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1 Nov 2010

Volume 97, Issue 18, Articles (18xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 97, 183105 (2010); http://dx.doi.org/10.1063/1.3506485 (3 pages)

Z. H. Zhang, X. Q. Deng, X. Q. Tan, M. Qiu, and J. B. Pan
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Urbach tail studies by luminescence filtering in moderately doped bulk InP

Arsen V. Subashiev, Oleg Semyonov, Zhichao Chen, and Serge Luryi

Appl. Phys. Lett. 97, 181914 (2010); http://dx.doi.org/10.1063/1.3510470 (3 pages) | Cited 4 times

Online Publication Date: 3 November 2010

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The shape of the photoluminescence line registered from a side edge of InP wafer is studied as a function of the distance from the excitation spot. The observed redshift in the luminescence maximum is well described by radiation filtering and is consistent with the absorption spectra. Our method provides an independent and accurate determination of the Urbach tails in moderately doped semiconductors.
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78.55.Cr III-V semiconductors
66.30.-h Diffusion in solids

Annealing effect on the optical response and interdiffusion of n-ZnO/p-Si (111) heterojunction grown by atomic layer deposition

Ching-Shun Ku, Jheng-Ming Huang, Ching-Yuan Cheng, Chih-Ming Lin, and Hsin-Yi Lee

Appl. Phys. Lett. 97, 181915 (2010); http://dx.doi.org/10.1063/1.3511284 (3 pages)

Online Publication Date: 3 November 2010

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Optical and structural properties of n-ZnO films grown on a p-Si (111) substrate by atomic layer deposition were observed using in situ synchrotron x-ray diffraction during annealing. The photoluminescence showed a complicated photon response with increasing annealing temperature. In situ x-ray diffraction indicated the growth of grains for an annealing temperature from 500 to 800 °C with the orientation altering from polycrystalline to preferential (200). Measurements with a time-of-flight secondary-ion mass spectrometer indicated that the outgassing of hydrogen atoms and ZnO/Si interdiffusion behavior were correlated with the intensity and position of emissions in photoluminescence spectra.
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78.66.Hf II-VI semiconductors
66.30.Ny Chemical interdiffusion; diffusion barriers
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
81.15.Kk Vapor phase epitaxy; growth from vapor phase
61.72.Cc Kinetics of defect formation and annealing
78.55.Et II-VI semiconductors

Microtwin reduction in 3C–SiC heteroepitaxy

A. Severino and F. La Via

Appl. Phys. Lett. 97, 181916 (2010); http://dx.doi.org/10.1063/1.3514559 (3 pages) | Cited 1 time

Online Publication Date: 3 November 2010

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In this letter, we have studied the density of microtwins in the vicinity of the film surface, by using in-plane grazing incidence diffraction technique, to suggest a reduction trend of such defects at different growth rates. In (100) 3C–SiC heteroepitaxy, microtwin density decreases when a slower growth rate process is performed. A reduction ratio of microtwins of 0.16, 0.2, and 0.28 for 2 μm/h, 5 μm/h, and 10 μm/h, respectively, has been obtained. The relationship between microtwin density and growth rate, or Si/H2 ratio, found with this technique is in perfect agreement with the pre-existent literature.
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68.55.ag Semiconductors
61.72.Mm Grain and twin boundaries

Prediction of thermal radiative properties (300–1000 K) of La2NiO4+δ ceramics

M. T. Ta, J. Y. Rolland, P. Echegut, B. Rousseau, M. Zaghrioui, F. Giovannelli, H. Gomart, P. Lenormand, and F. Ansart

Appl. Phys. Lett. 97, 181917 (2010); http://dx.doi.org/10.1063/1.3511344 (3 pages) | Cited 1 time

Online Publication Date: 4 November 2010

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A multiscale numerical model is developed to predict the thermal radiative properties (TRP) of rough La2NiO4+δ coatings. The model integrates intrinsic and extrinsic contributions related to the chemical composition and the texture, respectively. High-temperature infrared reflectivity and thermogravimetric measurements on a La2NiO4+δ single crystal make it possible to understand the role of the excess oxygen in the intrinsic TRP. We show that dense ceramics with thicknesses higher than 4 μm are optically thick, and that one can adjust the surface roughness parameters to predict their TRP.
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78.30.Hv Other nonmetallic inorganics
82.80.-d Chemical analysis and related physical methods of analysis
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
68.35.B- Structure of clean surfaces (and surface reconstruction)
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Physical mechanisms for picosecond laser ablation of silicon carbide at infrared and ultraviolet wavelengths

