| Records |
| 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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| Publisher |
Springer US |
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| ISSN |
0022-2291 |
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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 |
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| ISSN |
00381098 (ISSN) |
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| 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 |
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no |
| Call Number |
BT @ osquigui @ |
Serial |
418 |
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| Author |
Fasano, Y.; Szabó, P.; KaÄmarÄík, 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 |
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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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Edition |
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| ISSN |
0921-4526 |
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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 |
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| Publisher |
Aip |
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no |
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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 |
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Edition |
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00223697 (ISSN) |
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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 |
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no |
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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 |
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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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Edition |
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| ISSN |
0038-1098 |
ISBN |
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no |
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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 |
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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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Edition |
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| ISSN |
0921-4534 |
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Approved |
no |
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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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09214534 (ISSN) |
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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 |
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no |
| Call Number |
BT @ luzuriag @ |
Serial |
483 |
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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 |
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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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0038-1098 |
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no |
| Call Number |
BT @ pedrazp @ |
Serial |
724 |
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| Author |
L |
| Title |
Dynamic softening of vortex lines in YBa2Cu3O7-? single crystals |
Type |
Journal Article |
| Year |
1996 |
Publication |
Physica C: Superconductivity and its Applications |
Abbreviated Journal |
Phys C Supercond Appl |
| Volume |
260 |
Issue |
3-4 |
Pages |
211-216 |
| Keywords |
Crystal defects; Magnetic anisotropy; Magnetic couplings; Mathematical models; Single crystals; Transport properties; Vortex flow; Yttrium compounds; Dynamic softening; Flux transformer configuration; Pinning potential; Transport measurements; Vortex correlation; Vortex line; Yttrium barium cuprates; High temperature superconductors |
| Abstract |
Transport measurements in the mixed state of oxygen-deficient YBa2Cu3O7-? single crystals using the flux transformer configuration show that the flux liquid changes with increasing anisotropy from strongly correlated to uncorrelated in the field direction. For intermediate coupling, the current inducing loss of vortex correlation has a maximum near the irreversibility temperature. Thus, an effective softening of vortex lines with decreasing temperature is detected. We propose a simple model that accounts for this behavior by including the effects of the pinning potential on the dynamics of vortices. |
| Address |
Comn. Nac. de Ener. At |
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09214534 (ISSN) |
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| Notes |
Cited By (since 1996): 4; Export Date: 17 April 2009; Source: Scopus; CODEN: PHYCE; Language of Original Document: English; Correspondence Address: Righi, E.F.; Comn. Nac. de Ener. At |
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BT @ osquigui @ |
Serial |
384 |
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