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5 Nov 2007

Volume 91, Issue 19, Articles (19xxxx)

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Appl. Phys. Lett. 91, 191106 (2007); http://dx.doi.org/10.1063/1.2804016 (3 pages)

A. Pikulin, N. Bityurin, G. Langer, D. Brodoceanu, and D. Bäuerle
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Solid state reaction at the interface between Heusler alloys and Al cap accelerated by elevated temperature and rough surface

M. Kallmayer, K. Hild, T. Eichhorn, H. Schneider, G. Jakob, A. Conca, M. Jourdan, H. J. Elmers, A. Gloskovskii, S. Schuppler, and P. Nagel

Appl. Phys. Lett. 91, 192501 (2007); http://dx.doi.org/10.1063/1.2805812 (3 pages) | Cited 6 times

Online Publication Date: 6 November 2007

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We have investigated the solid state reaction at the interface of Co2Cr0.6Fe0.4Al, Co2FeSi, and Ni2MnGa Heusler alloy films and Al cap layers using x-ray absorption spectroscopy in transmission and total electron yield mode. At elevated temperatures and at rough surfaces the deposited Al severely reacts with the surface of a Heusler alloy indicated by changes of the absorption spectra. Microspectroscopy using photoemission electron microscopy reveals that the reaction proceeds inhomogeneously with reaction nuclei separated on a micron length scale.
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82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
78.70.Dm X-ray absorption spectra
79.60.Jv Interfaces; heterostructures; nanostructures

Geometric π Josephson junction in d-wave superconducting thin films

A. Gumann, C. Iniotakis, and N. Schopohl

Appl. Phys. Lett. 91, 192502 (2007); http://dx.doi.org/10.1063/1.2801387 (3 pages) | Cited 8 times

Online Publication Date: 7 November 2007

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A novel way to realize a π Josephson junction is proposed, based on a weak link in an unconventional d-wave superconductor with appropriately chosen boundary geometry. The critical current of such a junction is calculated from a fully self-consistent solution of microscopic Eilenberger theory of superconductivity. The results clearly show that a transition to a π Josephson junction occurs for both low temperatures and small sizes of the geometry.
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74.50.+r Tunneling phenomena; Josephson effects
74.78.-w Superconducting films and low-dimensional structures
74.20.Rp Pairing symmetries (other than s-wave)
74.25.Sv Critical currents
85.25.Cp Josephson devices
85.25.Am Superconducting device characterization, design, and modeling

Spin valve effect in self-exchange biased ferromagnetic metal/semiconductor bilayers

M. Zhu, M. J. Wilson, B. L. Sheu, P. Mitra, P. Schiffer, and N. Samarth

Appl. Phys. Lett. 91, 192503 (2007); http://dx.doi.org/10.1063/1.2806966 (3 pages) | Cited 13 times

Online Publication Date: 7 November 2007

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We report magnetization and magetoresistance measurements in hybrid ferromagnetic metal/semiconductor heterostructures comprised of MnAs/(Ga,Mn)As bilayers. Our measurements show that the (metallic) MnAs and (semiconducting) (Ga,Mn)As layers are exchange coupled, resulting in an exchange biasing of the magnetically softer (Ga,Mn)As layer that weakens with layer thickness. Magnetoresistance measurements in the current-perpendicular-to-the-plane geometry show a spin valve effect in these self-exchange biased bilayers. Similar measurements in MnAs/p-GaAs/(Ga,Mn)As trilayers show that the exchange coupling diminishes with spatial separation between the layers.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Pp Magnetic semiconductors
72.20.My Galvanomagnetic and other magnetotransport effects
75.30.Et Exchange and superexchange interactions

Negative spin polarization in (La,Sr)CoO3 probed by a magnetic tunnel junction with (La,Sr)MnO3

Y. Ishii, H. Yamada, H. Sato, H. Akoh, M. Kawasaki, and Y. Tokura

Appl. Phys. Lett. 91, 192504 (2007); http://dx.doi.org/10.1063/1.2806964 (3 pages) | Cited 4 times

Online Publication Date: 8 November 2007

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By using perovskite (La,Sr)MnO3 (LSMO)-based magnetic tunnel junctions with LaAlO3 barrier, we have experimentally revealed the spin state of (La,Sr)CoO3 (LSCO) that was employed as the counterelectrode of the junctions. Inverse tunnel magnetoresistance (TMR) up to −14% was observed at 10 K in low-bias measurement. This indicates that t2g↓ electrons are the majority at the Fermi level in the LSCO band structure, taking into account the half-metallic character of LSMO. The temperature dependence of the interfacial spin polarization of LSCO as deduced from the TMR ratio indicates the reduction of the Curie temperature at the interface by 70 K. The TMR ratio exhibits an asymmetric bias dependence in qualitative agreement with the calculated spin band structure of LSCO.
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72.20.My Galvanomagnetic and other magnetotransport effects
75.47.-m Magnetotransport phenomena; materials for magnetotransport
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
72.25.Mk Spin transport through interfaces
73.20.At Surface states, band structure, electron density of states

Damage-free electrodes fabrication for top emitting organic light emitting diodes by transfer fabrication

Soon-Min Seo and Chang-Hyun Jang

Appl. Phys. Lett. 91, 192505 (2007); http://dx.doi.org/10.1063/1.2806274 (3 pages) | Cited 4 times

Online Publication Date: 8 November 2007

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We report a simple procedure for the integration of the top emitting organic light emitting diode (TOLED), which permits minimum defects at the interface between a top metal electrode and an organic film. This method relies on the transfer of patterned metal electrodes to an organic substrate with a relatively high adhesive property. TOLED, integrated by the transfer fabrication, demonstrates better performance, a reduction of turn-on voltage and an increase of maximum current efficiency, in comparison with fabricated devices by conventional shadow mask method.
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85.60.Jb Light-emitting devices

Microwave power generated by a spin-torque oscillator in the presence of noise

Vasil Tiberkevich, Andrei Slavin, and Joo-Von Kim

Appl. Phys. Lett. 91, 192506 (2007); http://dx.doi.org/10.1063/1.2812546 (3 pages) | Cited 24 times

Online Publication Date: 9 November 2007

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An expression for the microwave power generated by a spin-torque oscillator in the presence of thermal noise is derived. This expression, when used in a subcritical (I<Ith) regime, demonstrates that generated power is determined by the noise level and provides a simple way to experimentally determine the threshold current Ith for microwave generation. The same expression gives a good quantitative description of the experimentally measured dependence of the generated power on the bias current p(I) in a moderate supercritical (Ith<I<1.5Ith) range of bias current variation.
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84.40.-x Radiowave and microwave (including millimeter wave) technology
84.30.Ng Oscillators, pulse generators, and function generators
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