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Author Dolz, M.I.; Pedrazzini, P.; Pastoriza, H.; Konczykowski, M.; Fasano, Y.
Title Effect of Quenched Disorder in the Entropy-Jump at the First-Order Vortex Phase Transition of Bi{2}Sr{2}CaCu{2}O{8 + \delta } Type Journal Article
Year 2015 Publication Journal of Low Temperature Physics Abbreviated Journal J. Low Temp. Phys.
Volume 179 Issue 1-2 Pages 28-34
Keywords High Tc superconductors; First order vortex phase transition; Quenched disorder
Abstract We study the effect of quenched disorder in the thermodynamic magnitudes entailed in the first-order vortex phase transition of the extremely layered Bi 2 Sr 2 CaCu 2 O 8+δ compound. We track the temperature-evolution of the enthalpy and the entropy jump at the vortex solidification transition by means of AC local magnetic measurements. Quenched disorder is introduced to the pristine samples by means of heavy-ion irradiation with Pb and Xe producing a random columnar-track pins distribution with different densities (matching field BΦ ). In contrast with previous magneto-optical reports, we find that the first-order phase transition persists for samples with BΦ up to 100 Gauss. For very low densities of quenched disorder (pristine samples), the evolution of the thermodynamic properties can be satisfactorily explained considering a negligible effect of pinning and only electromagnetic coupling between pancake vortices lying in adjacent CuO planes. This description is not satisfactory on increasing magnitude of quenched disorder.
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Corporate Author Thesis
Publisher Springer US Place of Publication Editor
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 Approved no
Call Number BT @ pedrazp @ Serial 707
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Author Esparza, D.A.; D'Ovidio, C.A.; Guimpel, J.; Osquiguil, E.; Civale, L.; de la Cruz, F.
Title The granular nature of bulk superconductivity at 40K in La1.8Sr0.2CuO4 Type Journal Article
Year 1987 Publication Solid State Communications Abbreviated Journal Solid State Commun.
Volume 63 Issue 2 Pages 137-140
Keywords CERAMIC MATERIALS; GRANULAR MATERIALS; LANTHANUM COMPOUNDS – Electric Conductivity; CRITICAL FIELDS; HIGH TEMPERATURE SUPERCONDUCTOR; MAGNETIC FLUX EXPULSION; TEMPERATURE DEPENDENCE; SUPERCONDUCTING MATERIALS
Abstract We have measured the electrical resistivity, magnetic flux expulsion and critical fields of the new high temperature superconductor La1.8Sr0.2CuO4 after different heat treatments. Our data show that the complete flux expulsion in these samples is consistent with the presence of shielding currents induced in multiple connected structures. The magnetization measurements indicate that the lowest field where flux penetrates into the sample should not be taken to be the bulk Hcl. It is shown that the absolute value of the electrical resistivity and its temperature dependence are not correlated with the superconducting critical field and temperature. We discuss the behaviour of the superconducting parameters and their relation with the electrical resistivity.
Address Basic Research Department, Centro At
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 00381098 (ISSN) ISBN Medium
Area Expedition Conference
Notes Export Date: 17 April 2009; Source: Scopus; CODEN: SSCOA; Language of Original Document: English; Correspondence Address: Esparza, D.A.; Applied Research Department; Centro At Approved no
Call Number BT @ osquigui @ Serial 418
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Author Fasano, Y.; Szabó, P.; Kačmarčík, J.; Pribulová, Z.; Pedrazzini, P.; Samuely, P.; Correa, V.F.
