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Author TROVARELLI, O.; SERENI, J.G.; SCHMERBER, G.; KAPPLER, J.P.
Title Low-temperature magnetic and thermal properties of CePdSb Type Journal Article
Year 1994 Publication Physical Review B – Condensed Matter and Materials Physics Abbreviated Journal Phys. Rev. B
Volume 49 Issue 21 Pages (down) 15179-15183
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Abstract Low-temperature ac and dc magnetic susceptibility, high-field magnetization, and specific-heat measurements have been carried out on CePdSb. The magnetic measurements confirm the ferromagnetic transition at T(C) = 17 K as previously reported. However, no anomaly in the specific heat is observed at that temperature, but only the onset of the magnetic contribution, C(M)(T). The maximum of C(M)(T) is observed at T(max) = 9.7 K. The lack of a C(M)(T) jump at T(C) is discussed in terms of the comparison of the exchange integrals between first- and second-nearest magnetic neighbors. Depending on their relative values, the magnetic structure can behave as low dimensional or incommensurate. The entropy of the magnetic phase (Rln2) and the low density of states (gamma = 11 mJ/mol K2) excludes a Kondo-lattice character for this compound.
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ISSN 0163-1829 ISBN Medium
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Notes ISI:A1994NR42500043 Approved no
Call Number BT @ hernan @ Serial 106
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Author López, D.; Nieva, G.; de la Cruz, F.; Jensen, Henrik Jeldtoft; O’Kane, Dominic
Title Flux cutting in YBa2Cu3O7-δ single crystals: Experiment and phenomenological model Type Journal Article
Year 1994 Publication Physical Review B Abbreviated Journal Phys. Rev. B
Volume 50 Issue Pages (down) 9684
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Abstract We measured the current-induced loss of vortex correlation in YBa2Cu3O7-δ crystals using the pseudo-dc-flux-transformer geometry. We find that the current density Jcut at which the top and bottom voltage drops differ is a linear function of temperature, is independent of pinning, and depends on the thickness of the sample. This thickness dependence strongly suggests that the electrical current flows at the surface of the sample. The observed behavior with temperature, magnetic field, and thickness is described by a phenomenological model.
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Call Number BT @ gnieva @ Serial 445
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Author López, D.; Nieva, G.; de la Cruz, F.
Title In- and out-of-plane vortex correlations in YBa2Cu3O7 Type Journal Article
Year 1994 Publication Physical Review B Abbreviated Journal Phys. Rev. B
Volume 50 Issue Pages (down) 7219
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Call Number BT @ gnieva @ Serial 444
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Author Sereni, J.G.; Kappler, J.P.
Title A comparison between volume and electronic concentration effects in Ce transformations Type Journal Article
Year 1994 Publication Journal of Physics: Condensed Matter Abbreviated Journal J. Phys.: Condens. Matter.
Volume 6 Issue 25 Pages (down) 4771-4777
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Abstract The crossover from magnetic to non-magnetic ground states in Ce compounds is analysed within the competition between the on-site and inter-site interactions proposed by Doniach. The comparison of the evolution of the ordering temperature, as a function of pressure and alloying, was performed in more than twenty Ce systems. This systematic shows that volume (Delta V) and electronic concentration (Delta Z) effects, as the driving forces for such a transformation, present different characteristics. The maximum in the ordering temperature (T-o), predicted by the model, is only observed under Delta V effects (induced by alloying or by pressure) and not under Delta Z variations. This study leads to the conclusion that the maximum in T-o cannot be considered intrinsic to a complete magnetic to non-magnetic transformation, but rather is a consequence of the Ce-Ce spacing decrease, before the wavefunction overlap turns on the hybridization mechanism.
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ISSN 0953-8984 ISBN Medium
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Notes ISI:A1994NT76300015 Approved no
Call Number BT @ hernan @ Serial 105
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Author Osquiguil, E.; Maenhoudt, M.; Wuyts, B.; Bruynseraede, Y.; Lederman, D.; Schuller, I.K.
