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2 Aug 1999

Volume 75, Issue 5, pp. 597-739

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Spin-interference device

Junsaku Nitta, Frank E. Meijer, and Hideaki Takayanagi

Appl. Phys. Lett. 75, 695 (1999); http://dx.doi.org/10.1063/1.124485 (3 pages) | Cited 27 times

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We propose a spin-interference device which works even without any ferromagnetic electrodes and any external magnetic field. The interference can be expected in the Aharonov–Bohm (AB) ring with a uniform spin-orbit interaction, which causes the phase difference between the spin wave functions traveling in the clockwise and anticlockwise direction. The gate electrode, which covers the whole area of the AB ring, can control the spin-orbit interaction, and therefore, the interference. A large conductance modulation effect can be expected due to the spin interference. © 1999 American Institute of Physics.
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85.35.Ds Quantum interference devices
75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.)
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect
73.23.-b Electronic transport in mesoscopic systems
85.30.De Semiconductor-device characterization, design, and modeling

Radio-frequency amplifier with tenth-kelvin noise temperature based on a microstrip direct current superconducting quantum interference device

Marc-Olivier André, Michael Mück, John Clarke, Jost Gail, and Christoph Heiden

Appl. Phys. Lett. 75, 698 (1999); http://dx.doi.org/10.1063/1.124486 (3 pages) | Cited 22 times

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A dc superconducting quantum interference device (SQUID) with a resonant microstrip input and a cooled heterostructure field-effect transistor as a postamplifier is used as a radio-frequency amplifier in the frequency range 90–500 MHz. At liquid 3He temperatures, gains of 24 and 20 dB and intrinsic noise temperatures of 0.06±0.02 and 0.12±0.10 K were achieved at 89.6 and 438 MHz, respectively. The system noise temperature at 438 MHz was also estimated from the Nyquist noise produced by a resonant circuit coupled to the input of the microstrip SQUID. © 1999 American Institute of Physics.
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85.25.Dq Superconducting quantum interference devices (SQUIDs)
84.40.Az Waveguides, transmission lines, striplines
84.30.Le Amplifiers
84.40.Dc Microwave circuits
85.30.Tv Field effect devices

Interface and tunneling barrier heights of NbN/AlN/NbN tunnel junctions

Zhen Wang, Hirotaka Terai, Akira Kawakami, and Yoshinori Uzawa

Appl. Phys. Lett. 75, 701 (1999); http://dx.doi.org/10.1063/1.124487 (3 pages) | Cited 37 times

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The tunneling barrier height of NbN/AlN/NbN tunnel junctions was measured by investigating the barrier thickness dependence of the current density, and the junction interface was studied by cross-sectional transmission electron microscopy (TEM). We found that the current density of the junctions has two distinct types of dependency on the AlN barrier thickness, corresponding to two average barrier heights in different regions for the current density. The TEM observations showed that the junctions had a very smooth and clear electrode–barrier interface, and the crystal structures of the counterelectrode NbN films were strongly dependent on the thickness of AlN barriers. The average barrier height was estimated to be 2.35 eV in the low-Jc region, Jc<5 kA/cm2, and to be 0.88 eV in the high-Jc region, Jc>5 kA/cm2. © 1999 American Institute of Physics.
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74.50.+r Tunneling phenomena; Josephson effects
74.45.+c Proximity effects; Andreev reflection; SN and SNS junctions
74.70.Ad Metals; alloys and binary compounds (including A15, MgB2, etc.)

Nonlinear electron transport in magnetic multilayers

F. G. Aliev, R. Schad, P. Lobotka, I. Vavra, E. Seynaeve, V. V. Moshchalkov, and Y. Bruynseraede

Appl. Phys. Lett. 75, 704 (1999); http://dx.doi.org/10.1063/1.124488 (3 pages) | Cited 1 time

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We report on measurements of the second harmonics in the magnetovoltage generated in [Fe(12 Å)/Cr(12 Å)]10 epitaxial multilayers. It is shown that the variation of the amplitude of the second-harmonic signal with magnetic field is up to three times larger compared to the first harmonic. The enhanced “magnetovoltage” second-harmonic effect may be of practical use in systems based on spin electronic phenomena. © 1999 American Institute of Physics.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
73.61.At Metal and metallic alloys
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)

Enhanced coercivity of exchange-bias Fe/MnPd bilayers

Y. J. Tang, B. Roos, T. Mewes, S. O. Demokritov, B. Hillebrands, and Y. J. Wang

Appl. Phys. Lett. 75, 707 (1999); http://dx.doi.org/10.1063/1.124489 (3 pages) | Cited 32 times

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We present detailed studies of the enhanced coercivity of exchange-bias bilayer Fe/MnPd, both experimentally and theoretically. We have demonstrated that the existence of large higher-order anisotropies due to exchange coupling between different Fe and MnPd layers can account for the large increase of coercivity in the Fe/MnPd system. The linear dependence of coercivity on inverse Fe thickness is well explained by a phenomenological model by introducing higher-order anisotropy terms into the total free energy of the system. © 1999 American Institute of Physics.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
65.20.-w Thermal properties of liquids
65.40.gd Entropy
75.30.Et Exchange and superexchange interactions
75.30.Gw Magnetic anisotropy

Blocking temperature, energy barrier, and reversal field variation of fine magnetic particles

Huei Li Huang and Jing Ju Lu

Appl. Phys. Lett. 75, 710 (1999); http://dx.doi.org/10.1063/1.124490 (3 pages) | Cited 9 times

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Blocking temperature, energy barrier, and reversal field variation of interacting fine magnetic particles display similar characteristics as a function of the bonding angle and interparticle distance in the context of the dipole interaction. The energy barrier and reversal field exhibit local maxima at the bonding angles β = 0° and π/2 and a global minimum at β ≃ 60°. Thus, the sample average of these quantities is found to reduce with decreasing interparticle distance, in agreement with the latest experimental data. For a system with easy-axis misorientation, magnetization reversal will traverse along the direction in which the misorientation angle and bonding angle have the same sign. © 1999 American Institute of Physics.
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75.50.Tt Fine-particle systems; nanocrystalline materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Influence of strain on the magnetic properties of epitaxial (100) chromium dioxide (CrO2) films

X. W. Li, A. Gupta, and Giang Xiao

Appl. Phys. Lett. 75, 713 (1999); http://dx.doi.org/10.1063/1.124491 (3 pages) | Cited 63 times

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Chromium dioxide (CrO2) films have been grown epitaxially on (100) TiO2 substrates using chemical vapor deposition and their magnetic properties were studied as a function of film thickness (500 Å–1.2 μm). Because of the lattice mismatch with the substrate, the films are strained as evidenced by x-ray diffraction measurements. The amount of strain depends on the thickness and also on the substrate cleaning conditions used prior to growth. Independent of their thickness, the films exhibit a sharp ferromagnetic transition with a Curie temperature in the range of 390–395 K. In-plane magnetic anisotropy is observed for the films, with [001] and [010] being the easy axis and hard axis directions, respectively, for the thicker films. The anisotropy field decreases with decreasing thickness, with the easy and hard axes switching directions for the thinnest films. The results are explained in terms of the competition between magnetocrystalline and strain anisotropies that favor the [001] and [010] magnetization directions, respectively. © 1999 American Institute of Physics.
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75.70.Ak Magnetic properties of monolayers and thin films
75.50.Dd Nonmetallic ferromagnetic materials
75.30.Gw Magnetic anisotropy
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
75.80.+q Magnetomechanical effects, magnetostriction
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
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