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1 Dec 2008

Volume 93, Issue 22, Articles (22xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 93, 221101 (2008); http://dx.doi.org/10.1063/1.3036234 (3 pages)

Soon Moon Jeong, Na Young Ha, Mu Guen Chee, Fumito Araoka, Ken Ishikawa, Hideo Takezoe, Suzushi Nishimura, and Goro Suzaki
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Layered high-gain lens antennas via discrete optical transformation

Wei Xiang Jiang, Tie Jun Cui, Hui Feng Ma, Xin Mi Yang, and Qiang Cheng

Appl. Phys. Lett. 93, 221906 (2008); http://dx.doi.org/10.1063/1.3040307 (3 pages) | Cited 15 times

Online Publication Date: 2 December 2008

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In reality, the optical-transformation media with complicated and continuous electromagnetic parameters are difficult to realize. In this work, we propose a discrete embedded optical transformation from which a layered high-gain lens antenna is designed. All layers of the lens antenna are composed of homogeneous and uniaxially anisotropic metamaterials, which are simple and realizable. When the layered lens is embedded in a horn antenna, the lens antenna provides a high-directivity radiation beam. We also use the discrete optical transformation to design a multibeam high-gain antenna.
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41.20.Jb Electromagnetic wave propagation; radiowave propagation
42.25.Gy Edge and boundary effects; reflection and refraction
42.79.Dj Gratings

Crystallization-induced stress in thin phase change films of different thicknesses

Qiang Guo, Minghua Li, Yi Li, Luping Shi, Tow Chong Chong, Johannes A. Kalb, and Carl V. Thompson

Appl. Phys. Lett. 93, 221907 (2008); http://dx.doi.org/10.1063/1.3040314 (3 pages) | Cited 8 times

Online Publication Date: 2 December 2008

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We have studied crystallization-induced stress in phase change films (Ge2Sb2Te5) as a function of thickness and with and without a capping layer, by measuring the deflection of microcantilevers. The stress is found to increase with decreasing film thickness. A thin dielectric capping layer leads to a further increase in stress compared to uncapped films. This observation can be explained by the suppression of stress relaxation in the phase change film in the presence of a capping layer. High stress will affect device performance as the size of phase change memory cells decreases.
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68.60.Bs Mechanical and acoustical properties
68.55.ag Semiconductors
81.40.Lm Deformation, plasticity, and creep
62.20.fg Shape-memory effect; yield stress; superelasticity
68.55.jd Thickness
64.70.kg Semiconductors

Efficient energy transfer for Ce to Nd in Nd/Ce codoped yttrium aluminum garnet

Jian Xin Meng, Jin Qing Li, Zhao Pu Shi, and Kok Wai Cheah

Appl. Phys. Lett. 93, 221908 (2008); http://dx.doi.org/10.1063/1.3035849 (3 pages) | Cited 13 times

Online Publication Date: 3 December 2008

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A two order of enhancement in near-infrared emission from Nd3+ in Ce3+/Nd3+ codoped yttrium aluminum garnet (YAG) matrix is obtained. This is due to efficient absorption by the allowed 4f-5d transition of Ce3+ ions then transfer to Nd3+ ions via a well matched energy level. This is among the most efficient near-infrared emission from Nd3+ ions strongly sensitized by exciting with an allowed transition in an inorganic matrix. This means that a new class of material, YAG:Ce,Nd, was produced and it potentially can be an efficient near-infrared phosphor that could be easily excited by a GaN light emitting diode, producing a new type of near-infrared emitter.
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78.55.Hx Other solid inorganic materials

Controllable light transmission through cascaded metal films perforated with periodic hole arrays

Meng-Dong He, Ling-Ling Wang, Jian-Qiang Liu, Xiang Zhai, Qing Wan, Xiaoshuang Chen, and B. S. Zou

Appl. Phys. Lett. 93, 221909 (2008); http://dx.doi.org/10.1063/1.3040301 (3 pages) | Cited 10 times

