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  • 1
    Electronic Resource
    Electronic Resource
    Calculations of the microwave conductivity of high-Tc superconducting thin films from power transmission measurements (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 5550-5553 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: To calculate the complex conductivity σ=σ1−jσ2, and thus the surface resistance Rs and penetration depth λL, of high Tc superconducting thin films from microwave power transmission measurements, new expressions are derived taking into account the film thickness. Numerical examples are given to show that, compared with the calculations which neglect the film thickness, corrections in σ1, σ2, Rs, and λL are a few percent for film thickness ranging between 0.65 and 0.46 λL and that corrections in σ1 and σ2 are greater than those in Rs and λL. Using the newly derived expressions, maximum errors in Rs and λL are estimated to be about 30% and 3%, respectively, if errors between −10% and +10% are tolerated in the measurements of the magnitude and phase shift of microwave transmission.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350530
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  • 2
    Electronic Resource
    Electronic Resource
    Numerical calculation of the height of velocity-matching step of flux-flow type Josephson oscillator (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 4703-4709 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The height of the velocity-matching step (VM step) of a flux-flow type Josephson oscillator is studied systematically by numerical simulations. It is defined by the phase velocity of the propagating fluxons equaling that of the electromagnetic wave in the junction structure. The height of VM step (γm) is an important parameter for the practical application of such a device. The results presented on γm are important data in order to save computer time in the simulation of electromagnetic properties, such as the output voltage, at the velocity-matching condition. The detailed simulations were performed using the perturbed sine-Gordon equation (PSGE) with a uniformly distributed bias current γ. The PSGE was solved numerically by using an implicit finite-difference scheme. The distributions of electromagnetic fields in an overlap, long Josephson junction in the flux-flow state are mapped. The parameters influencing γm are discussed. We show that γm increases almost linearly with an external magnetic field βe or with the quasiparticle damping α, while it is less dependent on surface loss β. γm increases slowly with junction length above a minimum length, and it levels out at long lengths. We also present an approximate expression for γm which fits numerical results well.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346150
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  • 3
    Electronic Resource
    Electronic Resource
    Spatial variation of the critical current density of the high Tc superconducting thin films (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 5350-5353 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Low-temperature scanning electron microscopy (LTSEM) is a promising measuring technique for probing the spatial distribution of the superconducting properties of high Tc thin films. In the presented article we have given some experimental observations on the spatial variation of the critical current density of two kinds of high Tc thin films using a LTSEM. The results show that in the polycrystalline TlBaCaCuO film prepared by dc magnetron sputtering, the maximum local critical current density is about 3–4 times greater than the minimum local critical current density. The microstructure analysis implies that the strong inhomogeneous critical current density distribution in the TlBaCaCuO film is due to its granular structures and the existence of several structural phases. For c-axis oriented epitaxial YBaCuO thin film deposited in situ by laser ablation, the results indicate a less inhomogeneous critical current density distribution. The maximum local critical current density is less than 1.5 times the minimum local critical current density in the epitaxial thin film.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351972
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  • 4
    Electronic Resource
    Electronic Resource
    30 Hz–10 kHz hysteresis loop tracer with field up to 0.1 T for high-Tc superconductors (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 2830-2833 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A hysteresis loop tracer to measure the ac magnetization of high-Tc superconductors in the frequency range of 30 Hz–10 kHz is described, with driving field amplitudes up to 0.1 T. Due to the high frequency of the magnetic field, the hysteresis loops could be displayed on an oscilloscope and their details could be observed. The demagnetization factor, the stability, and the frequency characteristics of the tracer were tested. The ac magnetization of granular high-Tc superconductors was studied as a function of field amplitude and frequency. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148203
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  • 5
    Electronic Resource
    Electronic Resource
    Intrinsic noise temperatures of YBa2Cu3O7−δ Josephson devices on bicrystal substrates and the upper frequency limit for their operation (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 6536-6538 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Following a method proposed by Divin and Modovets [Sov. Tech. Phys. Lett. 9, 108 (1983)], we have measured at millimeter waveband the intrinsic noise temperatures TN of YBa2Cu3O7−δ Josephson junctions or dc superconducting quantum interference devices (SQUIDs) fabricated on SrTiO3, yttria-stabilized ZrO2, or Si bicrystal substrates. Over wide ranges of physical temperatures TP and the junction's normal resistance RN, it was found that TN follows TP pretty well. This indicates that the intrinsic noise in the devices is dominated by Johnson noise. TN was also measured in cases where there is external magnetic field applied, or where there is another microwave radiation like the local oscillator in a mixer. The magnetic field or microwave radiation does not seem to affect TN in any appreciable way. To estimate the high frequency performance of the junctions on Si bicrystal substrates, direct irradiation by a far infrared laser at 1.81 THz is carried out and the clear first Shapiro step is observed. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363672
