Registration Number
0302U005159,
0100U003284
, R & D reports
Title
Optical, thermal and magnetic properties of systems with mesoscopic spatial nonuniformities
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Детальне дослідження поведінки внутрішніх коливань іонів РО4. Дослідження магнітних і теплових властивостей просторово-неоднорідної магнітної системи Li0,5Fe2,5-xGaxO4
Head
Popkov Yu.A.,
Registration Date
25-03-2002
Organization
Kharkov National University named after V.N.Karazin
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The results of analysis of the temperature behavior of Raman spectra in the region of v2 and v4 vibrations frequencies of tetrahedrons PO4 in the mixed crystal K1-xAxDP for diagonal component of scattering tensor are presented. Investigations performed have confirmed the fact that the structure glass phase is inhomogeneous and it is assemblage of ferroelectric, antiferroelectric clusters and "freezing" paraelectric phase. On the basis of analysis of temperature dependencies of investigated vibrations parameters it has been established that temperatures of antiferroelectric cluster structure formation are 50 K higher than temperatures of formation of ferroelectric cluster structure. Investigations are made, seeking to check experimentally the conclusions of the current thermodinamical theories about the influence of magnetic state spatial nonuniformity on the characteristic features of the second kind phase transition at the Curie point, namely, the temperature dependences of the low-field susceptibility, magnetization isotherms and critical behavior in the strong magnetic fields as well as the thermal expansion. For this aim the experimental model objects with various kinds of the mesoscopic spatial nonuniformity of magnetic states and corresponding fairly well to the theoretical models are worked out on the base of the system of Li0,5Fe2,5-xGaxO4 solid solutions. The experimental methods are selected, with the help of which one can reliably enough certify the samples from the viewpoint of their mesoscopic magnetic structure. As a result of the comprehensive study of magnetic and thermal properties it is established that in the real objects with mesoscopic nonuniformity relating to the Heisenberg systems with short-range interactions, the magnitude of the critical temperature, Tc, and critical behavior in strong fields are similar to those of uniform systems. On the contrary, the exhibition of singularity in the low-field susceptibility at T=Tc is connected explicitly with the nonuniformity character.
Product Description
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2020-04-03
