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22 Apr 2002

Volume 80, Issue 16, pp. 2821-3018

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Carbon: A bane for giant magnetoresistance magnetic multilayers

David X. Yang, Harsh Deep Chopra, B. Shashishekar, P. J. Chen, and W. F. Egelhoff

Appl. Phys. Lett. 80, 2943 (2002); http://dx.doi.org/10.1063/1.1469682 (3 pages) | Cited 2 times

Online Publication Date: 16 April 2002

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This study reports the highly deleterious role of a small amount of carbon on the structure and magnetic properties of “giant” magnetoresistance (GMR) NiO–Co–Cu-based spin valves. Controlled incorporation of 1–3 at. % carbon in the Co/Cu layers has been shown to completely eliminate the GMR effect. The presence of carbon gives rise to highly discontinuous Co/Cu layers, resulting in the formation of pinholes, and associated degradation of structure-sensitive magnetic properties. In addition, carbon promotes the formation of a high density of stacking faults in the Co/Cu layers, with carbon nanoprecipitates forming in the vicinity of the stacking faults. Results have implications for other multilayers and magnetoelectronics devices. © 2002 American Institute of Physics.
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75.47.De Giant magnetoresistance
81.05.Bx Metals, semimetals, and alloys
85.75.-d Magnetoelectronics; spintronics: devices exploiting spin polarized transport or integrated magnetic fields
72.25.Mk Spin transport through interfaces
72.15.Gd Galvanomagnetic and other magnetotransport effects
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
61.72.Nn Stacking faults and other planar or extended defects
73.61.At Metal and metallic alloys
68.65.Ac Multilayers

Quantum limit to phase coherence in thin superconducting wires

M. Tinkham and C. N. Lau

Appl. Phys. Lett. 80, 2946 (2002); http://dx.doi.org/10.1063/1.1473232 (3 pages) | Cited 22 times

Online Publication Date: 16 April 2002

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Spontaneous quantum phase slips by 2π in thin superconducting wires could cause errors in superconducting computers. The rate of such phase slips at T≪Tc is estimated, and shown to be very small as long as the wire is >20 nm in diameter. © 2002 American Institute of Physics.
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84.71.Mn Superconducting wires, fibers, and tapes
85.25.Hv Superconducting logic elements and memory devices; microelectronic circuits

Josephson effect in Nb/Al2O3/Al/MgB2 large-area thin-film heterostructures

G. Carapella, N. Martucciello, G. Costabile, C. Ferdeghini, V. Ferrando, and G. Grassano

Appl. Phys. Lett. 80, 2949 (2002); http://dx.doi.org/10.1063/1.1472470 (3 pages) | Cited 25 times

Online Publication Date: 16 April 2002

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We report the demonstration of dc and ac Josephson effects in Nb/Al2O3/Al/MgB2 thin-film heterostructure. The heterostructure exhibits moderately hysteretic current–voltage characteristic with a dc Josephson current branch and regular microwave-induced Shapiro steps. From conductance spectrum, a gap of about 2 meV at 7.7 K is estimated for the proximized surface of MgB2 electrode. © 2002 American Institute of Physics.
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74.50.+r Tunneling phenomena; Josephson effects
74.70.Ad Metals; alloys and binary compounds (including A15, MgB2, etc.)
74.72.-h Cuprate superconductors

Josephson device for quantum experiments

C. Granata, V. Corato, L. Longobardi, M. Russo, B. Ruggiero, and P. Silvestrini

Appl. Phys. Lett. 80, 2952 (2002); http://dx.doi.org/10.1063/1.1469653 (3 pages) | Cited 15 times

Online Publication Date: 16 April 2002

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We present the characterization of a fully integrated Josephson device consisting of a rf-superconducting quantum interference device (SQUID) coupled to a readout system based on a dc SQUID sensor. Particular care in the design is devoted to minimize the electromagnetic noise coming from the environment. We report data on dc SQUID performances as well as on the decay rate from metastable flux states of the rf SQUID in the classical regime. The low dissipation level and the good insulation of the probe from the external noise are encouraging in view of macroscopic quantum experiments. © 2002 American Institute of Physics.
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85.25.Dq Superconducting quantum interference devices (SQUIDs)
03.67.Lx Quantum computation architectures and implementations

Critical temperature of superconducting bilayers: Theory and experiment

G. Brammertz, A. A. Golubov, P. Verhoeve, R. den Hartog, A. Peacock, and H. Rogalla

Appl. Phys. Lett. 80, 2955 (2002); http://dx.doi.org/10.1063/1.1470712 (3 pages) | Cited 9 times

Online Publication Date: 16 April 2002

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A generalized model for the critical temperature TC of superconducting bilayers is presented, which is valid with no restrictions to film thicknesses, TC of the layers, and interface resistivity. The model is verified experimentally on a series of Nb–Al and Ta–Al bilayers with Nb, Ta layer thicknesses of 100 nm and Al layer thicknesses ranging from 5 to 200 nm. Excellent agreement between theory and experiment was found for the energy gap and the TC of bilayers. The results are important for designing practical superconducting devices. © 2002 American Institute of Physics.
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74.62.-c Transition temperature variations, phase diagrams
74.25.Jb Electronic structure (photoemission, etc.)
74.78.-w Superconducting films and low-dimensional structures
74.70.Ad Metals; alloys and binary compounds (including A15, MgB2, etc.)
74.10.+v Occurrence, potential candidates

Precessional switching of submicrometer spin valves

S. Kaka and S. E. Russek

Appl. Phys. Lett. 80, 2958 (2002); http://dx.doi.org/10.1063/1.1470704 (3 pages) | Cited 70 times

Online Publication Date: 16 April 2002

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Small spin valves are switched using a subnanosecond field pulse applied along the magnetization hard axis. The measured probability for switching due to pulsed hard-axis fields increases as the duration is decreased from 325 to 230 ps. This indicates a large-angle precessional motion in response to the transverse applied field. The behavior is modeled with a single-domain, Landau–Lifshitz simulation. Switching in this manner requires only single-polarity transverse pulses that toggle the state of magnetic devices. This process consumes less energy than traditional quasi-static switching using long-duration field pulses along both directions.
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85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
75.60.-d Domain effects, magnetization curves, and hysteresis
75.60.Jk Magnetization reversal mechanisms
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