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  • 6
    Electronic Resource
    Electronic Resource
    Harmonic mixing at mm waveband in a high temperature superconducting grain boundary Josephson junction (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 2286-2288 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using a high Tc superconducting grain boundary Josephson junction, harmonic mixing experiments in the mm waveband were carried out, aiming at as large a harmonic number and as high a signal frequency as possible. The dependencies of intermediate frequency output on dc bias, harmonic number, frequency of local oscillator (LO), and other parameters were carefully studied. Until now, our best result was the mixing between the signal at 95 GHz and the 105th harmonic of LO at about 900 MHz. Preliminary experiments using a high Tc harmonic mixer and phase-locking loop were tried to stabilize the frequency of a mm wave source.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356293
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  • 7
    Electronic Resource
    Electronic Resource
    Up to the 51st harmonic mixing in YBa2Cu3O7−y weak link operated in liquid nitrogen (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 1265-1267 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: When a signal at the nominal frequency of 76 GHz and a local oscillation (LO) at the frequency of a few gigahertz were both applied to a YBa2Cu3O7−y weak link immersed in liquid nitrogen, the former mixed with the harmonics of the latter giving rise to output at the intermediate frequency (IF) of about 150 MHz. The highest observed harmonic number was 51. Without exhaustive effort to optimize, the typical IF output power referred to the mixer output ranged between −103 and −112 dbm while the IF signal-to-noise ratio ranged between 16 and 4 db, depending strongly on the local oscillation power, the dc bias current, and the signal power. Reported in this letter are the experimental details as well as the requirements for a superconducting weak link to be a harmonic mixer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104229
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  • 8
    Electronic Resource
    Electronic Resource
    Magnetization of an epitaxial YBa2Cu3O7−δ film at the critical field sweep rate (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 82 (1997), S. 6116-6121 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have measured the magnetic hysteresis loops of an epitaxial YBa2Cu3O7−δ thin film using our recently developed device which can provide the field magnitude in the range of 0–1000 Oe and the field sweep rate up to 107 Oe/s. The shape of the hysteresis loop measured changes with the field-sweep rate up to the critical sweep rate; and over the critical sweep rate the ac magnetization reaches its real critical state where magnetization does not change even with a further increase in the field-sweep rate. The critical sweep rate is about 106 Oe/s at 77 K. With the hysteresis loops and Bean model, we have calculated the magnetization critical current density (Jcac) which is consistent with that obtained by I–V measurements. We have also studied flux motion and activation energy under the high sweep rate magnetic field. At temperature 77 K, the velocity of the flux motion is of the order 10 m/s and the pinning energy U0/k is about 339 K which is much smaller than the magnetization decay measurement. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.366484
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  • 9
    Electronic Resource
    Electronic Resource
    Parametric amplification using superconductor-insulator-superconductor junctions: A study carried out on an electronic simulator (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 60 (1992), S. 1390-1392 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An ideal superconductor-insulator-superconductor (SIS) junction biased below the gap voltage is a purely reactive device based on which reflection parametric amplifier can be built. Using an electronic simulator to model the junction, we have observed gain as high as 10 dB and have shown that the quantum reactance of the simulator are on the same orders of magnitudes as those of a SIS junction, thus demonstrating, for the first time, the feasibility of this new type of parametric amplifier.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.107300
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  • 10
    Electronic Resource
    Electronic Resource
    Interpretation of some experimental observations on a YBa2Cu3O7−x weak link in terms of series grain boundary junctions (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 3698-3702 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: To understand the behavior of a YBa2Cu3O7−x weak link (constriction), a simple model of two Josephson junctions in series with each other is proposed. Electronic simulation of this two-junction array under various conditions generates dc and ac IV curves. Some of these curves duplicate very well what has been observed on a real YBa2Cu3O7−x weak link, while others predict phenomena that have not yet been observed. These results suggest the possible applicability of this model to explain the complicated experimental features of a YBa2Cu3O7−x weak link.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.344082
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