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Information × Registration Number 0203U008028, 0100U003284 , R & D reports Title Optical, thermal and magnetic properties of systems with mesoscopic spatial nonuniformities popup.stage_title Head Anders A., Registration Date 10-04-2003 Organization Kharkov National University named after V.N.Karazin popup.description2 The investigation object - mixed crystals K1- x(NH4)xH2PO4 (x=0.0; 0.02; 0.04; 0.08; 0.22; 0.32; 0.53; 0.74; 0.82; 1.0) and Rb1- x(NH4)xH2PO4 (x=0.20). Polycrystalline samples of magnet spin-glass system Li0.5Fe2.5-xGaxO4 (х=0.9; 1.2; 1.4; 1.45; 1.6) - diluted cubic spinels with ferri-magnetic order at x=0. The project aim: finding-out and research of exhibition beaters and mechanisms of the phase transitions in a spatial heterogeneous frustrated electrical and magnetic systems with long-range order for the purpose of the states identification and construction of the phase diagrams. The investigation aim - Raman scattering spectra in the temperature interval 4.3ё300K and concentration range 0ЈxЈ1.0,the temperature dependencies of the static magnetic properties (magnetization, susceptibility) in a wide range of magnetic fields H and temperatures and low temperature specific heat C(T) at H=0; information about phase composition (X-ray analysis, intrinsic friction) spatial heterogeneity's of the basic competitive interactions and order parame-ters frustrations arise due to composite disorder in the multicomponent systems. It is established that at law temperatures the heterogeneity due to existence of mezoscopic size regions with elevated content of frustrations plays an important role in the formation of frustrated states. Vibrational spectrum of the mixed crystal K1-xAxDP (x=0,74; 0,53 and 0,02) in the frequen-cies region corresponding the librational vibration of the PO4 ions has been studied by Raman scattering method. It was established that the character of spectra transformation at phase transi-tions to various low-temperature phases is substantially different. On the temperature dependencies of frequencies and half-width of crystals K0,26A0,74DP and K0,47A0,53DP characteristic anomalies have been found at temperature Tm. On the basis of experimental data the activation energies were determined. The results obtained confirm the mechanism of the phase transition in according to that the ammonium ions positions in the crys-tals lattice are not fixed in the paraelectric phase. At the Tm temperature the correlated fixation of the ammonium ions occurs and it leads to the antiferroelectric cluster structure formation. It has been confirmed the fact that the structure glass phase is inhomogeneous and it is assemblage of ferroelectric, antiferroelectric clusters and "freezing" paraelectric phase. For magnetic system the existence of the line of the 2 order thermodynamic phase transi-tions and of the unknown earlier frustrated magnetic phase that becomes the ferrimagnetic spin glass type phase at temperature decrease has been bound. Spatial fluctuations of the order pa-rameter (magnetization) do not on the character of the critical behavior influence near Curie point TC far from percolation threshold. For the first time it was established that there the is criti-cal concentration xў=1.2 below which (x<1.2) the degree of the magnetization spatial heteroge-neity does not effect on the TC value. It was found how the trivial heterogeneity - a little but determined impurities of the phases distinguished from the spinel phase - effects on the magnetic properties and TC value. The investigation results can be used in the design of the functional materials for micro-wave devices, laser radiation generator, memory elements. Predicted suggestions concerning continuation of the investigations: on the present-day stage of the development of the insights into frustrated systems it needs to carry out the systematic investigations because its results are necessary for contraction of the general consistent theory. Product Description popup.authors popup.nrat_date 2020-04-02 Close