Online Publication Date: 3 December 2008

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The transmission of linearly polarized plane wave through cascaded metal films perforated with periodic hole arrays is investigated by using the three-dimensional finite-difference time-domain method. The results show that the transmission spectra can be controlled by changing the longitudinal interval G and/or the lateral displacements Lx and Ly, which are parallel and perpendicular to the polarization direction of the incident light, respectively. The variation in longitudinal interval G results in a redshift or blueshift of the transmission peak due to the coupling of the localized surface plasmon (LSP) modes on two metal layers. The lateral displacement Lx leads to the splitting of the transmission peak, originating from the variation in the coupling manner of LSP modes, while the lateral displacement Ly suppresses the transmission peak.
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78.66.Bz Metals and metallic alloys
42.70.Qs Photonic bandgap materials
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
68.55.jd Thickness

Transformation mechanisms from metallic Zn nanocrystals to insulating ZnSiO3 nanocrystals in a SiO2 matrix due to thermal treatment

J. M. Yuk, J. Y. Lee, Y. S. No, T. W. Kim, and W. K. Choi

Appl. Phys. Lett. 93, 221910 (2008); http://dx.doi.org/10.1063/1.3040320 (3 pages) | Cited 4 times

Online Publication Date: 3 December 2008

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Transmission electron microscopy (TEM), high-resolution TEM, and x-ray energy dispersive spectroscopy results showed that Zn metallic nanocrystals and ZnSiO3 insulating nanocrytals embedded in a SiO2 matrix were created from the ZnO thin films deposited on n-Si (001) substrates due to rapid thermal annealing. The formed Zn metallic nanocrystals were transformed into monoclinic ZnSiO3 insulating nanocrystals with increasing number of Zn atoms resulting from an increase in the annealing time up to 10 min. The transformation mechanisms from metallic Zn nanocrystals to insulating ZnSiO3 nanocrystals in a SiO2 matrix due to rapid thermal annealing are described on the basis of the experimental results.
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71.30.+h Metal-insulator transitions and other electronic transitions
82.80.Ej X-ray, Mössbauer, and other γ-ray spectroscopic analysis methods
61.72.Cc Kinetics of defect formation and annealing

Entropic origins of stability in silicon interstitial clusters

Sumeet S. Kapur and Talid Sinno

Appl. Phys. Lett. 93, 221911 (2008); http://dx.doi.org/10.1063/1.3042096 (3 pages) | Cited 2 times

Online Publication Date: 5 December 2008

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The role of entropy in the thermodynamic properties of small interstitial clusters in crystalline silicon is investigated using an empirical potential. It is shown that both vibrational and configurational entropies are potentially important in setting the properties of small silicon interstitial clusters and, in particular, contribute to the formation of “magic” sizes that exhibit special stability, which have been inferred by experimental measurements of dopant diffusion. The results suggest that a competition between formation energy and entropy of small clusters could be linked to the selection process between various self-interstitial precipitate morphologies observed in ion-implanted crystalline silicon.
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61.72.jj Interstitials
65.40.gd Entropy

Strain relaxation in transistor channels with embedded epitaxial silicon germanium source/drain

J. P. Liu, K. Li, S. M. Pandey, F. L. Benistant, A. See, M. S. Zhou, L. C. Hsia, Ruud Schampers, and Dmitri O. Klenov

Appl. Phys. Lett. 93, 221912 (2008); http://dx.doi.org/10.1063/1.3040323 (3 pages) | Cited 11 times

Online Publication Date: 5 December 2008

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We report on the channel strain relaxation in transistors with embedded silicon germanium layer selectively grown in source and drain areas on recessed Si(001). Nanobeam electron diffraction is used to characterize the local strain in the device channel. Our results show that strain is reduced in the device channel regions after implantation and thermal anneal.
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85.30.Tv Field effect devices
61.72.uf Ge and Si
61.72.Cc Kinetics of defect formation and annealing
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Charge storage characteristics of Mo nanocrystal dependence on Mo oxide reduction

