bluuebunny/crossref_metadata_2025 huggingface dataset:
Coexistence of colossal magnetoresistance, a Griffiths-like phase, and a ferromagnetic insulating ground state in single crystal La0.73Ba0.27MnO3
Authors: Jiang Wanjun , Zhou XueZhi , Williams Gwyn , Mukovskii Y. , Privezentsev R.
Published: April 2010

Detailed temperature/field-dependent magnetic and transport behaviors are reported for a nominally doped La0.73Ba0.27MnO3 single crystal. The magnetic analysis demonstrates an intriguing coincidence of critical exponents consistent with Heisenberg model values (γ=1.39, β=0.38, δ=4.83) and the presence of a Griffiths-like phase. The transport measurements yield a ferromagnetic insulating ground phase, but one complemented by the appearance of colossal magnetoresistance near the ferromagnetic to paramagnetic (FM-PM) phase transition temperature TC=245 K.
Electron paramagnetic resonance study of size and nonstoichiometry effects on magnetic ordering in half-doped La0.5Ca0.5MnO3 manganite
Authors: Auslender M. , Shames A. I. , Rozenberg E. , Sominski E. , Gedanken A. , Mukovskii Ya. M.
Published: April 2010

The X-band electron paramagnetic resonance in La0.5Ca0.5MnO3 was studied. Fitting the measured temperature dependence of the EPR linewidth and intensity to established models were employed to probe the effects of finite-size and nonstoichiometry. Regarding these effects, the complex mixed magnetic ordering inherent in bulk samples was shown to be unstable. The antiferromagnetic (AFM) and charge ordered component is suppressed in nanosamples. But the ferromagnetic (FM) state, appearing in nanograins, is frustrated due to (i) an AFM-like core-shell interaction and (ii) a strong spin disorder at the surfaces and core-shell transition layers. In addition, a weak nonstoichiometry which does not affect the crystal structure in bulk induces a strong decrease of the FM component in its magnetic ground state.
Magnetic properties, phase evolution, and microstructure of melt spun Sm(Co,M)xCy (M=Hf and Zr; x=5–9; y=–0.15) ribbons
Authors: Chang H. W. , Guo C. S. , Hsieh C. C. , Guo Z. H. , Zhao X. G. , Chang W. C.
Published: April 2010

Magnetic properties, phase evolution, and microstructure of melt spun Sm(Co0.97M0.03)xCy (M=Hf and Zr; x=5–9; y=0–0.15) ribbons quenched at the wheel speed of 40 m/s have been investigated. X-ray diffraction analysis show that the main phases exist in Sm(Co0.97M0.03)x ribbons are 1:5 for x=5 and 5.5, 1:5 and 1:7 for x=6 and 6.5, 1:7 for x=7 and 7.5, 1:7 and 2:17 for x=8, and 2:17 for x=8.5 and 9. The grain size of 200–500 nm for these two series of ribbons is almost unchanged when x is increased from 5 to 9. Accordingly, the magnetic properties of Sm(Co0.97M0.03)x ribbons (M=Hf and Zr) are mainly dominated by their phase constitutions. Furthermore, a slight addition of C to Sm(Co0.97M0.03)x ribbons refines the grain size down to 10–50 nm, resulting in the improvement of magnetic properties. Sm(Co0.97Hf0.03)7.5C0.1 ribbons show the optimal magnetic properties of Br=6.9 kG, Hic=9.2 kOe, and (BH)max=10.0 MGOe. For the Sm-lean Sm(Co,Hf)xCy (x=8.5–9) ribbons, higher Hf and C content are required to improve the magnetic properties. The magnetic properties of Br=6.8 kG, Hic=6.2 kOe, and (BH)max=7.2 MGOe could be obtained in Sm(Co0.94Hf0.06)9C0.15 ribbons.
Investigation of the c-axis and basal plane anisotropy in epitaxial NdCo5 thin films
Authors: Seifert M. , Schultz L. , Neu V.
Published: April 2010

The hexagonal NdCo5 phase has been prepared as an epitaxial film with an alignment of the c-axis perpendicular to the film plane and a unique orientation of the basal plane with respect to the substrate. In this highly textured film, the change in the magnetocrystalline anisotropy from easy c-axis to easy plane was observed by temperature dependent magnetization measurements. The specific orientation of the basal plane allows the investigation of the magnetic anisotropy in the easy plane state below 200 K without interference from the shape anisotropy of the thin film sample. We observe a difference between the a-axis and b-axis in saturation magnetization as well as in the magnetization reversal.
Temperature-driven microstructural, compositional, and magnetic changes in electrodeposited Fe–Pd thin films
Authors: Pečko D. , Rožman K. Žužek , McGuiness P. J. , Pihlar B. , Kobe S.
Published: April 2010

