Magnetic-stimuli rheological response of soft-magnetic manganese ferrite nanoparticle suspension.

The hydrothermal fabrication of crystalline manganese ferrite (MnFe2O4) nanoparticles and their application as a magnetorheological (MR) fluid dispersed in an insulating oil are described herein. The morphology and crystal structure of the MnFe2O4 nanoparticles are revealed by transmission electron microscopy, scanning electron microscopy, and X-ray diffraction. In addition, with a relatively high saturation magnetization of the MnFe2O4 particles, their typical MR behavior is demonstrated by rheometric steady shear and dynamic oscillation tests under an applied magnetic field. Moreover, the flow and yield stress curves for the MnFe2O4 nanoparticle-based MR fluid are shown to conform to the Herschel–Bulkley model with a slope of 1.5. Finally, under the same magnetic field strength, the dynamic yield stress is shown to be higher than the elastic yield stress. [ABSTRACT FROM AUTHOR]