Chao-Cheng Lin, Ting-Chang Chang, Chun-Hao Tu, Wei-Ren Chen, Chih-Wei Hu, Simon M. Sze, Tseung-Yuen Tseng, Sheng-Chi Chen, and Jian-Yang Lin

Appl. Phys. Lett. 93, 222101 (2008); http://dx.doi.org/10.1063/1.3039065 (3 pages) | Cited 9 times

Online Publication Date: 1 December 2008

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An oxygen incorporated Mo silicide was explored to form the Mo nanocrystals after rapid thermal annealing. Transmission electron microscopy showed the nanocrystals embedded in SiOx. Charge storage characteristics of Mo nanocrystals influenced by the Mo oxide and the surrounding oxide were investigated through x-ray photoelectron spectroscopy and the electrical measurement. X-ray photoelectron spectra analyses revealed the redox reaction in the oxygen incorporated Mo silicide layer after rapid thermal annealing. The memory window and retention were improved due to reduction in Mo oxide.
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73.63.Bd Nanocrystalline materials
81.16.Pr Micro- and nano-oxidation
81.16.Be Chemical synthesis methods
61.72.Cc Kinetics of defect formation and annealing
73.40.Ns Metal-nonmetal contacts

Improved endurance behavior of resistive switching in (Ba,Sr)TiO3 thin films with W top electrode

Wan Shen, Regina Dittmann, Uwe Breuer, and Rainer Waser

Appl. Phys. Lett. 93, 222102 (2008); http://dx.doi.org/10.1063/1.3039809 (3 pages) | Cited 44 times

Online Publication Date: 1 December 2008

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We compared the resistive switching performance of barium strontium titanate (BST) thin films with tungsten (W) and platinum (Pt) top electrodes, respectively. The yield, endurance, and reliability were strongly improved for the samples with W top electrode. Whereas the samples with Pt top electrode show a fast drop in the resistance for both high and low resistance states, the devices with W top electrode can be switched for 104 times without any obvious degradation. We attribute the improved switching performance to a reversible oxidation and reduction in a WOx layer at the W-BST interface, which was detected by time-of-flight secondary-ion-mass spectroscopy measurements.
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73.61.Le Other inorganic semiconductors
72.60.+g Mixed conductivity and conductivity transitions
73.40.Ns Metal-nonmetal contacts

Escape dynamics of a few electrons in a single-electron ratchet using silicon nanowire metal-oxide-semiconductor field-effect transistor

Satoru Miyamoto, Katsuhiko Nishiguchi, Yukinori Ono, Kohei M. Itoh, and Akira Fujiwara

Appl. Phys. Lett. 93, 222103 (2008); http://dx.doi.org/10.1063/1.3028649 (3 pages) | Cited 6 times

Online Publication Date: 1 December 2008

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Transport dynamics of a few electrons in a quantum dot are investigated in a single-electron ratchet using silicon nanowire metal-oxide-semiconductor field-effect transistors. Time-resolved measurements in a nanosecond regime are carried out to determine the escape times of the first, second, and third electrons from the quantum dot originally containing three electrons. The escape time strongly depends on the number of electrons due to the single-electron charging effect in the quantum dot, which makes it possible to achieve selective ejection of a desired number of electrons.
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73.63.Kv Quantum dots
85.30.Tv Field effect devices
72.20.Fr Low-field transport and mobility; piezoresistance
68.65.Hb Quantum dots (patterned in quantum wells)

The effects of the microstructure of ZnO films on the electrical performance of their thin film transistors

Byung-Il Hwang, Kyung Park, Ha-Suk Chun, Chee-Hong An, Hyoungsub Kim, and Hoo-Jeong Lee

Appl. Phys. Lett. 93, 222104 (2008); http://dx.doi.org/10.1063/1.3031726 (3 pages) | Cited 15 times

