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31 Dec 2001

Volume 79, Issue 27, pp. 4479-4603

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Response of superconducting Y–Ba–Cu–O films to millimeter wave radiation

K. Repšas, A. Laurinavičius, A. R. Vaškevičius, and F. Anisimovas

Appl. Phys. Lett. 79, 4544 (2001); http://dx.doi.org/10.1063/1.1428112 (3 pages) | Cited 6 times

Online Publication Date: 13 March 2002

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The origin of temperature and radiation power response dependencies to millimeter wave radiation is analyzed for Y–Ba–Cu–O thin films. These dependencies were both experimentally measured and described by an empirical formula. The results which were obtained indicate that the peak shape of temperature dependence for the nonbolometric response is determined by the temperature of the thermostat and is less inertial than for τ = 1/f (f = 35 GHz). © 2001 American Institute of Physics.
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74.78.-w Superconducting films and low-dimensional structures
74.25.N- Response to electromagnetic fields
74.72.-h Cuprate superconductors

Sputtered nanodots: A costless method for inducing effective pinning centers in superconducting thin films

A. Crisan, S. Fujiwara, J. C. Nie, A. Sundaresan, and H. Ihara

Appl. Phys. Lett. 79, 4547 (2001); http://dx.doi.org/10.1063/1.1428632 (3 pages) | Cited 61 times

Online Publication Date: 13 March 2002

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A straightforward and cheap method for creating extended defects, strong pinning centers, in superconducting thin films is proposed. Clearly, by very short time (3–5 s) rf sputtering at suitable substrate temperatures, we deposited Ag nanodots on SrTiO3 substrates prior to the growth of superconducting thin films. The nanodots were studied by atomic force microscopy. Due to the lattice mismatch and/or chemical poisoning, on top of the nanodots the superconducting phase does not form, creating in this way extended and effective pinning centers which increase the critical current density of the film. The method was applied to (Cu, Tl)BaSrCa2Cu3Oy films grown by amorphous phase epitaxy. Thin films grown in similar conditions, with and without nanodots, were characterized by x-ray diffraction and ac susceptibility. The results show that the nanodots increased the critical current density more than one order of magnitude. © 2001 American Institute of Physics.
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74.78.-w Superconducting films and low-dimensional structures
74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)
74.72.-h Cuprate superconductors
68.65.Hb Quantum dots (patterned in quantum wells)
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
74.25.Ha Magnetic properties including vortex structures and related phenomena
74.25.Sv Critical currents
81.07.Ta Quantum dots
81.15.Cd Deposition by sputtering

Ballistic magnetoresistance in a magnetic nanometer sized contact: An effective gate for spintronics

N. García, M. Muñoz, G. G. Qian, H. Rohrer, I. G. Saveliev, and Y.-W. Zhao

Appl. Phys. Lett. 79, 4550 (2001); http://dx.doi.org/10.1063/1.1427152 (3 pages) | Cited 53 times

Online Publication Date: 13 March 2002

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We present experimental results of unprecedented large magnetoresistance obtained in stable electrodeposited Ni–Ni nanocontacts 10–30 nm in diameter. The contacts exhibit magnetoresistance of up to 700% at room temperature and low applied fields and, therefore, act as very effective spin filters. These large values of the magnetoresistance are attributed to spin ballistic transport through a magnetic “dead layer” at the contact of width of about 1 nm or smaller. Nanometer sized, high sensitive magnetoresistive sensors could become key elements for magnetic storage in the terabit/in.2 range and in high density magnetic random access memories. © 2001 American Institute of Physics.
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75.75.-c Magnetic properties of nanostructures
85.75.Bb Magnetic memory using giant magnetoresistance
75.47.De Giant magnetoresistance
81.07.Lk Nanocontacts
73.63.Rt Nanoscale contacts
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
81.15.Pq Electrodeposition, electroplating

Low-resistance spin-dependent tunnel junctions with ZrAlOx barriers

Jianguo Wang, P. P. Freitas, and E. Snoeck

Appl. Phys. Lett. 79, 4553 (2001); http://dx.doi.org/10.1063/1.1428111 (3 pages) | Cited 23 times

Online Publication Date: 13 March 2002

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Spin-dependent tunnel junctions with ZrAlOx barriers were formed by natural oxidation (5 min at 10 Torr) of 7-Å-thick Zr–Al films. Resistance×area products of 6 Ω μm2 were achieved with a 15.3% tunnel magnetoresistance (TMR) signal. Bottom-pinned (MnIr) junctions were deposited on top of 600-Å-thick, ion-beam-smoothed, low-resistance, Al electrodes. Effective average barrier height and thickness are 0.28 eV and 8.2 Å, respectively, and breakdown voltage is 0.41 V for 1 μm2 junctions. The TMR signal decreases by half at a bias voltage of 210 mV. Junction TMR decreases for anneals above 250 °C. High-resolution transmission electron microscopy indicates that ZrAlOx forms an amorphous barrier that is smoother than pure crystalline ZrOx or pure amorphous AlOx barriers. These low-resistance tunnel junctions are attractive for read head applications above 100 Gbit/in.2 where competitive signal-to-noise ratios imply resistance×area products of few Ω μm2 and TMR signals near or above 20%. © 2001 American Institute of Physics.
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85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
75.50.Ss Magnetic recording materials
75.47.De Giant magnetoresistance
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
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