The effect of polydispersity on the magnetostatic properties of concentrated ferrofluids

Abstract A statistical model of highly concentrated polydisperse ferrocolloids is proposed. The study approach is based on the second-order modified mean-field theory (MMF2) [A.O. Ivanov, O.B. Kuznetsova, Magnetic properties of dense ferrofluids: an influence of interparticle correlations, Phys. Rev. E 64 (2001) 041405-1–12]. To increase the accuracy of the analytical expression of the magnetization we calculate the contribution of the dipole–dipole interaction energy up to the 2nd order in the pair distribution function for ferroparticles system. The obtained expression of magnetization corresponds to the theoretical expression of initial magnetic susceptibility proposed by the new polydisperse theory [A.O. Ivanov, E.A. Elfimova, Low-temperature magnetic susceptibility of concentrated ferrofluids: the influence of polydispersity, J. Magn. Magn. Matter. 374 (2015) 327–332] exactly. In conjunction it can be applied for magnetogranulometric analysis of polydisperse concentrated ferrofluids.