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27 Dec 2010

Volume 97, Issue 26, Articles (26xxxx)

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Appl. Phys. Lett. 97, 263701 (2010); http://dx.doi.org/10.1063/1.3530124 (3 pages)

Shu-Hsien Liao, Kai-Wen Huang, Hong-Chang Yang, Chang-Te Yen, M. J. Chen, Hsin-Hsien Chen, Herng-Er Horng, and Shieh Yueh Yang
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Magnetoresistance in a lithography defined single constrained domain wall spin-valve

Yudong Wang, C. H. de Groot, D. Claudio-Gonzalez, and Hans Fangohr

Appl. Phys. Lett. 97, 262501 (2010); http://dx.doi.org/10.1063/1.3531666 (3 pages) | Cited 2 times

Online Publication Date: 28 December 2010

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We have measured domain wall magnetoresistance in a single lithographically constrained domain wall. An H-shaped Ni nanobridge was fabricated by e-beam lithography with the two sides being single magnetic domains showing independent magnetic switching. The connection between the sides constrains the domain wall when the sides line up antiparallel. The magnetoresistance curve clearly identifies the magnetic configurations that are expected from a spin-valvelike structure. The value of the magnetoresistance at room temperature is around 0.1% or 0.4 Ω. This value is shown to be in agreement with a theoretical formulation based on spin accumulation. Micromagnetic simulations show that it is possible to reduce the size of the domain wall further by shortening the length of the bridge.
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72.15.Gd Galvanomagnetic and other magnetotransport effects
81.16.Nd Micro- and nanolithography
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
61.46.-w Structure of nanoscale materials
75.60.Ch Domain walls and domain structure

Spin-transfer pulse switching: From the dynamic to the thermally activated regime

D. Bedau, H. Liu, J. Z. Sun, J. A. Katine, E. E. Fullerton, S. Mangin, and A. D. Kent

Appl. Phys. Lett. 97, 262502 (2010); http://dx.doi.org/10.1063/1.3532960 (3 pages) | Cited 11 times

Online Publication Date: 30 December 2010

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The effect of thermal fluctuations on spin-transfer switching has been studied for a broad range of time scales (subnanoseconds to seconds) in a model system, a uniaxial thin film nanomagnet. The nanomagnet is incorporated into a spin-valve nanopillar, which is subject to spin-polarized current pulses of variable amplitude and duration. Two physical regimes are clearly distinguished: a long pulse duration regime, in which reversal occurs by spin-transfer assisted thermal activation over an energy barrier, and a short-time large pulse amplitude regime, in which the switching probability is determined by the spin-angular momentum in the current pulse.
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72.25.-b Spin polarized transport
75.75.-c Magnetic properties of nanostructures
75.50.Kj Amorphous and quasicrystalline magnetic materials
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)

Impact of edge-barrier pinning in superconducting thin films

W. A. Jones, P. N. Barnes, M. J. Mullins, F. J. Baca, R. L. S. Emergo, J. Wu, T. J. Haugan, and J. R. Clem

Appl. Phys. Lett. 97, 262503 (2010); http://dx.doi.org/10.1063/1.3529945 (3 pages)

Online Publication Date: 30 December 2010

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It has been suggested that edge-barrier pinning might cause the critical current density (Jc) in bridged superconducting films to increase. Subsequent work indicated that this edge-barrier effect does not impact bridges larger than 1 μm. However, we provide a theoretical assessment with supporting experimental data suggesting edge-barrier pinning can significantly enhance Jc for bridges of a few microns or even tens of microns thus skewing any comparisons among institutions. As such, when reporting flux pinning and superconductor processing improvements for Jc comparisons, the width of the sample has to be taken into consideration as is currently done with film thickness.
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74.78.-w Superconducting films and low-dimensional structures
74.25.Sv Critical currents
74.25.Wx Vortex pinning (includes mechanisms and flux creep)

Longitudinal spin-Seebeck effect in sintered polycrystalline (Mn,Zn)Fe2O4

Ken-ichi Uchida, Tatsumi Nonaka, Takeru Ota, and Eiji Saitoh

Appl. Phys. Lett. 97, 262504 (2010); http://dx.doi.org/10.1063/1.3533397 (3 pages) | Cited 6 times

Online Publication Date: 30 December 2010

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This paper reports that the longitudinal spin-Seebeck effect appears even in a sintered polycrystalline Mn-Zn ferrite [(Mn,Zn)Fe2O4] slab. The effect drives a spin current flowing across an interface between the (Mn,Zn)Fe2O4 slab and an attached Pt film along a temperature gradient and it generates electric voltage via the inverse spin-Hall effect in the Pt film. Since the observed phenomenon enables thermal generation of electric voltage from commonly used polycrystalline insulators, it can be used as a versatile and low-cost thermoelectric generator.
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72.20.Pa Thermoelectric and thermomagnetic effects
73.40.Ns Metal-nonmetal contacts
72.20.My Galvanomagnetic and other magnetotransport effects
75.50.Gg Ferrimagnetics

Ab initio studies of the effect of nanoclusters on magnetostriction of Fe1−xGax alloys

Hui Wang, Y. N. Zhang, Teng Yang, Z. D. Zhang, L. Z. Sun, and R. Q. Wu

Appl. Phys. Lett. 97, 262505 (2010); http://dx.doi.org/10.1063/1.3533659 (3 pages) | Cited 1 time

