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

Conference · Thu Feb 25 04:00:00 EST 1988 · AIP Conf. Proc.; (United States)

OSTI ID:6910676

Lynn, K G; Usmar, S G; Nielsen, B; van der Kolk, G; 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-//sub x/ x = 0.7, 0.4 and 0.0 and La/sub 1.85/Sr/sub 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 nonsuperconducting 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.

• Research Organization: Brookhaven National Laboratory, Upton, NY 11973
• OSTI ID: 6910676
• Report Number(s): CONF-871178-
• Conference Information: Journal Name: AIP Conf. Proc.; (United States) Journal Volume: 165:1
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360204* -- Ceramics
Cermets
& Refractories-- Physical Properties
ALKALINE EARTH METAL COMPOUNDS
ANNIHILATION
ANTILEPTONS
ANTIMATTER
ANTIPARTICLES
BARIUM COMPOUNDS
BASIC INTERACTIONS
CHALCOGENIDES
COPPER COMPOUNDS
COPPER OXIDES
DEPTH
DIMENSIONS
DOPPLER EFFECT
ELECTROMAGNETIC INTERACTIONS
ELEMENTARY PARTICLES
FERMIONS
FILMS
INTERACTIONS
LANTHANUM COMPOUNDS
LEPTONS
LIFETIME
LINE WIDTHS
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
POSITRONS
RARE EARTH COMPOUNDS
STRONTIUM COMPOUNDS
SUPERCONDUCTING FILMS
TEMPERATURE DEPENDENCE
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENT COMPOUNDS
TRANSITION TEMPERATURE
YTTRIUM COMPOUNDS