Temperature and depth dependence of positron annihilation parameters in YBa/sub 2/Cu/sub 3/O/sub 7-. / and La/sub 1. 85/Sr/sub 0. 15/CuO/sub 4/

Conference · Thu Jan 01 04:00:00 EST 1987

OSTI ID:5485120

Lynn, K G; Usmar, S G; Nielsen, B; van der Kolk, G J; Kanazawa, I; Sferlazzo, P; Moodenbaugh, A R

The temperature dependence of the positron annihilation parameters for YBa/sub 2/Cu/sub 3/O/sub 7-x/ x = 0.7, 0.4 and 0.0 and La/sub 1.85/Sr/0.15/CuO/sub 4/ were measured. The depth dependence of the YBa/sub 2/Cu/sub 3/O/sub 7/ was studied using a variable-energy positron beam showing a strong depth dependence in the Doppler line-shape extending up to an average depth of approx.5.0 ..mu..m. It was found that a transition in the Doppler line-shape parameter, ''S'', was associated with the superconducting transition temperature (T/sub c/) in YBa/sub 2/Cu/sub 3/O/sub 7-x/ x = 0.4 and 0.0 while no transition was observed in the superconducting YBa/sub 2/Cu/sub 3/O/sub 6.3/. Positron lifetime parameters in YBa/sub 2/Cu/sub 3/O/sub 7/ were found to be consistent with positrons localized at open volume regions (probably unoccupied crystallographic sites) in this material with a lifetime of 210 psec at 300 K. These results indicate that the electron density at these unoccupied sites increases, using a free electron model, approximately 9% between 100 and 12 K. 15 refs., 4 figs.

• Research Organization: Brookhaven National Lab., Upton, NY (USA)
• DOE Contract Number: AC02-76CH00016
• OSTI ID: 5485120
• Report Number(s): BNL-40445; CONF-871125-18; ON: DE88003494
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360202 -- Ceramics
Cermets
& Refractories-- Structure & Phase Studies
360204* -- Ceramics
Cermets
& Refractories-- Physical Properties
656003 -- Condensed Matter Physics-- Interactions between Beams & Condensed Matter-- (1987-)
656100 -- Condensed Matter Physics-- Superconductivity
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ALKALINE EARTH METAL COMPOUNDS
ANNIHILATION
ANTILEPTONS
ANTIMATTER
ANTIPARTICLES
BARIUM COMPOUNDS
BARIUM OXIDES
BASIC INTERACTIONS
BEAMS
CHALCOGENIDES
COPPER COMPOUNDS
COPPER OXIDES
DEPTH
DIMENSIONS
DOPPLER BROADENING
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
ELECTROMAGNETIC INTERACTIONS
ELECTRON DENSITY
ELECTRONIC STRUCTURE
ELEMENTARY PARTICLES
FERMIONS
INTERACTIONS
LANTHANUM COMPOUNDS
LANTHANUM OXIDES
LEPTON BEAMS
LEPTONS
LIFETIME
LINE BROADENING
OXIDES
OXYGEN COMPOUNDS
PARTICLE BEAMS
PHASE TRANSFORMATIONS
PHYSICAL PROPERTIES
POSITRON BEAMS
POSITRONS
RARE EARTH COMPOUNDS
STRONTIUM COMPOUNDS
STRONTIUM OXIDES
SUPERCONDUCTIVITY
TEMPERATURE DEPENDENCE
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENT COMPOUNDS
TRANSITION TEMPERATURE
YTTRIUM COMPOUNDS
YTTRIUM OXIDES