NQR study of local structures and cooling rate dependent superconductivity in La{sub 2}CuO{sub 4+{delta}}

Conference · Thu Oct 01 04:00:00 EDT 1992

OSTI ID:10181986

Reyes, A P; Ahrens, E T; Hammel, P C; Heffner, R H; Thompson, J D; Canfield, P C; Fisk, Z ^[1]; Schirber, J E ^[2]

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1. Los Alamos National Lab., NM (United States)
2. Sandia National Labs., Albuquerque, NM (United States)

Structural properties of oxygen-annealed polycrystals of La{sub 2}CuO{sub 4 + {delta}} ({delta}{approximately}0.03) have been studied using {sup 139}La NQR spectroscopy. Superconducting critical temperatures were found to depend on the rate of cooling through a narrow temperature range at about 195K. Preliminary analysis of the {sup 139}La NQR spectra suggest that the oxygen-rich phase-separated region is composed of two structurally distinct phases, both of which are metallic and super-conducting. One phase has a structure closely related to the stoichiometric oxygen-poor compound. The second shows a considerable amount of apical oxygen disorder, a large shift in NQR frequency {nu}{sub Q}, and a volume fraction which increases with cooling rate. The formation of the second phase below {minus}200K is indicative of the freezing Of CuO{sub 6} octahedral tilting. Abrupt shifts in {nu}{sub Q} above {Tc} were also observed for both phases, suggestive of a local structural anomaly or charge transfer to the Cu-O plane.

• Research Organization: Los Alamos National Lab., NM (United States)
• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: W-7405-ENG-36
• OSTI ID: 10181986
• Report Number(s): LA-UR--92-3022; CONF-921201--2; ON: DE93000680
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360202
665100
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ANTIFERROMAGNETISM
COPPER OXIDES
LANTHANUM 139
LANTHANUM OXIDES
MICROSTRUCTURE
NUCLEAR QUADRUPOLE RESONANCE
NUCLEAR TECHNIQUES IN CONDENSED MATTER PHYSICS
OXYGEN ADDITIONS
STRUCTURE AND PHASE STUDIES
SUPERCONDUCTIVITY
TRANSITION TEMPERATURE