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Author Morré, E.; Grigera, S.; Osquiguil, E.; Nieva, G.; de la Cruz, F.
Title (up) Angular restrictions on the glass transition and on the c-axis correlated liquid phase in twinned YBa2Cu3O7-? Type Journal Article
Year 1997 Publication Physics Letters A Abbreviated Journal Phys. Lett. A
Volume 233 Issue 1-2 Pages 130-134
Keywords
Abstract We have measured the angular dependence of the vortex velocity correlation temperature Tth(H) in twinned YBa2Cu3O7-? single crystals. The data show that the c-axis correlated vortex liquid phase exists up to angles much larger than expected within a single vortex pinning picture. Despite this, the second-order solid-liquid glass transition is shown to be restricted only to external magnetic fields applied within a few degrees from the c-axis direction.
Address Centro Atómico Bariloche
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ISSN 03759601 ISBN Medium
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Notes Cited By (since 1996): 13; Export Date: 17 April 2009; Source: Scopus; CODEN: PYLAA; Language of Original Document: English; Correspondence Address: Morr Approved no
Call Number BT @ osquigui @ Serial 381
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Author Kappler, J.P.; Besnus, M.J.; Haen, P.; Sereni, J.G.
Title (up) Ce ground state in CePd1-xNix Type Journal Article
Year 1997 Publication Physica B: Condensed Matter Abbreviated Journal Physica B
Volume 230-232 Issue Pages 162-164
Keywords
Abstract Alloying ferromagnetic CePd (Tc = 6.5 K) with the intermediate valence compound CeNi compresses the lattice, though the ferromagnetic order is present up to x = 0.94 in CePd1−xNix. We report here the competition of magnetic order and Kondo effect, through specific heat, magnetization and resistivity measurements. Detailed results gathered on the x = 0.95 sample show several features suggesting a non-Fermi liquid behaviour which may be due to the proximity to magnetic order: ϱ = ϱ0 + AT1.1 (3 < T ⩽ 30 K) and C/T ∝ − ln T(T ⩾ 0.9 K). At lower temperatures C/T tends to saturate at a value of 0.225 J/K2 mol, about three times the value observed for CeNi.
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Call Number BT @ pedrazp @ Serial 688
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Author Fernandez, G.E.; Berisso, M.G.; Trovarelli, O.; Sereni, J.G.
Title (up) Comparative study of the ferro-antiferromagnetic transition in Ce(Fe,Co)(2) and Ce(Fe,Al)(2) Type Journal Article
Year 1997 Publication Journal of Alloys and Compounds Abbreviated Journal J. Alloys Compd.
Volume 261 Issue 1-2 Pages 26-31
Keywords
Abstract The magnetic, thermal and transport properties of Ce(Fe,Co)(2) and Ce(Fe,Al)(2) around the ferro-antiferromagnetic (F-AF) transition are studied and compared in their thermodynamic aspects. We confirm the presence of a structural contribution to the enthalpy of the transition in the case of Co substitution, which is the main difference between the AF phase transitions in both systems. The role of the Ce hybridization in the Co case and the ''canted'' nature of the AF phase in Ce(Fe,Al)(2) are discussed. (C) 1997 Elsevier Science S.A.
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ISSN 0925-8388 ISBN Medium
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Notes ISI:A1997YE03600007 Approved no
Call Number BT @ hernan @ Serial 303
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Author Sereni, J.G.; Trovarelli, O.; Schmerber, G.; Kappler, J.P.
Title (up) Comparative study of thermal and magnetic properties of CeTyX4-y ferromagnets Type Journal Article
Year 1997 Publication Physical Review B – Condensed Matter and Materials Physics Abbreviated Journal Phys. Rev. B
Volume 56 Issue 9 Pages 5380-5386
Keywords
Abstract Low-temperature thermal (specific heat, C-P) and magnetic [ac susceptibility, chi(ac), and isothermal magnetization M(B)] measurements on CeTyX4-y ferromagnets (with T = Ni, Cu, Pd, Ag, Au, and X = Ga, Al, with 0.3 < y < 0.7) are reported. With the exception of T = Ni, all compounds with X = Ga show a typical second-order ferromagnetic transition. In the case of T = Ni, magnetic correlations set in at T approximate to 3T(C), (T-C being the Curie temperature) and the C-P(T) and chi(ac)(T) maxima (at 3.3 and 4.2 K, respectively) do not coincide, while the M(B) curves reveal an antiferromagnetic character at lower temperatures. In these systems, the magnetic entropy of the ordered phase is larger than 85% of Rln2, in coincidence with the low values of the Sommerfeld coefficient gamma less than or equal to 10 mJ/mol K-2. For T = Ag and X = Al, a strong diamagnetic signal was observed at T-s = 0.63 K in chi(ac)(T), with the characteristics of a superconducting component. The thermodynamical properties of these compounds confirm the lack of hybridization when the Ce atom is in a ferromagnetic ground state.
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ISSN 0163-1829 ISBN Medium
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Notes ISI:A1997XW94200062 Approved no
Call Number BT @ hernan @ Serial 89
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Author Pardo, F.; Mackenzie, A.P.; delaCruz, F.; Guimpel, J.
Title (up) Effect of the reversibility region on the low-temperature vortex structure imaged by Bitter magnetic decoration Type Journal Article
Year 1997 Publication PHYSICAL REVIEW B Abbreviated Journal
Volume 55 Issue 21 Pages 14610-14613
Keywords
Abstract We have combined magnetic measurements and imaging of the vortex lattice at low fields in Tl2Ba2CuO6-delta single crystals with different oxygen content. Those with high critical temperature T-c > 80 K have a reversible region while those with low T-c < 30 K have an irreversible magnetization in the whole range of temperatures, up to T-c. The presence of the reversible region allows the formation of ordered vortex structures, while amorphous structures are obtained when no reversible region is present below T-c. The results are discussed in terms of vortex nucleation processes in the individual pinning regime.
