| Records |
| Author |
Steren, L.B.; Sirena, M.; Guimpel, J. |
| Title |
Magnetic ordered phase in La0.6Sr0.4MnO3 ferromagnets |
Type |
Journal Article |
| Year |
2002 |
Publication |
PHYSICAL REVIEW B |
Abbreviated Journal |
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Volume  |
65 |
Issue |
9 |
Pages |
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| Abstract |
The ferromagnetic phase of La0.6Sr0.4MnO3 thin films has been investigated through measurements of magnetization loops at different temperatures, zero-field-cooled and field-cooled magnetization curves obtained under different magnetic fields. We have found that the main sources of the “bulk” coercivity in manganite films are the film/substrate interface and film surface. The temperature dependence of the coercivity is described by a “strong domain-wall pinning” model, independently of the thickness and substrate. The magnetization-vs-temperature curves, measured under different magnetic fields (10 Oe<H<2.5 kOe), have been explained in terms of the magnetic hysteresis of the films. We find no evidence of glass states or of the existence of single-domain clusters, as suggested by other authors. |
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| ISSN |
1098-0121 |
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| Notes |
ISI:000174547900096 |
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no |
| Call Number |
BT @ hernan @ |
Serial |
172 |
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| Author |
Sirena, M.; Steren, L.B.; Guimpel, J. |
| Title |
Magnetic relaxation in bulk and film manganite compounds |
Type |
Journal Article |
| Year |
2001 |
Publication |
PHYSICAL REVIEW B |
Abbreviated Journal |
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| Volume |
64 |
Issue |
10 |
Pages |
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| Abstract |
We have investigated the time dependence of the magnetic and transport properties of La0.6Sr0.4MnO3 films and bulk samples. A significant magnetic aftereffect has been observed in all the samples through magnetization and resistivity measurements. The relaxation effects can be described by the addition of a logarithmic to an exponential contribution. The weight of each contribution is strongly temperature dependent, with a relaxation that is predominantly logarithmic at low temperatures (T<30 K) and exponential at high temperatures (T>100 K). As the film thickness is decreased the magnetic relaxation becomes more important and the magnetic viscosity of the system increases. These results point out the important role of structural defects in the magnetic relaxation of the samples. |
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0163-1829 |
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| Notes |
ISI:000170978400046 |
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no |
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BT @ hernan @ |
Serial |
173 |
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| Author |
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 |
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| 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. |
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0022-2291 |
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ISI:A1986C112200008 |
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no |
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BT @ hernan @ |
Serial |
193 |
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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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00381098 (ISSN) |
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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 |
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BT @ osquigui @ |
Serial |
418 |
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| Author |
Fainstein, A.; Maiorov, B.; Guimpel, J.; Nieva, G.; Osquiguil, E. |
| Title |
Annealing disorder and photoinduced order of oxygen chains in detwinned YBa2Cu3O6.65 single crystals probed by Raman scattering |
Type |
Journal Article |
| Year |
2000 |
Publication |
Physical Review B – Condensed Matter and Materials Physics |
Abbreviated Journal |
Phys. Rev. B Condens. Matter Mater. Phys. |
| Volume |
61 |
Issue |
6 |
Pages |
4298-4304 |
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| Abstract |
Raman scattering in detwinned YBa2Cu3O6.65 single crystals is studied as a function of photoexcitation and annealing. Copper-oxygen chain-related forbidden Raman bands that are known to strongly bleach with illumination at low temperatures, increase their intensity with chain fragmentation induced by annealing at high temperature. This contrasting behavior proves the conjunction of short Cu-O fragments into longer chains on photoexcitation. We interpret the Raman modes as due to vibrations at the end of CuO chain fragments and Cu-O-Cu monomers, and use their evolution with illumination and annealing as anisotropic sensitive markers of oxygen reordering processes. The identification of the “forbidden” Raman bands is discussed in the context of our results and recent literature in the subject. We also present absorption measurements performed on GdBa2Cu3Ox thin films with varying oxygen content. These experiments show that the 2.2-eV absorption and the chain-related Raman peaks have different dependencies with oxygen content and illumination, ruling out an explanation that suggests that the Raman intensity reduction of these modes is due to a photobleaching of intermediate defect states. These results highlight the potentialities of Raman scattering for oxygen dynamics studies and demonstrate the presence of photoinduced oxygen ordering in these high-Tc superconductor compounds. |
