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18 Oct 1999

Volume 75, Issue 16, pp. 2347-2507

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Atomic structure and composition of the barrier in the modified interface high-Tc Josephson junction studied by transmission electron microscopy

J. G. Wen, N. Koshizuka, S. Tanaka, T. Satoh, M. Hidaka, and S. Tahara

Appl. Phys. Lett. 75, 2470 (1999); http://dx.doi.org/10.1063/1.125051 (3 pages) | Cited 21 times

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The atomic structure and composition of modified interface junctions which showed reproducible critical current Ic (Ic1σ<8% for 100 junctions) are investigated by transmission electron microscopy. Transmission electron microscopic observations show the existence of a thin barrier (1–2 nm) homogeneously covering the ion milled edge of the base YBa2Cu3Oy film although there is no barrier deposition and annealing process. High-resolution electron microscopy images and energy dispersive x-ray analysis with a spot size of 1 nm indicates that the barrier is a Ba-based perovskite-like structure, (Y1−xCux)BaOy with x<0.5. A thin amorphous layer whose composition deviates from YBa2Cu3Oy is formed due to the preferential sputtering of Cu. The amorphous layer recrystallizes into the nonequilibrium phase (Y1−xCux)BaOy after heating up to the deposition temperature. © 1999 American Institute of Physics.
Show PACS
74.72.-h Cuprate superconductors
74.78.-w Superconducting films and low-dimensional structures
74.50.+r Tunneling phenomena; Josephson effects
68.35.Ct Interface structure and roughness
85.25.Cp Josephson devices
74.25.Sv Critical currents
68.35.Fx Diffusion; interface formation
74.62.Bf Effects of material synthesis, crystal structure, and chemical composition

Domain structure of magnetic layers deposited on patterned silicon

S. Landis, B. Rodmacq, B. Dieny, B. Dal’Zotto, S. Tedesco, and M. Heitzmann

Appl. Phys. Lett. 75, 2473 (1999); http://dx.doi.org/10.1063/1.125052 (3 pages) | Cited 25 times

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Arrays of Si square dots down to 200 nm in size were patterned on silicon substrates, and thin films of different magnetic materials were sputter deposited on these patterned substrates. The magnetic film covers the top of the dots, the bottom of the grooves and to much less extent the sidewalls of the dots. Single domain magnetic dots were obtained for Co/NiO bilayers and Co/Pt multilayers, without significant direct coupling mediated by the magnetic deposit on the sidewalls of the dots. Our results indicate that, in these arrays, the magnetic pinning forces are stronger than the estimated value of the largest demagnetizing magnetostatic field on each individual dot. As a result, any magnetic configuration could in principle be stored in such arrays. This approach seems therefore very promising for the preparation of magnetic storage media with ultrahigh density. © 1999 American Institute of Physics.
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75.70.Kw Domain structure (including magnetic bubbles and vortices)
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.60.Ch Domain walls and domain structure
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
85.70.Li Other magnetic recording and storage devices (including tapes, disks, and drums)

Switching of vertical giant magnetoresistance devices by current through the device

K. Bussmann, G. A. Prinz, S.-F. Cheng, and D. Wang

Appl. Phys. Lett. 75, 2476 (1999); http://dx.doi.org/10.1063/1.125053 (3 pages) | Cited 69 times

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Experiments are reported that demonstrate current-perpendicular-to-the-plane giant magnetoresistance devices can be switched repeatably between the high- and low-resistance states by passing current vertically through the structure. The lithographically patterned devices, having diameters in the range of 0.3–0.7 μm, operate at room temperature and exhibit distinctly separate switching of the soft and hard layers. Designs for magnetoelectronic random access memory can utilize this scheme for storing and reading information. © 1999 American Institute of Physics.
Show PACS
75.47.De Giant magnetoresistance
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
84.30.Sk Pulse and digital circuits

LaNiO3 buffer layers for high critical current density YBa2Cu3O7−δ and Tl2Ba2CaCu2O8−δ films

C. M. Carlson, P. A. Parilla, M. P. Siegal, D. S. Ginley, Y.-T. Wang, R. D. Blaugher, J. C. Price, D. L. Overmyer, and E. L. Venturini

Appl. Phys. Lett. 75, 2479 (1999); http://dx.doi.org/10.1063/1.125054 (3 pages) | Cited 1 time

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We demonstrate high critical current density superconducting films of YBa2Cu3O7−δ (YBCO) and Tl2Ba2CaCu2O8−δ (Tl-2212) using LaNiO3 (LNO) buffer layers. YBCO films grown on an LNO buffer layer have only a slightly lower Jc (5 K, H = 0) than films grown directly on a bare LaAlO3 substrate. YBCO films grown on LNO buffer layers exhibit minor microstructural disorder and enhanced flux pinning. LNO-buffered Tl-2212 samples show large reductions in Jc at all temperatures and fields compared to those grown on bare LaAlO3, correlating to both a-axis grain and nonsuperconducting phase formation. LNO could be a promising buffer layer for both YBCO and Tl-based superconducting films in coated conductor applications. © 1999 American Institute of Physics.
Show PACS
74.25.Sv Critical currents
74.72.-h Cuprate superconductors
74.78.-w Superconducting films and low-dimensional structures
74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)
68.55.-a Thin film structure and morphology
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