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Articles 1 - 11 of 11
Full-Text Articles in Physical Sciences and Mathematics
Evidence For Weak Link And Anisotropy Limitations On The Transport Critical Current In Bulk Polycrystalline Y1Ba2Cu3O Χ , J.W. Ekin, A.I. Braginski, A.J. Panson, M.A. Janocko, D.W. Capone Ii, N.J. Zaluzec, B. Flandermeyer, O.F. De Lima, M. Hong, J. Kwo, Sy_Hwang Liou
Evidence For Weak Link And Anisotropy Limitations On The Transport Critical Current In Bulk Polycrystalline Y1Ba2Cu3O Χ , J.W. Ekin, A.I. Braginski, A.J. Panson, M.A. Janocko, D.W. Capone Ii, N.J. Zaluzec, B. Flandermeyer, O.F. De Lima, M. Hong, J. Kwo, Sy_Hwang Liou
Sy-Hwang Liou Publications
Measurements of the transport critical-current density (Jc), magnetization Jc, and magnetoresistance in a number of bulk sintered samples of Y1Ba2Cu3O χ from several different laboratories indicate that the transport Jc is limited by weak-link regions between high Jc regions. The weak-link Jc has a Josephson character, decreasing by two orders of magnitude as the magnetic field is increased from 0.1 to 10 mT at 77 K. An examination of the grain-boundary region in Y1Ba2Cu3O χ shows no observable impurities or …
Raman Detection Of The Superconducting Gap In Ba-Y-Cu-O Superconductors, K.B. Lyons, Sy_Hwang Liou, M. Hong, H.S. Chen, J. Kwo, T.J. Negran
Raman Detection Of The Superconducting Gap In Ba-Y-Cu-O Superconductors, K.B. Lyons, Sy_Hwang Liou, M. Hong, H.S. Chen, J. Kwo, T.J. Negran
Sy-Hwang Liou Publications
We have utilized an iodine absorption cell to enable detailed Raman studies at low frequency (down to 15 cm-1) in a thin film of the high-temperature superconductor Ba2YCu3O7. Subtraction of spectra just above and well into the superconducting phase reveals a weak broad feature (maximum near 400 cm-1, half width at half maximum approximately 250 cm-1), which we tentatively interpret as due to scattering near the superconducting gap. The large width of the feature may be partially related to smearing of the transition, or to gap anisotropy. Its …
Structural And Superconducting Properties Of Orientation-Ordered Y1Ba2Cu3O7-X Films Prepared By Molecular-Beam Epitaxy , J. Kwo, T.C. Hsieh, R.M. Fleming, M. Hong, Sy_Hwang Liou, B.A. Davidson, L.C. Feldman
Structural And Superconducting Properties Of Orientation-Ordered Y1Ba2Cu3O7-X Films Prepared By Molecular-Beam Epitaxy , J. Kwo, T.C. Hsieh, R.M. Fleming, M. Hong, Sy_Hwang Liou, B.A. Davidson, L.C. Feldman
Sy-Hwang Liou Publications
Superconducting Y1Ba2Cu3O7-x films were produced by metal molecular-beam epitaxy with one electron beam and two thermal cells and a molecular oxygen-gas source. The films were epitaxially grown on SrTiO3 (100) with an a-axis orientation perpendicular to the plane, and b and c axes ordered in the plane. A sharp resistive superconducting transition with Tc (R=0) at 82 K was obtained. A lower limit of the average Jc in the plane is 103 A/cm2 at 77 K, 5×104 A/cm2 at 70 K, and 10 …
Superconducting Y-Ba-Cu-O Oxide Films By Sputtering, M. Hong, Sy_Hwang Liou, J. Kwo, B.A. Davidson
Superconducting Y-Ba-Cu-O Oxide Films By Sputtering, M. Hong, Sy_Hwang Liou, J. Kwo, B.A. Davidson
Sy-Hwang Liou Publications
We have prepared superconducting thin films of Y-Ba-Cu-O with Tc onsets above 95 K by both diode and magnetron sputtering. Films with full superconductivity (R=0) at 85 K have been produced by dc magnetron sputtering. The compositions of the films are fairly uniform across an area 50 mm in diameter and through the film thickness. Structural properties of the films were studied by x-ray diffraction. Critical current densities in the range of 3000 to 104 A/cm2 have been measured at 4.2 K. Applied Physics Letters is copyrighted by The American Institute of Physics.
Antiphase Domain Boundaries In The Superconducting Phase Of The Y-Ba-Cu-O System, C.H. Chen, J. Werder, Sy_Hwang Liou, M. Hong
Antiphase Domain Boundaries In The Superconducting Phase Of The Y-Ba-Cu-O System, C.H. Chen, J. Werder, Sy_Hwang Liou, M. Hong
Sy-Hwang Liou Publications
Transmission-electron-microscopy examination of the superconducting phase of the Y-Ba-Cu-O system reveals the presence of dense antiphase boundaries. The structure of the superconducting phase was determined to be orthorhombic with space group Pm2m. The orthorhombic a and b axes are found to alternate across the antiphase boundary which runs parallel to the [110] direction.
