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Author (up) Ale Crivillero, M.V.; Amigó, M.L.; Franco, D.G.; Badía-Majós, A.; Guimpel, J.; Nieva, G.
Title In Plane Vortex Dynamic Anisotropy in the Iron Deficient Fe_{1-y}Se Superconductor Type Journal Article
Year 2015 Publication Journal of Low Temperature Physics Abbreviated Journal J. Low Temp. Phys.
Volume 179 Issue 1-2 Pages 9-14
Keywords Iron-based superconductors; Electrical transport; Critical currents
Abstract We present electrical transport measurements in the superconducting dissipative state of crystalline iron deficient Fe 1−y Se samples. These iron deficient samples were synthesized using NaCl/KCl flux and are characterized by the presence of correlated defects. The dissipation in electrical transport experiments, when the driving current is perpendicular or parallel to the crystal planes, depends strongly on the direction of the applied magnetic field , ( H=12 T), within the sample plane. There is a dissipation modulation each 60∘ due to the presence of the correlated defects. We correlate these angular dependent features with the variation of the critical currents ( Jc ) changing the direction of H confined in the crystals planes. Jc was measured from magnetization loops at fixed temperatures and angles of H always within the basal planes.
Address
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 708
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Author (up) Amigó, M.L.; Ale Crivillero, M.V.; Franco, D.G.; Guimpel, J.; Nieva, G.
Title Influence of the Fe Concentration on the Superconducting Properties of Fe_{1-y}Se Type Journal Article
Year 2015 Publication Journal of Low Temperature Physics Abbreviated Journal
Volume 179 Issue 1-2 Pages 15-20
Keywords Chalcogenide; Vortex pinning; Correlated defects; Electrical transport; Fe deficiency
Abstract We present a comparative study of electrical transport properties in the normal state and in the dissipative superconducting state between pure TeX -FeSe phase and Fe deficient Fe TeX Se crystals. We discuss the influence of the intergrowth of the magnetic hexagonal phase (Fe TeX Se TeX ) in Fe deficient samples when compared to pure TeX -FeSe samples. In the superconducting state, we measured the TeX -plane electrical resistivity with magnetic field up to 16 T and the electrical resistivity as a function of the angle between the TeX axis and the applied field. The angular dependence at fixed temperature below the superconducting critical temperature, TeX , is very different for both sets of crystals. The Fe deficient samples display a vortex pinning-related feature at TeX 57 TeX off the plane while the pure TeX -FeSe phase samples show the persistence of a strong angular-dependent magnetoresistance characteristic of the normal state electronic structure.
Address
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 712
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Author (up) Betancourth, D.; Correa, V.F.; García, D.J.
Title Evidence of a Low Energy Anisotropy in GdCoIn_5 Type Journal Article
Year 2015 Publication Journal of Low Temperature Physics Abbreviated Journal J. Low Temp. Phys.
Volume 179 Issue 1-2 Pages 90-93
Keywords Rare earth magnetism; Antiferromagnetic transition; Anisotropy
Abstract We investigate the effects of an applied magnetic field on the magnetic properties of the antiferromagnet GdCoIn 5 . The prominent anisotropy observed in the susceptibility below TN is rapidly suppressed by a field of just a few Tesla. Further evidence of this low energy-scale is obtained from magnetoresistance and magnetostriction experiments. The lattice length, particularly, shows a sudden change below 2 T when the magnetic field is applied perpendicular to the crystallographic c^ -axis.
Address
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 710
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Author (up) Cejas Bolecek, N.R.; Dolz, M.I.; Kolton, A.; Pastoriza, H.; Beek, C.Jvander; Konczykowski, M.; Menghini, M.; Nieva, G.; Fasano, Y.
Title Geometrical Confinement Effects in Layered Mesoscopic Vortex Matter Type Journal Article
Year 2015 Publication Journal of Low Temperature Physics Abbreviated Journal J. Low Temp. Phys.
Volume 179 Issue 1-2 Pages 35-41
Keywords Vortex matter; Mesoscopic physics; Layered superconductors
Abstract We study the geometrical confinement effect in Bi 2 Sr 2 CaCu 2 O 8+δ mesoscopic vortex matter with edge-to-surface ratio of 7–12 %. Samples have in-plane square and circular edges, 30 μ m widths, and ∼ 2 μ m thickness. Direct vortex imaging reveals the compact planes of the structure align with the sample edge by introducing topological defects. The defect density is larger for circular than for square edges. Molecular dynamics simulations suggest that this density is not an out-of-equilibrium property but rather determined by the geometrical confinement.
Address
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 711
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Author (up) Cruz, F. de la; Fasano, Y.; Seta, M.D.; Menghini, M.; Pastoriza, H.
Title Plastic and Elastic Symmetry Transformations Induced in the Vortex Lattice of Anisotropic and Layered Superconductors Type Journal Article
Year 2004 Publication Journal of Low Temperature Physics Abbreviated Journal
Volume 135 Issue Pages 99-110
Keywords
