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Title: Structure and transport properties in YBa{sub 2-x}Eu{sub x}Cu{sub 3}O{sub 7-{delta}} superconductors

Abstract

Structure and transport properties of Eu-doped YBa{sub 2-x}Eu{sub x}Cu{sub 3}O{sub 7-{delta}} (YBECO) have been studied. Eu is confirmed preferring to replace Ba at Ba sites. The averaged valence state of Eu, which is examined by x-ray photoemission spectroscopy, increases with increasing x. Eu doping in YBECO has a little influence on superconductivity in our studies, and the superconducting transition temperature T{sub c} is almost unchanged.

Authors:
; ; ; ;  [1];  [2];  [2];  [2]
  1. Laboratory of Solid State Microstructures, Department of Physics, Nanjing University, Nanjing 210093 (China)
  2. (China)
Publication Date:
OSTI Identifier:
20982861
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 101; Journal Issue: 9; Conference: 10. joint MMM/INTERMAG conference, Baltimore, MD (United States), 7-11 Jan 2007; Other Information: DOI: 10.1063/1.2712954; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; BARIUM COMPOUNDS; CHARGED-PARTICLE TRANSPORT; CUPRATES; DOPED MATERIALS; EUROPIUM COMPOUNDS; HIGH-TC SUPERCONDUCTORS; PHOTOEMISSION; SUPERCONDUCTIVITY; TRANSITION TEMPERATURE; VALENCE; X-RAY PHOTOELECTRON SPECTROSCOPY; YTTRIUM COMPOUNDS

