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Information × Registration Number 0200U004617, 0197U002455 , R & D reports Title Phase transitions and spectrum of elementary excitations in magnetic and electric spatially nonuniform systems popup.stage_title Head Popkov Yu., Registration Date 27-09-2000 Organization Kharkov National University named after V.N. Karazin popup.description2 Subjects of inquiry are polycrystal samples of the spin-glass systems of the Heisenberg magnets. The goal of the work is to investigate experimentally the phase x-T-diagram as well as to study mechanisms of phase transitions and phase states in the system. The studies of the Roman spectra in a wide range of temperatures and concentrations enabled to obtain the x-T phase diagram. It has been established that in the intermediate concentration range the low temperature transition into the dipole glass phase is realized with no change of the total symmetry of crystals. The temperature behavior analysis of the "soft" predamped mode B2 of symmetry and libration oscillation of the NH4 ions in formation of the various low-temperature phases. A new line of the first kind phase transitions of the order-order type appears in the phase diagram. A clear display of the phase transition at T(c) as a kink in the linear dependence evidences the cooperative character of the spin wave excitations. The existence of cluste rs leads to features of the critical behavior at H>0. In fields 150 Е<H<450 E for х = 1,45 a critical behavior is observed what is predicted by the mean field theory for uniform systems with exponents. Product Description popup.authors popup.nrat_date 2020-04-03 Close