Thermodynamic and magnetic properties of ferrofluids in external uniform magnetic field

The work is devoted to the theoretical investigation of the thermodynamic and magnetic properties of ferrofluids in applied magnetic field. Analytical expressions for the second and the third virial coefficients of dipolar hard spheres model were obtained by using the least-squares approximation to the simulation data (Elfimova et al., 2013 [4]). The expressions for the virial coefficients are presented as functions of the dipolar coupling constant λ and the Langevin parameter α . The analytical formulas for the virial coefficients were incorporated in to so-called logarithmic free energy theory (Elfimova et al., 2012 [8]). This theory yields the Helmholtz free energy and the magnetization. The comparison between theory and computer simulation shows good agreement for λ⩽2.The analytical expression of the Helmholtz free energy was also used to obtain a sedimentation equilibrium concentration profile of ferroparticles subjected to uniform magnetic and gravitational fields.