Online Publication Date: 3 December 2008

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This study examined a fundamental aspect of ZnO-based thin film transistors (TFTs): the connection between the deposition conditions and the microstructure of ZnO films, and the electrical performance of the TFTs. We characterized the microstructure of ZnO films deposited under various rf powers by using high resolution transmission electron microscopy and x-ray diffraction. In further investigating the effects of the microstructure on the device performance, we experimentally demonstrated that the electrical mobility of the devices was coupled to the grain size of the ZnO films in an exponential function.
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85.30.Tv Field effect devices

Ab initio description and visualization of charge transport in durene crystals

Frank Ortmann, Karsten Hannewald, and Friedhelm Bechstedt

Appl. Phys. Lett. 93, 222105 (2008); http://dx.doi.org/10.1063/1.3033830 (3 pages) | Cited 6 times

Online Publication Date: 3 December 2008

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We study the charge transport through crystalline durene which exhibits large hole mobilities. By means of ab initio calculations, we determine the temperature-dependent polaron bandwidth and the mobility tensor of the charge carriers. The origin of the bandlike mobility curves is discussed, and the strong anisotropy of the mobility is analyzed in detail. We put a special focus on the relationship between crystal packing geometry, molecular wave function overlap, and charge transport properties. The results include a visualization of the transport channels in durene which can be regarded as a prototypical herringbone-stacked crystal.
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72.20.Fr Low-field transport and mobility; piezoresistance
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.80.Le Polymers; organic compounds (including organic semiconductors)
71.15.-m Methods of electronic structure calculations
71.38.-k Polarons and electron-phonon interactions

Surface strain and its impact on the electrical resistivity of GaN channel in AlGaN/GaN high electron mobility transistor

Nadeemullah A. Mahadik, Syed B. Qadri, and Mulpuri V. Rao

Appl. Phys. Lett. 93, 222106 (2008); http://dx.doi.org/10.1063/1.3040315 (3 pages) | Cited 5 times

Online Publication Date: 3 December 2008

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Localized strain in AlGaN/GaN high electron mobility transistor (HEMT) device structures was studied by high resolution x-ray diffraction and rocking curve measurements, and the results were compared with the corresponding channel sheet resistance measurements. The map of in-plane tensile strain on the HEMT wafer showed a near one-to-one correspondence with the electrical resistivity. The in-plane strain variation in the range of (2.295–3.539)×10−4 resulted in a corresponding sheet resistance variation between 345 and 411 Ω/◻.
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85.30.Tv Field effect devices
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

Tunneling magnetoresistance effect in a few-electron quantum-dot spin valve

K. Hamaya, M. Kitabatake, K. Shibata, M. Jung, M. Kawamura, S. Ishida, T. Taniyama, K. Hirakawa, Y. Arakawa, and T. Machida

Appl. Phys. Lett. 93, 222107 (2008); http://dx.doi.org/10.1063/1.3042098 (3 pages) | Cited 3 times

Online Publication Date: 3 December 2008

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We demonstrate the tunneling magnetoresistance (TMR) effect through a semiconductor quantum dot (QD) with a few electrons in a lateral QD spin-valve device. At one-to-two electron transition, only inverse TMR effect is observed, where the TMR ratio is relatively large compared with the value based on the Julliere model. When the bias window reaches near the charging energy of the QD, the inverse TMR almost disappears. These features can be interpreted in terms of spin transport via the ground state of a two-electron QD.
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85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
85.75.-d Magnetoelectronics; spintronics: devices exploiting spin polarized transport or integrated magnetic fields
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.75.-c Magnetic properties of nanostructures
75.47.Pq Other materials
73.63.Kv Quantum dots

Theoretical consideration of step-flow and two-dimensional nucleation modes in homoepitaxial growth of 4H-SiC on (0001) vicinal surfaces under silicon-rich condition

K. Mochizuki

Appl. Phys. Lett. 93, 222108 (2008); http://dx.doi.org/10.1063/1.3043433 (3 pages) | Cited 1 time

