### Abstract

Substitution of Ge^{4+} in place of Cu in Tl_{0.85}Cr _{0.15}Sr_{2}CaCu_{2-x}Ge_{x}O _{7-δ} (x = 0-0.6) showed initial increase in zero critical temperature value, T_{c} _{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 T_{c} _{zero} is unexpected as tetravalent Ge^{4+} substitution is expected to strongly reduce hole concentration in the samples and suppress T_{c} _{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 Ge^{4+} substitution cause reduction in CuO _{2}/GeO_{2} interplanar distance while our calculation based on Lawrence-Doniach model revealed highest superconducting coherence length, ξ_{c}(0) and interplanar coupling, J at x = 0.3. On the other hand, substitution of divalent Mg^{2+} for Ca^{2+} in (Tl _{0.5}Pb_{0.5})(Sr_{1.8}Yb_{0.2})(Ca _{1-y}Mg_{y})Cu_{2}O_{7} (y = 0-1.0), which is not expected to directly vary hole concentration, surprisingly caused T_{c} _{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 T_{2D-} _{3D} was at y = 0.4. Similar calculation revealed highest values of ξ_{c}(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 Mg^{2+} substitution. The increased ξ_{c}(0) and J as a result of the Ge^{4+} and Mg^{2+} substitutions are suggested to contributed to sustenance of superconductivity above 80 K in the samples.

Original language | English |
---|---|

Pages (from-to) | 363-372 |

Number of pages | 10 |

Journal | Physica C: Superconductivity and its Applications |

Volume | 471 |

Issue number | 11-12 |

DOIs | |

Publication status | Published - 01 Jun 2011 |

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### All Science Journal Classification (ASJC) codes

- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Energy Engineering and Power Technology
- Electrical and Electronic Engineering

### Cite this

^{4+}and Mg

^{2+}doping on superconductivity, fluctuation induced conductivity and interplanar coupling of TlSr

_{2}CaCu

_{2}O

_{7-δ}superconductors.

*Physica C: Superconductivity and its Applications*,

*471*(11-12), 363-372. https://doi.org/10.1016/j.physc.2011.03.007

}

^{4+}and Mg

^{2+}doping on superconductivity, fluctuation induced conductivity and interplanar coupling of TlSr

_{2}CaCu

_{2}O

_{7-δ}superconductors',

*Physica C: Superconductivity and its Applications*, vol. 471, no. 11-12, pp. 363-372. https://doi.org/10.1016/j.physc.2011.03.007

**Effect of Ge ^{4+} and Mg^{2+} doping on superconductivity, fluctuation induced conductivity and interplanar coupling of TlSr _{2}CaCu_{2}O_{7-δ} superconductors.** / Ali Yusuf, A.; Yahya, A. K.; Khan, Nawazish A.; Salleh, F. Md; Marsom, E.; Huda, N.

Research output: Contribution to journal › Article

TY - JOUR

T1 - Effect of Ge4+ and Mg2+ doping on superconductivity, fluctuation induced conductivity and interplanar coupling of TlSr 2CaCu2O7-δ superconductors

AU - Ali Yusuf, A.

AU - Yahya, A. K.

AU - Khan, Nawazish A.

AU - Salleh, F. Md

AU - Marsom, E.

AU - Huda, N.

PY - 2011/6/1

Y1 - 2011/6/1

N2 - 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.

AB - 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.

UR - http://www.scopus.com/inward/record.url?scp=79955088861&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=79955088861&partnerID=8YFLogxK

U2 - 10.1016/j.physc.2011.03.007

DO - 10.1016/j.physc.2011.03.007

M3 - Article

AN - SCOPUS:79955088861

VL - 471

SP - 363

EP - 372

JO - Physica C: Superconductivity and its Applications

JF - Physica C: Superconductivity and its Applications

SN - 0921-4534

IS - 11-12

ER -

^{4+}and Mg

^{2+}doping on superconductivity, fluctuation induced conductivity and interplanar coupling of TlSr

_{2}CaCu

_{2}O

_{7-δ}superconductors. Physica C: Superconductivity and its Applications. 2011 Jun 1;471(11-12):363-372. https://doi.org/10.1016/j.physc.2011.03.007