High Temperature Superconductors
Mostrando 13-24 de 36 artigos, teses e dissertações.
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13. Unconventional magnetic properties of cuprates
Recently experiments on high critical temperature superconductors have shown that the doping levels and the superconducting gap are usually not uniform properties but strongly dependent on their positions inside a given sample. We show here that the large diamagnetic signal above the critical temperature Tc and the unusual temperature dependence of the upper
Brazilian Journal of Physics. Publicado em: 2003-12
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14. Superconductivity in magnetically ordered Ru1-xIr xSr2GdCu2O8 compounds
We have performed a systematic study of the structural, transport, and magnetic properties of polycrystalline samples of the magnetic superconductors Ru1-xIr xSr2GdCu2O8; x = 0, 0.02, 0.05, 0.10, and 0.15. The samples were prepared by solid state reaction and sintered at 1060 ºC for 72 h under O2 flow. X-ray diffraction analysis shows that all samples are n
Brazilian Journal of Physics. Publicado em: 2003-12
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15. ESTUDO DA FUSÃO E SOLIDIFICAÇÃO DA FASE BI-2212 E SEUS MECANISMOS DE SUPERCONDUÇÃO / STUDY OF BI-2212 PHASE MELTING AND SOLIDIFICATION AND ITS SUPERCONDUCTING MECHANISMS
High temperature superconductivity was discovered in 1986. Since then more than 150 new superconductors (cuprates, bismuthates, borides and fullerite) with critical temperature higher then 23,3K (the highest critical temperature for low temperature superconductors) have been synthesized. Many of them rise interest from the scientific viewpoint and are suitab
Publicado em: 2003
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16. ProduÃÃo e estudo da microestrutura e propriedade mecÃnica da cerÃmica Ba2HoZrO5,5 a base de zircÃnia para fabricaÃÃo de cadinhos de alta temperatura
In view of the need of use of crucibles for sintering and crystal growth of advanced ceramics in high temperature furnaces, a study has been realized on a new complex cubic perovskite oxide ceramic Ba2HoZrO5,5 based on zirconium in the Ba-H-Zr-O system. Complex perovskites, which have generally A2BBâO6 or A3B2BâO9 type composition, result by ordering of B
Publicado em: 2003
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17. Cooper pairing and superconductivity in a spin fluctuation model for high-Tc cuprate superconductors
We study the formation of Cooper pairs in high-Tc cuprate superconductors within a spin uctuation model for doped quantum Heisenberg antiferromagnets. The charge of the dopants (chargons) is associated to quantum skyrmion excitations of the Cu++ antiferromagnetic spin background. We then compute the quantum skyrmion e effective interaction potential as a fun
Brazilian Journal of Physics. Publicado em: 2002-09
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18. A novel percolation theory for high temperature superconductors
We present a percolation theory for the high-Tc oxides pseudogap and Tc dependence on the hole level. The doping dependent inhomogeneous charge structure is modeled by a distribution which may represent the stripe morphology and yield a spatial distribution of local Tc(r). The temperature onset of spatial dependent superconducting gap is identified with the
Brazilian Journal of Physics. Publicado em: 2002-09
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19. Development of Bulk Bi2+xSr3-yCa yCu 2O8+delta Superconductors by Partial-Melting Route for Fault Current Limiters Application
The production of bulk Bi2+xSr3-yCa yCu 2O8+delta (Bi-2212) superconductors for fault current limiter application was developed via a partial-melting route. Aiming high Ic (critical current), which is the essential superconducting characteristic for application of this material in the construction of Fault Current Limiters (FCL), the produced blocks have pre
Materials Research. Publicado em: 2002-06
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20. Comportamento de vortices em cupratos supercondutores e transição tipo supercondutor-isolante em grafite
In this thesis we have studied dynamics and pinning properties of the vortex matter in high temperature superconductors. It is found that the second magnetization peak (SMP) effect, an increase in the magnetization hysteresis loop width in Bi2212 single crystals vanishes with decreasing the crystal size. We showed that this effect is not related to the criti
Publicado em: 2002
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21. Critical Behavior of High Temperature Superconductors
We consider the scaling behavior in the critical domain of superconductors at zero external magnetic field. The Josephson's relation for a charged superfluid is proved without assuming the hyperscaling relation. On the other hand we discuss the dual Ginzburg-Landau model. In this dual model, due to the presence of two mass scales, a continuous family of non
Brazilian Journal of Physics. Publicado em: 2001-06
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22. Dinamica de Vortices Josephson em monocristais supercondutores de Bi2Sr2CaCu2O8 e ferromagnetismo em compostos supercondutores de Nb-Pt
We have studied the dynamics of Josephson vortices ( JV) and Abrikosov pancake vortices (PV) in Bi2Sr2CaCu208 Bi(2212) superconducting single crysta1s and a1so the possibility of ferromagnetism in A -15 : Nb -Pt superconducting compounds. The anomalous depinning of Josephson interlayer vortices in Bi2Sr2CaCu208 high -Tc superconductors occurring at nearly fi
Publicado em: 2001
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23. Construction of and auto-balanced ac suceptometer and study of eletronic conductor polymers for magnetic susceptibility and magnetic resonance. / Construção de um Susceptômetro AC Autobalanceado e Estudo de Polímeros Condutores Eletrônicos por Susceptibilidade Magnética e Ressonância Magnética.
A mutual inductance bridge which may be used for automatic measurement of ac magnetic susceptibilities from 4 K to room temperature, at frequencies up to 1 kHz, is described. The susceptometer employs an alternative and new arrangement for the probe. The coil set is kept at room temperature and moves in such a way to place the sample in the center of each of
Publicado em: 1998
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24. Propriedades magneticas e de transporte em monocristais dos supercondutores dopados com eletrons Ln2-x Cex CuO4-y (Ln=Nd, Sm, Pr)
The magnetic and transport properties of the electron-doped high temperature superconductors, Ln2-xCexCuO4-y (Ln = Nd, Sm, Pr), were investigated. A significant part of the study was conducted with single crystal samples. For this purpose a process for growing high quality single crystal using the flux method was developed. We observe that the superconductin
Publicado em: 1993