Senzomkhize,
MR is MagnetoRheological fluid?
Is it an industrial application, laboratory or research service?
If you have differents rheograms vs magnetic field intensity
and you have magnetic field intensity in your service and
evaluated shear stress is below 100 Pa, you should use centrifugal pump, if it is higher you should use positive displacement pump.
Since MR is a Non-Newtonian fluid, you should take care in calculation loss of pressure, corrections pump factors, etc., and take in mind that conventional correlations of fluids does not apply on this kind of fluid.
I Hope Its Helps