ИСТИНА

Effect of linear dichroism appears in magnetic fluids based on anisotropic particles under the influence of magnetic field, i.e. linearly polarized light transmission of such substances depends on the magnetic field and the mutual orientation of the polarization and magnetic field vectors [1]. To increase this effect the shape anisotropy of magnetic particles should be increased. Thus, the most promising system manifesting linear dichroism in magnetic field is a colloidal solution of magnetic plate-like nanoparticles with the greatest possible aspect ratio, as well as the magnetic moment of the particles should be oriented perpendicular to the basal plane to achieve the orientation under the influence of the magnetic field. We describe synthesis and optical properties of colloidal solutions of hard-magnetic plate-like strontium hexaferrite particles obtained via the glass crystallization technique and by the hydrothermal method. We obtained hexaferrite particles with coercive force >800 Oe, saturation magnetization >20 emu/g and aspect ratio 5-15. Colloidal solutions were characterized with optical spectroscopy. The difference in transmission is observed throughout the visible range, while the effect increased from red to purple. The ratio of optical densities of colloidal solution reached 3.8 (at the wavelength of 500 nm). Oscillations of the transmittance was observed in alternating magnetic field up to 2 KHz. 1. Llewellyn, J.P. Journal of Physics D-Applied Physics, 1983