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"Contribution to investigation of mechanisms of optical gratings creation in magnetic fluids"
(Supervisor: Ivan Turek)

What is a magnetic fluid

   Magnetic fluid is a matter, which can be perceived as a compromise between fluid and a magnet. The first colloid with magnetic properties was prepared in 1938 by Elmore and was used in order to see the domain structure of ferromagnetic materials. In the middle of sixties, the interest in magnetic fluids increased, again. It was mainly because of the various technical applications based on the most recent discoveries in chemical technologies.
   Magnetic fluid is a stable colloid system consisting of mono-domain ferro- or ferrimagnetic particles dispersed in a carrier non-magnetic fluid (water, oil, mineral oil, glycerine, saline,...). The oxides of iron (Fe3O4, Fe2O3), particles of transition metals (Fe, Ni, Co,...) or nitrides and borides of these metals are the most often used for preparing the solid-state part of the system. To maintain the long-term stability of physical properties of magnetic fluids, one needs to prevent creating of clusters of particles. Otherwise, it would mean the separation of the solid-state part of the system from the liquid one. Solution of the problem lays in small dimensions of the particles (in general (1-20) nm), what means they can move according to Brown motion. Another problem occurs due to force interactions among particles. To overcome the influence of attractive forces one adds into fluid the so called surfactants (surface-active substance) which cover particles and secure their repulsion. Magnetic fluid as a set of mono-domain magnetic particles dispersed in the carrier fluid thus behaves like a paramagnetic matter.

The aim of the work

   This work concerns with mechanisms which could be responsible for origin and/or decay of optical gratings created in magnetic fluids by means of optical interference field. This field was created by argon ion laser Zeiss, ILA 120-1. Studying of possible mechanisms taking place at investigated processes could expand our knowledge about properties of magnetic fluids, in general.



                         a)                                                                                                           b)

The wedge (black one in the left margin of the Fig. a)) splits the image into two parts. Bottom half of the figure represents the interference field illuminating the sample of magnetic fluid. The upper part of the image shows the light transmitted through the sample right after one of the laser beams creating the interference field is shut down. The grating created due to light with spatial distribution of intensity is clearly seen. Fig. b) is the same as Fig. a) except it is viewed in different mode.

  1. N. Tarjányi, Contribution to investigation of mechanisms of optical gratings creation in magnetic fluids, Diploma project, Dept. of Telecommunications, FEE University of Žilina, 1999 (in Slovak)

  2. I. Turek, N. Tarjányi, R. Žako, A Structuration of Grain Density Distribution in Magnetic Fluids. I. Influence of the Illumination, Proceedings of University of Žilina, 25 1999, 49 (in Slovak)

  3. I. Turek, R. Žako, N. Tarjányi, A Structuration of Grain Density Distribution in Magnetic Fluids. II. Influence of a Magnetic Field, Proceedings of University of Žilina, 25 1999, 57 (in Slovak)

  4. I. Turek, C. Musil, J. Štelina, J. Timko, K. Kopčanský, R. Žako, N. Tarjányi, Influence of the external magnetic field on self-diffraction of the light in magnetic fluids, Conference of Czech and Slovak Physicists, Zvolen, Slovakia, 1999 (in Slovak)