Journal ArticleDOI
The positron-annihilation anomaly near the superconducting transition-temperature in single-phase yba2cu3o7-x compounds
TLDR
The positron annihilation technique has been used for studying the high Tc-superconductor YBa2Cu3O7-x as discussed by the authors, and the positron lifetimes of the normal state and of the superconducting state have been measured.Abstract:
The positron annihilation technique has been used for studying the high-Tc-superconductor YBa2Cu3O7-x. The Doppler broadening lineshape parameter as a function of temperature between 75 and 300 K, and the positron lifetimes of the normal state and of the superconducting state have been measured. A sharp negative anomaly in the S-parameter was observed near the superconducting transition temperature. In addition, it was found that the S-parameter and mean lifetime decrease below the transition temperature Tc. These phenomena vanish for the samples annealed in vacuum at 800 degrees C. It is suggested that high-Tc superconductivity in the new oxide is probably accompanied by an adjustment in the positions of the oxygen vacancies and the occurrence of 'valence pairs', i.e. an enhancement of the covalent character of the electrons after the superconducting transition.read more
Citations
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Positron lifetime in oxide superconductors YBa2(Cu1-xMx)O7-y (M=Fe, Ni, Zn)
TL;DR: In this paper, temperature dependence of positron lifetime parameters measured on a series of specimens of YBa2(Cu1-xMx)3O7-y (M=Fe, Ni, Zn) in the temperature range 20-300 K was presented.
Journal ArticleDOI
Positronium in voids and superconductivity
V.L. Sedov,S.N. Kuznetsov +1 more
TL;DR: In this article, conditions under which different spin states of the positronium in the void occur have been established, and the conclusion that the transition to the superconducting state inhibits the processes of ortho-para conversion of the POSRONIUM has been reached.
Journal ArticleDOI
Internal friction in ErBa2Cu3Ox superconductors
TL;DR: The internal friction spectrum of ErBa 2 Cu 3 O x superconducting ceramics has been measured at two different frequencies (approx. 6 Hz and 250 Hz) as discussed by the authors.
Journal ArticleDOI
Positron annihilation in high-Tc superconductors: present status
TL;DR: In this paper, a review of the literature on high-Tc superconductors is presented, focusing on the investigation of the electronic structure of these materials and the fundamental issues with the present actual knowledge of superconductivity.
Journal ArticleDOI
The study of the high temperature superconductor YBaCuO by positron annihilation lifetime spectroscopy
TL;DR: Positron lifetime spectroscopy of Y-Ba-Cu-0 ceramics has been performed over the temperature range from 300 to 25 K as discussed by the authors, and two sets of samples, YBa 2 Cu 3 O x, x = 6.91 and x =6.75 respectively, were studied.
References
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Journal ArticleDOI
Possible high Tc superconductivity in the Ba-La-Cu-O system
TL;DR: In this paper, Ba−La−Cu−O system, with the composition BaxLa5−xCu5O5(3−y) have been prepared in polycrystalline form, and samples with x=1 and 0.75,y>0, annealed below 900°C under reducing conditions, consist of three phases, one of them a perovskite-like mixed-valent copper compound.
Journal ArticleDOI
Superconductivity at 93 K in a new mixed-phase Y-Ba-Cu-O compound system at ambient pressure
Maw-Kuen Wu,J. R. Ashburn,C. J. Torng,Pei-Herng Hor,R. L. Meng,Li Gao,Z. J. Huang,Yongmei Wang,Ching-Wu Chu +8 more
TL;DR: A stable and reproducible superconductivity transition between 80 and 93 K has been unambiguously observed both resistively and magnetically in a new Y-Ba-Cu-O compound system at ambient pressure.
Journal ArticleDOI
Superconductivity above 90 K in the square-planar compound system ABa2Cu3O6+x with A=Y, La, Nd, Sm, Eu, Gd, Ho, Er and Lu.
Pei-Herng Hor,R. L. Meng,Yongmei Wang,Li Gao,Z. J. Huang,J. Bechtold,K. Forster,Ching-Wu Chu +7 more
TL;DR: The results suggest that the unique square planar Cu atoms, each surrounded by four or six oxygen atoms, are crucial to the superconductivity of oxides in general.
Journal ArticleDOI
Structure of the single‐phase high‐temperature superconductor YBa2Cu3O7−δ
M. A. Beno,Lynda Soderholm,D. W. Capone,D. G. Hinks,James D. Jorgensen,J. D. Grace,Ivan K. Schuller,Carlo U. Segre,K. Zhang +8 more
TL;DR: In this paper, the crystal structure of the single-phase stoichiometric high-temperature superconductor in the Y•Ba•Cu•O system using high-resolution neutron powder diffraction was determined.
Journal ArticleDOI
Positron annihilation in the high-temperature superconductor YBa2Cu3O6+ delta.
Yan Ching Jean,S. J. Wang,Hiizu Nakanishi,Walter Hardy,M. E. Hayden,R. F. Kiefl,R. L. Meng,H. P. Hor,J. Z. Huang,C. W. Chu +9 more
TL;DR: Evidence is given that the oxygen vacancy and electronic structure change play an important role for high-${T}_{c}$ superconductivity.