Light-induced structuralization in magnetic fluids with the negative Soret constant

J. Štelina¹ - C. Musil¹ - J. Bracin\'{i}k¹ - P. Kopċanský² - M. Timko² - M. Hnatiċ² - M. Repašan² - I. Potoċová² - E. Ayrjan³

¹ Department of Physics, University of Żilina, Veľký Diel, 01026 Żilina, Slovakia
² Institute of Experimental Physics SAS, 47 Watsonova, 04353 Košice, Slovakia
³ Laboratory of Information Technologies JINR, 6 Joliot-Curie, 141980 Dubna, Russia

Abstract
The magnetite nanoparticle structuralization in magnetic fluids is observed as a consequence of the nano-particle thermo-diffusion. Temperature gradients can arise due to light-absorption on the accidental concentration fluctuations of particles or on well-defined geometric structures such as the concentration-diffraction grating. The obtained results have verified the negative value of the Soret constant in the studied kerosene-based magnetic fluid. The development of the structuralization of magnetic particle concentration in an illuminated thin sample, after the illumination intensity achieves some critical value I₀^c, was numerically simulated and verified experimentally. Figs 4, Refs 6.