Sha Tao, Ronald L. Jacobsen, and Benxin Wu

Appl. Phys. Lett. 97, 181918 (2010); http://dx.doi.org/10.1063/1.3511739 (3 pages)

Online Publication Date: 4 November 2010

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Investigations have been performed on the physical mechanisms of picosecond laser ablation of silicon carbide at 355 and 1064 nm, which have not been well understood yet. The study shows that the low-fluence ablation rates are close for 355 and 1064 nm, and the dominant material removal mechanism should be surface evaporation. At fluences above ∼ 2 J/cm2, the ablation rate increases very quickly for 355 nm, and the associated dominant mechanism is very likely to be critical point phase separation. For 1064 nm, the ablation rate variation with fluence above ∼ 2 J/cm2 follows the same trend as that for low fluences, and the mechanism should remain as surface evaporation.
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79.20.Eb Laser ablation
68.35.Rh Phase transitions and critical phenomena
64.75.Qr Phase separation and segregation in semiconductors

Relation between physical parameters and thermal stability of liquid-crystal blue phase

Hui-Yu Chen, Hsin-Hung Liu, Jia-Liang Lai, Chih-Hao Chiu, and Ji-Yi Chou

Appl. Phys. Lett. 97, 181919 (2010); http://dx.doi.org/10.1063/1.3509413 (3 pages)

Online Publication Date: 4 November 2010

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Correlations between the stability of blue phases and the physical parameters of liquid-crystal hosts are reported in this study. Experimental results show that liquid-crystal blue phases are more thermostabilized when the dielectric anisotropy is reduced or the elastic constants increased. These correlations can be explained by Defect theory and Landau theory for blue phases. Moreover, the results give us the clues to develop more suitable blue-phase materials for fundamental researches or fast photonic devices.
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61.30.Mp Blue phases and other defect-phases
62.10.+s Mechanical properties of liquids
61.30.Eb Experimental determinations of smectic, nematic, cholesteric, and other structures
61.30.Jf Defects in liquid crystals

Formation of In2O3 nanorings on Si substrates

C. L. Hsin, S. Y. Yu, C. W. Huang, and W. W. Wu

Appl. Phys. Lett. 97, 181920 (2010); http://dx.doi.org/10.1063/1.3511539 (3 pages)

Online Publication Date: 5 November 2010

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A new approach to form the In2O3 nanorings (NRs) has been proven by tailoring the difference between property of metal and metal oxide. The formation process of the In2O3 NRs is proposed to be resulted form a subtle competition between the oxidation and evaporation of indium at the rim and center, respectively. Patterned In2O3 NRs have been grown on (001) Si substrates in combination with nanosphere lithography. The size and morphology of the NRs can be controlled by the size of polystyrene nanospheres and the thickness of indium layer. The optical property measurements showed that the In2O3 NRs are sensitive in absorption and emission of light between 600 and 622 nm in wavelength. The patterned In2O3 NRs on silicon are advantageous for fabricating optical-response photonic devices at the desired locations and direct integration to the silicon-based photonic devices with current processing technology.
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81.16.Nd Micro- and nanolithography
61.66.-f Structure of specific crystalline solids
61.46.-w Structure of nanoscale materials
81.65.Mq Oxidation
78.67.-n Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures

Heavy noble gas (Kr, Xe) irradiated (111) InP nanoporous honeycomb membranes with enhanced ultrafast all-optical terahertz emission

K. Radhanpura, S. Hargreaves, R. A. Lewis, L. Sirbu, and I. M. Tiginyanu

Appl. Phys. Lett. 97, 181921 (2010); http://dx.doi.org/10.1063/1.3509404 (3 pages) | Cited 1 time

