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Author |
Herbsommer, Juan A. |
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Title |
Dinámica y estática de vórtices en superconductores de alta temperatura crítica con defectos correlacionados |
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Book Whole |
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Year |
2000 |
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Instituto Balseiro |
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Ph.D. thesis |
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Call Number  |
BT @ hernan @ |
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328 |
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Author |
Pedrazzini, P.; Schmerber, G.; Berisso, M.G.; Kappler, J.P.; Sereni, J.G. |
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Title |
Magnetic and superconducting properties of A(7)B(3) compounds (A = Th or La and B=Ni, Co, Fe or Pd, Rh, Ru) |
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Journal Article |
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Year |
2000 |
Publication |
PHYSICA C |
Abbreviated Journal |
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Volume |
336 |
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1-2 |
Pages |
10-18 |
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High-temperature magnetization, low temperature specific heat, and ac-susceptibility measurements on Th7X3 (X = Ni, Co, and Fe) and La(7)Z(3) (Z = Pd, Rh, and Ru) superconductors are presented. The magnetic behaviour of the Th7X3 group has the characteristics of Pauli paramagnets. The La(7)Z(3) group also shows Pauli paramagnetism for Z = Pd and Ru, and signs of spin fluctuations for La7Rh3. Specific heat (C-p) measurements indicate a conventional BCS behaviour for La7Pd3 and La7Rh3, like that of the previously measured Th7X3 superconductors. in the case of La7Ru3, the reduced specific heat jump at the transition, the anomalous temperature dependence of C-p under magnetic field and a large upper critical field slope are discussed. (C) 2000 Elsevier Science B.V. All rights reserved. |
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0921-4534 |
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ISI:000088047500002 |
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Call Number  |
BT @ hernan @ |
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78 |
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Author |
Sereni, J.G. |
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Title |
Evanescence of magnetic transitions in Ce systems |
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Journal Article |
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Year |
2000 |
Publication |
Physica B – Condensed Matter |
Abbreviated Journal |
Physica B |
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281-282 |
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337-339 |
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Three types of magnetic phase diagrams can be identified in Ce systems: (I) with ordering temperature T-ord --> 0 continuously, followed by a narrow non-Fermi-liquid (NFL) region, (II) with T-ord vanishing at finite temperature, followed by an extended NFL region, and (III) where the degrees of freedom condensed into the ordered phase decreases, without a concomitant decrease of T-ord. Intrinsic differences are found in the way that the degrees of freedom condense at T-ord and from the rising of the specific heat tails above T-ord. (C) 2000 Elsevier Science B.V. All rights reserved. |
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0921-4526 |
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ISI:000086570200141 |
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BT @ hernan @ |
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79 |
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Author |
Silhanek, K.; Guimpel, J.; Civale, L.; Lanza, H.; Levy, P. |
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Title |
Thickness effects on the pinning by columnar defects |
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Journal Article |
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Year |
2000 |
Publication |
PHYSICA C |
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Volume |
341 |
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Pages |
1217-1218 |
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We compare the angular dependence of the pinning of equivalent columnar defects in GdBa2Cu2O7 thin films and a thicker YBa2Cu3O7 single crystal. The tracks' related enhancement of the critical currents is much smaller for the case of the thin films. We interpret this thickness dependence as resulting from a competition between the pinning of the correlated structures, related to total sample thickness, and surface boundary conditions, which force the vortices to depin from the columnar defects near the sample surface. |
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0921-4534 |
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ISI:000165855700208 |
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no |
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BT @ hernan @ |
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175 |
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Author |
Sirena, M.; Steren, L.; Guimpel, J. |
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Title |
Thickness dependence of the properties of La0.6Sr0.4MnO3 thin films |
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Journal Article |
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Year |
2000 |
Publication |
Thin Solid Films |
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Volume |
373 |
Issue |
1-2 |
Pages |
102-106 |
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We have studied the thickness dependence of the transport and magnetic properties of strongly textured La0.6Sr0.4MnO3 thin films grown on MgO and SrTiO3, for thickness between 5 and 500 nm. While the resistivity and the magnetoresistance are strongly affected, the magnetization is only moderately changed. The effect on the metal-insulator transition, the low field magnetoresistance and carrier localization is dependent on the substrate, evidencing the effect of the induced defects and strains. (C) 2000 Elsevier Science S.A. All rights reserved. |
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0040-6090 |
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ISI:000090045900024 |
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no |
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BT @ hernan @ |
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176 |
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Author |
Steren, L.B.; Sirena, M.; Guimpel, J. |
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Title |
Substrate effect on the magnetic behavior of manganite films |
Type |
Journal Article |
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Year |
2000 |
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JOURNAL OF APPLIED PHYSICS |
Abbreviated Journal |
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Volume |
87 |
Issue |
9 |
Pages |
6755-6757 |
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The film thickness (t) dependence of the magnetic properties of La0.6Sr0.4MnO3 (LSMO) films grown on (001) MgO and (001) SrTiO3 substrates has been studied. Hysteresis loops measured at low temperature show a smooth increase of the retentivity accompanied by a decrease of the coercitive field as the film thickness increases. The increase of coercitivity with decreasing t can be interpreted in terms of a change in the domain structure of the films mainly due to an augmentation of domain pinning defects. The magnetic anisotropy has been measured using ferromagnetic resonance (FMR). A volume (VA) and a surface (SA) anisotropy contribution have been deduced from FMR angular dependence studies for both series of samples. In the LSMO films grown on MgO a VA component that corresponds to an easy-axis perpendicular to the plane of the films has been found while in contrast, the LSMO films grown on SrTiO3 present an easy-plane anisotropy. The SA is positive for both series favoring a perpendicular magnetic anisotropy. The measured magnetic anisotropy has been assigned to substrate-induced effects. (C) 2000 American Institute of Physics. [S0021-8979(00)55708-9]. |
