Fe3O4 and Ni0.5Zn0.5Fe2O4 nanoparticles were synthesized via precipitation and mechanical alloying, respectively, and assessed as a potential magnetorheogical (MR) additive. X-ray diffraction and transmission electron microscopy were employed to evaluate the phase formation and structural and morphological changes. Vibrating sample magnetometer (VSM) was used to measure magnetic characteristics of the samples. The MR characteristics of carbonyl iron (CI)-based and 1 wt.% (Ni0.5Zn0.5Fe2O4 + Fe3O4) CI-based suspensions were measured from a steady and rotational rheometry by applying magnetic field strengths ranging from 0 to 558.39 kA/m with 79.77-kA/m increments. The results indicated that the MR effect of the micron-sized, CI-based MR fluid significantly improved in the presence of nanoparticle additives, e.g., having higher-yield characteristics. Chain-like structure formed in the presence of nanoscale additives improved the MR performance and sedimentation stability of the CI particles
