Magnetic fluids: Magnetic forces and pumping mechanisms

Ferromagnetic fluids are a colloidal suspension of subdomain iron particles dispersed in a carrier fluid. The force exerted on the fluid by a magnetic field and the subsequent pressure exerted by the fluid cannot be explained by a continuum theory. Starting from the force on a dipole, continuum theory (using an average magnetization, M) of the fluid, predicts the pressure jump at the fluid surface. To test the theory, pressure measurements were made. The fluid was contained in a glass sphere or cylinder with tubes attached to the container at different points. The pressure necessary to force the fluid back to the container shape was measured using a differential manometer. Pressure measurements were made for the fluid in a uniform magnetic field and in a varying magnetic field. Using the fluid in a pumping scheme was also considered.