Superconductivity of (Hg0.7Tl0.3)2Ba2Y 1-xCaxCu2O8-δ (0 ≦ x ≦ 0.8) with a wide range of doping state

Ayako Yamamoto, Tadashi Tatsuki, Seiji Adachi, Keiichi Tanabe

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Abstract

(Hg,Tl)-based cuprates with the nominal compositions of (Hg0.7Tl0.3)2Ba2Y 1-xCaxCu2O8-δ (0 ≦ x ≦ 1.0, every 0.1 step) were prepared under high pressure, and nearly single phases were obtained for the samples with 0 ≦ x ≦ 0.8. We systematically investigated their unit cell dimensions, DC susceptibility, electrical resistivity, oxygen content and copper valence as a function of Ca content, x. For the samples with x = 0-0.4, Tc, which was determined by DC susceptibility, increased from 12 K to 84 K with increasing x, while the samples with x = 0.5-0.8 exhibited a Tc decrease from 84 K to 40 K. This result indicates that the doping state of the samples can be extensively varied from underdoped to overdoped states by the Ca substitution. This variation in the doping states was also supported by the systematic change in the temperature dependence of the electrical resistivity. Oxygen analysis revealed that the copper valence gradually increased from 2.12 to 2.26 with increasing x from 0 to 0.8. The copper valence with the maximum Tc of 84 K in these samples was determined to be 2.18-2.19, which is comparable to the value for the optimum Tc in other high-Tc cuprates.

Original languageEnglish
Pages (from-to)191-196
Number of pages6
JournalPhysica C: Superconductivity and its Applications
Volume268
Issue number3-4
Publication statusPublished - 1996 Sep 10
Externally publishedYes

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ASJC Scopus subject areas

  • Condensed Matter Physics

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