Online Publication Date: 5 November 2010

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Nanoporous honeycomb membranes on InP (111) surfaces emit ultrafast coherent terahertz pulses under near-infrared optical excitation. Irradiating the membranes with heavy noble gas Kr or Xe ions enhances the terahertz emission. The emission does not vary with in-plane magnetic field rotation and exhibits three-cycle dependence on azimuthal-angle rotation. Both suggest the terahertz source is not transient currents but optical rectification enhanced by the heavy-ion irradiation.
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78.67.Rb Nanoporous materials
78.70.Gq Microwave and radio-frequency interactions
78.47.D- Time resolved spectroscopy (>1 psec)
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Growth of thick heavily boron-doped diamond single crystals: Effect of microwave power density

R. Issaoui, J. Achard, F. Silva, A. Tallaire, A. Tardieu, A. Gicquel, M. A. Pinault, and F. Jomard

Appl. Phys. Lett. 97, 182101 (2010); http://dx.doi.org/10.1063/1.3511449 (3 pages) | Cited 1 time

Online Publication Date: 1 November 2010

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The fabrication of diamond-based vertical power devices which are the most suited for high current applications requires the use of thick heavily boron-doped (B-doped) diamond single crystals. Although the growth of thin B-doped diamond films is well controlled over a large concentration range, little is known about the growth conditions leading to heavily doped thick single crystals. In this paper, it was found that the microwave power densities (MWPD) coupled to the plasma used to synthesize B-doped diamond by chemical vapor deposition is one of the key parameters allowing tuning doping efficiencies over two orders of magnitude. At high MWPD (above 100 W cm−3) the boron doping efficiency (DE) is extremely low while further increasing the boron concentration in the gas phase is no use as this leads to plasma instability. On the other hand, when low MWPD are used (<50 W cm−3), DE can be strongly increased but twinning and defects formation hampers the surface morphology. The use of intermediate MWPD densities has been demonstrated as the key in obtaining thick heavily B-doped diamond crystals (>1020 cm−3) with good morphologies.
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81.10.-h Methods of crystal growth; physics and chemistry of crystal growth, crystal morphology, and orientation
68.35.B- Structure of clean surfaces (and surface reconstruction)
61.72.Mm Grain and twin boundaries
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
61.72.U- Doping and impurity implantation

Ultrafast carrier and phonon dynamics in Bi2Se3 crystals

J. Qi, X. Chen, W. Yu, P. Cadden-Zimansky, D. Smirnov, N. H. Tolk, I. Miotkowski, H. Cao, Y. P. Chen, Y. Wu, S. Qiao, and Z. Jiang

Appl. Phys. Lett. 97, 182102 (2010); http://dx.doi.org/10.1063/1.3513826 (3 pages) | Cited 3 times

Online Publication Date: 1 November 2010

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Ultrafast time-resolved differential reflectivity of Bi2Se3 crystals is studied using optical pump-probe spectroscopy. Three distinct relaxation processes are found to contribute to the initial transient reflectivity changes. The deduced relaxation timescale and the sign of the reflectivity change suggest that electron–phonon interactions and defect-induced charge trapping are the underlying mechanisms for the three processes. After the crystal is exposed to air, the relative strength of these processes is altered and becomes strongly dependent on the excitation photon energy.
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63.20.kd Phonon-electron interactions
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
78.47.jg Time resolved reflection spectroscopy
71.38.-k Polarons and electron-phonon interactions

Tunneling transport properties for metal-oxide-semiconductor diode consisting of ferromagnetic ZnMnO nanocrystals

Sejoon Lee, Youngmin Lee, Yoon Shon, Deuk Young Kim, and Tae Won Kang

Appl. Phys. Lett. 97, 182103 (2010); http://dx.doi.org/10.1063/1.3507894 (3 pages)

Online Publication Date: 2 November 2010

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Spin-dependent tunneling properties for the metal-semiconductor-oxide diode which was fabricated using ferromagnetic ZnMnO nanocrystals and Ti-Co ferromagnet were investigated. The diode revealed current oscillation packets after tunneling-on, and the peak-to-valley current ratio of the packets showed to be dependent on the temperature-dependent magnetization of the nanocrystals; i.e., the peak-to-valley current ratio of the packets was increased with decreasing the temperature. This result is ascribed to the increased conductance fluctuation due to the increased repulsion probability between spin-polarized and unpolarized carriers because the spin-polarized carriers which are supplied from Ti-Co and are to be injected into n+-Si are transferred through the nanocrystals.
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85.30.Kk Junction diodes
85.30.Tv Field effect devices
75.50.Pp Magnetic semiconductors
81.07.Bc Nanocrystalline materials
85.35.-p Nanoelectronic devices
85.75.-d Magnetoelectronics; spintronics: devices exploiting spin polarized transport or integrated magnetic fields

