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19 Oct 1998

Volume 73, Issue 16, pp. 2233-2380

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Direct-coupled second-order superconducting quantum interference device gradiometer from single layer of high temperature superconductor

Soon-Gul Lee, Yunseok Hwang, Byung-Chang Nam, Jin-Tae Kim, and In-Seon Kim

Appl. Phys. Lett. 73, 2345 (1998); http://dx.doi.org/10.1063/1.122456 (3 pages) | Cited 14 times

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We developed a noble design of the planar-type single-layer second-order superconducting quantum interference device (SQUID) gradiometer, and demonstrated that the gradiometer did not respond to a uniform field or the first-order gradient of the field but responded sensitively to the second-order gradient. The device consisted of three parallel-connected pickup loops, each of which is directly coupled to the step-edge junction SQUID. The entire structure was made from a single layer of YBa2Cu3O7 patterned by photolithography with ion milling technique. Response of the device to the field was tested with three identical wire-wound coils coupled to each loop and balancing was achieved by using a small piece of superconductor placed in the center loop. Measured off balance was about 0.6% for the uniform field and 1.4% for the first-order gradient, which were believed not due to intrinsic imbalance but mostly due to slight difference in alignment of the test coils. © 1998 American Institute of Physics.
Show PACS
85.25.Dq Superconducting quantum interference devices (SQUIDs)
07.55.Ge Magnetometers for magnetic field measurements
07.55.Jg Magnetometers for susceptibility, magnetic moment, and magnetization measurements
74.72.-h Cuprate superconductors

Demonstration of a current-controlled three-terminal Nb–InxGa1−xAs/InP Josephson contact

Th. Schäpers, J. Malindretos, K. Neurohr, S. Lachenmann, A. van der Hart, G. Crecelius, H. Hardtdegen, H. Lüth, and A. A. Golubov

Appl. Phys. Lett. 73, 2348 (1998); http://dx.doi.org/10.1063/1.122457 (3 pages) | Cited 25 times

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The supercurrent in a Nb–In0.53Ga0.47As/In0.77Ga0.23As/InP weak link structure is controlled by means of a current injected into the two-dimensional electron gas. For small injection currents the critical current to control current ratio is as large as 20. The measured features can be qualitively explained in terms of a modification of the Andreev level occupation by the injected carriers. © 1998 American Institute of Physics.
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85.25.Cp Josephson devices
74.50.+r Tunneling phenomena; Josephson effects
85.30.-z Semiconductor devices
74.70.Ad Metals; alloys and binary compounds (including A15, MgB2, etc.)
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
81.05.Ea III-V semiconductors
74.25.Sv Critical currents
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

Flux pinning in ternary (Nd0.33Eu0.33Gd0.33)Ba2Cu3Oy melt-processed superconductors

M. R. Koblischka, M. Muralidhar, and M. Murakami

Appl. Phys. Lett. 73, 2351 (1998); http://dx.doi.org/10.1063/1.122458 (3 pages) | Cited 36 times

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The flux pinning characteristics of ternary melt-processed (Nd0.33Eu0.33Gd0.33)Ba2Cu3Oy (NEG) superconductors are studied in the temperature range 60 ⩽ T ⩽ 90 K. NEG samples exhibit a strongly developed peak effect in the dependence of the critical current densities on the external field, Ha. The scaling of the pinning forces versus the reduced field h = Ha/Hirr (where Hirr denotes the irreversibility field) yields a peak at h0 = 0.5 which is an indication of pinning provided by a spatial variation of the transition temperature. The presence of a weaker superconducting second phase is demonstrated by means of field cooling and warming experiments in fields up to 7 T. Furthermore, we discuss the possible effect of the magnetic moments of Gd and Nd on the flux pinning. © 1998 American Institute of Physics.
Show PACS
74.72.-h Cuprate superconductors
74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)
74.25.Sv Critical currents
74.62.Yb Other effects

Superconductor–normal–superconductor Josephson junctions fabricated by oxygen implantation into YBa2Cu3O7−δ

F. Kahlmann, A. Engelhardt, J. Schubert, W. Zander, Ch. Buchal, and J. Hollkott

Appl. Phys. Lett. 73, 2354 (1998); http://dx.doi.org/10.1063/1.122459 (3 pages) | Cited 13 times

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We report Josephson junctions in YBa2Cu3O7−δ  films, fabricated by oxygen irradiation through a 50 nm wide slit in an implantation mask. After annealing the irradiated microbridges at 500 °C in an oxygen atmosphere, this process creates a homogeneous barrier region with a reduced but finite transition temperature, allowing Josephson coupling in a temperature window of ⩽15 K. Over the entire temperature range of Josephson coupling these junctions show resistively shunted junction behavior. The exponential dependence of the critical current on temperature is in good agreement with conventional superconductor–normal–superconductor proximity effect theory. © 1998 American Institute of Physics.
Show PACS
74.50.+r Tunneling phenomena; Josephson effects
85.25.Cp Josephson devices
74.72.-h Cuprate superconductors
74.78.-w Superconducting films and low-dimensional structures
74.45.+c Proximity effects; Andreev reflection; SN and SNS junctions
81.40.Gh Other heat and thermomechanical treatments
61.72.up Other materials
61.80.Jh Ion radiation effects
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
85.40.Ry Impurity doping, diffusion and ion implantation technology
74.10.+v Occurrence, potential candidates
74.62.Dh Effects of crystal defects, doping and substitution
74.25.Sv Critical currents

Numerical modeling of superconducting coplanar resonators for radio frequency superconducting quantum interference devices

H. R. Yi, Y. Zhang, and A. I. Braginski

Appl. Phys. Lett. 73, 2357 (1998); http://dx.doi.org/10.1063/1.122460 (3 pages) | Cited 5 times

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We have simulated the superconducting coplanar resonators of different designs that we have fabricated and tested as the tank circuit of radio frequency superconducting quantum interference devices. The coplanar resonator is formed by two microstrip lines surrounding a flux concentrator with each line having a slit. The simulated resonant frequencies agreed well with the experimental values, where frequencies decreased with an increasing mutual angular position between the two microstrip slits, and with a short circuit between the two microstrip lines. The simulation also showed that the loss in the system is mainly contributed by the dielectric loss of the substrate materials. © 1998 American Institute of Physics.
Show PACS
85.25.Dq Superconducting quantum interference devices (SQUIDs)
84.40.Az Waveguides, transmission lines, striplines
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