Equiatomic Fe–Pd thin films with thicknesses of 200 nm were deposited from a single electrolyte onto glass-based, Au-coated substrates using the electrodeposition method. The as-deposited films were annealed at temperatures from 400 to 600 °C for 1 h in Ar+7% H2. The phase formation, microstructure and the magnetic properties were analyzed. The L10 ordering was found to coincide with the grain growth and the interdiffusion reaction between the substrate and the thin film when temperatures above 500 °C were used, which resulted in lower coercivities. The highest coercivity of 870 Oe was achieved when modest temperatures (400 °C) were used.
Effects of Os spacer layers on the thermal stability, microstructures, and magnetic properties of FePt films on Si(100)
Authors: Chen S. Y. , Wu J. M. , Yao Y. D. , Huang H. H. , Yu C. C.
Published: April 2010

The thermal stability, interlayer diffusion, and magnetic properties of FePt(100 nm) single-layer and multilayer [Os(5 nm)/FePt(25 nm)]4 films on a Si(100) substrate with/without a 10-nm-thick Os underlayer have been studied as functions of the annealing temperatures between 400 and 800 °C. The insertion of a thin Os layer into the FePt and Si(100) interface results in better thermal stability. No diffusion evidence was found in samples with an Os underlayer for annealing temperatures up to 700 °C, as seen from x-ray, transmission electron microscopy, and magnetic studies. We have experimentally demonstrated that the Os underlayer can effectively prevent the diffusion of the intermixing between the FePt layer and the Si(100) substrate for temperatures up to 700 °C. As a result of this study, the Os has potential to be a better diffusion barrier to prevent the diffusion of the FePt film on a Si(100) substrate from forming an ordered face centered tetragonal (fct) L10 hard magnetic phase.
Effect of multilayer configuration of [Fe/Pt] multilayer to attain (001) oriented FePt ordered alloy thin films
Authors: Ogata Yuji , Imai Yasuharu , Nakagawa Shigeki
Published: April 2010

L 1 0 -FePt ordered alloy thin films with (001) preferential orientation were fabricated from [Pt(1 nm)/Fe(1 nm)]3/Pt(3 nm)/Fe(3 nm) multilayers to reduce the ordering temperature. Pt(3 nm)/Fe(3 nm) layer beneath the [Pt(1 nm)/Fe(1 nm)]3 multilayer played a role as a seed layer to attain perpendicular magnetic anisotropy. These films, after being annealed at 500 °C under hydrogen atmosphere, exhibited better growth characters of FePt(001) oriented crystallites than those of FePt prepared from [Pt(1 nm)/Fe(1 nm)]6. Additionally, [Pt(1 nm)/Fe(1 nm)]3/Pt(3 nm)/Fe(3 nm) multilayers, after being annealed at 500 °C, showed high value of saturation magnetization around 12 kG.
Anisotropic nanostructured magnets by magnetic-field-assisted processing
Authors: Rong Chuan-bing , Nguyen Van Vuong , Liu J. Ping
Published: April 2010

It has been a great challenge to produce anisotropic nanocrystalline bulk magnets. In this paper, we report our recent work in preparing anisotropic bonded magnets consisting of SmCo5 nanocrystalline particles. The work involved synthesis of nanocrystalline hard magnetic SmCo5 particles by ball milling in the presence of a magnetic field. Structural and magnetic characterizations show the alignment of the c-axis of the SmCo5 grains upon the magnetic-field-assisted ball milling, while the grain size was controlled under 15 nm. The formation of the texture may be attributed to the effect of magnetic fields on the grain orientation during the cold welding process during ball milling. The as-milled particles were then compacted under a magnetic field with a binder to form bonded bulk SmCo5 nanostructured magnets. X-ray diffraction patterns show c-axis alignment in the bulk magnets, which was consistent with the magnetic measurements.
Relaxation behaviors of the bismuth-substituted yttrium iron garnet in the microwave range
Authors: Hung D. S. , Fu Y. P. , Lee S. F. , Yao Y. D. , Abdul Ahad Faris B.
Published: April 2010

