Papers by Author: V.S. Gaviko

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Authors: V.S. Gaviko, A.G. Popov, G.V. Ivanova, N.V. Mushnikov, Y.V. Belozerov, A.S. Ermolenko, L.A. Shreder
Abstract: We have synthesized a novel intermetallic compound PrFe8Ga3C and studied its structure and magnetic properties. X-ray diffraction analysis revealed that the compound possesses a tetragonal BaCd11-type structure (space group I41/amd). In this structure Ga atoms occupy the same sites as Fe atoms with preferably filling the 4(b) site. Magnetization curves have been measured on the aligned powder samples. Below the Curie temperature TC = 400 K the easy magnetization direction was found to orient within the (100) plane. At 80 K the compound has a spontaneous magnetization of 97 emu/g and anisotropy constant of 4.2107 erg/cm3. At room temperature these values reduce to 78 emu/g and 4.7106 erg/cm3, respectively.
Authors: V.V. Stolyarov, A.S. Ermolenko, Dmitriy Gunderov, A.G. Popov, Georgy I. Raab, T.Z. Puzanova, Ruslan Valiev, V.S. Gaviko, E.V. Belozerov
Authors: E.G. Gerasimov, N.V. Mushnikov, V.S. Gaviko
Abstract: Magnetic properties of the La1xRxMn2Si2 (R is Gd, Tb, Dy; 0 x 1) compounds were investigated using magnetic measurements on quasi-single crystals. The x-T concentration magnetic phase diagrams are constructed. All obtained x-T magnetic phase diagrams are found to be similar. Six magnetic structures are realized in the compounds at different concentrations x. It was shown that all the compounds have strong magnetic anisotropy with the c-axis as the easy direction. For the compounds with x = 0.2, the irreversible magnetization processes are observed which can be attributed to the existence of a compensation point at which the R and Mn magnetic sublattices compensate each other. The nature of various spontaneous and field-induced phase transitions is also discussed.
Authors: N.V. Mushnikov, V.S. Gaviko, E.G. Gerasimov, P.B. Terentyev, I.A. Tkach, A.V. Korolyov
Abstract: Structure and magnetic properties of non-stoichiometric rare earth intermetallic compounds TbNi2Mnx and DyNi2Mnx x have been studied. It was found that for the compositions with x ≤ 1 the alloys retain the single-phase cubic structure despite the fact that the rare earth-to-3d metal ratio changes from 1:2 to 1:3. Magnetic measurements revealed that the Mn alloying leads to a substantial growth of the Curie temperature with a maximum at x ~ 0.5. At low temperatures the magnetization reversal of the Mn-containing samples is characterized by a considerable hysteresis caused by pinning of narrow domain walls by the structure defects. The observed experimental data are discussed within the assumption on a local distortion of the crystal electric field and the formation of a non-collinear magnetic structure of the rare earth sublattice.
Authors: Anatoly Ye. Yermakov, Mikhail A. Uimin, A.A. Mysik, A.Yu. Korobeinikov, A.V. Korolyov, N.V. Mushnikov, T. Goto, V.S. Gaviko, N.N. Shchegoleva
Authors: N.I. Vlasova, V.S. Gaviko, A.G. Popov, N.N. Shchegoleva, L.A. Stashkova, Dmitriy Gunderov, Xavier Sauvage
Abstract: Equiatomic FePd alloy in the ordered state has been processed by means of high-pressure torsion deformation (HPTD) and then annealed. X-ray diffraction (XRD), transmission electron microscopy (TEM), and magnetic measurements have been carried out. HPTD results in an order-disorder transformation of the initial ordered L10-phase (s.g. P4/mmm) into a disordered fcc phase (s.g. Fm-3m) through the body-centered tetragonal (bct) phase (s.g. I4/mmm). Subsequent annealing restores the L10-phase.
Authors: N.V. Mushnikov, P.B. Terent’ev, V.S. Gaviko, E.G. Gerasimov, E.V. Rosenfeld, L.A. Shreder
Abstract: Magnetization curves and magnetic susceptibility of Tb1 xRxMn6Sn6 (R = Gd, Y) compounds have been measured for aligned powder samples. Concentration dependences of the spin-reorientation transition temperature and temperature dependences of critical fields of the field-induced magnetic transitions have been determined. For the compound Tb0.1Y0.9Mn6Sn6 with the spiral magnetic structure, we found that application of hydrostatic pressure facilitates the ferrimagnetic ordering. This unusual feature is supported by the observation of a large negative spontaneous volume magnetostriction for TbMn6Sn6. The obtained results are discussed in a model considering three different interlayer Mn-Mn exchange interactions in these compounds.
Authors: L.A. Shreder, V.S. Gaviko, N.V. Mushnikov, P.B. Terent’ev
Abstract: Temperature dependences of the lattice parameters, magnetization and magnetic susceptibility have been measured for the ErFe2Hx hydrides with different hydrogen content x and for the ErFe2D3.1 deuteride. For the samples with a hydrogen content of about 3.1, structural transition from the cubic to the rhombohedral phase has been observed in the temperature range 280 – 310 K. Small variation of hydrogen content does not shift the transition temperature, but influences the amount of the low-temperature rhombohedral phase. The temperature dependence of magnetization shows up an anomaly in the range of the phase transition, which is due to the difference in the magnitudes of magnetic moments and exchange interactions in two phases. Structural and magnetic studies point to a diffusion nature of the phase transition. Upon heating the samples in vacuum there takes place decomposition of the hydride. The hydride with x = 1.6 which forms at the intermediate stage of decomposition possesses an ordering temperature higher than that for the parent ErFe2 compound.
Authors: Anatoly Ye. Yermakov, Mikhail A. Uimin, Vadim R. Galakhov, A.A. Mysik, O.V. Koryakova, V.G. Kharchuk, V.A. Vykhodetz, V.S. Gaviko, K. Kuepper, S. Robin, M. Neumann
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