Growth of (Cu_0.5Tl_0.5鈭?i>xHg_x)Ba₂Ca₃Cu₄O_12鈭?i>未 Superconductor with Optimal Carrier Density in CuO₂ Planes and Fluctuation-Induced Conductivity

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• 作者：M. Mumtaz (12) mmumtaz75@yahoo.com
  Nawazish A. Khan (2)
  S. M. Hasnain (2)
• 关键词：(Cu0.5Tl0.5− ; x Hg x )Ba2Ca3Cu4O12− ; δ ; superconductor &#8211 ; Fluctuation ; induced conductivity &#8211 ; Post ; annealing &#8211 ; Optimal carrier density
• 刊名：Journal of Superconductivity Incorporating Novel Magnetism
• 出版时间：May 2012
• 出版年：2012
• 期刊代码：18_08961107
• 类别：eco
• 卷：25
• 期：4
• 页码：835-840
• 数据来源：sp

摘要

The growth of (Cu_0.5Tl_0.5−x Hg _x )Ba₂Ca₃Cu₄O_12−δ (x=0, 0.25) superconductor with optimal carrier density in CuO₂ planes has been made possible by partial substitution of Hg at Tl sites in (Cu_0.5Tl_0.5)Ba₂O_4−δ charge reservoir layer of (Cu_0.5Tl_0.5)Ba₂Ca₃Cu₄O_12−δ superconductor. The fluctuation-induced conductivity (FIC) analysis has been carried out on resistivity vs. temperature curves by using Aslamazov–Larkin (AL) theory and the results have shown three-dimensional (3D) and two-dimensional (2D) fluctuations in order parameters. The microscopic parameters deduced from FIC analysis such as crossover temperature (T _o ), zero temperature c-axis coherence {ξ _c (0)} and the interlayer coupling strength (J) have been improved with Hg substitution. Also, 3D region has been shifted to higher temperature with Hg substitution. In order to verify the optimal carrier density in CuO₂ planes with Hg substitution, the post-annealing experiments have been carried out on these samples in nitrogen and air. These post-annealing experiments have caused under-doping of carriers from the optimal level resulting into a decrease in T _c (R=0) as well as the magnitude of diamagnetism.