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10 Apr 2000

Volume 76, Issue 15, pp. 1969-2136

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Silver ion implantation in epitaxial La2/3Ca1/3MnO3 thin films: Large temperature coefficient of resistance for bolometric applications

Ravi Bathe, K. P. Adhi, S. I. Patil, G. Marest, B. Hannoyer, and S. B. Ogale

Appl. Phys. Lett. 76, 2104 (2000); http://dx.doi.org/10.1063/1.126269 (3 pages) | Cited 21 times

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Epitaxial films of La2/3Ca1/3MnO3 were successively implanted with 100 and 200 keV silver ions at fluences of 4.5×1015 and 1×1016 ions/cm2, respectively, to achieve a fairly uniform implant distribution. The as-implanted films are insulating and do not show a metal–insulator transition. Postimplantation annealing at 950 °C shows a recovery of the high structural quality of the films, along with an increase in the metal–insulator transition temperature (Tp), magnetoresistance, and the peak temperature coefficient of resistance (TCR) at the transition. The peak TCR of 23% for manganite films is clearly significant for bolometric applications. © 2000 American Institute of Physics.
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61.72.up Other materials
61.82.Ms Insulators
73.61.Ng Insulators
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
71.30.+h Metal-insulator transitions and other electronic transitions
75.47.De Giant magnetoresistance

Trapped magnetic fields larger than 14 T in bulk YBa2Cu3O7−x

G. Fuchs, P. Schätzle, G. Krabbes, S. Gruß, P. Verges, K.-H. Müller, J. Fink, and L. Schultz

Appl. Phys. Lett. 76, 2107 (2000); http://dx.doi.org/10.1063/1.126278 (3 pages) | Cited 46 times

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High trapped fields were found in zinc-doped, bulk melt-textured YBa2Cu3O7−x (YBCO) material showing a pronounced peak effect in the field dependence of the critical current density. Trapped fields up to 1.1 T were found at 77 K at the surface of a YBCO disk (diameter 26 mm, height 12 mm). Very high trapped fields up to 14.35 T were achieved at 22.5 K for a YBCO disk pair (diameter 26 mm, height 24 mm) by the addition of silver and using a bandage made of stainless steel. The pinning forces and trapped fields obtained in bulk YBCO material are compared with results reported for melt-processed NdBa2Cu3O7−x and SmBa2Cu3O7−x.© 2000 American Institute of Physics.
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74.72.-h Cuprate superconductors
74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)
74.25.Sv Critical currents
74.25.Ha Magnetic properties including vortex structures and related phenomena

Structure and magnetic properties of nanocrystalline (Fe1−xCox)90Zr7B2Cu1 (0 ⩽ x ⩽ 0.6)

T. Kemény, D. Kaptás, L. F. Kiss, J. Balogh, L. Bujdosó, J. Gubicza, T. Ungár, and I. Vincze

Appl. Phys. Lett. 76, 2110 (2000); http://dx.doi.org/10.1063/1.126270 (3 pages) | Cited 11 times

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Nanocrystalline (Fe1−xCox)90Zr7B2Cu1 (0 ⩽ x ⩽ 0.6) alloys were investigated by x-ray diffraction, 57Fe Mössbauer spectroscopy, and magnetic measurements. The grain size did not change significantly with composition. Co was preferentially partitioned to the residual amorphous phase, and the bcc grains were accordingly enriched by Fe. The room-temperature coercive field increased with the Co addition, which is attributed to the increasing magnetostriction constant. © 2000 American Institute of Physics.
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61.46.-w Structure of nanoscale materials
75.50.Kj Amorphous and quasicrystalline magnetic materials
75.50.Vv High coercivity materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
81.07.-b Nanoscale materials and structures: fabrication and characterization
76.80.+y Mössbauer effect; other γ-ray spectroscopy
75.50.Bb Fe and its alloys
75.80.+q Magnetomechanical effects, magnetostriction

Coherent control of precessional dynamics in thin film permalloy

T. M. Crawford, P. Kabos, and T. J. Silva

Appl. Phys. Lett. 76, 2113 (2000); http://dx.doi.org/10.1063/1.126280 (3 pages) | Cited 37 times

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We demonstrate a method of eliminating overshoot and ringing in magnetization dynamics when the system bandwidth includes the intrinsic ferromagnetic resonance (FMR). The method employs staggered step excitation for the cancellation of FMR oscillations while maximizing the risetime of the magnetization response. The second-harmonic magneto-optic Kerr effect is used to measure the magnetic response at a localized spot on the sample. The measured response is adequately modeled with the Landau–Lifshitz–Gilbert differential equation. We explain the observed behavior in terms of destructive interference.
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75.70.Ak Magnetic properties of monolayers and thin films
75.50.Bb Fe and its alloys
75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
78.20.Ls Magneto-optical effects
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
76.50.+g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance
78.66.Bz Metals and metallic alloys
75.40.Mg Numerical simulation studies

Magnetoquenched superconducting valve with bilayer ferromagnetic film for uniaxial switching

T. W. Clinton and Mark Johnson

Appl. Phys. Lett. 76, 2116 (2000); http://dx.doi.org/10.1063/1.126271 (3 pages) | Cited 11 times

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A bilayer ferromagnetic film, consisting of a soft- and hard-magnetic layer separated by a nonmagnetic layer, has been incorporated into a magnetoquenched superconducting valve, making it possible to control the valve with uniaxial magnetic fields. Device switching is demonstrated with fields as small as 20 Oe. The switch is inherently nonvolatile, has linear output characteristics, and requires a single inductively coupled “write wire” for integrated operation, all of which make it promising for application as a storage cell in a high-density superconducting random-access memory. © 2000 American Institute of Physics.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
85.25.Cp Josephson devices
85.25.Hv Superconducting logic elements and memory devices; microelectronic circuits
85.70.Ec Magnetostrictive, magnetoacoustic, and magnetostatic devices

Very high-current-density Nb/AlN/Nb tunnel junctions for low-noise submillimeter mixers

Jonathan Kawamura, David Miller, Jian Chen, Jonas Zmuidzinas, Bruce Bumble, Henry G. LeDuc, and Jeff A. Stern

Appl. Phys. Lett. 76, 2119 (2000); http://dx.doi.org/10.1063/1.126272 (3 pages) | Cited 17 times

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We have fabricated and tested submillimeter-wave superconductor–insulator–superconductor (SIS) mixers using very high-current-density Nb/AlN/Nb tunnel junctions (Jc ≈ 30 kA cm−2). The junctions have low-resistance-area products (RNA ≈ 5.6 Ω μm2), good subgap-to-normal resistance ratios Rsg/RN ≈ 10, and good run-to-run reproducibility. From Fourier transform spectrometer measurements, we infer that ωRNC = 1 at 270 GHz. This is a factor of 2.5 improvement over what is generally available with Nb/AlOx/Nb junctions suitable for low-noise mixers. The AlN-barrier junctions are indeed capable of low-noise operation: we measure an uncorrected double-sideband receiver noise temperature of TRX = 110 K at 533 GHz for an unoptimized device. In addition to providing wider bandwidth operation at lower frequencies, the AlN-barrier junctions will considerably improve the performance of THz SIS mixers by reducing rf loss in the tuning circuits. © 2000 American Institute of Physics.
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84.30.Qi Modulators and demodulators; discriminators, comparators, mixers, limiters, and compressors
85.25.Cp Josephson devices
84.40.-x Radiowave and microwave (including millimeter wave) technology
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