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ISSN 0163-1829 ISBN Medium
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Notes ISI:A1997XE37100086 Approved no
Call Number BT @ hernan @ Serial 187
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Author Righi, E.F.; Grigera, S.A.; Lopez, D.; Nieva, G.; delaCruz, F.; Civale, L.; Pasquini, G.; Levy, P.
Title (up) Enhancement of c-axis vortex correlation by twin boundaries and columnar defects in YBa2Cu3O7-delta Type Journal Article
Year 1997 Publication PHYSICAL REVIEW B Abbreviated Journal
Volume 55 Issue 9 Pages 5663-5665
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Abstract We report on transport measurements using the flux transformer configuration in a twinned single crystal of YBa2Cu3O7-delta with columnar defects. The vortex liquid shows velocity correlation along the c axis (the direction of the applied magnetic field and the columnar defects) at temperatures that correspond to an uncorrelated liquid in unirradiated samples of the same thickness. These results and previous work about the effect of twin boundaries on vortex velocity correlation show that phase coherence in the field direction is not an intrinsic property of vortex liquids but one induced by extended defects.
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ISSN 0163-1829 ISBN Medium
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Notes ISI:A1997WN21800036 Approved no
Call Number BT @ hernan @ Serial 242
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Author Pardo, Flavio
Title (up) Estructura estática y dinámica de la red de vórtices : decoración magnética y otras técnicas experimentales Type Journal Article
Year 1997 Publication Abbreviated Journal
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Corporate Author Thesis Ph.D. thesis
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Call Number BT @ hernan @ Serial 325
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Author Trovarelli, O.; Weiden, M.; MullerReisener, R.; GomezBerisso, M.; Gegenwart, P.; Deppe, M.; Geibel, C.; Sereni, J.G.; Steglich, F.
Title (up) Evolution of magnetism and superconductivity in CeCu2(Si1-xGex)(2) Type Journal Article
Year 1997 Publication Physical Review B – Condensed Matter and Materials Physics Abbreviated Journal Phys. Rev. B
Volume 56 Issue 2 Pages 678-685
Keywords
Abstract We have determined the magnetic phase diagram of CeCu2(Si1-xGex)(2) using specific heat, susceptibility, and resistivity measurements and additional thermal expansion and muon spin resonance experiments. The system evolves continuously from the heavy-fermion state at x = 0 to an antiferromagnetically (AF) ordered state at x = 1, though the magnetic structure undergoes significant modifications. The results strongly suggest that the AF ordering emerges from the A phase of pure CeCu2Si2. The phase diagram can be divided into three regions: Low Ge content (x less than or equal to 0.2) leads to an enhancement of the A phase of pure CeCu2Si2 and to a moderate decrease of the Kondo temperature. Despite this increase of the magnetic character, we could observe superconductivity up to x = 0.1. At large Ge content (x > 0.5) the behavior resembles that of pure CeCu2Ge2. The intermediate region is characterized by the appearance of a second magnetic transition below T-N, which seems to be of first-order type. The appearance of this transition leads to a well-defined critical point at x = 0.3 and suggests the possibility of another critical point at x = 0.5.
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ISSN 0163-1829 ISBN Medium
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Notes ISI:A1997XL82700031 Approved no
Call Number BT @ hernan @ Serial 90
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Author Righi, E.F.; Grigera, S.A.; Nieva, G.; Lopez, D.; delaCruz, F.
Title (up) Finite vortex correlation in the c direction in YBa2Cu3O7-delta above the first-order melting transition Type Journal Article
Year 1997 Publication PHYSICAL REVIEW B Abbreviated Journal
Volume 55 Issue 21 Pages 14156-14159
Keywords
Abstract The in- and out-of-plane resistivities of untwinned YBa2Cu3O7-delta show that at the melting temperature of the vortex lattice T-m(H), the c-axis vortex correlation length has a finite value, demonstrating that the first-order transition is a true melting and not a decoupling transition. The vortex liquid just above T-m(H) has a correlation length in the field direction on the order of a micron. The in-plane I-V characteristics in the liquid state show non-Ohmic behavior, providing evidence that thermal fluctuations dominate the response even at the first-order transition.
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ISSN 0163-1829 ISBN Medium
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Notes ISI:A1997XE37100033 Approved no
Call Number BT @ hernan @ Serial 241
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Author Guimpel, J.; Maiorov, B.; Osquiguil, E.; Nieva, G.; Pardo, F.
Title (up) Interrelation between persistent photoconductivity and oxygen order in GdBa2Cu3Ox thin films Type Journal Article
Year 1997 Publication Physical Review B – Condensed Matter and Materials Physics Abbreviated Journal Phys. Rev. B Condens. Matter Mater. Phys.
Volume 56 Issue 7 Pages 3552-3555
Keywords
Abstract We study the metastable states induced by photoexcitation, oxygen disorder, and both effects combined in superconducting GdBa2Cu3Ox thin films. The states are identified by the temperature dependence of the resistivity. The relaxation dynamics is characterized through the time evolution of the conductivity. The results show that photoexcitation and oxygen disorder behave as noninteracting and do not cancel each other out. However, in both cases the relaxation dynamics is related to oxygen movement .
Address Centro At
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ISSN 01631829 (ISSN) ISBN Medium
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Notes Cited By (since 1996): 21; Export Date: 17 April 2009; Source: Scopus; CODEN: PRBMD; Language of Original Document: English; Correspondence Address: Guimpel, J.; Centro At Approved no
Call Number BT @ osquigui @ Serial 382
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