The spin damping behavior of the bismuth-substituted yttrium iron garnets (BixY3−xFe5O12) prepared by the coprecipitation process was investigated using the ferromagnetic resonant (FMR) in this study. By analyzing the FMR responses, the spin damping coefficient of the x=0.25–1.25 in polycrystalline Bi:YIG (yttrium aluminum garnet) samples was obtained from the 3 dB linewidth of their FMR spectra. The data demonstrated that the damping coefficient started from 3.21×10−3 for x=0.25 and went to its minimum value of 0.31×10−3 for x=0.75. However, the damping coefficient enhanced to 8.55×10−3 with increasing of the bismuth concentration to x=1.25. The results revealed that the spin damping behavior of the Bi:YIG garnets was strongly dependent on a YFeO3 (111) phase.
Rigid and flexible Fe–Zr–N magnetic thin films for microwave absorber
Authors: Liu Z. W. , Zeng D. C. , Ramanujan R. V. , Ong C. K.
Published: April 2010

FeZrN thin films with in-plane anisotropy were deposited on both rigid substrate (Si) and flexible substrate (Kapton) by magnetron sputtering. The as-prepared films had the microstructure of nanocrystallites with a small amount of intergranular amorphous phase. The thickness dependent coercivity showed different behaviors for flexible and rigid films. The dynamic magnetic properties of the films have been characterized. Although the high frequency characteristics are closely related to the thickness, composition, and anisotropy, the flexible films have relatively smaller values of real permeability μ′ but larger values of ferromagnetic resonance frequency fr than the rigid films. Due to the flexibility, the properties of the flexible films varied with each other. Nevertheless, both rigid and flexible films can find important applications in microwave absorber due to their excellent high frequency properties up to 5 GHz.
Analysis and improvement of detection accuracy for a wireless motion sensing system using integrated coil component
Authors: Hashi S. , Ishiyama K. , Yabukami S. , Kanetaka H. , Arai K. I.
Published: April 2010

Integration of the exciting coil and the pick-up coil array for the wireless magnetic motion sensing system has been investigated to clear the limitation of the system arrangement. From the comparison of the integrated-type and the sandwich-type, which was proposed by our previous study, regardless of the lower signal-to-noise ratio of the integrated-type than that of the sandwich-type a repeatable detection accuracy of around 1 mm is obtained at the distance of 120 mm from the pick-up coil array (sandwich-type: up to 140 mm). A different tendency of the detection errors in detection was also observed. In spite of different tendency, the cause of the errors has been clarified. The impedance change of the exciting coil due to a resonance of the LC marker perturbs strength of the magnetic field which is used for marker excitation. However, the errors are able to compensate to the actual positions and orientations of the marker by using compensatory method which was already established.
Integration of the electronics and batteries inside the hollow core of a search coil
Authors: Grosz Asaf , Paperno Eugene , Amrusi Shai , Liverts Edward
Published: April 2010

A novel design of a miniature search coil magnetometer is proposed based on the integration of the electronics and batteries within the hollow core of the search coil. In contrast with conventional designs, where the search coil and its electronics have individual housings and electrostatic shields, this paper presents a design in which the core of the search coil serves both as the housing and the magnetic shield for the electronics and batteries. Moreover, the electrostatic shield of the search coil also shields the electronics and batteries. We found that a thin-wall tube core with sufficient permeability is able to replace a solid rod core without decreasing the average flux sensed by the coil winding. In addition, the outer diameter of the tube core can be increased beyond its optimum size to provide more space for the electronics and batteries without considerably affecting the search coil resolution. To validate the effectiveness of this new design, a miniature search coil magnetometer was built and tested for very low frequencies and ultra-low power consumption.
Preparation of polarized molecules using coherent infrared multicolor ladder excitation
Authors: Mukherjee Nandini , Zare Richard N.
Published: April 2010

