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8 May 2000

Volume 76, Issue 19, pp. 2647-2800

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Electric-pulse-induced reversible resistance change effect in magnetoresistive films

S. Q. Liu, N. J. Wu, and A. Ignatiev

Appl. Phys. Lett. 76, 2749 (2000); http://dx.doi.org/10.1063/1.126464 (3 pages) | Cited 365 times

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A large electric-pulse-induced reversible resistance change active at room temperature and under zero magnetic field has been discovered in colossal magnetoresistive (CMR) Pr0.7Ca0.3MnO3 thin films. Electric field-direction-dependent resistance changes of more than 1700% were observed under applied pulses of ∼ 100 ns duration and as low as ±5 V magnitude. The resistance changes were cumulative with pulse number, were reversible and nonvolatile. This electrically induced effect, observed in CMR materials at room temperature has both the benefit of a discovery in materials properties and the promise of applications for thin film manganites in the electronics arena including high-density nonvolatile memory. © 2000 American Institute of Physics.
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75.47.Gk Colossal magnetoresistance
75.50.Dd Nonmetallic ferromagnetic materials
75.47.De Giant magnetoresistance

Picosecond hot-electron energy relaxation in NbN superconducting photodetectors

K. S. Il’in, M. Lindgren, M. Currie, A. D. Semenov, G. N. Gol’tsman, Roman Sobolewski, S. I. Cherednichenko, and E. M. Gershenzon

Appl. Phys. Lett. 76, 2752 (2000); http://dx.doi.org/10.1063/1.126480 (3 pages) | Cited 51 times

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We report time-resolved characterization of superconducting NbN hot-electron photodetectors using an electro-optic sampling method. Our samples were patterned into micron-size microbridges from 3.5-nm-thick NbN films deposited on sapphire substrates. The devices were illuminated with 100 fs optical pulses, and the photoresponse was measured in the ambient temperature range between 2.15 and 10.6 K (superconducting temperature transition TC). The experimental data agreed very well with the nonequilibrium hot-electron, two-temperature model. The quasiparticle thermalization time was ambient temperature independent and was measured to be 6.5 ps. The inelastic electron–phonon scattering time τe–ph tended to decrease with the temperature increase, although its change remained within the experimental error, while the phonon escape time τes decreased almost by a factor of two when the sample was put in direct contact with superfluid helium. Specifically, τe–ph and τes, fitted by the two-temperature model, were equal to 11.6 and 21 ps at 2.15 K, and 10(±2) and 38 ps at 10.5 K, respectively. The obtained value of τe–ph shows that the maximum intermediate frequency bandwidth of NbN hot-electron phonon-cooled mixers operating at TC can reach 16(+4/−3) GHz if one eliminates the bolometric phonon-heating effect. © 2000 American Institute of Physics.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
85.25.Am Superconducting device characterization, design, and modeling
85.25.Pb Superconducting infrared, submillimeter and millimeter wave detectors
63.20.K- Phonon interactions
71.38.-k Polarons and electron-phonon interactions
74.10.+v Occurrence, potential candidates
74.25.Kc Phonons
74.25.Gz Optical properties

Gap symmetry and critical current of YBa2Cu3O7 step-edge Josephson junctions

Soon-Gul Lee and Yunseok Hwang

Appl. Phys. Lett. 76, 2755 (2000); http://dx.doi.org/10.1063/1.126465 (3 pages) | Cited 6 times

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Effects of d-wave symmetry on the critical current of high Tc step-edge Josephson junctions were studied theoretically by using the concept of grain-boundary junctions, and the theory was compared with experimental results of YBa2Cu3O7 step-edge junctions on SrTiO3 (100) substrates. A step-edge junction contains two grain boundaries, and each grain boundary has both in-plane and out-of-plane misorientation angles at the same time. The critical current of the step-edge junction as a function of the in-plane misorientation angle has a periodic modulation with maxima when the step line is parallel to one of the major axes of the SrTiO3 (100) substrate. Experimental results of c-oriented YBa2Cu3O7 step-edge junctions with various in-plane misorientation angles were qualitatively in good agreement with the theory. The out-of-plane misorientation angle is formed between two grains usually with the c axes perpendicular to each other and is normally not controllable. © 2000 American Institute of Physics.
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74.50.+r Tunneling phenomena; Josephson effects

Suppression of magnetic-field pulse-induced magnetization precession by pulse tailoring

M. Bauer, R. Lopusnik, J. Fassbender, and B. Hillebrands

Appl. Phys. Lett. 76, 2758 (2000); http://dx.doi.org/10.1063/1.126466 (3 pages) | Cited 46 times

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Short magnetic-field pulses may be used in the near future to change the magnetization state in magnetic storage devices. In order to minimize the time required for this process, and thus to maximize the switching speed of such devices, the magnetization precession after the termination of the magnetic-field pulse needs to be suppressed to a maximum degree. It is demonstrated experimentally that the appropriate adjustment of the field pulse parameters may lead to a full suppression of the magnetization precession immediately upon termination of the field pulse. © 2000 American Institute of Physics.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Gg Ferrimagnetics
75.70.Ak Magnetic properties of monolayers and thin films
78.66.Nk Insulators
78.20.Ls Magneto-optical effects
78.47.-p Spectroscopy of solid state dynamics

Large zinc cation occupancy of octahedral sites in mechanically activated zinc ferrite powders

S. A. Oliver, V. G. Harris, H. H. Hamdeh, and J. C. Ho

Appl. Phys. Lett. 76, 2761 (2000); http://dx.doi.org/10.1063/1.126467 (3 pages) | Cited 43 times

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The cation site occupancy of a mechanically activated nanocrystalline zinc ferrite powder was determined as (Zn0.552+Fe0.183+)tet[Zr0.452+Fe1.823+]octO4 through analysis of extended x-ray absorption fine structure measurements, showing a large redistribution of cations between sites compared to normal zinc ferrite samples. The overpopulation of cations in the octahedral sites was attributed to the ascendance in importance of the ionic radii over the crystal energy and bonding coordination in determining which interstitial sites are occupied in this structurally disordered powder. Slight changes are observed in the local atomic environment about the zinc cations, but not the iron cations, with respect to the spinel structure. The presence of Fe3+ on both sites is consistent with the measured room temperature magnetic properties. © 2000 American Institute of Physics.
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75.50.Gg Ferrimagnetics
61.46.-w Structure of nanoscale materials
75.50.Kj Amorphous and quasicrystalline magnetic materials
78.70.Dm X-ray absorption spectra
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