Online Publication Date: 30 December 2010

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Using the density functional calculations, we investigated the effect of nanoprecipitation on the magnetostriction of Fe1−xGax alloys. While the B2-like FeGa clusters undergo slight tetragonal distortion, D03-like FeGa clusters remain cubic in the Fe matrix. Moreover, we found that B2-like nanostructures produce negative magnetostriction, whereas D03-like nanostructures give small positive magnetostriction in the hypothetical inhomogeneous structures. Therefore, the formation of nanoscale precipitates cannot be the reason for the extraordinary enhancement of magnetostriction of Fe1−xGax alloys.
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75.80.+q Magnetomechanical effects, magnetostriction
75.50.Bb Fe and its alloys
81.30.Mh Solid-phase precipitation
75.50.Tt Fine-particle systems; nanocrystalline materials
75.75.-c Magnetic properties of nanostructures

Simultaneous changes of nuclear and magnetic structures across the morphotropic phase boundary in (1−x)BiFeO3−xPbTiO3

Shuvrajyoti Bhattacharjee, Anatoliy Senyshyn, P. S. R. Krishna, H. Fuess, and Dhananjai Pandey

Appl. Phys. Lett. 97, 262506 (2010); http://dx.doi.org/10.1063/1.3533665 (3 pages) | Cited 4 times

Online Publication Date: 30 December 2010

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We present here the results of a powder neutron diffraction study on the (1−x)BiFeO3–xPbTiO3 (BF-xPT) system, which reveal an abrupt change in magnetic structure from a noncollinear antiferromagnetic one to a collinear G-type antiferromagnetic as the nuclear structure of the ferroelectric phase changes from monoclinic in Cc space group for x ≤ 0.27 to tetragonal in P4mm space group for x ≥ 0.31 across the morphotropic phase boundary (MPB). This reflects the multiferroic character of the MPB in the BF-xPT system.
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75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
61.05.fm Neutron diffraction
75.50.Ee Antiferromagnetics
75.85.+t Magnetoelectric effects, multiferroics
77.80.B- Phase transitions and Curie point

Embedded clusters and magnetism in Cr-doped AlAs: A first-principles study

Yao Qiu, Yong-Hong Zhao, Yong Liu, Guo-Ping Zhao, and Shao-Quan Wu

Appl. Phys. Lett. 97, 262507 (2010); http://dx.doi.org/10.1063/1.3533799 (3 pages) | Cited 1 time

Online Publication Date: 30 December 2010

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Extensive density functional theory investigations have been made on the spatial distribution of Cr atoms and associated magnetism of zinc-blende Cr:AlAs. The calculated results show that embedded Cr clusters, formed on the substitutional Al and interstitial sites, can lead to great changes in the local structure and magnetism of Cr:AlAs, which is very different from that assumed by the usual homogeneous model.
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71.20.Nr Semiconductor compounds
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
75.50.Pp Magnetic semiconductors
61.72.jj Interstitials
61.72.uj III-V and II-VI semiconductors

Microwave readout scheme for a Josephson phase qubit

T. Wirth, J. Lisenfeld, A. Lukashenko, and A. V. Ustinov

Appl. Phys. Lett. 97, 262508 (2010); http://dx.doi.org/10.1063/1.3533805 (3 pages) | Cited 2 times

Online Publication Date: 30 December 2010

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We present experimental results on a microwave scheme for reading out a Josephson phase qubit. A capacitively shunted superconducting quantum interference device (SQUID) is used as a nonlinear resonator which is inductively coupled to the qubit. The flux state of the qubit is detected by measuring the amplitude and phase of a microwave pulse reflected from the SQUID resonator. By this low-dissipative method, the qubit state measurement time is reduced to 25 μs, which is much faster than the conventional readout performed by switching the SQUID to its nonzero dc voltage state. The readout scheme presented here allows for reading out multiple qubits using a single microwave line by employing frequency-division multiplexing.
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03.67.Lx Quantum computation architectures and implementations
85.25.Cp Josephson devices
85.25.Dq Superconducting quantum interference devices (SQUIDs)

Modification of magnetic and magnetocaloric properties of Dy–Co–Al bulk metallic glass introduced by hydrogen

H. Fu, M. Zou, and Niraj K. Singh

Appl. Phys. Lett. 97, 262509 (2010); http://dx.doi.org/10.1063/1.3534794 (3 pages) | Cited 2 times

Online Publication Date: 30 December 2010

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Dy53.8Co17.3Al28.9 bulk metallic glass with a diameter of 3 mm exhibits spin-glass behavior and large coercivity and remanence. Hydrogenation of Dy53.8Co17.3Al28.9 suppresses the magnetic transition temperature and removes coercivity and remanence because of the expansion of average interatomic distance. The advantage of large magnetic entropy changes (17.5 and 9.5 J/kg K for the field changes from 0 to 50, and from 0 to 20 kOe, respectively) without any hysteresis loss makes Dy53.8Co17.3Al28.9 H170.6 alloy a promising magnetic refrigerant.
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75.30.Sg Magnetocaloric effect, magnetic cooling
75.50.Lk Spin glasses and other random magnets
75.50.Kj Amorphous and quasicrystalline magnetic materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
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