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Author Pasquini, G.; Levy, P.; Civale, L.; Nieva, G.; Lanza, H.
Title (up) Linear response in the AC susceptibility of vortices in YBa2Cu3O7 crystals with columnar defects Type Journal Article
Year 1997 Publication Physica C: Superconductivity Abbreviated Journal
Volume 274 Issue 1-2 Pages 165-172
Keywords
Abstract We explore the AC magnetic susceptibility of YBa2Cu3O7 single crystals with columnar defects. For vortices parallel to the defects the linear response is mainly determined by the Campbell penetration depth with a field independent Labusch parameter indicating that vortices are individually pinned. The small dissipation in this limit is likely to arise from thermal fluctuations of vortex segments between pairs of metastable states (two-level systems) in the Bose glass phase. Tilting vortices away from the tracks results in a reduction of the Bose glass temperature and an increase of the dissipation due to the reduction of the pinning forces. We discuss the onset of nonlinear response as the AC field increases.
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ISSN 0921-4534 ISBN Medium
Area Expedition Conference
Notes ISI:A1997WG88200021 Approved no
Call Number BT @ hernan @ Serial 243
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Author Weiden, M.; Hauptmann, R.; Richter, W.; Geibel, C.; Hellmann, P.; Koppen, M.; Steglich, F.; Fischer, M.; Lemmens, P.; Guntherodt, G.; Krimmel, A.; Nieva, G.
Title (up) Magnetic phase diagram of CuGe1-xSixO3 Type Journal Article
Year 1997 Publication PHYSICAL REVIEW B Abbreviated Journal
Volume 55 Issue 22 Pages 15067-15075
Keywords
Abstract The effect of Si doping on the magnetic properties of the spin-Peierls (SP) system CuGeO3 was found to differ strongly between polycrystals (PC's) and single crystals (SC's). In SC's, the SP state is suppressed much mon strongly, whereas the existence region of the antiferromagnetic (AF) state is enhanced. We investigated the origin of this difference by means of magnetic susceptibility, specific heat, thermal expansion, Raman scattering, elastic neutron scattering, and x-ray measurements on CuGe1-xSixO3 samples prepared under different conditions. The partial oxygen pressure and the temperature during the synthesis were found to have a profound influence on the magnetic properties: preparation under reduced oxygen pressure leads to a stabilization of the AF state, whereas heating above the melting point results in a strong decrease of T-SP in Si-doped samples. Therefore, both the AF stabilization and the TSP reduction observed in SC's are not an intrinsic effect of Si doping PC samples, which can be prepared at lower temperatures and more oxidizing conditions, reflect much better the intrinsic properties of CuGe1-xSixO3. We were able to prepare PC samples up to 50 at. % Si and found a continuous decrease of the one-dimensional character of the magnetic properties without pronounced changes in the structure.
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Series Volume Series Issue Edition
ISSN 1098-0121 ISBN Medium
Area Expedition Conference
Notes ISI:A1997XF60200055 Approved no
Call Number BT @ hernan @ Serial 240
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Author Luzuriaga, J.
Title (up) Measurements in the laminar and turbulent regime of superfluid4He by means of an oscillating sphere Type Journal Article
Year 1997 Publication Journal of Low Temperature Physics Abbreviated Journal J. Low Temp. Phys.
Volume 108 Issue 3-4 Pages 267-277
Keywords Calculations; Laminar flow; Oscillations; Spheres; Turbulence; Turbulent flow; Vibrations (mechanical); Oscillating sphere; Translational oscillation; Superfluid helium
Abstract The translational oscillations of a sphere in liquid helium have been measured as a way of studying superfluid turbulence. Experiments were carried out in the laminar flow regime for reference purposes, and good agreement found between measured and calculated quantities. In the turbulent region, the dissipation is found to be proportional to the square of the velocity of the sphere, as found previously by other workers. For high vibration amplitudes there is an increase in the hydrodynamic mass. This seems to scale with the superfluid fraction in a way that strongly suggests that the superfluid component plays an important role in the turbulent regime.
Address Comisi
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ISSN 00222291 (ISSN) ISBN Medium
Area Expedition Conference
Notes Cited By (since 1996): 2; Export Date: 28 April 2009; Source: Scopus; CODEN: JLTPA; Language of Original Document: English; Correspondence Address: Luzuriaga, J.; Comisi Approved no
Call Number BT @ luzuriag @ Serial 518
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Author Bauer, E.; Hauser, R.; Keller, L.; Fischer, P.; Trovarelli, O.; Sereni, J.G.; Rieger, J.J.; Stewart, G.R.
