Dependence of the flux-creep activation energy on the magnetization current for a La sub 1. 86 Sr sub 0. 14 CuO sub 4 single crystal
- Department of Metallurgical Engineering and Materials Science, Carnegie Mellon University, Pittsburgh, Pennsylvania (USA)
- Los Alamos National Laboratory, Los Alamos, New Mexico (USA)
- Institute of Inorganic Synthesis, Yamanashi University, Kofu 400 (Japan)
Magnetic relaxation and hysteresis studies have been performed for a {ital c}-axis-oriented single crystal of La{sub 1.86}Sr{sub 0.14}CuO{sub 4}. We demonstrate that the effective activation energy for flux creep, {ital U}{sub eff}, is a strongly nonlinear function of the current density {ital J} (as given by the irreversible magnetization). For fixed fields of 0.5, 1.0, 2.0, and 3.0 T and temperatures between 4 and 15 K (as consistent with full field penetration of the sample), {ital U}{sub eff}({ital J}) is seen to vary approximately logarithmically with {ital J}. A scaling relationship, {ital U}{sub eff}({ital J})=({minus}{ital U}{sub 1}{ital g}({ital T})/{ital H}{sup {ital n}})ln({ital J}/{ital J}{sub {ital c}}), is shown to be obeyed for this crystal with {ital n}{congruent}0.9 ({ital H} in T), {ital U}{sub 1}{congruent}180{ital k}{sub {ital B}}, and {ital J}{sub {ital c}}(1 T){congruent}3.2{times}10{sup 5} A/cm{sup 2}. Several functional forms of {ital g}({ital T}) have been explored and shown to give reasonable fits if monotonically decreasing in temperature over the range where flux creep is observed. We also explore the ramifications of this functional dependence in explaining an observed exponential temperature dependence of the hysterically determined critical current density. Finally, we show that comparison of the temperature dependence of logarithmic relaxation rate {ital A}={ital dM}/{ital d} ln({ital t}) and the derivative of the magnetization with respect to ln({ital T}) at fixed time, {ital dM}{sub 0}/{ital d} ln({ital T}), can be used to set a scale of the attempt frequency for flux motion consistent with the other measurements.
- OSTI ID:
- 5205887
- Journal Information:
- Physical Review, B: Condensed Matter; (United States), Vol. 44:14; ISSN 0163-1829
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
COPPER OXIDES
MAGNETIC FLUX
LANTHANUM OXIDES
STRONTIUM OXIDES
ACTIVATION ENERGY
CREEP
CRITICAL CURRENT
HIGH-TC SUPERCONDUCTORS
MAGNETIZATION
MONOCRYSTALS
ALKALINE EARTH METAL COMPOUNDS
CHALCOGENIDES
COPPER COMPOUNDS
CRYSTALS
CURRENTS
ELECTRIC CURRENTS
ENERGY
LANTHANUM COMPOUNDS
MECHANICAL PROPERTIES
OXIDES
OXYGEN COMPOUNDS
RARE EARTH COMPOUNDS
STRONTIUM COMPOUNDS
SUPERCONDUCTORS
TRANSITION ELEMENT COMPOUNDS
360204* - Ceramics
Cermets
& Refractories- Physical Properties