Magnetic Soret effect in a hydrocarbon based colloid containing surfacted Mn-Zn ferrite particles

The Soret effect has been investigated in a hydrocarbon based magnetic fluid containing surfacted Mn0.5Zn0.5Fe2O4 nanoparticles with a magnetic volume concentration of 2.3%. The magnetic fluid fills up a vertical diffusion column which consists of a flat vertical channel between two walls and two reservoirs at the ends of the channel. One wall of the channel is being heated while the another one is cooled, maintaining a temperature gradient over the channel's width that leads to separation of particles due to the Soret effect as well as the convective flow in the channel. The combination of the two mentioned effects brings up a measurable change of the concentration of magnetic particles in both reservoirs. The results have been obtained for uniform magnetic fields, aligned parallelly and normally to the temperature gradient respectively, by measuring the concentration of magnetic particles in the reservoirs. Obtained results are in good qualitative agreement with thermodiffusion column theory, published earlier (E. Blums, J. Magn. Magn. Mater. 149 (1995) 111). (C) 1999 Elsevier Science B.V. All rights reserved.