Abstract: The formula for first-order magnetic buoyancy is derived based on the Bernoulli＇s equation of ferrofluid. The distribution of first-order magnetic buoyancy is studied at various axes by the experimental method in order to understand the basic reason of first-order magnetic buoyancy. The first-order magnetic buoyancy is influenced by magnetic field intensity, magnetic field gradient, saturation magnetization and susceptibility of ferrofluid. With decreasing magnetic field intensity and magnetic field gradient along z direction, the first-order magnetic buoyancy grows smaller gradually and goes to zero at the end; therefore suspending power of ferrofluid weakens. Saturation magnetization and susceptibility of MFP-1 ferrofluid are bigger than MFP-2 ferrofluid and first-order magnetic buoyancy of MFP-1 ferrofluid is bigger. When the current is 3.00A, glass, aluminum, brass, red copper and lead bails have been suspended and Rosensweig peaks appeared in the MFP-1 ferrofluid, but glass, aluminum and brass balls were only suspended in the MFP-2 ferrofluid. The distributions of magnetic field intensity and mag- netic field gradient are different along r direction at various heights. Magnetic field gradient goes to zero gradually with increasing the height and is the primary affecting factor for first-order magnetic buoyancy. Nonmagnetic balls are moved to the sidewall of glass beaker where the first-order magnetic buoyancy is smaller.

Key words: ferrofluid, first-order magnetic buoyancy, magnetic field