Title Photoexcitation and oxygen ordering in YBa2Cu3Ox films Type Journal Article
Year 1994 Publication Physical Review B Abbreviated Journal
Volume 49 Issue 5 Pages (down) 3675-3678
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Abstract We report on the photoinduced enhancement of the critical temperature ?Tc and the in-plane conductivity ??ab measured in a c-axis-oriented YBa2Cu3Ox film as a function of oxygen concentration (6.4?x?7). Both ?Tc and ??ab decrease with the oxygen content, display a plateaulike behavior for 6.6?x?6.75, and become zero at x=7. This dependence of ?Tc on x is similar to that observed for the Tc enhancement due to ordering effects in oxygen-deficient YBa2Cu3Ox single crystals. We propose that the persistent photoinduced changes in YBa2Cu3Ox films are due to photoassisted oxygen ordering.
Address Physics Department-0319, University of California-San Diego, San Diego, CA 92093-0319, United States
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ISSN 01631829 (ISSN) ISBN Medium
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Notes Cited By (since 1996): 86; Export Date: 17 April 2009; Source: Scopus; doi: 10.1103/PhysRevB.49.3675; Language of Original Document: English; Correspondence Address: Osquiguil, E.; Laboratorium Voor Vaste Stof-Fysika en Magnetisme; Katholieke Universiteit Leuven; Celestijnenlaan 200 D B-3001 Leuven, Belgium Approved no
Call Number BT @ osquigui @ Serial 385
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Author van Dalen, A.J.J.; Griessen, R.; Libbrecht, S.; Osquiguil, E.; Bruynseraede, Y.
Title Observation of quantum creep in oxygen deficient YBa2Cu3O7-? at fields up to 7 T Type Journal Article
Year 1994 Publication Physica C: Superconductivity and its applications Abbreviated Journal Phys C Supercond Appl
Volume 235-240 Issue PART 5 Pages (down) 2959-2960
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Abstract Superconducting current densities js and dynamic relaxation rates Q ? d ln js/d ln (dBe/dt) in an oxygen deficient YBa2Cu3O7-? epitaxial film were measured as a function of temperature (1.5K < T < Tirr) in magnetic fields up to 7 T by means of high sensitivity capacitance torquemeters. Below 5 K, the relaxation rate remains high and does not extrapolate to Q = 0 at T = 0K. This is associated to the quantum tunneling of vortices through the energy barrier separating two adjacent vortex configurations. In the case of ohmic dissipation the quantum creep rate is proportional to the normal state resistivity ?{variant}n(0) at T = 0 K. In order to check this theoretical prediction we measured Q as a function of the oxygen content of the sample. The quantum creep rate increases systematically with increasing ?{variant}n(0). However, Q remains finite even when ?{variant}n = 0.
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Notes Export Date: 17 April 2009; Source: Scopus; CODEN: PHYCE; Language of Original Document: English; Correspondence Address: van Dalen, A.J.J.; Faculty of Physics and Astronomy; Free University 1081 HV Amsterdam, Netherlands Approved no
Call Number BT @ osquigui @ Serial 393
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Author H. Pastoriza, M. F. Goffman, A. Arribére, and F. de la Cruz
Title First order phase transition at the irreversibility line of Bi$2$Sr$2$CaCu$_2$O8+? Type Journal Article
Year 1994 Publication Phys. Rev. Lett. Abbreviated Journal
Volume 72 Issue 18 Pages (down) 2951-2954
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Abstract Magnetization and susceptibility measurements show a first order phase transition in the magnetic flux structure at the irreversibility line of Bi2Sr2CaCu2O8+ delta single crystals, in the field range 0<H<360 Oe. The resistivity in the c direction drops 5 orders of magnitude in less than 0.1 K, and there is a discontiuous change in the magnetization at the same temperature. The change in magnetization together with the Clausius-Clapeyron equation gives a variation of entropy of 0.06kB per vortex layer, at the transition. Above 360 Oe the irreversibility line has the known frequency dependence.
