Investigations were made to determine the Soret coefficient of magnetic particles in a ferrofluid. Based on zero field measurements from which the Soret coefficient is quantitatively determined with a theoretical model, the influence of a magnetic field on this parameter will be shown. A clear dependence of the intensity of the thermodiffusive process on the magnetic field strength could be found. In addition it could be shown, that the direction of the field relative to the driving temperature gradient has a significant influence too. In particular a change of the sign of the Soret coefficient was observed if the magnetic field is orientated parallel to the temperature gradient.

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We report both theoretical and numerical results on convection for a magnetic fluid under rotation in a viscoelastic carrier liquid. The viscoelastic properties are given by the Oldroyd model. We focus on the stationary convection for idealized boundary conditions. Close to the first bifurcation, the coefficients of the corresponding amplitude equation are determined. The effect of the Kelvin force and of the rotation on instability thresholds for a diluted suspension are also emphasized.

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