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Author Izbizky, M.A.; Núñez Regueiro, M.; Esquinazi, P.; Fainstein, C.
Title Thermal conductivity and superconductivity in EuBa2Cu3O7-x Type Journal Article
Year 1988 Publication Physical Review B Abbreviated Journal Phys. Rev. B
Volume 38 Issue 13 Pages (down) 9220-9223
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Publisher American Physical Society Place of Publication Editor
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Notes Approved no
Call Number BT @ pedrazp @ 10.1103/PhysRevB.38.9220 Serial 573
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Author Núñez Regueiro, M.; Castello, D.; Izbizky, M.A.; Esparza, D.; D'Ovidio, C.
Title Anomalous thermal conductivity of La2-xSrxCuO4: Possibility of a polaronic glass Type Journal Article
Year 1987 Publication Physical Review B Abbreviated Journal Phys. Rev. B
Volume 36 Issue 16 Pages (down) 8813-8815
Keywords
Abstract e present measurements of the thermal conductivity of La2CuO4 and La1.85Sr0.15CuO4. The results on the pure sample show that lattice conduction is predominant with a T1.8 dependence at low temperatures and a strong T-independent scattering above 30 K. We observe a similar behavior for the superconductor but with a T1.4 law at low temperature and a small electronic contribution in the normal state. These results together with the behavior of the specific heat and sound attenuation are consistent with the existence of a two-level tunneling system for an amorphous state.
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Publisher American Physical Society Place of Publication Editor
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Notes Approved no
Call Number BT @ pedrazp @ 10.1103/PhysRevB.36.8813 Serial 574
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Author Núñez Regueiro, M.; Esquinazi, P.; Izbizky, M.A.; Duran, C.; Castello, D.; Luzuriaga, J.; Nieva, G.
Title Evidence of tunneling systems through thermal and acoustic measurements in ceramic materials Type Journal Article
Year 1988 Publication Physica C: Superconductivity and its applications Abbreviated Journal Physica C
Volume 153-155 Issue PART 2 Pages (down) 1016-1017
Keywords Acoustic Variables Measurement--Wave Velocity; Ceramic Materials--Thermal Conductivity; Europium Barium Copper Oxides; Superconducting Materials
Abstract We have neasured the sound velocity, internal friction, thermal conductivity and specific heat of La-based and (Y/Eu)- based ceramics. The low temperature data can be understood in terms of the Tunneling Model assuming the existence of Tunneling Systems (TS). From these measured properties we obtain values for the parameter C=P?2/?v2, where P is the density of states of TS, ? the coupling constant between phonons and TS, ? the mass density and v the sound velocity close to those obtained for amorphous and “orientational” disordered crystalline materials. Our data would indicate that the TS are intrinsic defects independent of the sample porosity.
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ISSN 09214534 (ISSN) ISBN Medium
Area Expedition Conference International Conference on High Temperature Superconductors and Materials and Mechanisms of Superconductivity
Notes Export Date: 28 April 2009; Source: Scopus; CODEN: PHYCE; Language of Original Document: English; Correspondence Address: Regueiro, M.N.; Centro At Approved no
Call Number BT @ luzuriag @ Serial 496
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Author Castello, D.; Jaime, M.; Núñez Regueiro, M.
Title Thermal conductivity of high temperature superconductor TlBaCaCuO Type Journal Article
Year 1991 Publication Solid State Communications Abbreviated Journal Solid State Commun.
Volume 79 Issue 11 Pages (down) 967-970
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Abstract We have measured the thermal conductivity of ceramic samples of TlBaCaCuO between 2 and 250 K. At high temperatures it follows a constant behaviour down to the superconducting transition temperature where a sudden increase of the thermal conductivity occurs, attributed to reduced phonon scattering by condensating electrons. At low temperatures a T2 law is observed, confirming the assumption that it is a common feature in most of the high temperature superconducting oxides. Phonon scattering against tunneling systems analogous to those found in amorphous solids can explain this behaviour.
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Publisher Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0038-1098 ISBN Medium
Area Expedition Conference
Notes Approved no
Call Number BT @ pedrazp @ Serial 581
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Author Durán, C.; Esquinazi, P.; Fainstein, C.; Núñez Regueiro, M.
Title Anomalies in the internal friction and sound velocity in YBa2Cu3O7-x and EuBa2Cu3O7-x superconductors Type Journal Article
Year 1988 Publication Solid State Communications Abbreviated Journal Solid State Commun.
Volume 65 Issue 9 Pages (down) 957-961
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Abstract Internal friction Q-1 and Young Modulus sound velocity vE measurements at 1 kHz in YBa2Cu3O7?x and EuBa2Cu3O7?x polycrystalline samples reveal anomalies at the superconducting transition and at not, vert, similar37 K. The anomaly in vE at not, vert, similar90 K is accompanied by an absorption peak and is in agreement with published ultrasonic measurements, suggesting a lattice deformation at the superconducting transition.
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ISSN 0038-1098 ISBN Medium
Area Expedition Conference
Notes Approved no
Call Number BT @ pedrazp @ Serial 569
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Author Rodriguez, E.; Luzuriaga, J.; Núñez Regueiro, M.; Fainstein, C.
