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  • 1
    Digitale Medien
    Digitale Medien
    Electric forming and telegraph noise in tunnel junctions (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 2564-2568 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The normal state resistance of Pb/Bi/In-oxide-Pb/Bi and Pb/Bi/In-oxide-Ag can be changed by applying sufficiently high voltage across the oxide barrier. To explain this effect we discuss an electrical dipole, a donor, a metal ion, and an oxygen migration model. The oxygen migration model best accounts for the experimental observations. Our investigations include telegraph noise measurements. A significant change in the low-frequency noise spectrum before and after electrical forming is found. It is possible to create and destroy two-level signals by applying an electric field on the order of 2.5×108 V/m.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.353066
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  • 2
    Digitale Medien
    Digitale Medien
    Telegraph-like noise in Y-Ba-Cu oxide thin-film dc SQUID's (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 621-623 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We have observed a telegraph-like noise in dc superconducting quantum interference devices (SQUID's) made of low-temperature synthesized superconducting Y-Ba-Cu oxide thin films. The voltage of the SQUID jumps among two to four discrete levels randomly with time, and exhibits a Lorentzian type frequency dependence in the power spectrum. Periodic modulations of the voltage with magnetic flux are observed in a SQUID having narrow bridges of submicrometer width. The flux noise of the SQUID is dominated by the telegraph-like noise at low frequencies.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.100637
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  • 3
    Digitale Medien
    Digitale Medien
    Effects of alternating bias current on the low-frequency noise in dc SQUIDs (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 239-241 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We have analyzed the characteristics of flux modulated voltages of a dc SQUID for both positive and negative bias currents. It is shown that the change in the modulated voltage caused by fluctuations of the junction critical currents is eliminated after subtraction between the modulated voltages for the two biased currents. In the flux feedback mode using an alternating bias current, a large reduction of 1/f noise is observed for dc SQUIDs made of NbN junctions with amorphous Si tunnel barriers.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.341470
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  • 4
    Digitale Medien
    Digitale Medien
    A second-order planar gradiometer composed of concentric superconductive loops (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 781-784 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A planar gradiometer composed of three concentric superconductive loops is analyzed. The gradiometer performs the second derivative with a rotational symmetry in a form of ∂2Bz/∂r2, where r2=x2+y2. In response to the biomagnetic field generated by a current dipole, an isoflux line distribution which resembles well the magnetic field distribution is obtained. The location and the strength of the current-dipole source can readily be estimated from the isoflux pattern. Reduction of the magnetic field noise from distant sources with respect to the signal of a near source is calculated to be comparable with that of conventional axial gradiometers.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.338233
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  • 5
    Digitale Medien
    Digitale Medien
    Low-frequency noise of planar dc SQUIDs made of various Josephson junctions (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 692-696 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The noise characteristics at low frequencies are studied for various planar dc SQUIDs made of junctions with different barrier materials of a-Si, aluminum oxide, and niobium oxide. It is found that fluctuations of the parameters of individual junctions contribute to the flux noise of the SQUIDs in a magnitude of the same order with the apparent flux noise. The magnitude of the flux noise due to the parameter fluctuations depends on the barrier material and on the inductance parameter βL . We have observed a telegraph noise in the voltage time trace and a Lorentzian in the voltage power spectrum for a current-biased SQUID. As a source of the parameter fluctuations, capture and emission of electrons at the trapping sites in the barrier are indicated.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.343106
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  • 6
    Digitale Medien
    Digitale Medien
    Direct detection of the magnetic flux noise from moving vortices in wide YBa2Cu3O7−δ grain boundary junctions (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 1715-1717 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We measured the flux of a wide bicrystal grain boundary of YBa2Cu3O7−δ film, cooled to 77 K in a field of 10 μT, using a superconducting thin-film coil and Nb-based superconducting quantum interference device (SQUID). When the applied field was changed to, and above, a small threshold value, the sample showed random switching noises with a sharp increase in low-frequency noise power. The results suggested that there was long-distance movement of vortices over 20–500 μm within the grain boundary, driven by the shielding current. The vortex movement was suppressed to lengths of less than 1 μm in a slotted grain boundary by making an array of SQUIDs that can hold vortices stably. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1355669
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  • 7
    Digitale Medien
    Digitale Medien
    Active compensation in combination with weak passive shielding for magnetocardiographic measurements (2002)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 73 (2002), S. 440-445 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: We studied different schemes of noise reduction using active compensation of environmental magnetic field noises in order to develop a high-temperature-superconductor (HTS) magnetometer system for the measurement of magnetocardiographic signals. The active compensation was combined with weak passive shielding of about 20 dB by the use of a magnetically shielded room (MSR) having a single layer of surrounding μ-metal. A novel method using a normal detection coil and compensation coils that were wound around the walls of the MSR to enable magnetic coupling was examined. Effective suppression of environmental field noises of more than 20 dB at 0.5–10 Hz and 10 dB at 10–100 Hz, covering the low-frequency range of biological signals, was obtained. In an alternative method using a reference HTS magnetometer in the MSR for noise detection, a compensation coil was set in the MSR and served as a feedback coil in operating the magnetometer. Residual field noises that were limited by the intrinsic noise of the reference magnetometer were obtained. Using such active compensation and weak passive shielding, measurement of magnetocardiogram was possible with a sensing HTS magnetometer in a wide frequency range of 0.5–100 Hz. © 2002 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1435843
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  • 8
    Digitale Medien
    Digitale Medien
    Vortex dynamics of Nb variable-thickness bridges measured by direct flux detection method (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 7819-7823 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: In order to study the dynamical behavior of vortices moving through superconducting thin film devices, we constructed a probe having a concentric thin-film planar gradiometer coupled to a direct current SQUID. The probe was designed to directly detect the flux generated by a single vortex, based on the monopole approximation. Measurements of static current–voltage (I–V) and flux noise characteristics were made for variable-thickness bridges (VTB) made on epitaxial Nb films. The critical current was unambiguously determined from the onset of vortex motion. Multiple step noise of the flux with a minimum step height of 0.28Φ0 was observed above the critical current in the time traces. This step height is in agreement with the numerical calculation for single vortex motion, confirming the validity of the monopole approximation. It is suggested that the multiple step noise is generated by the successive entry of single vortices into the bridge. VTBs made on polycrystalline Nb films were also measured. The I–V characteristic showed asymmetric voltage increases and a multiple peak structure of the flux noise was observed above the critical current, suggesting the successive depinning of trapped vortices as flux bundles from widely distributed pinning potentials. © 1999 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.370591
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  • 9
    Digitale Medien
    Digitale Medien
    Fabrication and measurement of cylindrical Nb3Ge rf SQUIDs (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 1749-1750 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Nb3Ge thin-film microbridges are fabricated on a cylindrical substrate to form rf SQUIDs. High temperature operations well above 10 K (up to 17.5 K) are obtained. An intrinsic flux noise of the order of 10−4 Φ0/(Hz)1/2 is estimated from the step rise parameter. Comparison with a theoretical noise indicates a nonsinusoidal current phase relation of the microbridge.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.334449
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  • 10
    Digitale Medien
    Digitale Medien
    Defect structure and local conduction in YY"2O"3Au junctions
    Amsterdam : Elsevier
    Thin Solid Films 48 (1978), S. 43-50 
    Details
    ISSN: 0040-6090
    Quelle: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Thema: Physik
    Materialart: Digitale Medien
    URL: http://linkinghub.elsevier.com/retrieve/pii/0040-6090(78)90329-2
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