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  • 1
    Electronic Resource
    Electronic Resource
    Interaction of picosecond optical pulses with high Tc superconducting films (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 2470-2472 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Infrared pulses (1.06 μm wavelength, ≈150 ps long) from a Nd:YAG laser illuminated a superconducting YBa2Cu3O7 granular film, 0.7 μm thick. This caused the film to switch from the superconducting to the normal (resistive) state in less than 2 ns, followed by a much slower recovery ∼1 μs. The initial fast switching may be explained by nonequilibrium hot-electron energy transfer from the top absorbing layer (≈100 nm thick) through the film, followed by an essentially bolometric response and cooldown via equilibrium thermal conduction out of the film.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.101538
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  • 2
    Electronic Resource
    Electronic Resource
    Bolometric and nonbolometric infrared photoresponses in ultrathin superconducting NbN films (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 7069-7074 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The photoresponse of 10 nm thick superconducting NbN meander lines is measured using an amplitude modulated infrared semiconductor laser operating at a wavelength of 1300 nm. The response time of the film is found to be less than 1 ns with a measured responsivity of up to 1500 V/W of absorbed power at 100 kHz. Thermal properties of the film are extracted from current–voltage characteristics using a self-heating hot spot model. At temperatures well below the superconducting transition, the magnitude of the photoresponse is found to be an order of magnitude too large to be purely bolometric, even when electron heating and effects due to intergranular weak links are taken into account. The photoresponse is seen to be bolometric near Tc. Other contributions to photoresponse are discussed, including kinetic inductance and the photofluxonic effect. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361426
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  • 3
    Electronic Resource
    Electronic Resource
    Hall effect and giant magnetoresistance in lanthanum manganite thin films : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 5179-5181 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetoresistance and Hall coefficient have been investigated as a function of temperature in patterned thin films of La–Ca–Mn–O. Our data on magnetoresistance show a maximum magnetoresistance ratio Δρ/ρ(0) of ≈−60% at 1.5 T and 240 K. The Hall coefficient indicates that the carriers are predominantly holes, with apparent density that varies as a function of temperature. Although changes in mobility were also observed, our results indicate that changes in carrier density become more important than changes in mobility at temperatures lower than the Curie temperature. We interpret our data in terms of a simple picture that includes two parallel contributions to the carrier density and the conductivity. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361331
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  • 4
    Electronic Resource
    Electronic Resource
    Rapid flux motion and critical state dynamics in a superconducting disk (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 372-379 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A disk of superconducting thin film partially screens an externally applied magnetic field. If the film temperature is increased, the depression of the critical current density allows the excluded flux to move in. When the film is driven to its resistive state by rapid heating, the fast decay of the screening currents results in rapid flux motion. We have developed a numerical technique for analyzing this transient flux motion along with the temporal variation of current density and magnetic field. Our theoretical model has been verified experimentally by heating a high-temperature superconducting film with short laser pulses and by measuring the induced voltage across a coil coupled closely to the film. This concept can be used to make a fast contactless opening switch for high-power applications, such as energy extraction from inductive energy storage systems. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360780
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  • 5
    Electronic Resource
    Electronic Resource
    Film thickness dependence of microwave surface resistance for YBa2Cu3O7 thin films (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 5295-5297 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Microwave surface resistance close to 10 GHz has been measured as a function of temperature for epitaxial thin films of YBa2Cu3O7 (YBCO) on LaAlO3 in the film thickness range of 0.2–0.8 μm. The films were made by a reduced-temperature post-anneal technique. The surface resistance (Rs) scaled to 10 GHz decreases with increasing film thickness as is expected due to the finite film thickness with respect to the magnetic penetration depth. Below about 70 K there is an increase in Rs for the thickest films, attributed to a change in microstructure from c axis normal to the substrate plane, to c axis in the plane of the substrate; the resulting minimum in Rs occurs at a film thickness of 0.6 μm. The critical current density (Jc) at 77 K is highest for the thinner films, so that films with the highest Jc do not have the lowest measured Rs. These results suggest that the optimum YBCO film thickness for microwave devices patterned from these films may be about 0.6 μm, depending on operating temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353764