Formation of epitaxial metastable NiGe2 thin film on Ge(100) by pulsed excimer laser anneal

Phyllis S. Y. Lim, Dong Zhi Chi, Poh Chong Lim, Xin Cai Wang, Taw Kuei Chan, Thomas Osipowicz, and Yee-Chia Yeo

Appl. Phys. Lett. 97, 182104 (2010); http://dx.doi.org/10.1063/1.3514242 (3 pages) | Cited 1 time

Online Publication Date: 2 November 2010

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Epitaxial nickel digermanide (NiGe2), a metastable phase, was formed by laser annealing Ni on (100) germanium-on-silicon substrates. The NiGe2 formation was investigated using transmission electron microscopy, energy dispersive x-ray spectroscopy, x-ray diffraction, Rutherford backscattering spectroscopy, and first-principles calculations. The formation mechanism of NiGe2 is discussed and is attributed to both the reduced interfacial energy at the NiGe2/Ge(100) interface and the kinetic aspects of the laser annealing reaction associated with phase transformation and film agglomeration.
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81.15.Fg Pulsed laser ablation deposition
61.72.Cc Kinetics of defect formation and annealing
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
68.35.Md Surface thermodynamics, surface energies
68.35.Ct Interface structure and roughness
68.35.Rh Phase transitions and critical phenomena

Electric field modulation of thermopower for transparent amorphous oxide thin film transistors

Hirotaka Koide, Yuki Nagao, Kunihito Koumoto, Yuka Takasaki, Tomonari Umemura, Takeharu Kato, Yuichi Ikuhara, and Hiromichi Ohta

Appl. Phys. Lett. 97, 182105 (2010); http://dx.doi.org/10.1063/1.3512870 (3 pages) | Cited 1 time

Online Publication Date: 3 November 2010

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To clarify the electronic density of states (DOS) around the conduction band bottom for state of the art transparent amorphous oxide semiconductors (TAOSs), InGaZnO4 and In2MgO4, we fabricated TAOS-based transparent thin film transistors (TTFTs) and measured their gate voltage dependence of thermopower (S). TAOS-based TTFTs exhibit an unusual S behavior. The |S|-value abruptly increases but then gradually decreases as Vg increases, clearly suggesting the antiparabolic shaped DOS is hybridized with the original parabolic shaped DOS around the conduction band bottom.
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85.30.Tv Field effect devices

High conductivity carbon nanotube wires from radial densification and ionic doping

Jack Alvarenga, Paul R. Jarosz, Chris M. Schauerman, Brian T. Moses, Brian J. Landi, Cory D. Cress, and Ryne P. Raffaelle

Appl. Phys. Lett. 97, 182106 (2010); http://dx.doi.org/10.1063/1.3506703 (3 pages) | Cited 1 time

Online Publication Date: 4 November 2010

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Application of drawing dies to radially densify sheets of carbon nanotubes (CNTs) into bulk wires has shown the ability to control electrical conductivity and wire density. Simultaneous use of KAuBr4 doping solution, during wire drawing, has led to an electrical conductivity in the CNT wire of 1.3×106 S/m. Temperature-dependent electrical measurements show that conduction is dominated by fluctuation-assisted tunneling, and introduction of KAuBr4 significantly reduces the tunneling barrier between individual nanotubes. Ultimately, the concomitant doping and densification process leads to closer packed CNTs and a reduced charge transfer barrier, resulting in enhanced bulk electrical conductivity.
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81.07.De Nanotubes
81.40.Gh Other heat and thermomechanical treatments
81.40.Lm Deformation, plasticity, and creep
73.63.Fg Nanotubes
73.40.Gk Tunneling
61.48.De Structure of carbon nanotubes, boron nanotubes, and other related systems

Spin polarized electric currents in semiconductor heterostructures induced by microwave radiation

