Evidence for symmetry breaking local distortions in Tl{sub 2}Ba{sub 2}NuO{sub 6}

Conference · Sat Dec 31 04:00:00 EST 1994

OSTI ID:68437

Nickel, J H; Allen, P G; Li, Guonguang; Mustre de Leon, J; Raistrick, I D; Conradson, S D ^[1]

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1. Los Alamos National Laboratory, NM (United States)

High temperature superconductors (HTSC) are perhaps the most extensively characterized materials of recent times. The average crystallographic structures have been determined by X-ray, neutron and electron diffraction techniques. Recent investigations using extended x-ray absorption fine structures (EXAFS) and pair distribution analysis (PDF), however, have shown that there are significant local deviations from the average crystallographic structure. These local structural anomalies have been observed in several systems, including YBa{sub 2}Cu{sub 3}O{sub 7}, Nd{sub 2-x}Ce{sub x}CuO{sub 4{minus}y}, Bi{sub 2}Ca{sub 2}SrCu{sub 2}O{sub 8}, and TlBa{sub 2}Ca{sub 3}Cu{sub 4}O{sub 11}. Comparison of the x-ray absorption near edge spectra (XANES) of several superconducting systems indicate that structural anomalies also exist in Tl{sub 2}Ba{sub 2}CuO{sub 6} (2201), and these anomalies reduce the crystal symmetry. The authors interpret this lowering of symmetry as an indication of the existence of localized states in this structure. Powder EXAFS experiments on the Tl based superconductors, as well as preliminary EXAFS results on oriented samples support this conclusion.

• Research Organization: Los Alamos National Lab., NM (United States)
• OSTI ID: 68437
• Report Number(s): LA-UR--94-1148; CONF-931247--; ON: DE94009293
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
66 PHYSICS
ASYMMETRY
BARIUM OXIDES
COPPER OXIDES
CRYSTAL STRUCTURE
HIGH-TC SUPERCONDUCTORS
THALLIUM OXIDES