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Information × Registration Number 0307U001720, 0106U003119 , R & D reports Title Local magnetic fields on nucleus 57Fe in volume and on surface of hexaferrite crystals of different scale popup.stage_title Отримання об'єктів дослідження й визначення їх магнітних характеристик Head Kuncevich Stanislav Petrovich, Registration Date 19-04-2007 Organization Kharkov Natuional university named after V.N.Karazin popup.description2 Object of study - hexagonal ferrites of M and other structural types in the form of monocrystals and powder samples with single-domain particle sizes in the range of nanometers and micrometers. Aim of work - NMR determination of temperature variation in local fields on ferric nuclei in M structural type hexaferrite macrocrystals and of applicability of theoretical models to description of such variation. Moessbauer study of local fields on ferric nuclei on the surface and near-surface layers of hexaferrite macro- and microcrystals, determination of the role of surface anisotropy in effective magnetic anisotropy of barium hexaferrite nanocrystalline system. Task of current stage - synthesis of hexaferrite macro- and microcrystals, study of their magnetic characteristics. Research methods - X-ray, magnetic resonance, static magnetic study (T=77-295 K, H<22 kOe); electronic microscopy. By methods of spontaneous crystallization and buildup on rotating seed large M-structure hexaferrite crystals have been synthesized, both having natural content of 57Fe isotope and enriched with this isotope up to 95%. The obtained crystals were tested by X-ray study, static and resonance measurement of their magnetic characteristics. Using optimized cryochemical technology we obtained some systems of hexagonal barium ferrite single-domain monocrystals. Basic morphological and magnetic parameters have been specified. The obtained powder samples were shown to remain model systems of "large" Stoner-Wolfahrt particles in the range 300-700 K. A temperature dependence was found for medium field of effective magnetic anisotropy. The magnetic anisotropy of hexagonal barium ferrite in the form of both nano- and microcrystalline system was shown to be formed by three types of anisotropy: magnetic crystalline, shape and "surface". Product Description popup.authors popup.nrat_date 2020-04-02 Close