Staff View: Effect of Ge4+ and Mg2+ doping on superconductivity, fluctuation induced conductivity and interplanar coupling of TlSr 2CaCu2O7-δ superconductors

Effect of Ge4+ and Mg2+ doping on superconductivity, fluctuation induced conductivity and interplanar coupling of TlSr 2CaCu2O7-δ superconductors

Substitution of Ge4+ in place of Cu in Tl0.85Cr 0.15Sr2CaCu2-xGexO 7-δ (x = 0-0.6) showed initial increase in zero critical temperature value, Tc zero from 98 K (x = 0) to 100 K (x = 0.1) and in the range of 85-86 K for x = 0.2-0.3. The slow decrease in Tc zero is unexpected as tetravalent Ge4+ subs...

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Main Authors:	Ali Yusuf, A., Yahya, A.K., Khan, N.A., Salleh, F.M., Marsom, E., Huda, N.
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Published:	2017
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spelling	my.uniten.dspace-57562018-04-28T16:39:20Z Effect of Ge4+ and Mg2+ doping on superconductivity, fluctuation induced conductivity and interplanar coupling of TlSr 2CaCu2O7-δ superconductors Ali Yusuf, A. Yahya, A.K. Khan, N.A. Salleh, F.M. Marsom, E. Huda, N. Substitution of Ge4+ in place of Cu in Tl0.85Cr 0.15Sr2CaCu2-xGexO 7-δ (x = 0-0.6) showed initial increase in zero critical temperature value, Tc zero from 98 K (x = 0) to 100 K (x = 0.1) and in the range of 85-86 K for x = 0.2-0.3. The slow decrease in Tc zero is unexpected as tetravalent Ge4+ substitution is expected to strongly reduce hole concentration in the samples and suppress Tc zero. Excess conductivity analyses of resistance versus temperature data based on Asmalazov-Larkin (AL) theory revealed that the substitution induced 2D-to-3D transition of fluctuation induced conductivity with the highest transition temperature, T 2D-3D observed at x = 0.1. FTIR spectroscopy analysis indicates Ge4+ substitution cause reduction in CuO 2/GeO2 interplanar distance while our calculation based on Lawrence-Doniach model revealed highest superconducting coherence length, ξc(0) and interplanar coupling, J at x = 0.3. On the other hand, substitution of divalent Mg2+ for Ca2+ in (Tl 0.5Pb0.5)(Sr1.8Yb0.2)(Ca 1-yMgy)Cu2O7 (y = 0-1.0), which is not expected to directly vary hole concentration, surprisingly caused Tc zero to increase from 89.6 K (y = 0) to an optimum value of 95.9 K (y = 0.6) before decreasing with further increase in y. Excess conductivity analyses showed 2D-to-3D transition of fluctuation induced conductivity for all samples where the highest T2D- 3D was at y = 0.4. Similar calculation revealed highest values of ξc(0) and J also at y = 0.4. FTIR analysis of the samples indicates inequivalent Cu(1)O(2)Pb/Tl lengths and possible tilting of CuO 2 plane as a result of Mg2+ substitution. The increased ξc(0) and J as a result of the Ge4+ and Mg2+ substitutions are suggested to contributed to sustenance of superconductivity above 80 K in the samples. © 2011 Elsevier B.V. All rights reserved. 2017-12-08T07:18:00Z 2017-12-08T07:18:00Z 2011 Article 10.1016/j.physc.2011.03.007 en_US Physica C: Superconductivity and its Applications Volume 471, Issue 11-12, June 2011, Pages 363-372
institution	Universiti Tenaga Nasional
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language	en_US
description	Substitution of Ge4+ in place of Cu in Tl0.85Cr 0.15Sr2CaCu2-xGexO 7-δ (x = 0-0.6) showed initial increase in zero critical temperature value, Tc zero from 98 K (x = 0) to 100 K (x = 0.1) and in the range of 85-86 K for x = 0.2-0.3. The slow decrease in Tc zero is unexpected as tetravalent Ge4+ substitution is expected to strongly reduce hole concentration in the samples and suppress Tc zero. Excess conductivity analyses of resistance versus temperature data based on Asmalazov-Larkin (AL) theory revealed that the substitution induced 2D-to-3D transition of fluctuation induced conductivity with the highest transition temperature, T 2D-3D observed at x = 0.1. FTIR spectroscopy analysis indicates Ge4+ substitution cause reduction in CuO 2/GeO2 interplanar distance while our calculation based on Lawrence-Doniach model revealed highest superconducting coherence length, ξc(0) and interplanar coupling, J at x = 0.3. On the other hand, substitution of divalent Mg2+ for Ca2+ in (Tl 0.5Pb0.5)(Sr1.8Yb0.2)(Ca 1-yMgy)Cu2O7 (y = 0-1.0), which is not expected to directly vary hole concentration, surprisingly caused Tc zero to increase from 89.6 K (y = 0) to an optimum value of 95.9 K (y = 0.6) before decreasing with further increase in y. Excess conductivity analyses showed 2D-to-3D transition of fluctuation induced conductivity for all samples where the highest T2D- 3D was at y = 0.4. Similar calculation revealed highest values of ξc(0) and J also at y = 0.4. FTIR analysis of the samples indicates inequivalent Cu(1)O(2)Pb/Tl lengths and possible tilting of CuO 2 plane as a result of Mg2+ substitution. The increased ξc(0) and J as a result of the Ge4+ and Mg2+ substitutions are suggested to contributed to sustenance of superconductivity above 80 K in the samples. © 2011 Elsevier B.V. All rights reserved.
format	Article
author	Ali Yusuf, A. Yahya, A.K. Khan, N.A. Salleh, F.M. Marsom, E. Huda, N.
spellingShingle	Ali Yusuf, A. Yahya, A.K. Khan, N.A. Salleh, F.M. Marsom, E. Huda, N. Effect of Ge4+ and Mg2+ doping on superconductivity, fluctuation induced conductivity and interplanar coupling of TlSr 2CaCu2O7-δ superconductors
author_facet	Ali Yusuf, A. Yahya, A.K. Khan, N.A. Salleh, F.M. Marsom, E. Huda, N.
author_sort	Ali Yusuf, A.
title	Effect of Ge4+ and Mg2+ doping on superconductivity, fluctuation induced conductivity and interplanar coupling of TlSr 2CaCu2O7-δ superconductors
title_short	Effect of Ge4+ and Mg2+ doping on superconductivity, fluctuation induced conductivity and interplanar coupling of TlSr 2CaCu2O7-δ superconductors
title_full	Effect of Ge4+ and Mg2+ doping on superconductivity, fluctuation induced conductivity and interplanar coupling of TlSr 2CaCu2O7-δ superconductors
title_fullStr	Effect of Ge4+ and Mg2+ doping on superconductivity, fluctuation induced conductivity and interplanar coupling of TlSr 2CaCu2O7-δ superconductors
title_full_unstemmed	Effect of Ge4+ and Mg2+ doping on superconductivity, fluctuation induced conductivity and interplanar coupling of TlSr 2CaCu2O7-δ superconductors
title_sort	effect of ge4+ and mg2+ doping on superconductivity, fluctuation induced conductivity and interplanar coupling of tlsr 2cacu2o7-δ superconductors
publishDate	2017
_version_	1644493767957282816
score	13.211869

Effect of Ge4+ and Mg2+ doping on superconductivity, fluctuation induced conductivity and interplanar coupling of TlSr 2CaCu2O7-δ superconductors

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