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Call Number BT @ hernan @ pastoriza94e Serial 34
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Author Libbrecht, S.; van Dalen, A.J.J.; Wuyts, B.; Maenhoudt, M.; Gao, Z.X.; Osquiguil, E.; Griessen, R.; Bruynseraede, Y.
Title Magnetic properties of oxygen deficient Yba2Cu3Ox thin films Type Journal Article
Year 1994 Publication Physica C: Superconductivity and its applications Abbreviated Journal Phys C Supercond Appl
Volume 235-240 Issue PART 5 Pages (down) 2889-2890
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Abstract We have invesitgated several superconducting properties of oxygen defiecient YBa2Cu3Ox thin films, with oxygen contents ranging from x = 6.55 to x = 7. By means of torque magnetometry, the temperature dependence of the superconducting current dendity js and relaxation rate of the magnetization Q is measured in an (almost perpendicular) applied magnetic induction of 0.6 T. As the oxygen content is reduced, js decreases, whereas Q increases. Both properties are influenced by the decreased dpoing level as well as the enhanced anisotropy of oxygen depleted YBa2Cu3Ox. Using the Generalixed Inversion Scheme derived by Schnak et al. we obtain the current dependence of the activation energy U(f). We show that U(j) is lowered when the oxygen content is reduced.
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Notes Export Date: 17 April 2009; Source: Scopus; CODEN: PHYCE; Language of Original Document: English; Correspondence Address: Libbrecht, S.; Laboratorium voor Vaste-Stoffysika en Magnetisme; Katholieke Universiteit B-3001 Leuven, Belgium Approved no
Call Number BT @ osquigui @ Serial 387
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Author Galván, D. H.; Avalos-Borja, M.; Farías, M. H.; Cota-Araiza, L.; Reyes, A.; Cruz-Reyes, J.; Early, E. A.; Nieva, G.; De Andrade, M.; Maple, M. B.
Title Effect of silver in Y1Ba2Cu3O7−x samples Type Journal Article
Year 1994 Publication Journal of Materials Science Abbreviated Journal
Volume 29 Issue 10 Pages (down) 2713-2718
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Abstract Two techniques for preparing Y-Ba-Cu-O/Ag specimens are presented: (a) solid-state reaction, and (b) normal precursors dissolved in hot concentrated nitric acid and dried in air. The samples are characterized by scanning electron microscopy (SEM), scanning Auger, X-ray diffraction, optical microscopy and electrical resistivity measurements. In comparison with a normal 1-2-3 superconductor it was found that the normalized resistance [R(T)/R(280 K)] decreases for both preparation methods. The material retained a high initial temperature of superconductivity, T c, for a maximum of 6% w/o Ag2O during solid-state reaction and 6.5% w/o Ag2O for samples dissolved in hot concentrated nitric acid and dried in air.
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Publisher Springer Netherlands Place of Publication Editor
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ISSN 0022-2461 ISBN Medium
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Notes Approved no
Call Number BT @ gnieva @ Serial 449
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Author Safar, H.; Lopez, D.; Gammel, P.L.; Huse, D.A.; Majumdar, S.N.; Schneemeyer, L.F.; Bishop, D.J.; Nieva, G.; de la Cruz, F.
Title Experimental evidence of a non-local resistivity in a vortex line liquid Type Journal Article
Year 1994 Publication Physica C: Superconductivity Abbreviated Journal Physica C
Volume 235-240 Issue 4 Pages (down) 2581-2582
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Abstract We present transport measurements on YBCO single crystals in the vortex liquid regime using the DC flux transformer geometry. We show that the data are inconsistent with the material being an anisotropic, local conductor. The results provided evidence for non-local transport which indicate that there can be correlated vortex motion over macroscopic distances in this system. We have shown that this correlated vortex motion can be destroyed by either thermal fluctuations or the applications of large driving forces.
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Call Number BT @ gnieva @ Serial 450
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