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Transition conductivity study of high temperature superconductor compounds: the role of fluctuations; Etude de la transition resistive sur des composes supraconducteurs a haute temperature critique le role des fluctuations

Thesis/Dissertation:

Abstract

This memory subject is the transition conductivity study of high temperature superconductors in corelation with their anisotropy. Systematic conductivity measurements were made on YBaCuO and BaSrCaCuO in relation with temperature from 4.2 K to 1200 K, and with a magnetic field up to 8 T in several directions. Oxygen order has an effect on the characteristics at YBaCuO transition conductivity. The activation energy for oxygen absorption is about 0.5eV. One method of analysis of the conductivity fluctuations about the transition temperature is proposed. Two separate rates are noticeable in YBaCuO compound. The 3 D fluctuations rate in the immediate neighbourghood of the transition lets place to the 2 D fluctuations rate at high temperature. Transitions temperatures governing each rate are different, that`s incompatible with the formula proposed by Lawrence and Doniach. On the other hand, the analogy with quasi-2 D magnetic systems seems more relevant. A magnetic field application or a lowering of oxygen concentration removes the 3 D fluctuations rate. Non ohmic effects observed at the transition conductivity foot are analysis as a non-linear 2 D excitation manifestation of the supraconductive phase. Finally, by measurements on strontium doped YBaCuO crystals, we confirm a metal-insulator transition along the C-Axe when  More>>
Authors:
Publication Date:
Apr 01, 1991
Product Type:
Thesis/Dissertation
Report Number:
FRCEA-TH-349
Reference Number:
SCA: 360207; 665411; PA: FRD-91:003745; SN: 92000621292
Resource Relation:
Other Information: TH: These (D. es Sc.)Thesis; PBD: Apr 1991
Subject:
36 MATERIALS SCIENCE; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; HIGH-TC SUPERCONDUCTORS; FLUCTUATIONS; ELECTRIC CONDUCTIVITY; YTTRIUM OXIDES; BISMUTH OXIDES; BARIUM OXIDES; COPPER OXIDES; TRANSITION TEMPERATURE; QUANTITY RATIO; STRONTIUM OXIDES; CALCIUM OXIDES; HEAT TREATMENTS; OXYGEN; 360207; 665411
OSTI ID:
10104880
Research Organizations:
CEA Centre d`Etudes de Grenoble, 38 (France); Grenoble-1 Univ., 38 (France)
Country of Origin:
France
Language:
French
Other Identifying Numbers:
Other: ON: DE92743645; TRN: FR9103745
Availability:
OSTI; NTIS (US Sales Only)
Submitting Site:
FRN
Size:
168 p.
Announcement Date:
Jun 30, 2005

Thesis/Dissertation:

Citation Formats

Pagnon, V. Transition conductivity study of high temperature superconductor compounds: the role of fluctuations; Etude de la transition resistive sur des composes supraconducteurs a haute temperature critique le role des fluctuations. France: N. p., 1991. Web.
Pagnon, V. Transition conductivity study of high temperature superconductor compounds: the role of fluctuations; Etude de la transition resistive sur des composes supraconducteurs a haute temperature critique le role des fluctuations. France.
Pagnon, V. 1991. "Transition conductivity study of high temperature superconductor compounds: the role of fluctuations; Etude de la transition resistive sur des composes supraconducteurs a haute temperature critique le role des fluctuations." France.
@misc{etde_10104880,
title = {Transition conductivity study of high temperature superconductor compounds: the role of fluctuations; Etude de la transition resistive sur des composes supraconducteurs a haute temperature critique le role des fluctuations}
author = {Pagnon, V}
abstractNote = {This memory subject is the transition conductivity study of high temperature superconductors in corelation with their anisotropy. Systematic conductivity measurements were made on YBaCuO and BaSrCaCuO in relation with temperature from 4.2 K to 1200 K, and with a magnetic field up to 8 T in several directions. Oxygen order has an effect on the characteristics at YBaCuO transition conductivity. The activation energy for oxygen absorption is about 0.5eV. One method of analysis of the conductivity fluctuations about the transition temperature is proposed. Two separate rates are noticeable in YBaCuO compound. The 3 D fluctuations rate in the immediate neighbourghood of the transition lets place to the 2 D fluctuations rate at high temperature. Transitions temperatures governing each rate are different, that`s incompatible with the formula proposed by Lawrence and Doniach. On the other hand, the analogy with quasi-2 D magnetic systems seems more relevant. A magnetic field application or a lowering of oxygen concentration removes the 3 D fluctuations rate. Non ohmic effects observed at the transition conductivity foot are analysis as a non-linear 2 D excitation manifestation of the supraconductive phase. Finally, by measurements on strontium doped YBaCuO crystals, we confirm a metal-insulator transition along the C-Axe when oxygen concentration reduces. This is connected with the specific heat jump. All these results uplighten the fundamental bidimensional character of high transition temperature superconductivity.}
place = {France}
year = {1991}
month = {Apr}
}