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30 Apr 2012

Volume 100, Issue 18, Articles (18xxxx)

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Appl. Phys. Lett. 100, 181901 (2012); http://dx.doi.org/10.1063/1.4705414 (4 pages)

Etienne Brasselet, Arnaud Royon, and Lionel Canioni
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Nanowire arrays, surface anisotropy, magnetoelastic effects and spintronics

C. Tannous, A. Ghaddar, and J. Gieraltowski

Appl. Phys. Lett. 100, 182401 (2012); http://dx.doi.org/10.1063/1.4709427 (4 pages)

Online Publication Date: 1 May 2012

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Resonance field Hres variation obtained from ferromagnetic resonance measurements performed versus field angle on ferromagnetic nickel nanowire arrays with different diameters (15 nm to 100 nm) and with temperature varying from liquid helium (4.2 K) to room value indicate presence of large surface anisotropy for small diameter (<50 nm) and strong magnetoelastic effects for all diameters. Extracting this information from temperature variation of anisotropy terms allows us to infer that magnetoelastic behavior versus temperature and nanowire diameter might have important implications for the design of nanowire based spintronic devices such as magnetic racetrack memory, logic and storage media, and devices.
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81.05.Bx Metals, semimetals, and alloys
81.07.Gf Nanowires
85.75.-d Magnetoelectronics; spintronics: devices exploiting spin polarized transport or integrated magnetic fields
75.80.+q Magnetomechanical effects, magnetostriction
75.50.Cc Other ferromagnetic metals and alloys
75.30.Gw Magnetic anisotropy

Measurement and simulation of anisotropic magnetoresistance in single GaAs/MnAs core/shell nanowires

J. Liang, J. Wang, A. Paul, B. J. Cooley, D. W. Rench, N. S. Dellas, S. E. Mohney, R. Engel-Herbert, and N. Samarth

Appl. Phys. Lett. 100, 182402 (2012); http://dx.doi.org/10.1063/1.4710524 (5 pages)

Online Publication Date: 1 May 2012

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We report four probe measurements of the low field magnetoresistance (MR) in single core/shell GaAs/MnAs nanowires (NWs) synthesized by molecular beam epitaxy, demonstrating clear signatures of anisotropic magnetoresistance that track the field-dependent magnetization. A comparison with micromagnetic simulations reveals that the principal characteristics of the magnetoresistance data can be unambiguously attributed to the nanowire segments with a zinc blende GaAs core. The direct correlation between magnetoresistance, magnetization, and crystal structure provides a powerful means of characterizing individual hybrid ferromagnet/semiconductor nanostructures.
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73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
75.50.Tt Fine-particle systems; nanocrystalline materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.A- Nucleation and growth

Spin-transfer switching in full-Heusler Co2FeAl-based magnetic tunnel junctions

Hiroaki Sukegawa, Zhenchao Wen, Kouta Kondou, Shinya Kasai, Seiji Mitani, and Koichiro Inomata

Appl. Phys. Lett. 100, 182403 (2012); http://dx.doi.org/10.1063/1.4710521 (5 pages) | Cited 2 times

Online Publication Date: 2 May 2012

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We demonstrated spin-transfer magnetization switching using magnetic tunnel junctions (MTJs) with a full-Heusler alloy Co2FeAl (CFA). We prepared CFA (1.5 nm)/MgO/CoFe (4 nm) (“CFA-free”) and CFA (30 nm)/MgO/CoFeB (2 nm) (“CFA-reference”) MTJs on a Cr(001) layer. The intrinsic critical current density (Jc0) of the CFA-free (CFA-reference) MTJ was 29 MA/cm2 (7.1 MA/cm2). The larger Jc0 of the CFA-free MTJ is attributed to the significant enhancement of the Gilbert damping factor (∼0.04) of the CFA due to the Cr layer. The Jc0 of the CFA-reference is as small as that reported for typical CoFeB/MgO/CoFeB MTJs.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.30.Ds Spin waves
75.47.-m Magnetotransport phenomena; materials for magnetotransport
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
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Resonant microwave-to-spin-wave transducer