Citation Formats

Qian, B., Xing, J. H., Wu, X. S., Jiang, Z. S., Tang, S. L., Jiangsu Laboratory of Advanced Functional Materials, Changshu Institute of Technology, Changshu 215500, Department of Physics, Changshu Institute of Technology, Changshu 215500, and Laboratory of Solid State Microstructures, Department of Physics, Nanjing University, Nanjing 210093. Structure and transport properties in YBa{sub 2-x}Eu{sub x}Cu{sub 3}O{sub 7-{delta}} superconductors. United States: N. p., 2007. Web. doi:10.1063/1.2712954.
Qian, B., Xing, J. H., Wu, X. S., Jiang, Z. S., Tang, S. L., Jiangsu Laboratory of Advanced Functional Materials, Changshu Institute of Technology, Changshu 215500, Department of Physics, Changshu Institute of Technology, Changshu 215500, & Laboratory of Solid State Microstructures, Department of Physics, Nanjing University, Nanjing 210093. Structure and transport properties in YBa{sub 2-x}Eu{sub x}Cu{sub 3}O{sub 7-{delta}} superconductors. United States. doi:10.1063/1.2712954.
Qian, B., Xing, J. H., Wu, X. S., Jiang, Z. S., Tang, S. L., Jiangsu Laboratory of Advanced Functional Materials, Changshu Institute of Technology, Changshu 215500, Department of Physics, Changshu Institute of Technology, Changshu 215500, and Laboratory of Solid State Microstructures, Department of Physics, Nanjing University, Nanjing 210093. Tue . "Structure and transport properties in YBa{sub 2-x}Eu{sub x}Cu{sub 3}O{sub 7-{delta}} superconductors". United States. doi:10.1063/1.2712954.
@article{osti_20982861,
title = {Structure and transport properties in YBa{sub 2-x}Eu{sub x}Cu{sub 3}O{sub 7-{delta}} superconductors},
author = {Qian, B. and Xing, J. H. and Wu, X. S. and Jiang, Z. S. and Tang, S. L. and Jiangsu Laboratory of Advanced Functional Materials, Changshu Institute of Technology, Changshu 215500 and Department of Physics, Changshu Institute of Technology, Changshu 215500 and Laboratory of Solid State Microstructures, Department of Physics, Nanjing University, Nanjing 210093},
abstractNote = {Structure and transport properties of Eu-doped YBa{sub 2-x}Eu{sub x}Cu{sub 3}O{sub 7-{delta}} (YBECO) have been studied. Eu is confirmed preferring to replace Ba at Ba sites. The averaged valence state of Eu, which is examined by x-ray photoemission spectroscopy, increases with increasing x. Eu doping in YBECO has a little influence on superconductivity in our studies, and the superconducting transition temperature T{sub c} is almost unchanged.},
doi = {10.1063/1.2712954},
journal = {Journal of Applied Physics},
number = 9,
volume = 101,
place = {United States},
year = {Tue May 01 00:00:00 EDT 2007},
month = {Tue May 01 00:00:00 EDT 2007}
}
  • Epitaxial YBa[sub 2]Cu[sub 3]O[sub 7[minus][delta]] thin films irradiated with swift heavy ions under different directions showed a strongly changed angular dependence of the critical current density [ital J][sub [ital c]]([ital B],[ital T],[var theta]) in the mixed state. Additional peaks, which dominate the angular dependence of [ital J][sub [ital c]], appear at angles where the magnetic field is parallel to the irradiation direction, due to the strong pinning of the introduced linear defects. Irradiated YBa[sub 2]Cu[sub 3]O[sub 7[minus][delta]]/PrBa[sub 2]Cu[sub 3]O[sub 7[minus][delta]] superlattices, however, reveal no additional [ital J][sub [ital c]] peaks but an isotropic [ital J][sub [ital c]] enhancement in amore » wide angular range. This contrary behavior could be explained by flux lines of different dimensionality.« less
  • The electronic structures of three high-temperature superconducting materials, YBa/sub 2/Cu/sub 3/O/sub 7/..sqrt../sub delta/, GdBa/sub 2/Cu/sub 3/O/sub 7/..sqrt../sub delta/, and EuBa/sub 2/Cu/sub 3/O/sub 7/..sqrt../sub delta/, were studied with angle-integrated photoemission. The effects of sample treatment and preparation, including mechanical scraping, ion sputtering, and temperature cycling, were examined. High-resolution spectra were obtained from samples prepared by mechanical scraping at 90 K in the vacuum chamber to minimize contamination and the loss of oxygen. The resonance behavior of the various valence and core states in the photoemission spectra was investigated to identify the atomic origin of the states. The Cu- and O-derived statesmore » dominated the valence-band region at low photon energies, as shown by a comparison of the energy distribution curves for all three compounds. The measured density of states at the Fermi edge was very low. All of the spectral features, including the valence bands, core levels, Fermi-edge emission, and the Cu 3d satellites did not show any noticeable changes as a function of sample temperature between 20 and 300 K« less
  • X-ray-absorption measurements of the high-T/sub c/ superconductors YBa/sub 2/Cu/sub 3/O/sub 7-//sub delta/ and GdBa/sub 2/Cu/sub 3/O/sub 7-//sub delta/ show that their near edge and extended fine structures (EXAFS) are essentially identical over the temperature range of 4.2 to 688 K. The results indicate that not only are YBa/sub 2/Cu/sub 3/O/sub 7-//sub delta/ and GdBa/sub 2/Cu/sub 3/O/sub 7-//sub delta/ very similar to each other in local bonding and electronic structure, but also remain virtually unchanged, electronically and structurally, over this wide range in temperature, from far below to well above T/sub c/. The positions of the Cu near-edge spectra for thesemore » superconductors indicate a Cu valence between that of Cu in CuO, which has a formal valence of II, and that in KCuO/sub 2/, with a formal valence of III. Our EXAFS structural results agree well with those from neutron diffraction data. Recently proposed alternate structures are shown to be inconsistent with our data. The characteristic vibration frequencies of the near-neighbor atoms show that the two-dimensional Cu: O planes and the one-dimensional Cu: O chains form the most rigid parts of the structure, and these layers are bound more weakly along the c axis via the Ba and Y planes. These oscillator frequencies are identified with specific near-neighbor pairs, and the values are consistent with those for some of the modes seen by inelastic neutron scattering as well as by infrared and Raman spectroscopy. No evidence of phonon softening is apparent in any of the phonon modes studied, providing evidence against a strong electron-phonon coupling mechanism.« less
  • We analyze the frequency-dependent photoinduced infrared conductivity, {sigma}{sub {ital P}}({omega}), obtained from photoinduced absorption measurements of the insulators Tl{sub 2}Ba{sub 2}Ca{sub 0.98}Gd{sub 0.02}Cu{sub 2}O{sub 8}, YBa{sub 2}Cu{sub 3}O{sub 6.3}, and La{sub 2}CuO{sub 4} in terms of {sigma}{sub PT}({omega}) calculated from nonadiabatic polaron-transport theory. The calculated {sigma}{sub PT}({omega}) is in good agreement with the experimental {sigma}{sub {ital P}}({omega}) in the midinfrared. We also compare {sigma}{sub {ital P}}({omega}) with the infrared conductivity, {sigma}({omega}), of the high-{Tc} superconductors Tl{sub 2}Ba{sub 2}CaCu{sub 2}O{sub 8}, YBa{sub 2}Cu{sub 3}O{sub 7}, and La{sub 1.85}Sr{sub 0.15}CuO{sub 4}. The similar spectral shape and systematic trends in both {sigma}{sub {italmore » P}}({omega}) and {sigma}({omega}) indicate that the carriers in the concentrated (metallic) regime retain much of the character of the carriers in the dilute (photoexcited) regime. Together, these results imply that in the superconducting cuprates and in their parent'' insulators, the carriers are polarons dressed with a phonon polarization cloud.« less
  • We report on the successful fabrication of bulk samples satisfying the nominal composition YBa{sub 2}Cu{sub 3-x}Te{sub x}O{sub 7-{delta}} and containing highly single-crystal-like texture. While this type of crystal growing process is not new, our process requires only the existence of spatial temperature gradient in some parts of the common tube furance. The samples with tellurium were found to be much more stable and better superconductors than the Y-123 specimen. Large layer textures with cross-section approximately 50 x 500 {mu}m{sup 2} were observed to grow inside the usual bulk sample. The critical currents were measured by the d.c. magnetization method andmore » found to be easily greater than 6000 A cm{sup -2} for the samples with Te. 19 refs., 7 figs.« less