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Information × Registration Number 0218U001872, 0114U001859 , R & D reports Title Preparation and research of model 4f - electron systems under extreme conditions popup.stage_title Head Filipov Volodymyr, Registration Date 14-12-2018 Organization Frantzevich Insitute for Materials Science Problems of the Ukranian National Academy of Sciences popup.description2 The high-purity powders and perfect single crystal samples of REE tetraborades: GdB4, TmB4, LuB4 - and their solid solutions were obtained and tested. There are prepare samples for their physical properties study. In low fields, its are antiferromagnetics, in high fields - ferrimagnetics, in intermediate ones its are characterized by a plateau at magnetization corresponding to the fractional value from the magnetization of saturation and form stripe-structures. The complex nature of the magnetic ordering of these phases is revealed, which is determined both by the nature of the RE ion and by the geometric and exchange frustrations of the ThB4 type lattice, the magnetic phase diagrams are constructed, and the assumptions about the evolution of their magnetic structure are made. There are obtained powders and grown perfect single crystals of YB6, LaB6 hexaborides with individual boron isotopes and natural boron, which are used for study of the "mass" effect influence, isotopic disorder and non-stoichiometry on the nature of superconductivity in the CaB6 structural type borides. There are obtained and tested high-purity source powders and perfect single crystals of solid solutions based on the samarium hexaboride with different level of doping with trivalent ions of lanthanum - SmxLa1-xB6 (0.5?x?1.0) and divalent alkaline and rare earth ions: Sm1-xSrxB6 (x = 0.01, 0.03), Sm1-xEuxB6 (x = 0.005, 0.02, 0.05, 0.95, 0.995), Sm1-xYbxB6 (x = 0.005, 0.02, 0.05, 0.1). Samples from single crystals of all compositions were prepared to study the physical properties of these phases. The influence of the type of the impurity on the valence of the Sm ions, the density of the Kondo-states and topological dielectric SmB6, evolution of the transport and spin gap at the Fermi level by different methods (thermal, magnetic, spectroscopy, high pressure) is found. Technology of growing of the topological dielectric YbB6 single crystals with different Yb/B ratios is worked. Perfect single crystals YbB5.96 and YbB5.994 with varying level of boron deficiency have been obtained. The influence of the completeness of the boron sublattice on the transport and magnetic properties of the ytterbium hexaboride depending on the level of deficiency of boron is ascertained. First the non-metallic trend of the temperature dependence of the resistance and the complex character of the Seebeck coefficient was obtained. It is determined that low-temperature anomalies of transport properties are due to the intersection between bulk and surface charges of electronic states in charge transport. The perfect single crystals of dodecaboride lutetium (LuB12) and holmium (HoB12) with natural boron and individual boron isotopes are grown. The study of the features of the crystalline structure of LuB12 in a wide temperature range is carried out. A reduction of the LuB12 cubic symmetry to the tetragonal in the range (50 ? 75) K is detected, it is accompanied by pass to the frame glass state at T *, an anisotropy of its physical properties and an asymmetry of the distribution of the electron density near the Lu lattice point. For HoB12 crystals with isotopic and natural boron below the temperature of AFM ordering (7.3 K) a significant difference in the character of the magnetoresistance was revealed, which indicates the difference in the components of the exchange, which leads to a difference in the nature of their magnetic structures. It is assumed that the substantial anisotropy of the HoB12 magnetoresistance with natural boron is provoked by a decrease in the lattice symmetry due to the reduction in the symmetry of the cuboctahedron B12 due to the presence of a mixture of two individual isotopes of boron - 10B and 11B in the natural boron with a 10% difference in their masses. Product Description popup.authors Духненко Анатолій Васильович Забуга Володимир Іванович Левченко Ганна Василівна Лященко Альфред Борисович Мартиненко Ганна Миколаївна Падерно Варвара Миколаївна Половець Світлана Євгеніївна Січкар Зоріслав Васильович Шіцевалова Наталя Юріївна popup.nrat_date 2020-04-02 Close