[Zurück]

A. Irizawa, T. Ohmura, T. Shibata, M. Kato, K. Yoshimura, K. Kosuge, Y. Ito, H. Michor, G. Hilscher:
"Collapse of Superconductivity in the Y123/Y124 Superlattice System Y₂Ba₄Cu₇O_15-δ";
Journal of the Physical Society of Japan, 71 (2002), S. 574 - 581.

Collapse of Superconductivity in the Y123/Y124 Superlattice System Y₂Ba₄Cu₇O_15-δ

Akinori Irizawa*, Tomohiko Ohmura, Tomohiko Shibata, Masaki Kato, Kazuyoshi Yoshimura, Koji Kosuge, Yutaka Ito 1, Herwig Michor 2 and Gerfried Hilscher 2
Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502
1 Superconductivity Research Laboratory, International Superconductivity Technology Center, Tokyo 135-0062
2 Institut für Experimentalphysik, Technische Universität Wien, Wien A-1040, Austria

(Received November 13, 2000)

Magnetic susceptibility and electric resistivity were measured on Y₂Ba₄Cu₇O_15-δover the whole oxygen deficiency range, 0 <= δ <= 1. Complete collapse of superconductivity was observed for Y₂Ba₄Cu₇O₁₄in both resistivity and susceptibility measurements, although there still reside the metallic conduction. This is the first observation of under-doped normal metallic state in high-T_c cuprates without applying any external factors such as magnetic field, hydrostatic pressure or substitution of impurity for plane-Cu site for breaking the superconducting state. The behavior of electric conduction due to the CuO₂ plane was observed in resistivity measurement as changing from the T-linear dependence to the under-doped S-shaped temperature dependence, giving the spin-gap temperature which agree well with the results from the spin-lattice relaxation rate 1/T₁ for Cu NQR at plane-site in various YBCO compounds. The temperature dependence of 1/T₁ on plane-site Cu in Y₂Ba₄Cu₇O₁₄ is discussed to be of itinerant-electron type with finite magnetic correlation between them as in the case of nearly and/or weak magnetic systems. The temperature dependence of 1/T₁ on chain-site is also discussed among various YBCO compounds.

KEYWORDS: Y247, YBCO, high-T_c, under-doped metal, NQR

http://jpsj.ipap.jp/link?JPSJ/71/574/