Y. Au, E. Ahmad, O. Dmytriiev, M. Dvornik, T. Davison, and V. V. Kruglyak

Appl. Phys. Lett. 100, 182404 (2012); http://dx.doi.org/10.1063/1.4711039 (5 pages) | Cited 4 times

Online Publication Date: 2 May 2012

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We use time resolved scanning Kerr microscopy and analytical and numerical calculations to demonstrate coupling of uniform global microwave field to propagating spin waves for emerging magnonic architectures. The coupling is mediated by the local dynamic dipolar field produced by the magnetization of a resonantly driven all-metallic magnetic microwave-to-spin-wave transducer. The local dipolar field can exceed that of the incident microwave field by one order of magnitude. Our numerical simulations demonstrate the ability of the transducer to unidirectionally emit coherent exchange spin waves of nanoscale wavelengths with the emission direction programmed by the magnetic state of the transducer.
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07.07.Mp Transducers
02.60.-x Numerical approximation and analysis
85.70.-w Magnetic devices

Room-temperature ferromagnetism in epitaxial Mg-doped SnO2 thin films

Ping Wu, Baozeng Zhou, and Wei Zhou

Appl. Phys. Lett. 100, 182405 (2012); http://dx.doi.org/10.1063/1.4711220 (4 pages) | Cited 3 times

Online Publication Date: 3 May 2012

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The magnetic behavior of epitaxial Mg-doped SnO2 thin films prepared by radio-frequency magnetron sputtering was investigated in this work. Room-temperature ferromagnetism with the saturation magnetization of about 6.9 emu/cm3 was observed in 6% Mg-doped SnO2 samples. And the saturation magnetization decreases when further doped to 8%, while the optical band-gap increases. The room-temperature ferromagnetism was induced by the holes created by Mg on the substitutional site. Additionally, Mg interstitials and oxygen vacancies play an important role in reducing the magnetic moments.
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75.70.Ak Magnetic properties of monolayers and thin films
81.15.Cd Deposition by sputtering
61.72.jj Interstitials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Pp Magnetic semiconductors
75.30.Cr Saturation moments and magnetic susceptibilities

Vortex mode dynamics and bandwidth tunability in a two-dimensional array of interacting magnetic disks

Federico Montoncello and Loris Giovannini

Appl. Phys. Lett. 100, 182406 (2012); http://dx.doi.org/10.1063/1.4710549 (4 pages) | Cited 3 times

Online Publication Date: 4 May 2012

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We calculate the spin wave spectrum and band diagram of a planar array of interacting disks in the vortex state at zero and finite applied field. We found that the circular polarization of modes depends on the Bloch wavevector k, and that the apparent spin wave profile can change as k increases from Γ to zone boundary as a consequence of the array periodicity, although the cell function remains the same. Focusing on the gyrotropic mode, we found that application of an external field can reduce or enhance the mode bandwidth, and hence slow down or boost the information carrier propagation along orthogonal directions.
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75.30.Ds Spin waves
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Room temperature single GaN nanowire spin valves with FeCo/MgO tunnel contacts

Hyun Kum, Junseok Heo, Shafat Jahangir, Animesh Banerjee, Wei Guo, and Pallab Bhattacharya

Appl. Phys. Lett. 100, 182407 (2012); http://dx.doi.org/10.1063/1.4711850 (4 pages) | Cited 1 time

Online Publication Date: 4 May 2012

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We report the direct measurement of spin transport characteristics in a GaN spin valve, with a relatively defect-free single GaN nanowire (NW) as the channel and FeCo/MgO as the tunnel barrier spin contact. Hanle spin precession and non-local transport measurements are made in an unintentionally doped nanowire spin valves. Spin diffusion length and spin lifetime values of 260 nm and 100 ps, respectively, are derived. Appropriate control measurements have been made to verify spin injection, transport, and detection.
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85.75.-d Magnetoelectronics; spintronics: devices exploiting spin polarized transport or integrated magnetic fields
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