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Information × Registration Number 0308U001434, 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 Резонансні дослідження локальних полів на ядрах 57Fe гексаферитів. Дослідження температурної залежності мінімальних полів анізотропії системи нанокристалів Head Kuncevich Stanislav Petrovich, Registration Date 04-02-2008 Organization Kharkov Natuional university named after V.N.Karazin popup.description2 Object of research - hexagonal ferrite of M structural type and other types as single crystals and powder samples with nano- and a micrometer sized one-domain particles. The purpose of work - to determine temperature changes of local fields on iron nuclei by method of a nuclear magnetic resonance (NMR) in macrocrystals of hexaferrite of M structural type and to test an applicability of theoretical models for the description of these changes. - to carry out Mossbauer research of local fields on iron nuclei on the surface and in superficial layers of hexaferrite macro-and microcrystals, to determine the contribution of superficial anisotropy to effective magnetic anisotropy of the system of nanocrystals of barium hexaferrite. Aim of a stage: - NMR-research of local fields on 57Fe nuclei and of their temperature dependence in an interval 4.2-295?K in domains and domain walls of M-type hexaferrite; - research of conditions of formation of temperature dependence of the minimum field of anisotropy of the system with an account of thermal fluctuations and changes of the magnetic conditions of nanocrystals. Mossbauer researches of local fields on 57Fe nuclei in surfaces and superficial areas of M-type hexaferrite crystals. The data was obtained on temperature dependences of local fields on 57Fe nuclei in domains and domain walls, and also in surface and superficial layer of M-type hexaferrite. Temperature dependence of effective magnetic field Нef (T?) on nuclei of surface ions of iron is first determined in direct comparison with a volumetric part of BaFe12O19 single crystal by simultaneous application of gamma-, x-ray and electronic Mossbauer spectroscopy methods. Gradual destruction of the magnetic order in superficial areas is revealed to begins 50?К and ends 5?К below Curie temperature of a volumetric part of a crystal. The methodology of reproduction of true temperature dependence of the low-field borders distribution on fields of magnetic anisotropy Наmin is developed and tested on a model system of nanocrystals of highly anisotropic ferrimagnetic BaFe12O19. Product Description popup.authors popup.nrat_date 2020-04-02 Close