Title Unconventional superconductivity in the strong-coupling limit for the heavy fermion system CeCoIn5 Type Journal Article
Year 2018 Publication Physica B: Condensed Matter Abbreviated Journal Physica B
Volume 536 Issue Pages 798-802
Keywords Heavy fermion superconductors; Scanning tunneling spectroscopy; Superconducting phase; Pseudogap phase
Abstract We present scanning tunneling spectroscopy measurements of the local quasiparticles' excitation spectra of the heavy fermion CeCoIn5 between 440mK and 3K in samples with a bulk Tc=2.25K. The spectral shape of our low-temperature tunneling data, quite textbook nodal-Δ conductance, allow us to confidently fit the spectra with a d-wave density of states considering also a shortening of quasiparticles' lifetime term Γ. The Δ(0) value obtained from the fits yields a BCS ratio 2Δ/kTc=7.73 suggesting that CeCoIn5 is an unconventional superconductor in the strong coupling limit. The fits also reveal that the height of coherence peaks in CeCoIn5 is reduced with respect to a pure BCS spectra and therefore the coupling of quasiparticles with spin excitations should play a relevant role. The tunneling conductance shows a depletion at energies smaller than Δ for temperatures larger than the bulk Tc, giving further support to the existence of a pseudogap phase that in our samples span up to T*∼1.2Tc. The phenomenological scaling of the pseudogap temperature observed in various families of cuprates, 2Δ/kT*∼4.3, is not fulfilled in our measurements. This suggests that in CeCoIn5 the strong magnetic fluctuations might conspire to close the local superconducting gap at a smaller pesudogap temperature-scale than in cuprates.
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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 0921-4526 ISBN Medium
Area Expedition Conference
Notes Approved no
Call Number BT @ pedrazp @ Serial 766
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Author Fernandes, A.; Chan, I.; Guimpel, J.; Nakamura, O.; Lederman, D.; Schuller, I.
Title Scaling of critical currents in high-temperature superconducting superlattices and thin films Type Journal Article
Year 1992 Publication Applied Physics Letters Abbreviated Journal Appl. Phys. Lett.
Volume 61 Issue 26 Pages 3181
Keywords High?Tc Superconductors; Thin Films; Superlattices; Critical Current; Temperature Dependence; Scaling Laws; Anisotropy
Abstract
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Corporate Author Thesis
Publisher Aip Place of Publication Editor
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Notes Approved no
Call Number BT @ jguimpel @ Serial 608
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Author Gonzalez, E.M.; Sefrioui, Z.; Maiorov, B.; Osquiguil, E.; Santamar
Title Effects of structural microdomains on the vortex correlation length in a-axis oriented EuBa2Cu3O7 thin films Type Journal Article
Year 2006 Publication Journal of Physics and Chemistry of Solids Abbreviated Journal J Phys Chem Solids
Volume 67 Issue 1-3 Pages 399-402
Keywords A. Superconductors; A. Thin films; B. Epitaxial growth; D. Superconductivity; D. Transport properties; Activation energy; Anisotropy; Epitaxial growth; Europium compounds; Magnetron sputtering; Superconductivity; Thin films; Transport properties; Anisotropic superconductors; Domain boundaries; Structural microdomains; Vortex correlation; Superconducting materials
Abstract We have grown a-axis oriented EuBa2Cu3O7 thin films on SrTiO3 (001) substrates using a magnetron sputtering technique. In these films the CuO2 planes are aligned parallel to the substrates. The film microstructure shows microdomains. The microdomains are grains with a 90
Address Centro At
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 00223697 (ISSN) ISBN Medium
Area Expedition Conference
Notes Export Date: 17 April 2009; Source: Scopus; CODEN: JPCSA; doi: 10.1016/j.jpcs.2005.10.093; Language of Original Document: English; Correspondence Address: Vicent, J.L.; Departamento F Approved no
Call Number BT @ osquigui @ Serial 364
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Author Haberkorn, N.; Suárez, S.; Bud'ko, S.L.; Canfield, P.C.
Title Strong pinning and slow flux creep relaxation in Co-doped CaFe2As2 single crystals Type Journal Article
Year 2020 Publication Solid State Communications Abbreviated Journal Solid State Commun.