C. Drexler, V. V. Bel’kov, B. Ashkinadze, P. Olbrich, C. Zoth, V. Lechner, Ya. V. Terent’ev, D. R. Yakovlev, G. Karczewski, T. Wojtowicz, D. Schuh, W. Wegscheider, and S. D. Ganichev

Appl. Phys. Lett. 97, 182107 (2010); http://dx.doi.org/10.1063/1.3507896 (3 pages) | Cited 1 time

Online Publication Date: 4 November 2010

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We report on microwave (mw) radiation induced electric currents in (Cd,Mn)Te/(Cd,Mg)Te and InAs/(In,Ga)As quantum wells subjected to an external in-plane magnetic field. The current generation is attributed to the spin-dependent energy relaxation of electrons heated by mw radiation. The relaxation produces equal and oppositely directed electron flows in the spin-up and spin-down subbands yielding a pure spin current. The Zeeman splitting of the subbands in the magnetic field leads to the conversion of the spin flow into a spin-polarized electric current.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
72.25.-b Spin polarized transport
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect

Magnetocurrent of ballistically injected electrons in insulating silicon

Hyuk-Jae Jang and Ian Appelbaum

Appl. Phys. Lett. 97, 182108 (2010); http://dx.doi.org/10.1063/1.3511681 (3 pages) | Cited 1 time

Online Publication Date: 5 November 2010

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By using ballistic hot-electron injection to achieve lateral conduction through an otherwise fully insulating undoped silicon channel, we are able to study magnetic field suppression of charge transport in a regime normally excluded in Ohmic magnetoresistance measurements. Exceptionally large magnetocurrent changes of >16 000% at 45 K in magnetic fields of ≈ 2 T are observed, with differential reduction of over 6.2 T−1. Temperature-, electrostatic back-gate-, and magnetic field angle-dependence are presented. This phenomenon is attributed to strong space-charge effects in the dilute three-dimensional electron gas created by nonequilibrium injection.
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72.20.My Galvanomagnetic and other magnetotransport effects
72.20.Ht High-field and nonlinear effects
72.25.Hg Electrical injection of spin polarized carriers
77.22.Jp Dielectric breakdown and space-charge effects
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Nonvolatile multiple-valued memory device using lateral spin valve

T. Kimura and M. Hara

Appl. Phys. Lett. 97, 182501 (2010); http://dx.doi.org/10.1063/1.3502475 (3 pages) | Cited 2 times

Online Publication Date: 1 November 2010

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The authors propose a nonvolatile multiple-valued memory based on a nonlocal spin valve structure. Multibit informations are formed by changing the magnetization configuration in a nonlocal voltage probe consisting of a magnetic multilayer. A simple calculation method for the spin-accumulation voltage induced in lateral ferromagnetic/nonmagnetic multilayered hybrid structures is also developed on the basis of the spin resistance model. The developed model enables us to find the thickness of each ferromagnetic layer for the optimized operation of the multiple-valued memory.
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85.70.Ec Magnetostrictive, magnetoacoustic, and magnetostatic devices
85.75.Bb Magnetic memory using giant magnetoresistance
85.75.Dd Magnetic memory using magnetic tunnel junctions

Temperature dependence of spin resonance in cobalt substituted NiZnCu ferrites

A. Lucas, R. Lebourgeois, F. Mazaleyrat, and E. Labouré

Appl. Phys. Lett. 97, 182502 (2010); http://dx.doi.org/10.1063/1.3507266 (3 pages) | Cited 1 time

Online Publication Date: 2 November 2010

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Cobalt substitutions were investigated in Ni0.4Zn0.4Cu0.2Fe2O4 ferrites, initial complex permeability was then measured from 1 MHz to 1 GHz. It appears that cobalt substitution led to a decrease in the permeability and an increase in the μs×fr factor. As well, it gave to the permeability spectrum a sharp resonance character. We also observed a spin reorientation occurring at a temperature depending on the cobalt content. Study of the complex permeability versus temperature highlighted that the most resonant character was obtained at this temperature. This shows that cobalt contribution to second order magnetocrystalline anisotropy plays a leading role at this temperature.
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76.50.+g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance
75.30.Ds Spin waves
75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Gg Ferrimagnetics
75.30.Gw Magnetic anisotropy

