ИСТИНА

Strontium hexaferrite is a hard magnetic M-type hexaferrite with high magnetocrystalline anisotropy. Such materials are well-known and widely used for the production of ceramic magnets, magnetic tapes and microwave devices. High coercetivity leads to remanence in hexaferrite nanoparticles. Combined with anisotropic form of these nanoparticles it gives rise of particularly interesting phenomenon — colloidal magneto-optical effect. In the present work we studied the complex dynamic behavior of strontium hexaferrite nanoplatelets in various viscous media under application of AC and DC external magnetic field using optical, magnetic and rheological methods. Nanoparticles were synthesized by glass-ceramic route using borate matrix. According to the TEM data the diameter and thickness of the particles are 50 nm and 5 nm respectively. Stable colloids in aqueous, ethanol, glycerol and ethylene glycol media were prepared. We show that dynamics of the hexaferrite nanoprartices are highly depended of viscous properties of surrounding media. The magnetooptical response of aqueous colloids can be observed in weak AC magnetic fields (20 Oe) with frequency of 2000 Hz. High viscosity of the media significantly slows down the rotation of nanoparticles. Glycerol colloids lose response to the AC fields with frequency as high as 100 Hz. The work is supported by the RFBR grant 16-03-01052.