Ferrofluids with monomer, dimer, and trimer nanoparticles: Effects of the dipole–dipole moment and magnetic field on the cluster formation

Abstract

In this research, using molecular dynamic simulations, we investigated the aggregation, average characteristics of the cluster, and magnetization of three distinct ferrofluid systems constituted of monomer, dimer, and trimer nanoparticles. There are two cases studied, in the first case we assign the dipole–dipole moment to parallel to the direction of the external applied magnetic field, and in the second case perpendicular to the direction of the external applied magnetic field. We observed the orientation of the particles due to dipole–dipole interaction for different values of the dipole interaction parameter and then used the Langevin parameter to apply an external magnetic field. The simulation results show that when the dipole interaction parameter increases, particles form longer clusters, and aggregation of particles occurred. In the presence of an external magnetic field, the particles form chain-like and column-like structures. For the perpendicular configuration, thick and sturdy chain-like structures were developed with their larger average cluster size. The magnetization of the particles increases significantly as the assigned dipole–dipole moment over the particles is increased by an external magnetic field, and magnetic saturation begins at higher magnetic fields. With the help of experimental data, we investigated and compared the effects of particle size and monomer mixture into trimer systems on average characteristics and saturation magnetization, and revealed that larger particles (trimer) systems have significantly higher average characteristics and saturation magnetization for every magnetic dipole parameter and Langevin parameter.