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Author (up) Braun, E.; Bürger, A.; Nieva, G.L.; Roden, B.; Sereni, J.G.
Title Unexpected magnetic behaviour in a singlet crystal field ground state induced by Tb 4f-instability Type Journal Article
Year 1988 Publication Zeitschrift für Physik B Condensed Matter Abbreviated Journal Z. Phys. B
Volume 70 Issue 2 Pages 187-192
Keywords
Abstract The magnetic susceptibility (chi) of Th1-x Tb x alloys (with 5<x<55a/o Tb) in the range of 1 K<T<350K and the specific heat (forx=1.5a/o Tb) for 0.5<T<10 K were measured. A maximum in chi(T) was observed at a temperature which depends on concentration. The crystal field level scheme that fits the specific heat measurements shows two non-magnetic singlets as lowest levels. Such ambiguity is discussed within the framework of the 4f-Tb instability. The results are in agreement with the matrix superconductiveT c decrease. The contribution of the interconfigurational mixing on chi and the specific heat is also discussed.
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Corporate Author Thesis
Publisher Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0722-3277 ISBN Medium
Area Expedition Conference
Notes ISI:A1988M112900009 Approved no
Call Number BT @ hernan @ Serial 127
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Author (up) Braun, E.; Bürger, A.; Roden, B.; Sereni, J.G.
Title Spin glass-like behaviour of the singlet ground state system: ThTb Type Journal Article
Year 1988 Publication Solid State Communications Abbreviated Journal Solid State Commun.
Volume 66 Issue 11 Pages 1141-1144
Keywords
Abstract We have studied the temperature and field dependence of the magnetic susceptibility, X, on the single-ground-state Th1?nTbn system, in the 0.2 < n < 0.6 concentration range. The characteristic maximum of a spin glass transition was found at a temperature Tg, which increases linearly with the impurity concentration. As expected, the maximum of X is reduced by the increment of the applied magnetic field. The spin glass order parameter, as well as its critical exponent were evaluated by using the Sherrington-Kirkpatrick theory.
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Publisher Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0038-1098 ISBN Medium
Area Expedition Conference
Notes Approved no
Call Number BT @ pedrazp @ Serial 577
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Author (up) Braun, E.; Jackel, G.; Roden, B.; Sereni, J.G.; Wohlleben, D.
Title Comparative study of the specific heat of superconducting and non-superconducting YBa2Cu3O7-x Type Journal Article
Year 1988 Publication Zeitschrift für Physik B Condensed Matter Abbreviated Journal Z. Phys. B
Volume 72 Issue 2 Pages 169-173
Keywords
Abstract We have measured the specific heat, the electrical resistance and the magnetic susceptibility of YBa2Cu3O7−x in a superconducting (sc) and in a non-superconducting (nsc) version. The latter was obtained by inducing a small loss of oxygen. In the sc sample we find a jump of the specific heat with ΔC=3.6 J mole−1 K−1. Below the maximum nearT c the specific heat of the sc version drops too fast for an electronic effect alone: there is a cross-over from excess to deficiency already at 0.9T c . The specific heat of the nsc version shows a change of slope in the temperature range between 70 and 80 K, which indicates the existence of a second specific heat anomaly, which apparently exists independently of that due to the onset of superconductivity and explains at least partially the premature crossover.
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Corporate Author Thesis
Publisher Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0722-3277 ISBN Medium
Area Expedition Conference
Notes ISI:A1988P796500004 Approved no
Call Number BT @ hernan @ Serial 125
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Author (up) Causa, M. T.; Fainstein, C.; Nieva, G.; S\'anchez, R.; Steren, L. B.; Tovar, M.; Zysler, R.; Vier, D. C.; Schultz, S.; Oseroff, S. B.; Fisk, Z.; Smith, J. L.
Title Crystal-field interaction in the GdxEu1-xBa2Cu3O7-? superconductors Type Journal Article
Year 1988 Publication Physical Review B Abbreviated Journal Phys. Rev. B
Volume 38 Issue Pages 257-261
Keywords
Abstract We report here experimental data on the crystal-field interaction of gadolinium ions with their environment in GdxEu1-xBa2Cu3O7-?. The ESR spectrum and a Schottky anomaly in the specific heat of dilute samples (x?1) indicate the existence of a crystal-field splitting of the 8S7/2 ground state of Gd3+ ions of about 1.5 K. We discuss the parametrization of the measured splitting in terms of an effective Hamiltonian, and the microscopic origin of the interaction within the framework of a superposition model. Since the single-ion energies involved are of the same order of magnitude as the energies associated with the magnetic ordering of the Gd3+ moments in GdBa2Cu3O7-? (TN?2.24 K), we analyze the effects of the crystal-field interaction on the magnetic transition.
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Notes Approved no
Call Number BT @ gnieva @ Serial 433
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Author (up) Causa, M.T.; Dutrus, S.M.; Fainstein, C.; Nieva, G.; Sanchez, R.; Steren, L.B.; Tovar, M.; Zysler, R.; Oseroff, S.B.; Vier, D.C.; Schultz, S.; Fisk, Z.; Smith, J.L.
