Scanning Hall micro-probe measurements of YBa[sub 2]Cu[sub 3]O[sub 7-y]

Miscellaneous · Wed Jan 01 00:00:00 EST 1992

OSTI ID:7166457

Brawner, D A

A new scanning Hall micro-probe technique was developed to measure the magnetic field around superconductors. This was used to make precision measurements of the [open quote]critical state[close quote] profiles in single crystals of YBa[sub 2]Cu[sub 3]O[sub 7[minus]y]. This technique showed an unexpected [open quote]field induced rotation[close quote] of the magnetization profile in single crystal YBa[sub 2]Cu[sub 3]O[sub 7[minus]y]. The remanent state was studied. For crystals with a rectangular aspect ratio, the remanent ridge was rotated. This rotation takes on an opposite sense when the field is reversed, leading to a field induced asymmetry. This unexpected phenomemon disappears above 25 K, and coincides with a collapse of the remanent peak in an applied field. For zero field cooled samples, there are positions on the superconductor where the measured fields actually oppose the applied fields. The time dependent behavior of these magnetic fields was also studied. Precision measurements of the relaxation of the remanent magnetic fields in single-crystal YBa[sub 2]Cu[sub 3]O[sub 7[minus]y] have been made and compared with more conventional magnetometer measurements. For all temperatures from 4.2 to 85 K, the relaxation follows a power law decay B(t) [approximately] (1+t/[tau])[sup [minus]1/[sigma]] more convincingly than a logarithmic decay. The detailed temperature dependence of the exponent (1/[sigma]) is compared with a recent calculation by Vinokur, Feigel'man, and Geshkenbein predicting such a power law decay. The field around a superconducting crystal is calculated, enabling a quantitative analysis of the critical state profiles and a novel method to determine J[sub C]. The invasion of magnetic flux above H[sub C1] was examined and this provides direct evidence for the existence of a surface barrier inhibiting the entry of magnetic flux lines.

• Research Organization: Princeton Univ., NJ (United States)
• OSTI ID: 7166457
• Resource Relation: Other Information: Thesis (Ph.D.)
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
BARIUM OXIDES
HALL EFFECT
MAGNETIZATION
CUPRATES
YTTRIUM OXIDES
HIGH-TC SUPERCONDUCTORS
INTERMETALLIC COMPOUNDS
MAGNETIC FIELDS
MONOCRYSTALS
TEMPERATURE DEPENDENCE
TIME DEPENDENCE
ALKALINE EARTH METAL COMPOUNDS
ALLOYS
BARIUM COMPOUNDS
CHALCOGENIDES
COPPER COMPOUNDS
CRYSTALS
OXIDES
OXYGEN COMPOUNDS
SUPERCONDUCTORS
TRANSITION ELEMENT COMPOUNDS
YTTRIUM COMPOUNDS
360204* - Ceramics
Cermets
& Refractories- Physical Properties
360207 - Ceramics
Cermets
& Refractories- Superconducting Properties- (1992-)