NMR studies of the sedimentation of ferromagnetic nanoparticles in a magnetic fluid

A method has been proposed for studying the sedimentation of ferromagnetic nanoparticles in a magnetic fluid from the rate of decrease in its magnetization measured by the NMR technique. The dependence of the rate of variations in the magnetization of the magnetic fluid over time on the concentration of the stabilizer is investigated. A colloidal aqueous solution of magnetite nanoparticles with varying concentrations of the sodium oleate stabilizer was used as the magnetic fluid. It has been found that the ratio of the mass concentrations of the stabilizer and magnetite in a stable magnetic fluid must satisfy the condition $C\ge$ 0.7, which corresponds to the formation of a double layer of stabilizer on the surface of magnetite nanoparticles.