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18 Apr 2011

Volume 98, Issue 16, Articles (16xxxx)

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Appl. Phys. Lett. 98, 163701 (2011); http://dx.doi.org/10.1063/1.3579156 (3 pages)

Thomas Jetzfellner, Amir Rosenthal, K.-H. Englmeier, Alexander Dima, Miguel Ángel Araque Caballero, Daniel Razansky, and Vasilis Ntziachristos
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Fine tuning of phase qubit parameters for optimization of fast single-pulse readout

Leonid S. Revin and Andrey L. Pankratov

Appl. Phys. Lett. 98, 162501 (2011); http://dx.doi.org/10.1063/1.3582615 (3 pages)

Online Publication Date: 18 April 2011

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We analyze a two-level quantum system, describing the phase qubit, during a single-pulse readout process by a numerical solution of the time-dependent Schroedinger equation. It has been demonstrated that the readout error has a minimum for certain values of the system’s basic parameters. In particular, the optimization of the qubit capacitance and the readout pulse shape leads to significant reduction in the readout error. It is shown that in an ideal case the fidelity can be increased to almost 97% for 2 ns pulse duration and to 96% for 1 ns pulse duration.
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03.67.Lx Quantum computation architectures and implementations
03.65.Ge Solutions of wave equations: bound states

Spin-torque switching window, thermal stability, and material parameters of MgO tunnel junctions

T. Devolder, L. Bianchini, K. Miura, K. Ito, Joo-Von Kim, P. Crozat, V. Morin, A. Helmer, C. Chappert, S. Ikeda, and H. Ohno

Appl. Phys. Lett. 98, 162502 (2011); http://dx.doi.org/10.1063/1.3576937 (3 pages) | Cited 4 times

Online Publication Date: 18 April 2011

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We study the use of in-plane magnetized free layers with artificially lowered effective magnetization, in the context of spin-torque random access memories with magnetic tunnel junctions. We determine the field-voltage window for direct overwrite switching and thermal stability. We relate them to the magnetic constants extracted from the telegraph noise and high frequency noise exhibited by the junctions under specific conditions.
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85.75.Dd Magnetic memory using magnetic tunnel junctions

Bound magnetic polarons and p-d exchange interaction in ferromagnetic insulating Cu-doped ZnO

Yufeng Tian, Yongfeng Li, Mi He, Irwan Ade Putra, Haiyang Peng, Bin Yao, Siew Ann Cheong, and Tom Wu

Appl. Phys. Lett. 98, 162503 (2011); http://dx.doi.org/10.1063/1.3579544 (3 pages) | Cited 26 times

Online Publication Date: 18 April 2011

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A systematic study on the magnetic and electrical transport properties of single-phase wurtzite Zn1−xCuxO is performed. Efros variable range hopping dominates the conduction, which is accompanied by a ferromagnetic order up to 700 K for x>1%. Both the first-principles calculations and Cu/Al co-doping experiments suggest that the spontaneous spin polarization originates from the p-d exchange interaction between O 2p and Cu 3d orbitals. Furthermore, our results are consistent with the scenario that the intrinsic ferromagnetism is established through indirect interactions between bound magnetic polarons mediated by magnetic impurities.
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75.30.Et Exchange and superexchange interactions
71.38.-k Polarons and electron-phonon interactions
75.50.Dd Nonmetallic ferromagnetic materials
75.50.Pp Magnetic semiconductors
72.80.Ey III-V and II-VI semiconductors
72.25.-b Spin polarized transport
75.30.Hx Magnetic impurity interactions

Hall effect-induced acceleration of electromigration failures in spin valve multilayers under magnetic field

Jing Jiang, Ding Gui Zeng, Kyung-Won Chung, Jongryoul Kim, and Seongtae Bae

Appl. Phys. Lett. 98, 162504 (2011); http://dx.doi.org/10.1063/1.3581042 (3 pages)

Online Publication Date: 19 April 2011

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It was observed that electromigration (EM)-induced failures in spin valve multilayers were severely accelerated by an externally applied magnetic field. The theoretical and experimental analysis results confirmed that Hall effect-induced Lorentz force applied to the perpendicular-to-the-film-plane direction is primarily responsible for the severe acceleration of the EM failures due to its dominant contribution to abruptly increasing local temperature and current density. The proposed failure model and the theoretical calculations were demonstrated to agree well with the experimental observations.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
66.30.Qa Electromigration

Improved tunneling magnetoresistance at low temperature in manganite junctions grown by molecular beam epitaxy

