| 1. |
- Jonsson, B J, et al.
(author)
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Method to extract the critical current density and the flux-creep exponent in high-T-c thin films using ac susceptibility measurements
- 1998
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In: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 58:9, s. 5862-5867
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Journal article (peer-reviewed)abstract
- High-precision ac susceptibility measurements have been made on high-quality Hg-1212 thin films. A method to analyze chi(1)'(T,H-0,f) and chi(1)" (T,H-0,f) and extract the temperature dependence of the critical current density J(c)(T), as well as the temperature and field-dependent flux-creep exponent n(T,H-0), is presented. With specific measurements at external ac fields Ho in the range 7-100 Oe(rms) we determine the temperature dependence of the critical current density from a single temperature scan. The obtained temperature dependence, J(c)(T), is found to be in good agreement with data obtained from measurements using the traditional "loss-maximum" approach. In addition we present a method to extract the temperature and ac field-dependent flux-creep exponent n(T,H-0) from a set of temperature scans taken at different cc fields and driving frequencies. The observed power law describing the frequency dependence of chi' is consistent with a current-dependent effective activation energy of the form U(J)= U(0)ln(J(c)/J). Furthermore, the flux creep is found to increase with ac field and with temperature except at about 20-30 K below T-c, where our data suggest a slowing down of the flux creep.
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| 2. |
- Jukna, A, et al.
(author)
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Electric properties of planar Ag/HgBa2CaCu2O6+delta interface
- 1999
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In: Physica. C, Superconductivity. - 0921-4534 .- 1873-2143. ; 316:1-2, s. 83-88
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Journal article (peer-reviewed)abstract
- Silver coatings were magnetron sputtered onto the surface of highly c-axis-oriented HgBa2CaCu2O6+delta superconducting thin films exhibiting zero resistance T-c at about 120 K and the critical current density similar to 10(5) A/cm(2) at 100 K. Electrical resistance of the Ag/HgBa2CaCu2O6+delta planar interface and current-voltage dependencies were investigated in a course of post-deposition annealing of the Ag/HgBa2CaCu2O6+delta at 50-350 degrees C in both purl oxygen and oxygen-free ambient. Results of the electrical measurements are explained in terms of the insulating layer formation at the Ag/HgBa2CaCu2O6+delta interface. It is assumed this insulator is a product created by oxygen non-stoichiometry and decomposition of the superconductor at the interface between both materials. (C) 1999 Elsevier Science B.V. All rights reserved.
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| 3. |
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| 4. |
- YUN, H, et al.
(author)
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CHARCOAL POROUS LAYER OPEN-TUBULAR COLUMN GAS-CHROMATOGRAPHY FOR PERMANENT GAS-ANALYSIS
- 1995
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In: JOURNAL OF MICROCOLUMN SEPARATIONS. - : MICROSEPARATIONS INC. - 1040-7685. ; 7:3, s. 207-212
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Journal article (peer-reviewed)abstract
- The preparation of charcoal porous layer open tabular (PLOT) columns, and their application to the separation of permanent gases and light hydrocarbons are reported. Two types of charcoal, coconut and darco charcoal, were used to prepare columns from fus
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| 5. |
- Yun, S H, et al.
(author)
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Growth of a-axis-oriented HgBa2CaCu2Ox thin films by rapid quenching
- 1999
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In: Journal of Materials Research. - 0884-2914 .- 2044-5326. ; 14:8, s. 3181-3184
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Journal article (peer-reviewed)abstract
- High-quality a-axis-oriented HgBa2CaCu2Ox superconducting thin films have been grown on (100) LaAlO3 substrates using a modified conventional method that contains a short annealing time of 5 min, rapid-quenching process, and an alternative encapsulated approach. We found that the preferred orientations of HgBa2CaCu2Ox thin films can be controlled by rapid quenching at specific temperatures: 800, 700, 600, and 500 degrees C. The films rapidly quenched in water from 700 degrees C during a cooling cycle showed predominantly a-axis orientation perpendicular to the film surface. Phase was confirmed by x-ray diffraction pole figures. The a-axis films exhibited a zero-resistance transition temperature >120 K, which is comparable to epitaxial c-axis-oriented films.
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