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Centro At |
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01631829 (ISSN) |
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Cited By (since 1996): 18; Export Date: 17 April 2009; Source: Scopus; CODEN: PRBMD; Language of Original Document: English; Correspondence Address: Fainstein, A.; Centro At |
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no |
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BT @ osquigui @ |
Serial |
374 |
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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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Aip |
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no |
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BT @ jguimpel @ |
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608 |
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| Author |
Nakamura, O.; Guimpel, J.; Sharifi, F.; Dynes, R.; Schuller, I. |
| Title |
Synthesis and properties of a-axis and b-axis oriented GdBa2Cu3O7-d high Tc thin films |
Type |
Journal Article |
| Year |
1992 |
Publication |
Applied Physics Letters |
Abbreviated Journal |
Appl. Phys. Lett. |
| Volume |
61 |
Issue |
21 |
Pages |
2598 |
| Keywords |
Gadolinium Oxides; Barium Oxides; Copper Oxides; Quaternary Compounds; High?Tc Superconductors; Film Growth; Sputtering; Magnetrons; Crystal Orientation; Control; Temperature Effects; X?Ray Diffraction |
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Aip |
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no |
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BT @ jguimpel @ |
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609 |
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| Author |
Nieva, G.; Osquiguil, E.; Guimpel, J.; Maenhoudt, M.; Wuyts, B.; Bruynseraede, Y.; Maple, M.B.; Schuller, I.K. |
| Title |
Photoinduced enhancement of superconductivity |
Type |
Journal Article |
| Year |
1992 |
Publication |
Applied Physics Letters |
Abbreviated Journal |
Appl. Phys. Lett. |
| Volume |
60 |
Issue |
17 |
Pages |
2159-2161 |
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| Abstract |
We show clear and conclusive experimental evidence for the enhancement of superconductivity in GdBa2Cu3Ox and YBa 2Cu3Ox thin films by photoexcitation. Upon laser illumination the critical temperature increases while the resistivity of the material decreases. The relaxation back to the original state is very slow, of the order of days at room temperature. The existence of this effect opens the possibility of fabricating weak-link devices with in situ tunable superconducting characteristics. |
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Laboratorium voor Vaste Stof-Fysika en Magnetisme, Katholieke Universiteit Leuven, B3001 Leuven, Belgium |
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00036951 (ISSN) |
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Cited By (since 1996): 61; Export Date: 17 April 2009; Source: Scopus; doi: 10.1063/1.107069; Language of Original Document: English; Correspondence Address: Nieva, G.; Physics Department-0319; University of California-San Diego San Diego, CA 92093-0319, United States |
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no |
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BT @ osquigui @ |
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404 |
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| Author |
Nakamura, O.; Fullerton, E.; Guimpel, J.; Schuller, I. |
| Title |
High Tc thin films with roughness smaller than one unit cell |
Type |
Journal Article |
| Year |
1992 |
Publication |
Applied Physics Letters |
Abbreviated Journal |
Appl. Phys. Lett. |
| Volume |
60 |
Issue |
1 |
Pages |
120 |
| Keywords |
High?Tc Superconductors; Thin Films; Superlattices; Epitaxy; Magnetrons; Sputtering; Roughness; Thickness |
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no |
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BT @ jguimpel @ |
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610 |
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| Author |
Nakamura, O.; Chan, I.; Guimpel, J.; Schuller, I. |
| Title |
New buffer layer for high?temperature superconducting ceramics on sapphire: LaBa2Cu3Oy/Ag bilayers |
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Journal Article |
| Year |
1991 |
Publication |
Applied Physics Letters |
Abbreviated Journal |
Appl. Phys. Lett. |
| Volume |
59 |
Issue |
10 |
Pages |
1245 |
| Keywords |
Superconducting Films; Fabrication; High?Tc Superconductors; Lanthanum Oxides; Barium Oxides; Copper Oxides; Silver; Superconducting Junctions; Superconductivity; Dysprosium Oxides; Sputtering; Sapphire; Crystal Structure; Crystal Growth; Very High Temperature |
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no |
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BT @ jguimpel @ |
Serial |
611 |
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