• Crystallization Pathways of Cerium(IV) Phosphates Under Hydrothermal Conditions: A Search for New Phases with a Tunnel Structure
    Shekunova T.O., Istomin S.Ya, Mironov A.V., Baranchikov A.E., Yapryntsev A.D., Galstyan A.A., Simonenko N.P., Gippius A.A., Zhurenko S.V., Shatalova T.B., Skogareva L.S., Ivanov V.K.
    2019 г.
    Hydrothermal crystallization pathways of amorphousceric phosphate gels were found to be determined by ammonia concentration in a reaction medium. This allows forhighlyselective hydrothermal synthesis of various finely crystalline ceric phosphates,including Ce(PO4)(HPO4)0.5(H2O)0.5, (NH4)2Ce(PO4)2(H2O) andpreviously unknown NH4Ce2(PO4)3. The structure of the latter compound was solvedfrom powder X-ray diffraction data. It appeared to be isostructural to ammonium thorium phosphate, NH4Th2(PO4)3; in this crystal structure, large channels (5.07 -3.79 Å) located along the c-axis are occupied by NH4+ions

  • «Exotic phases of frustrated antiferromagnet LiCu2O2»
    Bush A.A., Büttgen N., Gippius A.A., Horvatić M., Jeong M., Kraetschmer W., Marchenko V.I., Sakhratov Yu A., Svistov L.E.
    Phys. Rev. B, Том: 97, Номер: 5, с. 054428-(1-15), 2018 г.
    7Li NMR spectra were measured in a magnetic field up to 17 T at temperatures 5–30 K on single crystalline LiCu2O2. Earlier reported anomalies on magnetization curves correspond to magnetic field values where we observe changes of the NMR spectral shape. For the interpretation of the field and temperature evolutions of our NMR spectra, the magnetic structures were analyzed in the frame of the phenomenological theoretical approach of the Dzyaloshinskii-Landau theory. A set of possible planar and collinear structures was obtained. Most of these structures have an unusual configuration; they are characterized by a two-component order parameter and their magnetic moments vary harmonically not only in direction, but also in size. From the modeling of the observed spectra, a possible scenario of magnetic structure transformations is obtained.

  • «Antiferromagnetic ground state in the MnGa4 intermetallic compound»
    Verchenko V.Yu, Tsirlin A.A., Kasinathan D., Zhurenko S.V., Gippius A.A., Shevelkov A.V.
    Том: 2, Номер: 4, 2018 г.
    Physical Review Materials

  • «Локальные магнитные поля в диамагнитных BiSbO4 и Bi4Si3O12: ЯКР 209Bi»
    Кравченко Э.А., Гиппиус А.А., Ткачев А.В., Чаркин Д.О., Долгих В.А.
    ЖЭТФ, 2018 г.
  • Crystal structure and magnetic properties of intermetallic semiconductor FeGa3 lightly doped by Co and Ni
    Churakov Andrei V., Vinokurov Alexander A., Znamekov Konstantin O., Mordvinova Natalia E., Gippius Andrei A., Zhurenko Sergei V., Michael Baenitz, Istomin Sergey Ya
    2018 г.
    We have explored the crystal structure and magnetic properties of two intermetallic solid solutions of the IrIn3 structure type. Although Fe0.95Co0.05Ga3 and Fe0.975Ni0.025Ga3 are isomorphous and possess exactly the same concentration of valence electrons, they display noticeable differences in their crystal structure associated with a different nature of the Fesingle bondCo and Fesingle bondNi dumbbells. The former contains an odd number of electrons compared to an even number of the latter dumbbell. Responding to localized spins of the Fesingle bondCo dumbbells, the 69Ga NQR relaxation rate in Fe0.95Co0.05Ga3 is governed by temperature independent spin-lattice relaxation typical for diluted paramagnetic centers at low temperatures. In Fe0.975Ni0.025Ga3 with zero magnetic moment of the dumbbells the 69Ga spin-lattice relaxation rate is strongly reduced and in-gap states in the energy gap show up as a broad maximum near 70 K.

  • Investigation of proton spin relaxation in water with dispersed silicon nanoparticles for potential magnetic resonance imaging applications
    Kargina Yu V., Gongalsky M.B., Perepukhov A.M., Gippius A.A., Minnekhanov A.A., Zvereva E.A., Maximychev A.V., Timoshenko V.Yu
    2018 г.
    Porous and nonporous silicon (Si) nanoparticles (NPs) prepared by ball-milling of electrochemically etched porous Si layers and crystalline Si wafers were studied as potential agents for enhancement of the proton spin relaxation in aqueous media. While nonporous Si NPs did not significantly influence the spin relaxation, the porous ones resulted in strong shortening of the transverse relaxation times. In order to investigate an effect of the electron spin density in porous Si NPs on the proton spin relaxation, we use thermal annealing of the NPs in vacuum or in air. The transverse relaxation rate of about 0.5 l/(g s) was achieved for microporous Si NPs, which were thermally annealing in vacuum to obtain the electron spin density of the order of 1017 g1. The transverse relaxation rate was found to be almost proportional to the concentration of porous Si NPs in the range from 0.1 to 20 g/l. The obtained results are discussed in view of possible biomedical applications of Si NPs as contrast agents for magnetic resonance imaging. Published by AIP Publishing.

  • Sb121,123 nuclear quadrupole resonance as a microscopic probe in the Te-doped correlated semimetal FeSb2 : Emergence of electronic Griffith phase, magnetism, and metallic behavior
    Gippius A.A., Zhurenko S.V., Hu R., Petrovic C., Baenitz M.
    Phys. Rev. B, 2018 г.
    121,123Sb nuclear quadrupole resonance (NQR) was applied to Fe(Sb1−xTex )2 in the low doping regime (x = 0, 0.01, and 0.05) as a microscopic zero field probe to study the evolution of 3d magnetism and the emergence of metallic behavior. Whereas the NQR spectra itself reflects the degree of local disorder via the width of the individual NQR lines, the spin lattice relaxation rate (SLRR) 1/T1(T ) probes the fluctuations at the Sb site. The fluctuations originate either from conduction electrons or from magnetic moments. In contrast to the semimetal FeSb2 with a clear signature of the charge and spin gap formation in 1/T1(T )T [∼ exp /(kBT )], the 1% Te-doped system exhibits almost metallic conductivity and the SLRR nicely confirms that the gap is almost filled. A weak divergence of the SLRR coefficient 1/T1(T )T ∼ T −n ∼ T −0.2 points towards the presence of electronic correlations towards low temperatures. This is supported by the electronic specific heat coefficient γ = (Cel/T ) showing a power-law divergence γ (T ) ∼ T −m ∼ (1/T1T ) 1/2 ∼ T −n/2 ∼ Cel/T which is expected in the renormalized Landau Fermi liquid theory for correlated electrons. In contrast to that the 5% Te-doped sample exhibits a much larger divergence in the SLRR coefficient showing 1/T1(T )T ∼ T −0.72. According to the specific heat divergence a power law with n = 2m = 0.56 is expected for the SLRR. This dissimilarity originates from admixed critical magnetic fluctuations in the vicinity of antiferromagnetic long range order with 1/T1(T )T ∼ T −3/4 behavior. Furthermore Te-doped FeSb2 as a disordered paramagnetic metal might be a platform for the electronic Griffith phase scenario. NQR evidences a substantial asymmetric broadening of the 121,123Sb NQR spectrum for the 5% sample. This has a predominant electronic origin in agreement with the electronic Griffith phase and stems probably from an enhanced Sb-Te bond polarization and electronic density shift towards the Te atom inside Sb-Te dumbbell.