Title Magnetic ordering in dilute GdxEu1−xBa2Cu3O7−δ superconductors Type Journal Article
Year 1988 Publication Physica C: Superconductivity Abbreviated Journal Physica C
Volume 153 Issue Pages 188-189
Keywords
Abstract We have measured the specific heat of GdxEu1−xBa2Cu3O7−δ (0 ≤ × ≤ 1). The data show a λ-type anomaly at high concentrations and a broad Schottky type anomaly at intermediate and low concentrations. We compare this behavior with theoretical predictions for a 2-dimensional Ising system.
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Notes Approved no
Call Number BT @ gnieva @ Serial 432
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Author (up) Causa, M.T.; Fainstein, C.; Nieva, G.; Sánchez, R.; Steren, L. B.; Tovar, M.; Zysler, R.; Vier, D. C.; Schultz, S.; Oseroff, S. B.; Fisk, Z.; Smith, J. L.
Title Crystal Field Interaction and Magnetic Order in GdBa2Cu3O7 Type Book Chapter
Year 1988 Publication Progress in High Temperature Superconductivity Abbreviated Journal
Volume 5 Issue Pages
Keywords
Abstract
Address
Corporate Author Thesis
Publisher World Scientific Place of Publication N.J. Editor J. L. Heiras
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN ISBN 978-9971505837 Medium
Area Expedition Conference
Notes Approved no
Call Number BT @ gnieva @ Serial 430
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Author (up) Civale L.; Martinez, E. N.
Title Linear temperature dependence of the resistivity in the new superconductors Type Journal Article
Year 1988 Publication Physical Review B Abbreviated Journal Phys. Rev. B
Volume 38 Issue 1 Pages 928-930
Keywords
Abstract We present an elementary proof that, irrespective of dimensionality, the electrical resistivity of a simple conductor should be linear with temperature for T>2PFS / kB??D if PF?h? / a, where PF is the Fermi momentum, s the speed of sound, a the lattice constant, and ?D the Debye temperature.
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Corporate Author Thesis
Publisher American Physical Society Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
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ISSN ISBN Medium
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Notes Approved no
Call Number BT @ pedrazp @ 10.1103/PhysRevB.38.928 Serial 575
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Author (up) Durán, C.; Esquinazi, P.; Fainstein, C.; Núñez Regueiro, M.
Title Anomalies in the internal friction and sound velocity in YBa2Cu3O7-x and EuBa2Cu3O7-x superconductors Type Journal Article
Year 1988 Publication Solid State Communications Abbreviated Journal Solid State Commun.
Volume 65 Issue 9 Pages 957-961
Keywords
Abstract Internal friction Q-1 and Young Modulus sound velocity vE measurements at 1 kHz in YBa2Cu3O7?x and EuBa2Cu3O7?x polycrystalline samples reveal anomalies at the superconducting transition and at not, vert, similar37 K. The anomaly in vE at not, vert, similar90 K is accompanied by an absorption peak and is in agreement with published ultrasonic measurements, suggesting a lattice deformation at the superconducting transition.
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Publisher Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0038-1098 ISBN Medium
Area Expedition Conference
Notes Approved no
Call Number BT @ pedrazp @ Serial 569
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Author (up) Esquinazi, P.; Durán, C.
Title Magnetization and pinning measurements with the vibrating Reed on high-Tc ceramics Type Journal Article
Year 1988 Publication Physica C: Superconductivity Abbreviated Journal Physica C
Volume 153-155 Issue Part 3 Pages 1499-1500
Keywords
Abstract By means of the vibrating reed technique we have measured the lower critical field and the elastic coupling of vortices to pinning centers in La-Sr-Cu-O and Eu-Cu-O ceramics.our results indicate that the diamagnetism probed by the reed and the pinning scaling behaviour depend on the amount of oxygen in the La-based ceramic. In the Eu-based sample the lower critical field has a highly anomalous temperature dependence.
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Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0921-4534 ISBN Medium
Area Expedition Conference
Notes Proceedings of the International Conference on High Temperature Superconductors and Materials and Mechanisms of Superconductivity Part II Approved no
Call Number BT @ pedrazp @ Serial 531
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Author (up) Esquinazi, P.; Durán, C.; Fainstein, C.; Núñez Regueiro, M.
Title Evidence of low-energy tunneling excitations in the high-Tc superconductor YBa2Cu3O7-x Type Journal Article
Year 1988 Publication Physical Review B Abbreviated Journal Phys. Rev. B
Volume 37 Issue 1 Pages 545-547
Keywords
Abstract We have measured the internal friction Q-1 and the Young's-modulus sound velocity vE at 1 kHz for YBa2Cu3O7-x. Below 20 K the relative change in the sound velocity and the temperature dependence of the internal friction perfectly resemble the behavior obtained for Suprasil W. Below 1 K we observe a logarithmic temperature dependence for the sound velocity and between 1 and 5 K a well-defined plateau in the internal friction is obtained. We find quantitative agreement with the predictions of the standard tunneling model which is widely used to explain the low-temperature properties of amorphous materials. The implications of the existence of tunneling systems in these materials are discussed.
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Corporate Author Thesis
Publisher American Physical Society Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
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ISSN ISBN Medium
Area Expedition Conference
Notes Approved no
Call Number BT @ pedrazp @ 10.1103/PhysRevB.37.545 Serial 576
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