ekaterinburg, Russian FederationFerrocolloids are stable colloidal suspensions of ferro- and ferrimagnetic nanoparticles innonmagnetic liquid carriers. The small size of colloidal ferroparticles (typically of the order of10-20 nm) provides the particle with a permanent magnetic moment. The main feature of theferrocolloids is the interparticle dipole-dipole interaction which depends both on the distancebetween ferroparticle centers and the mutual orientations of their magnetic moments. In presentwork thermodynamic properties of dense ferrocolloids are studied theoretically paying the majorattention to a part of multi-particle correlations, which play a dominant part in concentratedsystems. The ferrocolloid is modeled as a system of homogeneously magnetized monodispersehard spheres (dipolar hard spheres). The Helmholtz free energy is obtained on the basis ofvirial expansion over the ferropartice concentration. To calculate the dipolar hard spheresvirial coefficients we suggest their expansion in power series over the intensity of dipole-dipoleinteraction; this method is described in details in [1]. Applied uniform magnetic field changesconsiderably the structure of free energy virial coefficients because of the presence of additionalinteraction of the particle magnetic moments with an external field. The obtained Helmholtz freeenergy is conveniently expressed as explicit function of the ferroparticle volume concentration,the dipolar coupling constant and the dimensionless magnetic field (Langevin parameter). Onthis basis the osmotic pressure, the chemical potential, the specific heat capacity and the gradientdiffusion coefficient are calculated and examined via the experimental data and the computersimulations. The work was supported by the Grant No. MK-1673. 2010. 2 of the President ofRussian Federation.[1] E. A. Elfimova, A. O. Ivanov, J. Exp. Theor. Phys. 111, N. 1 (2010) 146.51