Magneto-viscosity of MnZn-ferrite ferrofluid

Mn0.75Zn0.25Fe2O4 (MZF) ferrofluid was synthesized using a precipitation method in ethylene glycol colloidal media. The x-ray diffraction and transmission electron microscope studies show nanophase of the M ultra fine nanoparticles. The magnetization (M) vs magnetic field (H) show zero coercivity and high saturation field characteristic of superparamagnetic behavior. The dynamic light scattering (DLS) data show the formation of aggregates or clusters with size distribution ranging from 50 to 600 nm. Magneto-viscosity of the ferrofluid is studied using rheological measurements under magnetic field up to 1.3 T. The behavior of shear rate vs effective shear viscosity (eta) plot in zero and higher magnetic field changes from non-Newtonian to Newtonian as shear rate increases. At a steady shear rate irreversible nonlinear behavior is observed in eta vs H plots. The data indicate the particle size distribution and formation of chains in the ferrofluid with increase in magnetic field. (C) 2014 Elsevier B.V. All rights reserved.