Title (up) Onset of magnetic order in YbCu5-xAlx Type Journal Article
Year 1997 Publication Physical Review B Abbreviated Journal Phys. Rev. B
Volume 56 Issue 2 Pages 711-718
Keywords
Abstract Spectroscopic, magnetic, thermal, and transport measurements under pressure are presented which were performed on YbCu5-xAlx intermetallics. The substitution of Cu by Al in YbCu5 drives the system from an almost divalent behavior of the Yb ion in YbCu5 to a trivalent state in YbCu3Al2. A compensation between the normal thermal expansion and a valence-driven contraction was found for YbCu4Al. Antiferromagnetic order sets in for x>1.5, where an increasing Al content causes both a growing transition temperature and rising saturation moments reaching 2 K and about 2.1 mu(B), respectively, for x=2. At the critical concentration (x approximate to 1.5) the possibility of a non-Fermi-liquid state is analyzed together with its tuning by pressure.
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ISSN 0163-1829 ISBN Medium
Area Expedition Conference
Notes ISI:A1997XL82700035 Approved no
Call Number BT @ hernan @ Serial 91
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Author Trovarelli, O.; Sereni, J.G.; Kappler, J.P.
Title (up) Role of Ce sublattices in the thermal and magnetic properties of Ce7X3 (X=Ni, Ru, Rh, Ir, Pd, and Pt) compounds Type Journal Article
Year 1997 Publication Journal of Low Temperature Physics Abbreviated Journal J. Low. Temp. Phys.
Volume 108 Issue 1-2 Pages 53-85
Keywords
Abstract The role of the Ce sublattices in the thermal and magnetic properties of the Ce7X3 (X = Ni, Ru, Rh, Ir, Pd, and Pt) family of compounds is studied by means of ac and dc magnetic susceptibility, mngnetization and mainly specific-heat experiments in applied magnetic field. The experimental data show that in these compounds there is coexistence of magnetic order, heavy-fermion and intermediate-valence behavior, which is interpreted in terms of the contribution of the three different sublattices present in the crystalline structure of Th7Fe3-type (denoted by 1Ce(I), 3Ce(II) and 3Ce(III)). From the available volume of the Ce-III atoms in their crystallographic environment it is found that sublattice Ce-III has an intermediate-valence behavior, whereas from entropic considerations sublattices Ce-I and Ce-II are identified as responsible for the magnetic order or heavy-fermion behavior, depending on the Ce-ligand electronic structure. This systematics evidences a clear correlation between the thermal and magnetic properties of these compounds and the position of the respective Ce-ligands in the periodic table, through the particular sensitivity of Ce to the environmental conditions.
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Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0022-2291 ISBN Medium
Area Expedition Conference
Notes ISI:A1997XK19200004 Approved no
Call Number BT @ hernan @ Serial 92
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Author Sereni, J.G.; Geibel, C.; Berisso, M.G.; Hellmann, P.; Trovarelli, O.; Steglich, F.
Title (up) Scaling of the ''C-p proportional to TlnT'' dependence in Ce systems Type Journal Article
Year 1997 Publication Physica B – Condensed Matter Abbreviated Journal Physica B
Volume 230-232 Issue Pages 580-582
Keywords
Abstract We analyze the T ln T dependence of the specific heat (C-p) in several Ce binaries and ternaries. We find that these systems can be directly compared by using a scaling law of the type: C-p/t = -D log t + ET0, where t = T/T-0, with the scaling temperature T-0 similar to T-K, D = 7.2 J/(mol K) and 0 < E < 0.14 J/(mol K-2). This general function describes those systems within the 0.005 < t < 0.5 range and accounts for nearly 1/2 of the expected entropy of the Ce-doublet.
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Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0921-4526 ISBN Medium
Area Expedition Conference
Notes ISI:A1997WW40300168 Approved no
Call Number BT @ hernan @ Serial 93
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Author Goffman, Marcelo F.
Title (up) Vórtices en superconductores laminares de alta temperatura crítica Type Book Whole
Year 1997 Publication Abbreviated Journal
Volume Issue Pages
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Abstract
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Corporate Author Thesis Ph.D. thesis
Publisher Place of Publication Editor
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Notes Approved no
Call Number BT @ hernan @ Serial 323
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