Online Publication Date: 4 December 2008

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Reported experimental results on homoepitaxial growth of 4H-SiC on (0001) Si-face vicinal surfaces under silicon-rich conditions in a SiH4–C3H8–H2 system are quantitatively analyzed according to the surface-diffusion theory dealing with step dynamics. The surface-diffusion length of C2H2 molecules, which are the main carbon-containing chemical species reacting with silicon adatoms on the surface, is determined to be 12–36 nm at 1500 °C. According to the two-dimensional nucleation theory using these values, the maximum growth rate for step-flow growth is estimated as a function of the off-angle of 4H-SiC substrates.
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68.55.ag Semiconductors
81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.35.Fx Diffusion; interface formation
68.43.Jk Diffusion of adsorbates, kinetics of coarsening and aggregation

Quantum resistance metrology in graphene

A. J. M. Giesbers, G. Rietveld, E. Houtzager, U. Zeitler, R. Yang, K. S. Novoselov, A. K. Geim, and J. C. Maan

Appl. Phys. Lett. 93, 222109 (2008); http://dx.doi.org/10.1063/1.3043426 (3 pages) | Cited 24 times

Online Publication Date: 5 December 2008

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We performed a metrological characterization of the quantum Hall resistance in a 1 μm wide graphene Hall bar. The longitudinal resistivity in the center of the ν = ±2 quantum Hall plateaus vanishes within the measurement noise of 20 mΩ up to 2 μA. Our results show that the quantization of these plateaus is within the experimental uncertainty (15 ppm for 1.5 μA current) equal to that in conventional semiconductors. The principal limitation of the present experiments is the relatively high contact resistances in the quantum Hall regime, leading to a significantly increased noise across the voltage contacts and a heating of the sample when a high current is applied.
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73.43.-f Quantum Hall effects
06.20.-f Metrology
73.23.-b Electronic transport in mesoscopic systems

Discrete breathers in ac-driven nanoelectromechanical shuttle arrays

Jan Wiersig, Sergej Flach, and Kang-Hun Ahn

Appl. Phys. Lett. 93, 222110 (2008); http://dx.doi.org/10.1063/1.3043434 (3 pages) | Cited 5 times

Online Publication Date: 5 December 2008

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We investigate the dynamics of electrically ac-driven nanoelectromechanical shuttle arrays. The electromechanical coupling enforces long-range interactions. We find multistability regimes upon changing the voltage and frequency. We show that the instability driven by parametric amplification of sinusoidal mechanical waves leads to the creation of spatially localized mechanical oscillations, discrete breathers, and subsequently to an abrupt change in the electrical transport properties. In particular, we find current rectification, which is induced by the excitation of discrete breathers. This is of potential interest and use for nanomechanical sensor application.
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73.23.-b Electronic transport in mesoscopic systems
73.63.-b Electronic transport in nanoscale materials and structures

Alkanethiol-based single-molecule transistors

Chun-Lan Ma, Diu Nghiem, and Yu-Chang Chen

Appl. Phys. Lett. 93, 222111 (2008); http://dx.doi.org/10.1063/1.3043438 (3 pages) | Cited 5 times

Online Publication Date: 5 December 2008

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We have investigated the transport properties of alkanethiol molecules in the two-terminal and three-terminal junctions by using first-principles approaches. We observe that states around the Fermi levels are introduced in the amino-substituted butanethiol junction. It leads to a sharp increase in the current, which is credited to the resonant tunneling. The current-voltage characteristics suggest that the amino-substituted butanethiol molecular junction may be a promising candidate for field-effect transistors.
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85.30.Tv Field effect devices
71.15.-m Methods of electronic structure calculations
71.20.Rv Polymers and organic compounds

Ultraviolet radiation sensing in composite oxide semiconductor films

M. Bahoura, A. Lee, R. Mundle, R. B. Konda, G. Kogo, O. Bamiduro, O. Yasar, W. Moore, K. Zhang, F. Williams, and A. K. Pradhan