Volume 318 Issue Pages 113963
Keywords Iron based superconductors; Single crystals; Vortex dynamics; Magnetization
Abstract We report on measurements of critical current densities Jc and flux creep rates S of freestanding Ca(Fe1−xCox)2As2 (x ≈ 0.033) single crystals with Tc ≈ 15.7 K by performing magnetization measurements. The magnetic field dependences of Jc at low temperature display features related to strong pinning. In addition, we find that the system displays small flux creep rates. The characteristic glassy exponent, μ, and the pinning energy, U0, display exceptional high values for pristine crystals. We find that for magnetic fields between 0.3 T and 1 T, μ decreases from ≈ 2.8 to ≈ 2 and U0 remains ≈ 300 K. Analysis of the pinning force indicates that the mechanism is similar to the observed in polycrystalline systems in which grain boundaries and random disorder produce the vortex pinning. Considering the large U0 observed in the single crystal, we attempt to improve the pinning by adding random point disorder by 3 MeV proton irradiation with a fluence of 2 × 1016 proton/cm2. The results show that, unlike other iron-based superconductors, the superconducting fraction is sharply reduced by irradiation. This fact indicates that the superconductivity in the system is extremely fragile to an increment in the disorder. The superconducting volume fraction in the irradiated crystal systematically recovers after removal disorder by thermal annealing, which evidences as to the observation of critical state in curves of magnetization versus magnetic field. No features related to a reentrant antiferromagnetic transition are observed for the irradiated sample.
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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 859
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Author Haberkorn, N.; Suárez, S.; Pérez, P.D.; Troiani, H.; Granell, P.; Golmar, F.; Lee, J.-H.; Moon, S.H.
Title Effect of mixed pinning landscapes produced by 6 MeV oxygen irradiation on the resulting critical current densities Jc in 1.3 µm thick GdBa2Cu3O7-d coated conductors grown by co-evaporation Type Journal Article
Year 2017 Publication Physica C: Superconductivity and its Applications Abbreviated Journal Physica C
Volume 542 Issue Pages 6-11
Keywords Coated conductors; Vortex dynamics; Glassy exponents; Irradiation
Abstract We report the influence of crystalline defects introduced by 6 MeV 16O3+ irradiation on the critical current densities Jc and flux creep rates in 1.3 µm thick GdBa2Cu3O7-δ coated conductor produced by co-evaporation. Pristine films with pinning produced mainly by random nanoparticles with diameter close to 50 nm were irradiated with doses between 2 × 1013 cm−2 and 4 × 1014 cm−2. The irradiations were performed with the ion beam perpendicular to the surface of the samples. The Jc and the flux creep rates were analyzed for two magnetic field configurations: magnetic field applied parallel (H║c) and at 45° (H║45°) to the c-axis. The results show that at temperatures below 40 K the in-field Jc dependences can be significantly improved by irradiation. For doses of 1 × 1014 cm−2 the Jc values at μ0H = 5 T are doubled without affecting significantly the Jc at small fields. Analyzing the flux creep rates as function of the temperature in both magnetic field configurations, it can be observed that the irradiation suppresses the peak associated with double-kink relaxation and increases the flux creep rates at intermediate and high temperatures. Under 0.5 T, the flux relaxation for H‖c and H||45° in pristine films presents characteristic glassy exponents μ = 1.63 and μ = 1.45, respectively. For samples irradiated with 1 × 1014 cm−2, these values drop to μ = 1.45 and μ = 1.24, respectively
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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 0921-4534 ISBN Medium
Area Expedition Conference
Notes Approved no
Call Number BT @ pedrazp @ Serial 771
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Author Herbsommer, J.A.; Luzuriaga, J.; Cheong, S.-W.
Title Vortex glass melting in single crystal La1.825 Sr0.075CuO4 Type Journal Article
Year 1996 Publication Physica C Abbreviated Journal Physica C
Volume 258 Issue 1-2 Pages 169-174
Keywords Copper compounds; Crystal lattices; Frequency response; Glass; Magnetic field measurement; Magnetic permeability measurement; Melting; Phase diagrams; Single crystals; Temperature; Vortex flow; AC susceptibility; Cuprates; Pinned flux lattice; Oxide superconductors
Abstract The vortex phase diagram in single crystalline La1.85Sr0.075CuO4 has been studied using an AC-susceptibility technique. A peak in the out-of-phase (x?) component of the susceptibility indicates a transition from a pinned flux lattice (FLL) to an unpinned one. This peak is frequency dependent for all the values of the magnetic field measured (0.01 to 4 T), and this, as well as the general behavior found in the cuprates, has prompted us to interpret our data as evidence for a vortex-glass to liquid transition in the FLL. The activation energies obtained can be fitted to a theory developed by Vinokur et al. Measurements with the magnetic field at an angle with the Cu-O planes may also be understood qualitatively within this framework.