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0021-8979 |
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ISI:000086728800281 |
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no |
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Call Number  |
BT @ hernan @ |
Serial |
178 |
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Author |
Steren, L.B.; Sirena, M.; Guimpel, J. |
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Title |
Substrate influence on the magnetoresistance and magnetic order in La0.6Sr0.4MnO3 films |
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Journal Article |
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Year |
2000 |
Publication |
JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS |
Abbreviated Journal |
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Volume |
211 |
Issue |
1-3 |
Pages |
28-34 |
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We report structural, magnetic and transport measurements on La0.6Sr0.4MnO3 thin films grown on MgO and TiSrO3 substrates with thickness varying from 5 to 500 nm. We find that the lattice mismatch between substrates and films affects the morphology and induced-strains of the films. We show that these two different effects strongly influence the ferromagnetic order, the metal-insulator transition, the localization of the current carriers and the magnetoresistance of these materials. (C) 2000 Elsevier Science B.V. All rights reserved. |
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0304-8853 |
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ISI:000085772100006 |
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no |
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BT @ hernan @ |
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179 |
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Author |
Fasano, Y.; Menghini, M.; de la Cruz, F.; Nieva, G. |
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Title |
Weak interaction and matching conditions for replicas of vortex lattices |
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Journal Article |
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Year |
2000 |
Publication |
PHYSICAL REVIEW B |
Abbreviated Journal |
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Volume |
62 |
Issue |
22 |
Pages |
15183-15189 |
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We present experiments demonstrating the conditions under which weak interaction between replicas of vortex structures break their translational and rotational symmetry. The Fe clumps introduced by Bitter decorations of vortex structures are used to induce an extremely weak interaction fur subsequent vortex structures in low and high temperature superconducting crystals. The matching between the Fe pattern acid the vortex configuration require the structure to be prepared under quite stringent conditions: The field creating the structure has to be the same in magnitude although it can differ in orientation from that used for the preparation of the Fe pattern. The interaction between vortex replicas as represented by the Fe clumps of Bitter decorations makes it possible to differentiate the vortex nucleation and propagation mechanisms in low and high temperature superconductors. |
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0163-1829 |
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ISI:000165883800075 |
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no |
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BT @ hernan @ |
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219 |
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Author |
Herbsommer, J.A.; Nieva, G.; Luzuriaga, J. |

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Title |
Reproducibility of the disordered vortex structure in twinned single crystals of YBCO |
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Journal Article |
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Year |
2000 |
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Physica C |
Abbreviated Journal |
Physica C |
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341 |
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1087-1088 |
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Bitter decorations of the vortices in twinned single crystal YBCO have been obtained to study the disordered structure formed on successive cooldowns of the sample under the same conditions of field and temperature. Between succesive decorations, the iron dots could be removed completely, giving a surface clean enough for further decoration. It was found that successive realizations of the disordered vortex state were very similar at long range, and differed mostly on short scales, compared to the average vortex separation. We have quantified the correlation between successive structures, and double sided decorations have been also performed to compare with the extent of spatial correlation in the applied field direction. The coincidence of the position of the vortices in successive realizations of the structure, is unexpected, and indicates an unusual behavior for a glassy system. Our technique makes it possible to image the position of the vortices in detail and repeatedly, providing us with a model amorphous system in which to study the reproducibility of the disordered structure. |
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0921-4534 |
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ISI:000165855700143 |
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BT @ hernan @ |
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220 |
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Author |
Correa, V.F.; Herbsommer, J.A.; Kaul, E.E.; de la Cruz, F.; Nieva, G. |
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Title |
Onset of the 0-dimensional vortex pinning behavior in the optimally doped and overdoped Bi2Sr2CaCu2O8+delta system |
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Journal Article |
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Year |
2000 |
Publication |
PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS |
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341 |
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1285-1286 |
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We report results of transverse AC magnetic permeability in the linear regime and DC magnetization loops for optimally doped and oxygen overdoped samples of Bi2Sr2CaCu2O8+delta The data cover the low temperature (T < 25K) and low held (H-a < 1000 Oe) region of the magnetic (H-a-T) phase diagram. In optimally doped as well as in overdoped samples a crossover to a O-dimensional pinning regime (Larkin length, L-C(C), shorter than the inter-plane CuO2 distance) is observed at a characteristic temperature Too for all investigated fields. The order-disorder transition, identified by the second peak in magnetization and a non monotonous field dependence of the AC penetration depth, is quenched below T-0D. |
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0921-4534 |
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ISI:000165855700242 |
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BT @ hernan @ |
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221 |
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