Appl. Phys. Lett. 93, 222112 (2008); http://dx.doi.org/10.1063/1.3043455 (3 pages) | Cited 2 times

Online Publication Date: 5 December 2008

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We report on the ultraviolet (UV)-radiation sensing of pulsed-laser deposited In2O3:SnO2:ZnO films grown on glass substrates. The films demonstrate sharp increase ( ∼ 0.35 Ω) in electrical resistance on UV illumination. The resistance of the films shows strong spectral (in the vicinity of 325 nm) and power dependence. This is explained due to the presence of defects located at lattice disorders that generate levels within the semiconductor band gap and originate depletion region around them when charged. This reduces the effective conduction region, increasing the effective resistance. These results show new possibilities for the low-cost high performance UV radiation sensors for biosafety.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
68.55.ag Semiconductors
73.50.Dn Low-field transport and mobility; piezoresistance
81.15.Fg Pulsed laser ablation deposition
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Magnetism in Mn doped yttrium nitride: First-principles calculations

Xingtao Jia, Wei Yang, and Minghui Qin

Appl. Phys. Lett. 93, 222501 (2008); http://dx.doi.org/10.1063/1.3040684 (3 pages) | Cited 1 time

Online Publication Date: 3 December 2008

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The magnetism and aggregation trends in 25% and 12.5% Mn doped yttrium nitride (YN) have been investigated using the first-principles calculations. We demonstrate that the ferromagnetic delta doping is the ground state in higher concentration Mn doped YN, and the ferromagnetic homogeneous half-delta doping is the ground state in lower concentration Mn half-delta-doped YN. The latter shows ferromagnetic stabilization energy of 424.8 meV/Mn–Mn pair, which is substantially higher than many other compound semiconductor based magnetic semiconductors. Finally, we anticipate the potential spintronics application of Mn doped YN.
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75.30.Hx Magnetic impurity interactions
61.72.sd Impurity concentration
71.20.Nr Semiconductor compounds
71.15.-m Methods of electronic structure calculations
75.50.Dd Nonmetallic ferromagnetic materials
75.50.Pp Magnetic semiconductors

Magnetic properties of Co-doped TiO2 anatase nanopowders

L. C. J. Pereira, M. R. Nunes, O. C. Monteiro, and A. J. Silvestre

Appl. Phys. Lett. 93, 222502 (2008); http://dx.doi.org/10.1063/1.3036534 (3 pages) | Cited 13 times

Online Publication Date: 4 December 2008

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This letter reports on the magnetic properties of Ti1−xCoxO2 anatase phase nanopowders with different Co contents. It is shown that oxygen vacancies play an important role in promoting long-range ferromagnetic order in the material studied in addition to the transition-metal doping. Furthermore, the results allow ruling out the premise of a strict connection between Co clustering and the ferromagnetism observed in the Co:TiO2 anatase system.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Dd Nonmetallic ferromagnetic materials
75.50.Kj Amorphous and quasicrystalline magnetic materials
75.50.Pp Magnetic semiconductors
61.72.jd Vacancies

Influence of an interface domain wall on spin-valve giant magnetoresistance

T. Hauet, F. Montaigne, M. Hehn, Y. Henry, and S. Mangin

Appl. Phys. Lett. 93, 222503 (2008); http://dx.doi.org/10.1063/1.3041640 (3 pages) | Cited 3 times

Online Publication Date: 4 December 2008

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The magnetotransport properties of a Gd40Fe60/Gd10Fe90/Cu/Gd40Fe60 spin-valve based on amorphous ferrimagnetic GdFe layers are reported. The Gd40Fe60/Gd10Fe90 bilayer is an exchange spring structure that allows an interfacial domain wall to be controlled by an applied field. As this domain wall is nucleated, compressed, and annihilated, changes in the spin-valve current-in-plane magnetoresistance are observed. After separating the various magnetoresistance contributions we could deduce the effect of the interface domain wall on both the giant and anisotropic magnetoresistances.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.60.Ch Domain walls and domain structure
75.47.De Giant magnetoresistance
75.47.Np Metals and alloys
75.30.Et Exchange and superexchange interactions
75.50.Kj Amorphous and quasicrystalline magnetic materials