Address AT and T Bell Laboratories, Murray Hill, NJ, United States
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ISSN 09214534 (ISSN) ISBN Medium
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Notes Cited By (since 1996): 2; Export Date: 28 April 2009; Source: Scopus; CODEN: PHYCE; doi: 10.1016/0921-4534(95)00812-8; Language of Original Document: English; Correspondence Address: Luzuriaga, J.; Centro At Approved no
Call Number BT @ luzuriag @ Serial 483
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Author Hofer, J.A.; Bengio, S.; Haberkorn N.
Title Effect of Gd magnetic impurities on the superconducting properties of highly disordered molybdenum nitride microstrips Type Journal Article
Year 2023 Publication Applied Physics A Abbreviated Journal Appl. Phys. A
Volume 129 Issue 9 Pages 631
Keywords Disordered superconductors; Metal nitrides; Magnetic impurities
Abstract We investigated the impact of Gd magnetic impurities on the superconducting properties of disordered MoNx thin films grown by reactive co-sputtering at room temperature. The samples were fabricated in the two gun cluster using Mo and Gd targets in an Ar + N2 atmosphere with a total pressure of 0.67 Pa and a N2 concentration of 7%. The study focuses in thin films with thickness between 22 and 27 nm. We modified the chemical composition by varying the power of the Gd target from 0 to 24 W, fixing the Mo in 100 W. The chemical state of the samples was analysed using X-ray Photoelectron Spectroscopy. The samples primarily exhibit an amorphous metallic Mo and Gd nitride structure. With the addition of Gd, the superconducting critical temperature is suppressed, dropping from 7.4 K for pure MoNx to below 3 K for samples containing ≈ 4.5 at.% Gd. Furthermore, the temperature dependence of the upper critical field (Hc2) and the vortex dissipation mechanism are also affected. Specifically, Hc2(0) is reduced from 10 to 7.7 T for samples with 3.1 at.% Gd. Moreover, at a temperature of 3 K, there is an increase in the magnetic field dependence of the critical current density for low Gd doping. These alterations also impact the instability of the vortex lattice, limiting the maximum achievable vortex velocity during dissipation.
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Notes Approved no
Call Number BT @ pedrazp @ Serial 890
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Author Kim, J.; Haberkorn, N.; Gofryk, K.; Graf, M.J.; Ronning, F.; Sefat, A.S.; Movshovich, R.; Civale, L.
Title Superconducting properties in heavily overdoped Ba(Fe0.86Co0.14)2As2 single crystals Type Journal Article
Year 2015 Publication Solid State Communications Abbreviated Journal Solid State Commun.
Volume 201 Issue Pages 20-24
Keywords A. Iron arsenide superconductors; B. Upper critical field; C. Magnetic penetration depth; D. Vortex pinning
Abstract Abstract

We report the intrinsic superconducting parameters in a heavily overdoped Ba(Fe1−xCox)2As2 (x=0.14) single crystal and their influence in the resulting vortex dynamics. We find a bulk superconducting critical temperature of 9.8 K, magnetic penetration depth λab (0)=660±50 nm, coherence length ξab (0)=6.4±0.2 nm, and the upper critical field anisotropy γT→Tc≈3.7. The vortex phase diagram, in comparison with the optimally doped compound, presents a narrow collective creep regime. The intrinsic pinning energy plays an important role in the resulting vortex dynamics as compared with similar pinning landscape and comparable intrinsic thermal fluctuations.
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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 724
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