Break-Junction Tunneling Measurements Of The High-TC Superconductor Y1Ba2Cu3O9- Δ , J. Moreland, J.W. Ekin, L.F. Goodrich, T.E. Capobianco, A.F. Clark, J. Kwo, M. Hong, Sy_Hwang Liou
Break-Junction Tunneling Measurements Of The High-TC Superconductor Y1Ba2Cu3O9- Δ , J. Moreland, J.W. Ekin, L.F. Goodrich, T.E. Capobianco, A.F. Clark, J. Kwo, M. Hong, Sy_Hwang Liou
Sy-Hwang Liou Publications
Current-voltage tunneling characteristics in a high-critical-temperature superconducting material containing predominately Y1Ba2Cu3O9- δ have been measured using the break-junction technique. Sharp gap structure was observed, with the largest superconductive energy gap measured to be Δ=19.5±1 meV, assuming a superconductor-insulator-superconductor junction. This energy gap corresponds to 2Δ/kBTc=4.8 at T=4 K, for a critical temperature of 93 K (midpoint of the resistive transition).
Enhanced Magnetism In Amorphous Fe-Based Alloys, Sy_Hwang Liou, S.H. Ge, J.N. Taylor, C.L. Chien
Enhanced Magnetism In Amorphous Fe-Based Alloys, Sy_Hwang Liou, S.H. Ge, J.N. Taylor, C.L. Chien
Sy-Hwang Liou Publications
Systematic investigations of binary amorphous Fe–T alloys (T=an early transition-metal elements Ti, Zr, Nb, Hf, Ta...) over wide composition ranges reveal depressed magnetic properties with anomalously low magnetic ordering temperature and magnetization. We show in this work, via a prototype amorphous Fe70Ti30 alloy, the substitution of Fe by Co, Ni, or Cu greatly enhances the magnetic ordering temperature and the magnetization. Our results indicate that this is primarily caused by the increased Fe moment upon alloying.
Magnetic Granular Fe-(Sio2) Solids, C.L. Chien, Gang Xiao, Sy_Hwang Liou, J.N. Taylor, A. Levy
Magnetic Granular Fe-(Sio2) Solids, C.L. Chien, Gang Xiao, Sy_Hwang Liou, J.N. Taylor, A. Levy
Sy-Hwang Liou Publications
We have synthesized a series of granular Fe-SiO2 solids consisting of Fe metal granules of nanometer sizes embedded in an insulating SiO2 matrix. The ultrafine microstructures, revealed by TEM, are achieved by using a high-rate magnetron sputtering system. The magnetic properties of such solids are determined by the granular size and the metal volume fraction. Below the percolation threshold, isolated single-domain particles having large magnetic coercivity in the blocked state exhibit superparamagnetic relaxation, which has been studied by using SQUID magnetometry and Mössbauer spectroscopy. Above the percolation threshold, magnetic coercivity drops dramatically and the magnetic properties approach that …
Magnetic Characteristics Of Ultrafine Fe Particles Reduced From Uniform Iron Oxide Particles, K. Bridger, J. Watts, M. Tadros, Gang Xiao, Sy_Hwang Liou, C.L. Chien
Magnetic Characteristics Of Ultrafine Fe Particles Reduced From Uniform Iron Oxide Particles, K. Bridger, J. Watts, M. Tadros, Gang Xiao, Sy_Hwang Liou, C.L. Chien
Sy-Hwang Liou Publications
Uniform, cubic 0.05-µm iron oxide particles were formed by forced hydrolysis of ferric perchlorate. These particles were reduced to α-Fe by heating in hydrogen at temperatures between 300 and 500 °C. The effect of reduction temperature and various prereduction treatments on the microstructure of the iron particles will be discussed. Complete reduction to α-Fe was established by 57Fe Mössbauer spectroscopy and x-ray diffraction. Magnetic measurements on epoxy and polyurethane films containing these particles with various mass fractions gave coercivities as high as 1000 Oe. The relationship between the magnetic measurements and the microstructure will be discussed. Na2SiO …
Mössbauer Study Of Spin Reorientation In Y1.8Er0.2Fe14B, M. Abe , Sy_Hwang Liou, C.L. Chien, N.C. Koon, B.N. Das, E. Callen
Mössbauer Study Of Spin Reorientation In Y1.8Er0.2Fe14B, M. Abe , Sy_Hwang Liou, C.L. Chien, N.C. Koon, B.N. Das, E. Callen
Sy-Hwang Liou Publications
Fe57 Mössbauer spectra were taken from 300 K down to 4.2 K for two single-crystal samples of Y1.8Er0.2Fe14B, one cut with its [001] axis normal to the surface, the other with its diagonal of [100], [010], and [001] axes normal to the surface. The former sample has shown that the angle between the Fe spin and the [001] increases continuously below ~90 K. This qualitatively agrees with the spin reorientation (i.e., the easy axis of magnetization rotates away from the [001] toward [100] on cooling below ~90 K) which have already been observed …
Composition Range Of Binary Amorphous Alloys, Sy_Hwang Liou, C.L. Chien
Composition Range Of Binary Amorphous Alloys, Sy_Hwang Liou, C.L. Chien
Sy-Hwang Liou Publications
We have studied a number of binary metal-metal and metalloid alloy systems made by a single vapor-quench method under very consistent conditions. In each case, amorphous alloys are found in one continuous composition range (xmin≤x≤xmax) regardless of the number of eutectic points in the equilibrium phase diagrams. It is found that the atomic size difference is the single most important factor in the quantitative determination of the composition range.