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22 Mar 2004

Volume 84, Issue 12, pp. 2013-2211

Issue Cover Spotlight Figure

Appl. Phys. Lett. 84, 2100 (2004); http://dx.doi.org/10.1063/1.1688997 (3 pages)

P. Sutter, E. Sutter, and T. R. Ohno
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A class of spin injection-precession ultrafast nanodevices

V. V. Osipov and A. M. Bratkovsky

Appl. Phys. Lett. 84, 2118 (2004); http://dx.doi.org/10.1063/1.1667002 (3 pages) | Cited 22 times

Online Publication Date: 16 March 2004

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Spin valve ultrafast spin injection devices with small dissipated power are described: an amplifier, a frequency multiplier, and a square-law detector. Their operation is based on injection of spin polarized electrons from one ferromagnet to another through a semiconductor layer and spin precession of the electrons in the semiconductor layer in a magnetic field induced by a (base) current in an adjacent nanowire. The base current can control the emitter current between the magnetic layers with frequencies up to several 100 GHz. © 2004 American Institute of Physics.
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72.25.Hg Electrical injection of spin polarized carriers
72.25.Mk Spin transport through interfaces
85.35.Ds Quantum interference devices
85.75.-d Magnetoelectronics; spintronics: devices exploiting spin polarized transport or integrated magnetic fields
85.35.Kt Nanotube devices
75.50.Dd Nonmetallic ferromagnetic materials
75.47.-m Magnetotransport phenomena; materials for magnetotransport
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.

Angular-dependent vortex pinning mechanisms in YBa2Cu3O7 coated conductors and thin films

L. Civale, B. Maiorov, A. Serquis, J. O. Willis, J. Y. Coulter, H. Wang, Q. X. Jia, P. N. Arendt, J. L. MacManus-Driscoll, M. P. Maley, and S. R. Foltyn

Appl. Phys. Lett. 84, 2121 (2004); http://dx.doi.org/10.1063/1.1655707 (3 pages) | Cited 115 times

Online Publication Date: 16 March 2004

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We compare the angular-dependent critical current density (Jc) in YBa2Cu3O7 films deposited on MgO templates grown by ion-beam-assisted deposition (IBAD), and on single-crystal substrates. We identify three angular regimes in which pinning is dominated by different types of correlated and uncorrelated defects. Those regimes are present in all cases, but their extension and characteristics are sample dependent, reflecting differences in texture and defect density. The more defective nature of the films on IBAD turns into an advantage as it results in higher Jc, demonstrating that the performance of the films on single crystals is not an upper limit for the IBAD coated conductors. © 2004 American Institute of Physics.
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74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)
74.25.Sv Critical currents
74.78.-w Superconducting films and low-dimensional structures
74.72.-h Cuprate superconductors
81.15.Jj Ion and electron beam-assisted deposition; ion plating
74.81.Bd Granular, melt-textured, amorphous, and composite superconductors

Giant magnetostriction on Fe85Ga15 stacked ribbon samples

G. D. Liu, L. B. Liu, Z. H. Liu, M. Zhang, J. L. Chen, J. Q. Li, G. H. Wu, Y. X. Li, J. P. Qu, and T. S. Chin

Appl. Phys. Lett. 84, 2124 (2004); http://dx.doi.org/10.1063/1.1688452 (3 pages) | Cited 16 times

Online Publication Date: 16 March 2004

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Large magnetostrictions of −1300 and +1100 ppm related in the different directions have been obtained in our stacked Fe85Ga15 ribbon samples. In the case of non-180° domain magnetization in the high anisotropic samples, the magnetostrictions are mainly attributed to the existence of Ga clusters which preferentially orient with the ribbon normal due to the ribbon grain texturing. Forming the modified DO3 structure, the Ga–Ga atom pairs distribute in the matrix and cause the x-ray diffraction peak split in melt-spun ribbons. As a special micromorphology, Ga clusters highly condensed in some nanoscale dots have also been experimentally observed. © 2004 American Institute of Physics.
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75.80.+q Magnetomechanical effects, magnetostriction
75.30.Gw Magnetic anisotropy
75.60.Ch Domain walls and domain structure
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization

Significantly enhanced critical current density in Ag-sheathed (Bi,Pb)2Sr2Ca2Cu3Ox composite conductors prepared by overpressure processing in final heat treatment

Y. Yuan, J. Jiang, X. Y. Cai, D. C. Larbalestier, E. E. Hellstrom, Y. Huang, and R. Parrella

Appl. Phys. Lett. 84, 2127 (2004); http://dx.doi.org/10.1063/1.1682675 (3 pages) | Cited 17 times