R. Werner, A. Yu. Petrov, L. Alvarez Miño, R. Kleiner, D. Koelle, and B. A. Davidson

Appl. Phys. Lett. 98, 162505 (2011); http://dx.doi.org/10.1063/1.3581885 (3 pages) | Cited 7 times

Online Publication Date: 20 April 2011

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We report resistance versus magnetic field measurements for a La0.65Sr0.35MnO3/SrTiO3/La0.65Sr0.35MnO3 tunnel junction grown by molecular-beam epitaxy, that show a large field window of extremely high tunneling magnetoresistance (TMR) at low temperature. Scanning the in-plane applied field orientation through 360°, the TMR shows fourfold symmetry, i.e., biaxial anisotropy, aligned with the crystalline axis but not the junction geometrical long axis. The TMR reaches ∼ 1900% at 4 K, corresponding to an interfacial spin polarization of >95% assuming identical interfaces. These results show that uniaxial anisotropy is not necessary for large TMR, and lay the groundwork for future improvements in TMR in manganite junctions.
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75.47.Lx Magnetic oxides
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
75.30.Gw Magnetic anisotropy
72.25.-b Spin polarized transport
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Magnetic properties and phonon behavior of Pr2NiMnO6 thin films

M. P. Singh, K. D. Truong, S. Jandl, and P. Fournier

Appl. Phys. Lett. 98, 162506 (2011); http://dx.doi.org/10.1063/1.3575564 (3 pages) | Cited 1 time

Online Publication Date: 20 April 2011

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We report on the magnetic properties and the phonon behavior of epitaxial Pr2NiMnO6 (PNMO) films. The temperature dependence of their magnetic properties shows a ferromagnetic behavior up to 214 K owing to a dominant Ni2+/Mn4+ ordering. The observation of a secondary low-temperature magnetic transition around 126 K indicates that a small proportion of Ni/Mn disordered lattice remains in our films. Unlike La2NiMnO6, the temperature dependence of the 651 cm−1 Raman active phonon of our films reflects the presence of a weak spin–phonon coupling in PNMO.
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75.70.Ak Magnetic properties of monolayers and thin films
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
78.66.Nk Insulators
78.30.Hv Other nonmetallic inorganics
63.20.K- Phonon interactions

Structural controlled magnetic anisotropy in Heusler L10−MnGa epitaxial thin films

Kangkang Wang, Erdong Lu, Jacob W. Knepper, Fengyuan Yang, and Arthur R. Smith

Appl. Phys. Lett. 98, 162507 (2011); http://dx.doi.org/10.1063/1.3582244 (3 pages) | Cited 3 times

Online Publication Date: 20 April 2011

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Ferromagnetic L10−MnGa thin films have been epitaxially grown on GaN, sapphire, and MgO substrates using molecular beam epitaxy. Using diffraction techniques, the epitaxial relationships are determined. It is found that the crystalline orientation of the films differ due to the influence of the substrate. By comparing the magnetic anisotropy to the structural properties, a clear correlation could be established indicating that the in-plane and out-of-plane anisotropy is directly determined by the crystal orientation of the film and could be controlled via selection of the substrates. This result could be helpful in tailoring magnetic anisotropy in thin films for spintronic applications.
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75.30.Gw Magnetic anisotropy
68.55.at Other materials
75.50.Cc Other ferromagnetic metals and alloys
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
75.70.Ak Magnetic properties of monolayers and thin films
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Optical communication of spin information between light emitting diodes

R. Farshchi, M. Ramsteiner, J. Herfort, A. Tahraoui, and H. T. Grahn

Appl. Phys. Lett. 98, 162508 (2011); http://dx.doi.org/10.1063/1.3582917 (3 pages) | Cited 3 times

Online Publication Date: 21 April 2011

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For the full implementation of spintronic circuits, it is necessary to transmit spin information from one device to another. Electrons in semiconductors often suffer from high spin relaxation rates, making electrical transport of spin information highly inefficient. Here, we propose optical transport of spin information as an alternative. We demonstrate that the spin information associated with electrons injected from Co2FeSi and Fe layers into the quantum wells of spin light emitting diodes (spin-LEDs) can be transported optically in the form of circularly polarized light and deciphered electrically via the magnetic field dependence of the photocurrent in a distant detector spin-LED.
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85.60.Jb Light-emitting devices
85.75.-d Magnetoelectronics; spintronics: devices exploiting spin polarized transport or integrated magnetic fields
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