Enhanced ferromagnetic and metal insulator transition in Sm0.55Sr0.45MnO3 thin films: Role of oxygen vacancy induced quenched disorder

M. K. Srivastava, P. K. Siwach, A. Kaur, and H. K. Singh

Appl. Phys. Lett. 97, 182503 (2010); http://dx.doi.org/10.1063/1.3505327 (3 pages) | Cited 5 times

Online Publication Date: 3 November 2010

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Effect of quenched disorder (QD) caused by oxygen vacancy (OV) and substrate induced inhomogeneous compressive strain, on the magnetic and transport properties of oriented polycrystalline Sm0.55Sr0.45MnO3 thin films is investigated. QD is related intimately to the ordering/disordering of the OVs and controls the paramagnetic-ferromagnetic/insulator-metal transition. OV ordered films show enhanced TC/TIM ∼ 165 K, which is depressed by oxygen annealing. OV disordering realized by quenching reduces TC/TIM. The first order IM transition observed in SSMO single crystals is transformed into nonhysteretic and continuous one in the OV ordered films. QD appears to be diluted by OV disorder/annihilation and results in stronger carrier localization.
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75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.70.Ak Magnetic properties of monolayers and thin films
71.30.+h Metal-insulator transitions and other electronic transitions
72.60.+g Mixed conductivity and conductivity transitions
61.72.jd Vacancies
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)

Continuously graded anisotropy in single (Fe53Pt47)100−xCux films

C. L. Zha, R. K. Dumas, Y. Y. Fang, V. Bonanni, J. Nogués, and Johan Åkerman

Appl. Phys. Lett. 97, 182504 (2010); http://dx.doi.org/10.1063/1.3505521 (3 pages) | Cited 8 times

Online Publication Date: 3 November 2010

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We report on continuously graded anisotropy. During deposition, a compositional gradient is achieved by varying the Cu concentration from Cu-rich (Fe53Pt47)70Cu30 to Cu-free Fe53Pt47. The anisotropy gradient is then realized after annealing using the composition dependence of the low-anisotropy (A1) to high-anisotropy (L10) ordering temperature. The critical role of the annealing temperature on the resultant anisotropy gradient is investigated. Magnetic measurements support the creation of an anisotropy gradient in properly annealed films which exhibit both a reduced coercivity and moderate thermal stability. These results demonstrate that an anisotropy gradient can be realized, and tailored, in single continuous films without the need for multilayers.
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75.30.Gw Magnetic anisotropy
81.40.Gh Other heat and thermomechanical treatments
75.70.Ak Magnetic properties of monolayers and thin films
68.55.at Other materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Observation of tunable exchange bias in Sr2YbRuO6

R. P. Singh, C. V. Tomy, and A. K. Grover

Appl. Phys. Lett. 97, 182505 (2010); http://dx.doi.org/10.1063/1.3505525 (3 pages) | Cited 4 times

Online Publication Date: 3 November 2010

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The double perovskite compound, Sr2YbRuO6, displays reversal in the orientation of magnetic moments along with negative magnetization due to an underlying magnetic compensation phenomenon. The exchange bias (EB) field below the compensation temperature could be the usual negative or the positive depending on the initial cooling field. This EB attribute has the potential of getting tuned in a preselected manner, as the positive EB field is seen to crossover from positive to negative value above Tcomp.
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74.25.Ha Magnetic properties including vortex structures and related phenomena
74.70.Pq Ruthenates
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Ee Antiferromagnetics
75.30.Cr Saturation moments and magnetic susceptibilities

Current-induced resonant depinning of a transverse magnetic domain wall in a spin valve nanostrip

P. J. Metaxas, A. Anane, V. Cros, J. Grollier, C. Deranlot, Y. Lemaître, S. Xavier, C. Ulysse, G. Faini, F. Petroff, and A. Fert

Appl. Phys. Lett. 97, 182506 (2010); http://dx.doi.org/10.1063/1.3507895 (3 pages)