Online Publication Date: 16 March 2004

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Overpressure (OP) processing otherwise fully treated, commercial Ag-sheathed multifilament (Bi,Pb)2Sr2Ca2Cu3Ox (2223) composite conductors increased the critical current density Jc (0.1 T, 77 K) by 37% to 30.8 kA/cm2 and the self-field Jc (SF, 77 K) to 69.6 kA/cm2. These improvements were obtained on full-size high current conductors such that critical current Ic (0.1 T, 77 K) reached 80.6 A and Ic (SF, 77 K) 181.7 A, even though there was a very strong self-field suppression of Ic. Estimated values for the non-self-field-limited Ic and Jc (0 T, 77 K) reached 235 A and 90 kA/cm2. Scanning electron microscopy and superconducting quantum inference device measurement revealed that OP processing effectively suppressed cracks, porosity, and the volume fraction of the Bi2Sr2Ca1Cu2Oy (2212) phase, which are all major current-limiting mechanisms in present 2223 conductors. © 2004 American Institute of Physics.
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74.72.-h Cuprate superconductors
84.71.Mn Superconducting wires, fibers, and tapes
81.40.Vw Pressure treatment
74.25.Sv Critical currents
62.50.-p High-pressure effects in solids and liquids
81.05.Mh Cermets, ceramic and refractory composites
74.25.Ld Mechanical and acoustical properties, elasticity, and ultrasonic attenuation

Unidirectional magnetostrictive Terfenol/epoxy composite

Jong Chul Kim, Oh Yeoul Kwon, and Zin Hyoung Lee

Appl. Phys. Lett. 84, 2130 (2004); http://dx.doi.org/10.1063/1.1688449 (3 pages) | Cited 3 times

Online Publication Date: 16 March 2004

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We have developed a unidirectional composite for improving magnetostrictive properties and mechanical properties of giant magnetostrictive composite. The composite consists of bulk RFe2 dendrites with a preferred orientation of 〈112〉 and an electrically insulated binder between the dendrites, which is analogous to a lamination pattern. We investigated the magnetostrictive properties of composites by varying the volume fraction of RFe2 phase in the range of 60%–80%. The results demonstrated that the unidirectional composites had much higher strain and d33 than a monolithic Terfenol-D at the same volume fraction of RFe2 phase and these results were compared with the model for uniform strain. © 2004 American Institute of Physics.
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75.80.+q Magnetomechanical effects, magnetostriction
75.50.Bb Fe and its alloys
75.47.De Giant magnetoresistance

Timing jitter measurement of single-flux-quantum pulse in Josephson transmission line

Hirotaka Terai, Zhen Wang, Yoshihito Hishimoto, Shinichi Yorozu, Akira Fujimaki, and Nobuyuki Yoshikawa

Appl. Phys. Lett. 84, 2133 (2004); http://dx.doi.org/10.1063/1.1650912 (3 pages) | Cited 18 times

Online Publication Date: 16 March 2004

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Timing jitter is an important factor in determining the limit of speed and scale of single-flux-quantum circuits. We estimated the timing jitter by a simple method using 2-bit shift registers. It was estimated by observing the transition between 1- and 2-mode operations while changing the bias current to the clock line. A sharp transition was observed in the shift register with a smaller number of Josephson junctions in the clock and data lines, suggesting the existence of a finite timing jitter. The timing jitter per Josephson junction was estimated to be 0.09 ps at a designed bias current. The temperature dependence supported that the timing jitter comes from thermal fluctuation. © 2004 American Institute of Physics.
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84.30.Sk Pulse and digital circuits
85.25.Hv Superconducting logic elements and memory devices; microelectronic circuits

Electron-doped infinite-layer thin films with TC over 40 K grown on DyScO3 substrates

Shin-ichi Karimoto and Michio Naito

Appl. Phys. Lett. 84, 2136 (2004); http://dx.doi.org/10.1063/1.1688979 (3 pages) | Cited 8 times

Online Publication Date: 16 March 2004

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We report high-quality electron-doped infinite-layer superconducting thin films with a TC of over 40 K grown on lattice-matched DyScO3 substrates by molecular-beam epitaxy. The optimally doped film seems to be free from strain, thus leading to a low resistivity of 75 μΩ cm at room temperature and 15 μΩ cm just above TC. © 2004 American Institute of Physics.
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74.62.Dh Effects of crystal defects, doping and substitution
74.25.F- Transport properties
68.55.A- Nucleation and growth
74.78.-w Superconducting films and low-dimensional structures
74.10.+v Occurrence, potential candidates
68.55.-a Thin film structure and morphology
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Capping-layer-induced magnetic coupling in a two-dimensional nanostructured system

E. Navarro, Y. Huttel, C. Clavero, G. Armelles, and A. Cebollada

Appl. Phys. Lett. 84, 2139 (2004); http://dx.doi.org/10.1063/1.1689739 (3 pages) | Cited 11 times

Online Publication Date: 16 March 2004

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The magnetic polarization of a Pt capping layer leads to an increase of the interisland magnetic coupling in a two-dimensional array of Fe islands. For small superparamagnetic islands, Pt deposition leads to a superparamagnetic–ferromagnetic transition. For larger ferromagnetic but weakly coupled islands, Pt deposition produces a stronger interisland coupling. Polar Kerr spectroscopy measurements and simulations evidence the magnetic polarization of Pt in contact with Fe. The described effects and their interpretation are supported by the use of a nonpolarizable Al capping, where both the superparamagnetic-to-ferromagnetic transition and the increase of the interisland coupling are absent. © 2004 American Institute of Physics.
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75.50.Tt Fine-particle systems; nanocrystalline materials
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.20.En Metals and alloys
78.20.Ls Magneto-optical effects
61.46.-w Structure of nanoscale materials
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