Unusual copper environment in YBa sub 2 Cu sub 3 O sub 7-. delta. superconductors as found by XAFS

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Careful X-ray absorption fine structure (XAFS) measurements on oriented powders of YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} were made as a function of temperature and for {delta} = 0, 0.35, 0.82. Particle size of the samples was varied to check for thickness effect distortions. The smaller values of {delta} correlate to larger concentrations of Ba atoms at noncrystalline sites, consistent with the samples becoming more unstable at {Tc} increases. These Ba defects in the {delta} = 0 superconductor constitute about 15% of the volume of the sample and have consequences that can explain the anomalous'' temperature dependence of its resistivity in the ... continued below

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Stern, E.A.; Qian, M. (Washington Univ., Seattle, WA (United States). Dept. of Physics); Yacoby, Y. (Hebrew Univ., Jerusalem (Israel). Racah Inst. of Physics); Heald, S.M. (Brookhaven National Lab., Upton, NY (United States)) & Maeda, H. (Okayama Univ., Okayama (Japan). Dept. of Chemistry) January 1, 1991.

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Careful X-ray absorption fine structure (XAFS) measurements on oriented powders of YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} were made as a function of temperature and for {delta} = 0, 0.35, 0.82. Particle size of the samples was varied to check for thickness effect distortions. The smaller values of {delta} correlate to larger concentrations of Ba atoms at noncrystalline sites, consistent with the samples becoming more unstable at {Tc} increases. These Ba defects in the {delta} = 0 superconductor constitute about 15% of the volume of the sample and have consequences that can explain the anomalous'' temperature dependence of its resistivity in the normal state and its anomalous'' linear specific heat at low temperatures. In agreement with other measurements we find the Cu(1)-O(4) apical oxygen bond distribution is anomalous and is fitted as a double well distribution with a splitting of about 0.1{Angstrom}. The occupancy of the two wells is found to be equal within uncertainties for the three values of {delta} investigated. An unphysical negative means squared vibrational amplitude {sigma}{sup 2} within the wells is found which partially is caused by thickness effect distortion and the remaining by inaccuracy of XAFS theory. Near {Tc} the splitting decreases with a concomitant increase of {sigma}{sup 2}. This change near {Tc} is larger for the higher {Tc} value.

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Pages: (14 p)

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OSTI; NTIS; GPO Dep.

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  • Lattice effects in high Tc superconductors, Santa Fe, NM (United States), 13-15 Jan 1992

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  • Other: DE92009158
  • Report No.: BNL-47204
  • Report No.: CONF-920141--5
  • Grant Number: AC02-76CH00016
  • Office of Scientific & Technical Information Report Number: 5737489
  • Archival Resource Key: ark:/67531/metadc1092951

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  • January 1, 1991

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  • Feb. 10, 2018, 10:06 p.m.

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  • April 23, 2018, 12:53 p.m.

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Stern, E.A.; Qian, M. (Washington Univ., Seattle, WA (United States). Dept. of Physics); Yacoby, Y. (Hebrew Univ., Jerusalem (Israel). Racah Inst. of Physics); Heald, S.M. (Brookhaven National Lab., Upton, NY (United States)) & Maeda, H. (Okayama Univ., Okayama (Japan). Dept. of Chemistry). Unusual copper environment in YBa sub 2 Cu sub 3 O sub 7-. delta. superconductors as found by XAFS, article, January 1, 1991; Upton, New York. (digital.library.unt.edu/ark:/67531/metadc1092951/: accessed November 18, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.