Anomalous training effect of perpendicular exchange bias in Pt/Co/Pt/IrMn multilayers

Z. Shi, X. P. Qiu, S. M. Zhou, X. J. Bai, and J. Du

Appl. Phys. Lett. 93, 222504 (2008); http://dx.doi.org/10.1063/1.3039059 (3 pages) | Cited 8 times

Online Publication Date: 5 December 2008

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For perpendicularly magnetized Pt/Co/Pt and Pt/Co/Pt/IrMn multilayers, the magnetization reversal process is accompanied by the pinned domain wall motion. For Pt/Co/Pt/IrMn multilayers, the asymmetry of hysteresis loops is always equal to zero and the exchange field HE decreases during consecutive hysteresis loops. It is interesting to find that the variation in HE with the cycle number n cannot be fitted by the empirical 1/math function. Meanwhile, the coercivity almost does not change. The unique feature of the training effect is caused by the magnetization reversal mechanism of the pinned domain wall motion in the Pt/Co/Pt multilayers.
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75.30.Et Exchange and superexchange interactions
75.30.Gw Magnetic anisotropy
75.60.Jk Magnetization reversal mechanisms

Exchange bias effect in a granular system of NiFe2O4 nanoparticles embedded in an antiferromagnetic NiO matrix

Z. M. Tian, S. L. Yuan, S. Y. Yin, L. Liu, J. H. He, H. N. Duan, P. Li, and C. H. Wang

Appl. Phys. Lett. 93, 222505 (2008); http://dx.doi.org/10.1063/1.3039071 (3 pages) | Cited 15 times

Online Publication Date: 5 December 2008

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A granular system composed of ferrimagnetic NiFe2O4 nanoparticles, about 8 nm in size, embedded in an antiferromagnetic NiO matrix has been synthesized by a high-temperature phase precipitation method from Fe-doped NiO matrix. Both the exchange bias field and vertical magnetization shift can be observed in this system below 250 K after field cooling, above which the exchange bias disappears. Furthermore, the exchange bias field shows a linear dependence on the magnetization shift. This observed exchange bias effect is explained in terms of the exchange interaction between the ferrimagnetic phase and the spin-glass-like phase at the interface.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.75.-c Magnetic properties of nanostructures
75.50.Gg Ferrimagnetics
75.50.Ee Antiferromagnetics
75.50.Tt Fine-particle systems; nanocrystalline materials
75.30.Et Exchange and superexchange interactions

Effect of oxygen vacancy on ferromagnetism and electric transport of bulk polycrystalline (In0.8Mo0.05Fe0.15)2O3

B. C. Zhao, H. W. Ho, B. Xia, L. H. Tan, A. C. Huan, and L. Wang

Appl. Phys. Lett. 93, 222506 (2008); http://dx.doi.org/10.1063/1.3039807 (3 pages) | Cited 5 times

Online Publication Date: 5 December 2008

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We report the effect of sintering pressure on ferromagnetism and electric transport properties of bulk polycrystalline (In0.8Mo0.05Fe0.15)2O3. Structural characterization by powder x-ray diffraction, magnetic and electronic characterization by magnetometry, and ac transport measurement indicate that (In0.8Mo0.05Fe0.15)2O3 shows intrinsic ferromagnetism under suitable fabrication condition. The ferromagnetism and electronic transport property of (In0.8Mo0.05Fe0.15)2O3 can be tuned by the oxygen vacancy in the sample.
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72.20.Fr Low-field transport and mobility; piezoresistance
75.50.Pp Magnetic semiconductors
75.50.Dd Nonmetallic ferromagnetic materials
72.80.Jc Other crystalline inorganic semiconductors
61.72.jd Vacancies
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation
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