Study of some magnetic properties of ferrofluids filtered in magnetic field gradient

The magnetic properties of some ferrofluids obtained by a new technique, in which the stabilization of particles was done by hydrofobization in the absence of the dispersion medium, and the filtration was done in the presence of a magnetic field gradient, are studied. Measurements were performed on three samples originated from the same ferrofluid with magnetite particles dispersed in kerosene. They are distinguished by the type of filtration: in the absence of the field gradient (sample A), in the presence of the field gradient (sample B), and in the presence of the field gradient with a filamentary matrix introduced in the filtration vessel (sample C). The measurements performed in static magnetic field show an increase of approximately 12% and 40% in the saturation magnetization of samples B and C, respectively, in comparison to sample A, due to the increase of the concentration of the magnetic phase, as a result of the filtration in the presence of the field gradient. A decrease of the mean magnetic diameter of the particles in the ferrofluid can be noticed, from the dimensional distribution of the particles, determined by the Chantrell method (from 9.15 nm (sample A) to 7.97 nm (sample C)).