A novel superparamagnetic magnetic fluid based on Fe3O4-immobilized-SiO2-nanospheres (MSiNPs) was developed. Both the experimental analyses and computational simulations were conducted to investigate its magnetorheology. In comparison to the pure Fe3O4 based magnetic fluid, the magnetorheological (MR) effect of the MSiNPs based magnetic fluid was about 25 times larger. To demonstrate the improving mechanical properties, a modified magnetic dipolar model was proposed to describe the magnetic interaction of two close magnetized particles. Moreover, the molecular dynamic simulations were carried out to understand the microstructure evolution under an applied magnetic field. The simulation results showed that chain-like and column-like particulate structures were formed in the stationary state and transferred into lamellar microstructures in the steady shear flow. Particle-level simulations were in good agreement with experimental data. The dramatic increase in MR effect of the MSiNPs based magnetic fluid originated from the intensity of the magnetic attractions and the size scale of the particulate structures.