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  • 6
    Electronic Resource
    Electronic Resource
    Duality and fluxonics in superconducting devices (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 5741-5749 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The concept of electrical duality is reviewed, with a focus on the symmetry between the motion of charge and the motion of magnetic flux. This approach is especially illuminating for the case of a superconductor, in which flux is quantized in units of Φ0=h/2e. In a two-dimensional superconductor, a quantized vortex or fluxon can be viewed as the dual of an electron. Based on this analogy, new superconducting "fluxonic'' device concepts are proposed, including optical detectors and transistors. Finally, the implications of this picture for low- and high-temperature superconductors are evaluated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346969
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  • 7
    Electronic Resource
    Electronic Resource
    High performance isotropic permanent magnet based on Nd-Fe-B (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 3577-3579 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have fabricated a macroscopically isotropic permanent magnet material (Ovonic Hi-RemTM) which significantly exceeds conventionally understood performance limits for a material with saturation magnetization Ms =16 kG. Enhanced magnetic properties, including a remanent magnetization Mr =9–10 kG or more, and a maximum energy product in excess of 20 MGOe, are observed without preferred orientation. This material has been fabricated by rapid solidification of an alloy structurally and compositionally similar to Nd2Fe14B, but which depends on critical alloying additions and process parameters to obtain optimum magnetic performance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.338706
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  • 8
    Electronic Resource
    Electronic Resource
    Photofluxonic detection: A new mechanism for infrared detection in superconducting thin films (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 2847-2849 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A new model is proposed in which a photon of energy E=hf is absorbed by a superconducting film to create a pair of equal and opposite fluxons (or vortices), each with quantized flux Φ0=h/2e. An applied current sweeps these fluxons to opposite edges of the film, causing a voltage pulse with time-integrated magnitude Φ0, and leading to a time-averaged voltage responsivity Rv = Φ0/E = 1/(2ef). This is directly analogous to photoconductive detection in a semiconductor via creation of electron-hole pairs. Data on an ultrathin granular NbN film are presented which indicate a responsivity of 6000 V/W in red light, in agreement with the model. This is promising for the development of a sensitive, high-speed infrared detector using thin films of either low or high Tc superconductors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.103760
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  • 9
    Electronic Resource
    Electronic Resource
    Nonequilibrium photon-induced hotspot: A new mechanism for photodetection in ultrathin metallic films (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 3938-3940 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A new class of photodetectors is proposed, based on localized heating of an ultrathin metallic film due to absorption of individual photons. For a 1 eV photon, the transient temperature rise can be of order 10 K or greater in a nonequilibrium "hotspot'' on the nm spatial scale and ps timescale. If current is flowing in a metallic film with a temperature-dependent resistance, such a hotspot can give rise to a voltage pulse. This can provide the basis for an ultrafast photodetector with spectral sensitivity, in contrast to a conventional bolometer. Prospects for practical realization of infrared photodetectors based on this mechanism are discussed. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.117576
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  • 10
    Electronic Resource
    Electronic Resource
    Phenomenological model for giant magnetoresistance in lanthanum manganite (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 2747-2749 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electrical conductivity of doped lanthanum manganite exhibits activated semiconducting behavior at high temperatures, and a transition to metallic behavior at low temperatures in the ferromagnetic state. These two regimes are combined in a new phenomenological equation for the conductivity that uses a mean-field magnetization and physically reasonable fitting parameters. This allows us to account quantitatively for reports of giant negative magnetoresistance in single crystals and thin films. We present new data on sputtered epitaxial thin films of La1−xCaxMnO3, and analyze other recent reports in the literature. The physical basis for such an expression is discussed. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.115585
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