Abstract We make a comparative analysis of the response of the three-dimensional vortex lattice in Bi$2$Sr$2$CaCu$8$ and NbSe$2$ to the presence of square arrays of pinning sites localized at one extremity of the vortex crystals. The absence of the hexagonal to square symmetry transformation and the induction of a distorted hexagonal symmetry in the vortex lattice of NbSe$2$ contrast to the observed symmetry change in Bi$2$Sr$2$CaCu$8$. The dissimilar response in both cases is explained taking into account the vortex structure solidification mechanisms in both materials: The plastic response in the case of the layered material Bi$2$Sr$2$CaCu$8$ is suggested to be a result of the simultaneity of solidification and coupling of bidimensional pancake vortices whereas a viscous solidification is the responsible for the three-dimensional elastic response in NbSe$_2$.
Address
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 ISBN Medium
Area Expedition Conference
Notes Approved no
Call Number BT @ hernan @ delacruz04 Serial 15
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Author (up) 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.
Address
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 (up) Encina, S.; Pedrazzini, P.
Title Low Temperature Thermoelectric Power of Ce(Pd{1-x}Cux)2Si2 Type Journal Article
Year 2015 Publication Journal of Low Temperature Physics Abbreviated Journal J. Low Temp. Phys.
Volume 179 Issue 1-2 Pages 21-27
Keywords Heavy fermions; Antiferromagnetic transition; Thermopower; Electrical resistivity
Abstract We present the thermoelectric power S(T) of the Ce(Pd 1−x Cu x ) 2 Si 2 alloy for temperatures \(1.5\,\mathrm{K} K. We observe three characteristic features across the \(0 substitution range: two positive maxima and a negative minimum, that are typical for Ce compounds that display, or lie close to, magnetism. Our analysis of the data shows that the high- T maximum is related to the Kondo effect on excited crystal-field levels, but that the low- T one cannot be simply associated with the Kondo scale, TK . We speculate that disorder induced by alloying can be at the origin of this discrepancy and can also be responsible for the low S(T) measured at low temperatures in the \(0.2 concentration range. We have extended electrical resistivity measurements on Ce(PdCu)Si 2 ( x=0.5 ) down to T∼40 mK in applied fields as high as 16 T.
Address
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 706
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Author (up) Guimpel, J.; de la Cruz, M.E.; de la Cruz, F.; Fink, H.J.; Laborde, O.; Villegier, J.C.
Title Size dependence of the Superconducting critical temperature and fields of Nb/Al multilayers Type Journal Article
Year 1986 Publication Journal of Low Temperature Physics Abbreviated Journal J. Low Temp. Phys.
Volume 63 Issue 1-2 Pages 151-165
Keywords
Abstract The critical temperatureT cof Nb/Al multilayers decreases as the total sample thicknessd Tis decreased while the thickness of each Nb and Al layer is kept constant. To understand this behavior, models based on the proximity effect and on weak two-dimensional (2D) localization are employed. The latter uses a characteristic length, the thermal diffusion length, in relation tod Tto obtain 2D behavior and leads to a reasonable explanation ofT c(d T). It is also found that the slope atT c(d T) of the critical magnetic field perpendicular to the layers is independent ofd Twhen the Nb and Al layer thicknesses are kept constant. The angular dependence of the critical field is also measured.
Address
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 0022-2291 ISBN Medium
Area Expedition Conference
Notes ISI:A1986C112200008 Approved no
Call Number BT @ hernan @ Serial 193
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Author (up) Guimpel, J.; Haberkorn, N.; Sirena, M.; Steren, L.B.; Saldarriaga, W.; Baca, E.; Gomez, M.E.
Title Interface effects in perovskite superlattices Type Journal Article
Year 2004 Publication JOURNAL OF LOW TEMPERATURE PHYSICS Abbreviated Journal
Volume 135 Issue 1-2 Pages 115-118
Keywords
Abstract The effect of interface disorder in perovskite superlattices, either with the substrate or between layers dominates the physics of the material, even when the lattice parameter of the component materials differs in less than 1%. Unexpected behavior emerges, like exchange bias in a system where no antiferromagnetic material has been included in the superlattice design.
Address
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 0022-2291 ISBN Medium
Area Expedition Conference
Notes ISI:000189139000012 Approved no
Call Number BT @ hernan @ Serial 166
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Author (up) Hernandez,A.; Ares,O.; Hart, C.; Domínguez,D.; Pastoriza,H.; Butera, A.
Title Dissipation in mesoscopic superconductors with ac magnetic fields Type Journal Article
Year 2004 Publication Journal of Low Temperature Physics Abbreviated Journal
Volume 135 Issue Pages 119-122
Keywords
Abstract The response of mesoscopic superconductors to an ac magnetic field is investigated both experimentally

and with numerical simulations. We study small square samples with dimensions of the order of the penetration depth.

We obtain the ac susceptibitity $\chi=\chi'+\chi“$ at microwave frequencies as a function of the dc magnetic field

$H{dc}$. We find that the dissipation, given by $\chi”$, has a non monotonous behavior in mesoscopic samples.

In the numerical simulations we obtain that the dissipation increases before the penetration of vortices and

then it decreases abruptly after vortices have entered, the sample. This is verified experimentally, where we

find that $\chi"$ has strong oscillations as a function of $H
{dc}$ in small squares of Pb
Address
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 ISBN Medium
Area Expedition Conference
Notes Approved no
Call Number BT @ hernan @ hernandez04 Serial 24
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