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

Conference · Wed Jan 01 04:00:00 EST 1992

OSTI ID:7081324

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]

---

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: DOE; USDOE, Washington, DC (United States)
• DOE Contract Number: W-7405-ENG-36
• OSTI ID: 7081324
• 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* -- Ceramics
Cermets
& Refractories-- Structure & Phase Studies
665100 -- Nuclear Techniques in Condensed Matter Physics -- (1992-)
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ANTIFERROMAGNETISM
CHALCOGENIDES
COPPER COMPOUNDS
COPPER OXIDES
CRYSTAL STRUCTURE
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
INTERMEDIATE MASS NUCLEI
ISOTOPES
LANTHANUM 139
LANTHANUM COMPOUNDS
LANTHANUM ISOTOPES
LANTHANUM OXIDES
MAGNETISM
MICROSTRUCTURE
NUCLEAR QUADRUPOLE RESONANCE
NUCLEI
ODD-EVEN NUCLEI
OXIDES
OXYGEN ADDITIONS
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
RARE EARTH COMPOUNDS
RARE EARTH ISOTOPES
RARE EARTH NUCLEI
RESONANCE
STABLE ISOTOPES
SUPERCONDUCTIVITY
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENT COMPOUNDS
TRANSITION TEMPERATURE