Concentration and Magnetic Field Effects on Thermal Fluctuation of Magnetic Weight of Magnetite Nanoparticles During Agglomeration Under Magnetic Field

摘要

Agglomeration process of the magnetic nanoparticles under the magnetic field is studied by monitoring the magnetic weight of the sample, the magnetic force that the magnetic sample experiences under the magnetic field. The magnetic weight of the single domain magnetite nanoparticles in aqueous solution increases slowly with fluctuation as the nanoparticles agglomerate. The fluctuation of the magnetic weight coincides with the temperature change. We observe the thermal fluctuation of the magnetic weight of the samples of different concentrations at different magnetic fields. We employ the energy distribution function in order to simulate the thermal fluctuation of the magnetic weight. The simulation results suggest that the interparticle interactions, which restrict the motions of nanoparticles, play important roles in the agglomeration of high concentration samples at high magnetic fields. The interparticle interactions make the effective temperature lower than the experimental temperature by raising the magnetic anisotropy energy barrier.