| 1. |
- Ivanov, Alexander V., et al.
(författare)
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Structural organization of silver(I) complexes with O,O′-dialkyl dithiophosphates : Solid-state 13C and 31P CP/MAS NMR and single-crystal X-ray diffraction studies
- 2007
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Ingår i: Russian journal of coordination chemistry. - 1070-3284 .- 1608-3318. ; 33:1, s. 20-31
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Tidskriftsartikel (refereegranskat)abstract
- Silver(I) complexes with four symmetrically substituted O,O′-dialkyl derivatives of dithiophosphoric acid of the general formula [Ag{S2P(OR)2}] n (R = C2H5, i-C3H7, C4H9, and s-C4H9) were obtained. Their structures and spectroscopic characteristics were studied by solid-state 13C and 31P CP/MAS NMR spectroscopy and X-ray diffraction analysis. The parameters of the anisotropy of the 31P chemical shift 31P-δ aniso and η (δ aniso is the chemical shift anisotropy and η is the asymmetry parameter) calculated from the diagrams of the x 2-statistic revealed that the (RO)2PS2 groups act as bridging ligands in all the silver(I) complexes obtained. The hexanuclear complex [Ag6{S2P(O-i-C3H7)2}6] was found to form two modifications α and β. According to the X-ray diffraction data, the silver(I) complex with O,O′-di-s-butyl dithiophosphate exists as discrete hexanuclear molecules [Ag6{S2P(O-s-C4H9)2}6]. In the clear molecules β-[Ag6{S2P(O-i-C3H7)2}6], the signals for the phosphorus atoms were assigned to their positions determined from the X-ray diffraction data.
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| 2. |
- Ivanov, S.A., et al.
(författare)
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Ba3Fe2WO9-delta : Effect of oxygen non-stoichiometry on structural and magnetic properties
- 2006
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Ingår i: Journal of Solid State Chemistry. - : Elsevier BV. - 0022-4596 .- 1095-726X. ; 179:8, s. 2645-2655:8, s. 2645-2655
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Tidskriftsartikel (refereegranskat)abstract
- The magnetic and structural properties of oxygen-deficient perovskites with composition Ba3Fe2WO9-6 (BFWO) have been systematically studied for two different oxygen contents corresponding to delta = 0.00 and 0.55 in the chemical formula in order, to determine and correlate their chemical composition, structural and magnetic properties. The evolution of nuclear and magnetic structures with temperature has been investigated by neutron powder diffraction. It was shown that at room temperature the stoichiometric compound (delta = 0.00) adopts a hexagonal 6H-perovskite structure (space group P6(3)/mmc). This phase, when heated at high temperature under a stream of Ar gas, transforms to an oxygen-deficient phase delta = 0.55), which is an ordered cubic perovskite structure (space group Fm-3m). The crystallographic and magnetic properties of the obtained phases are compared, and it is clear that the magnetic properties are significantly affected by oxygen non-stoichiometry. These changes of magnetic properties for such a slight decrease in oxygen content are interpreted as a result of structural transformations. Together with the experimental results based on neutron powder diffraction data a discussion of some aspects of the structural transformation (P6(3)/mmc -> Fm-3m) is presented.
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| 3. |
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| 4. |
- Ivanov, S.A., et al.
(författare)
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The magnetoelectric perovskite Sr2CoMoO6: An insight from neutron powder diffraction
- 2005
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Ingår i: Materials Research Bulletin. - : Elsevier BV. - 0025-5408. ; 40, s. 840-849
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Tidskriftsartikel (refereegranskat)abstract
- A study of the crystallographic and magnetic structure of the double perovskite Sr2CoMoO6 (SCMO) has been carried out on a polycrystalline sample using neutron powder diffraction (NPD) data between 10 and 700 K. An analysis of the NPD patterns at room temperature has shown that this compound crystallises in the tetragonal space group I4/m with a = 5.5616(1) Å and c = 7.9470(2) Å and has a 1:1 ordered arrangement of Co and Mo at the B-sites. This compound undergoes a I4/m → Fm3m improper ferroelectric phase transition near 560 K. A low-temperature antiferromagnetic ordering (below TN = 36 K) has been followed from sequential NPD data analysis. The antiferromagnetic structure is defined by the propagation vector k = (1/2, 0, 1/2). In addition to the obtained experimental results on magnetic and electric properties some aspects of magnetoelectricity in this perovskite are also discussed.
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| 5. |
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| 6. |
- Scandale, W., et al.
(författare)
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First observation of multiple volume reflection by different planes in one bent silicon crystal for high-energy protons
- 2009
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 682:3, s. 274-277
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Tidskriftsartikel (refereegranskat)abstract
- Multiple volume reflection by different planes in a bent silicon crystal with its 〈111〉 axis orientation close to the beam direction was observed for the first time for 400 GeV/c protons at the CERN SPS. The proton beam was deflected to the side opposite to the crystal bend by an angle of about 67 μrad, which is five times larger than in a single volume reflection by the (110) bent planes. The registered efficiency of one side deflection was about 84%. It was shown that multiple volume reflection transforms to a single volume reflection when the orientation angle of the 〈111〉 axis relative to the beam direction is increased. © 2009 Elsevier B.V. All rights reserved.
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| 7. |
- Scandale, W., et al.
(författare)
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High-efficiency deflection of high-energy negative particles through axial channeling in a bent crystal
- 2009
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 680:4, s. 301-304
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Tidskriftsartikel (refereegranskat)abstract
- Deflection due to axial channeling in a silicon crystal bent along the 〈111〉 axis was observed for 150 GeV/c negative particles, mainly π- mesons, at one of the secondary beams of the CERN SPS. The whole beam was deflected to one side with the efficiency of about 90% and with the peak position at the bend crystal angle α = 43 μrad. The deflection occurs mainly due to doughnut scattering of above-barrier particles by the atomic strings of the crystal. However, due to a high probability of particle recapture into bound states with the atomic strings their contribution to the deflection should be about 15% for our case according to simulation results. © 2009 Elsevier B.V. All rights reserved.
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| 8. |
- Scandale, W., et al.
(författare)
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Observation of channeling and volume reflection in bent crystals for high-energy negative particles
- 2009
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 681:3, s. 233-236
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Tidskriftsartikel (refereegranskat)abstract
- Deflection due to planar channeling and volume reflection in short bent silicon crystals was observed for the first time for 150 GeV / c negative particles, π- mesons, at one of the secondary beams of the CERN SPS. The deflection efficiency was about 30% for channeling and higher than 80% for volume reflection. Volume reflection occurs, in spite of the attractive character of the forces acting between the particles and the crystal planes, in a wide angular range of the crystal orientations determined by the crystal bend angle. © 2009 Elsevier B.V. All rights reserved.
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| 9. |
- Scandale, W., et al.
(författare)
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Observation of nuclear dechanneling for high-energy protons in crystals
- 2009
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 680:2, s. 129-132
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Tidskriftsartikel (refereegranskat)abstract
- Channeling in a short bent silicon crystal was investigated at the CERN SPS using 400-GeV/c protons with an angular spread much narrower than the critical channeling angle. Particle dechanneling due to multiple scattering on the atomic nuclei of the crystal was observed and its dechanneling length was measured to be about 1.5 mm. For a crystal with length comparable to such dechanneling length, an efficiency of 83.4% was recorded, which is close to the maximum value expected for a parallel beam and exceeds the previously known limitation of deflection efficiency for long crystals. © 2009 Elsevier B.V. All rights reserved.
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| 10. |
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