Online Publication Date: 4 November 2010

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We study the impact of rf and dc currents on domain wall depinning in the soft layer of a 120 nm wide Co/Cu/NiFe spin valve nanostrip. A strong resonant reduction in the depinning field (from ∼ 75 to 25 Oe) is observed for rf currents near 3.5 GHz. Notably, the features of the resonant depinning depend not only on the rf current but also on the simultaneously applied dc current. Consequently, we discuss both the role of the adiabatic spin torque at resonance and that of the current generated Oersted fields.
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75.60.Ch Domain walls and domain structure
75.47.-m Magnetotransport phenomena; materials for magnetotransport
75.75.-c Magnetic properties of nanostructures

Amplitude and phase noise of magnetic tunnel junction oscillators

M. Quinsat, D. Gusakova, J. F. Sierra, J. P. Michel, D. Houssameddine, B. Delaet, M.-C. Cyrille, U. Ebels, B. Dieny, L. D. Buda-Prejbeanu, J. A. Katine, D. Mauri, A. Zeltser, M. Prigent, J.-C. Nallatamby, et al.

Appl. Phys. Lett. 97, 182507 (2010); http://dx.doi.org/10.1063/1.3506901 (3 pages) | Cited 5 times

Online Publication Date: 5 November 2010

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The microwave emission linewidth of spin transfer torque nano-oscillators is closely related to their phase and amplitude noise that can be extracted from the magnetoresistive voltage signal V(t) using single shot time domain techniques. Here we report on phase and amplitude noise studies for MgO based magnetic tunnel junction oscillators. The analysis of the power spectral densities allows one to separate the linear and nonlinear contributions to the phase noise, the nonlinear contribution being due to the coupling between phase and amplitude. The coupling strength as well as the amplitude relaxation rate can be directly extracted.
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84.30.Ng Oscillators, pulse generators, and function generators
84.40.-x Radiowave and microwave (including millimeter wave) technology
85.75.-d Magnetoelectronics; spintronics: devices exploiting spin polarized transport or integrated magnetic fields
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.

Exchange-coupling of c-axis oriented L10–FePd and Fe in FePd/Fe thin films

T. Ichitsubo, S. Takashima, E. Matsubara, Y. Tamada, and T. Ono

Appl. Phys. Lett. 97, 182508 (2010); http://dx.doi.org/10.1063/1.3514582 (3 pages) | Cited 2 times

Online Publication Date: 5 November 2010

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This letter reports the control of the c-axis orientation and the magnetic properties of L10 FePd in the well-annealed FePd/Fe thin films Fe(20 nm)/FePd(10 nm)/Fe(5 nm)/SiO2-substrate and Fe(20 nm)/FePd(5 nm)/Fe(5 nm)/SiO2-substrate, with the compositions of dual phase region in phase equilibrium. After annealing at 550 °C for 24 h, the c-axis of L10 FePd is controlled to be oriented in the normal direction in the soft Fe matrix. These thin films exhibit the exchange-coupling of hard FePd with soft Fe, and a characteristic spring-magnet behavior showed up reversibly as a significant jump from positive to negative in the magnetization reversal.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.50.Bb Fe and its alloys
75.30.Et Exchange and superexchange interactions
75.60.Nt Magnetic annealing and temperature-hysteresis effects
81.40.Gh Other heat and thermomechanical treatments
75.60.Jk Magnetization reversal mechanisms

Competition of the antiferromagnetic superexchange with the ferromagnetic double exchange in dicobalt complexes

Lin He and Lin Guo

Appl. Phys. Lett. 97, 182509 (2010); http://dx.doi.org/10.1063/1.3514583 (3 pages) | Cited 2 times

Online Publication Date: 5 November 2010

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Here we report the competition of superexchange and double exchange interactions in the molecule [(NH3)4Co(OH)2Co(NH3)4]4+. Magnetic data reveal a S = 3 ground state arising from the competition. The canting angle between the magnetic moments of the Co2+ and Co4+ ions is about 92.5°. The double exchange parameter is estimated to be sevenfold of the superexchange parameter. The result presented here opens a way to introducing of ferromagnetic double exchange interaction to the single molecular magnets via the charge disproportionation between valence-variable transition-metal ions.
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75.30.Et Exchange and superexchange interactions
75.50.Ee Antiferromagnetics
75.50.Xx Molecular magnets
75.50.Dd Nonmetallic ferromagnetic materials
75.30.Cr Saturation moments and magnetic susceptibilities
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