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5 Jun 1989

Volume 54, Issue 23, pp. 2287-2377

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Transport critical current density in Bi2Sr2CaCu2Ox single crystals

Donglu Shi, Ming Tang, Y. C. Chang, P. Z. Jiang, K. Vandervoort, B. Malecki, and D. J. Lam

Appl. Phys. Lett. 54, 2358 (1989); http://dx.doi.org/10.1063/1.101527 (3 pages) | Cited 13 times

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The transport crystal current density Jc has been measured in Bi2Sr2CaCu2Ox single crystals. With a voltage criterion of 1.0 μV/cm, current density measurements yield Jc values ranging from 300 to 1000 A/cm2 at 77 K and zero field, depending upon crystal quality. The crystals are grown by using a flux method and have a typical size of approximately 10×4×1.5 mm. X‐ray diffraction, scanning electron microscopy, electrical resistivity, and magnetization shielding data are reported.
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74.70.-b Superconducting materials other than cuprates
74.25.Sv Critical currents
74.25.Ha Magnetic properties including vortex structures and related phenomena
61.66.Fn Inorganic compounds

Coupling strengths and flux pinning in oxide superconductors

R. L. Lichti, K. C. B. Chan, D. W. Cooke, and C. Boekema

Appl. Phys. Lett. 54, 2361 (1989); http://dx.doi.org/10.1063/1.101528 (3 pages) | Cited 16 times

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Muon spin relaxation measurements have been performed to obtain penetration depth versus temperature for several high‐temperature oxide superconductors. Comparison with theoretical results based on the Eliashberg equations indicates that at 1 kOe the (RE)Ba2Cu3O7 materials (data for RE=Gd, Er, and Eu) are in the very strong coupling, extremely dirty limit, while data at 5 kOe for Bi2CaSr2Cu2O8 and Tl2Ca2Ba2Cu3O10 follow the strong coupling, clean limit curve.
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74.25.Ha Magnetic properties including vortex structures and related phenomena
74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)
74.70.-b Superconducting materials other than cuprates
76.75.+i Muon spin rotation and relaxation

Epitaxial film growths of artificial (Bi‐O)/(Sr‐Ca‐Cu‐O) layered structures

J. Fujita, T. Tatsumi, T. Yoshitake, and H. Igarashi

Appl. Phys. Lett. 54, 2364 (1989); http://dx.doi.org/10.1063/1.101529 (3 pages) | Cited 15 times

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Epitaxial film growth of artificial (Bi‐O)/(Sr‐Ca‐Cu‐O) layered structures on MgO substrates was carried out using reactive‐oxygen‐gas dual ion beam sputtering and shuttering technique. A 12 Å Sr‐Ca‐Cu‐O buffer layer seems suitable for perfect epitaxial film growth. Single‐phase films having periodicities of 12, 15, and 18 Å (which correspond to bulk 24, 30, and 36 Å phases in Bi oxide superconductors) were selectively grown by adjusting the thickness of a Sr‐Ca‐Cu‐O layer sandwiched by Bi‐O bi‐planes. A high Tc phase film with a total thickness of about 300 Å showed an onset Tc of 110 K and a zero resistivity temperature of 45 K without post‐deposition annealing. The shuttering technique seems to enable the layer‐by‐layer film growth, and it is very effective for the formation of smooth and perfect epitaxial structures.
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74.78.-w Superconducting films and low-dimensional structures
74.70.-b Superconducting materials other than cuprates
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
81.15.Cd Deposition by sputtering

Preparation and superconducting properties of ultrathin YBa2Cu3O7−x films

X. X. Xi, J. Geerk, G. Linker, Q. Li, and O. Meyer

Appl. Phys. Lett. 54, 2367 (1989); http://dx.doi.org/10.1063/1.101530 (3 pages) | Cited 55 times

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Ultrathin films of YBa2Cu3O7−x with thicknesses down to 2 nm were grown on(100)SrTiO3 and (100)MgO by inverted cylindrical magnetron sputtering. Metallic behavior and zero resistance temperatures above 4.2 K were obtained in 3‐nm‐thick films on SrTiO3. Thinner films revealed temperature‐activated conductivity and only partial transitions to superconductivity due to inhomogeneities in the film morphology. On MgO, the critical film thickness leading to deteriorations of the transport properties was 6 nm. An analysis of the fluctuation‐enhanced conductivity near Tc in terms of the Aslamazov–Larkin theory [Phys. Lett. A 26, 238 (1968)] revealed three‐dimensional behavior even in the thinnest fully superconducting films.
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74.78.-w Superconducting films and low-dimensional structures
74.70.-b Superconducting materials other than cuprates
81.15.Cd Deposition by sputtering
68.55.-a Thin film structure and morphology

Exponential temperature dependence of the critical transport current in Y‐Ba‐Cu‐O thin films

S. S. Yom, T. S. Hahn, Y. H. Kim, H. Chu, and S. S. Choi

Appl. Phys. Lett. 54, 2370 (1989); http://dx.doi.org/10.1063/1.101531 (3 pages) | Cited 9 times

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We have measured the critical currents in rf‐sputtered YBa2Cu3O7−x thin films deposited on polycrystalline yttria‐stabilized zirconia substrates as a function of temperature down to 10 K. The dependence of the granular films at low temperature indicated exponential behavior which is similar to the superconductor‐normal metal‐superconductor (S‐N‐S) type tunneling junctions. For the films with a grain size of approximately 1 μm, we observed two exponential decay constants, which suggest that Josephson junctions limiting the transport critical current are possible both at the grain boundaries and at twin boundaries.
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74.25.Sv Critical currents
74.78.-w Superconducting films and low-dimensional structures
74.70.-b Superconducting materials other than cuprates
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Reduced reactivity to air on HF‐treated YBa2Cu3O7−x surfaces

R. P. Vasquez, B. D. Hunt, and M. C. Foote

Appl. Phys. Lett. 54, 2373 (1989); http://dx.doi.org/10.1063/1.101532 (3 pages) | Cited 16 times

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Treatment of YBa2Cu3O7−x films with a nonaqueous solution of HF in absolute ethanol results in the formation of an oxyfluoride with relative Y:Ba:Cu concentrations of 1:4:3 on the surface, as determined by x‐ray photoelectron spectroscopy. The passivation properties of chemically treated films were tested by monitoring the growth of the high binding energy O 1s peak, associated with nonsuperconducting surface species, as a function of air exposure time, for both HF‐treated and untreated films. The native oxyfluoride is shown to reduce the reactivity of the superconductor to air.
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81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
81.65.-b Surface treatments
74.70.-b Superconducting materials other than cuprates
74.78.-w Superconducting films and low-dimensional structures

Magnetic and magneto‐optic properties of In‐alloyed TbFe amorphous films

Tetsuo Iijima, Osamu Ishii, and Iwao Hatakeyama

Appl. Phys. Lett. 54, 2376 (1989); http://dx.doi.org/10.1063/1.101086 (2 pages) | Cited 4 times

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The magnetic and magneto‐optic characteristics of indium (In) ‐alloyed TbFe amorphous films are investigated. Alloying with In drastically decreases the compensation temperature, and increases the Kerr rotation by more than 20%. Both the compensation composition and the compensation temperature are observed to shift to the Tb‐rich side when alloying with In. These magnetic property changes are attributed to the influence of In on the Fe and/or Tb moments.
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75.70.Ak Magnetic properties of monolayers and thin films
78.20.Ls Magneto-optical effects
78.66.Bz Metals and metallic alloys
75.50.Kj Amorphous and quasicrystalline magnetic materials
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