Title Low temperature internal friction peak in high Tc superconductors Type Journal Article
Year 1991 Publication Solid State Communications Abbreviated Journal Solid State Commun.
Volume 77 Issue 10 Pages (down) 777-780
Keywords Ceramic Materials; Oxides – Acoustic Properties; Yttrium Compounds – Acoustic Properties; Acoustic Variables Measurement; Attenuation Peak; Calcium Compounds; Low Temperature Internal Friction Peak; Strontium Compounds; Thermally Activated Relaxation Behavior; High Temperature Superconductors
Abstract We measure the internal friction Q-1 in YBa2Cu3O7-x and Bi2Sr2CaCu2O8+x samples. At temperatures near 35 K for KHz frequencies we observe an attenuation peak. In the case of YBa2Cu3O7-x, assuming a thermally activated relaxation behaviour, we are able to show that it corresponds to the same process as other peaks observed at higher frequencies. For Bi2Sr2CaCu2O8+x this is not the case, and the origin of the peak, found in all the measured samples, remains unknown.
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Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0038-1098 ISBN Medium
Area Expedition Conference
Notes ISI:A1991FA71400006 Approved no
Call Number BT @ hernan @ Serial 256
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Author Esquinazi, P.; Durán, C.; Fainstein, C.; Núñez Regueiro, M.
Title Evidence of low-energy tunneling excitations in the high-Tc superconductor YBa2Cu3O7-x Type Journal Article
Year 1988 Publication Physical Review B Abbreviated Journal Phys. Rev. B
Volume 37 Issue 1 Pages (down) 545-547
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Abstract We have measured the internal friction Q-1 and the Young's-modulus sound velocity vE at 1 kHz for YBa2Cu3O7-x. Below 20 K the relative change in the sound velocity and the temperature dependence of the internal friction perfectly resemble the behavior obtained for Suprasil W. Below 1 K we observe a logarithmic temperature dependence for the sound velocity and between 1 and 5 K a well-defined plateau in the internal friction is obtained. We find quantitative agreement with the predictions of the standard tunneling model which is widely used to explain the low-temperature properties of amorphous materials. The implications of the existence of tunneling systems in these materials are discussed.
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Publisher American Physical Society Place of Publication Editor
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Notes Approved no
Call Number BT @ pedrazp @ 10.1103/PhysRevB.37.545 Serial 576
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Author Núñez Regueiro, M.; Izbizky, M.A.; Esquinazi, P.
Title Thermal conductivity and “disorder” in high temperature superconductors Type Journal Article
Year 1988 Publication Solid State Communications Abbreviated Journal Solid State Commun.
Volume 67 Issue 4 Pages (down) 401-404
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Abstract We analyze the controversial thermal conductivity results on high temperature superconductors by scaling the data with material parameters to compare them to other materials with similar behaviour. We show that they have the same general features observed in amorphous and disordered crystalline materials. Possible origins of the disorder are discussed.
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Series Volume Series Issue Edition
ISSN 0038-1098 ISBN Medium
Area Expedition Conference
Notes Approved no
Call Number BT @ pedrazp @ Serial 583
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Author Núñez Regueiro, M.; Esquinazi, P.; Izbizky, M.A.; Durán, C.; Castello, D.; Luzuriaga, J.
Title Tunneling systems in high temperature superconductors Type Journal Article
Year 1988 Publication Annales de Physique Abbreviated Journal Ann. Phys. Fr.
Volume 13 Issue 5 Pages (down) 401-406
Keywords acoustic wave absorption; acoustic wave velocity; barium compounds; high temperature superconductors; lanthanum compounds; rare earth compounds; strontium compounds; superconductive tunnelling; thermal conductivity of solids; tunnelling systems; high temperature superconductors; thermal conductivity; sound attenuation; sound velocity; model; low temperature specific heat; La Sr Cu O
Abstract We have measured the thermal conductivity, sound attenuation and relative variation of sound velocity of compounds of the La-Sr-Cu-O and RBa2Cu3O7 families, where R is a rare-earth. We have found that all these properties can be quantitatively correlated within a tunneling system model similar to that used in amorphous materials. This interpretation would naturally explain the anomalous linear term of the low temperature specific heat observed in these materials.
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Series Editor Series Title Abbreviated Series Title
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ISSN 0003-4169 ISBN Medium
Area Expedition Conference
Notes ISI:A1988Q715000009 Approved no
Call Number BT @ hernan @ Serial 264
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Author Izbizky, M.A.; Núñez Regueiro, M.; Esquinazi, P.; Durán, C.; Fainstein, C.
Title Phonon transport in superconducting EuBa2Cu3O7-x Type Journal Article
Year 1988 Publication Physics Letters A Abbreviated Journal Phys. Lett. A
Volume 129 Issue 1 Pages (down) 71-75
Keywords
Abstract We have measured the thermal conductivity, Young modulus sound velocity and internal friction of a polycrystalline sample of the ceramic superconductor EuBa2Cu3O7-x. The low temperature data can be quantitavely understood assuming the interaction of phonons with tunneling systems.
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Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0375-9601 ISBN Medium
Area Expedition Conference
Notes Approved no
Call Number BT @ pedrazp @ Serial 571
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