A density matrix treatment is presented for a general process of preparing polarized molecules through their coherent interaction with two or more infrared photons of different frequencies, each tuned to cause a transition between real levels. This process, which might be called infrared stimulated Raman adiabatic passage, allows complete population transfer to selected rotational-vibrational levels and controls the direction of the rotational angular momentum vector J of the molecule with the possibility of preparing higher moments of the J spatial distribution. HCl molecules in a supersonic molecular beam are considered as a candidate system. Theory predicts that under collision-free conditions two infrared laser pulses of microsecond duration and milliwatt power are able to achieve complete population transfer and alignment of HCl (v=2, J=2, and M=0) for mutually parallel excitation and HCl (v=2, J=2, and M=±1) for mutually perpendicular excitation. Orientation of the HCl (v=2, J=2, and M=±2) can also be achieved using two circularly polarized pulses of the same helicity. For simplicity, our treatment ignores nuclear spin depolarization, which would be the case for molecules such as C12O16 and C12O16O2. Polarized molecules in higher vibrational levels can be prepared using additional infrared pulses.
Electrical tuning of magnetism in Fe3O4/PZN–PT multiferroic heterostructures derived by reactive magnetron sputtering
Authors: Liu Ming , Obi Ogheneyunume , Cai Zhuhua , Lou Jing , Yang Guomin , Ziemer Katherine S. , Sun Nian X.
Published: April 2010

Strong magnetoelectric (ME) coupling was demonstrated in Fe3O4/PZN–PT (lead zinc niobate–lead titanate) multiferroic heterostructures obtained through a sputter deposition process. The dependence of the magnetic anisotropy on the electric field (E-field) is theoretically predicted and experimentally observed by ferromagnetic resonance spectroscopy. A large tunable in-plane magnetic anisotropy of up to 600 Oe, and tunable out-of-plane anisotropy of up to 400 Oe were observed in the Fe3O4/PZN–PT multiferroic heterostructures, corresponding to a large ME coefficient of 100 Oe cm/kV in plane and 68 Oe cm/kV out of plane, which match well with predicted results. In addition, the electric field manipulation of magnetic anisotropy is also demonstrated by the electric fields dependence of magnetic hysteresis loops, showing a large squareness ratio change of 44%. These Fe3O4/PZN–PT multiferroic heterostructures exhibiting large E-field tunable magnetic properties provide great opportunities for novel electrostatically tunable multiferroic devices.
Fully relativistic calculations of NMR shielding tensors using restricted magnetically balanced basis and gauge including atomic orbitals
Authors: Komorovský Stanislav , Repiský Michal , Malkina Olga L. , Malkin Vladimir G.
Published: April 2010

A recently developed relativistic four-component density functional method for calculation of nuclear magnetic resonance (NMR) shielding tensors using restricted magnetically balanced basis sets for the small component (mDKS-RMB) was extended to incorporate the gauge including atomic orbitals (GIAO) approach. The combined method eliminates a strong dependence of the results, calculated with a finite basis set, on the choice of the gauge origin for the magnetic potential of a uniform external magnetic field. Benchmark relativistic calculations have been carried out for xenon dimer and the HX series (X=F, Cl, Br, I), where spin-orbit effects are known to be very pronounced for hydrogen shieldings. Our results clearly demonstrate that shieldings calculated at the four-component level with a common gauge (i.e., without GIAO, IGLO, or similar methods to treat the gauge problem) depend dramatically on the choice of the common gauge. The GIAO approach solves the problem in fully relativistic calculations as it does in the nonrelativistic case.
Drift kinetic equation in the moving reference frame and reduced magnetohydrodynamic equations
Authors: Smolyakov A. I. , Garbet X.
Published: April 2010

The drift kinetic equation is formulated by using the phase space conservation law and drift equations of particle motion in the reference frame moving with plasma fluid velocity. The latter includes the parallel and ExB drift, diamagnetic velocity, and diamagnetic velocity due to the parallel viscosity tensor (anisotropic pressure). It is shown explicitly that the particle drift equations conserve the adiabatic invariant and kinetic equation conserves the phase space volume. The resulting drift kinetic equation is used to obtain a set of moment equations corresponding to the conservation laws for plasma density, momentum, and energy. These equations are compared with reduced equations obtained from hierarchy of extended magnetohydrodynamic equations including the evolution equation for the heat flux (Grad hydrodynamics). The reduction is done in the drift limit by using 1/B as an expansion parameter. We demonstrate that reduced moment equations derived from our drift kinetic equation are identical to the reduced equations obtained from extended magnetohydrodynamic equations. The structure of the reduced equations and implications for the closure problem, including neoclassical effects, are discussed.
Multiprobe experiments under high pressure: Resistivity, magnetic susceptibility, heat capacity, and thermopower measurements around 5 GPa
Authors: Jaccard D. , Sengupta K.
Published: April 2010

We have performed multiprobe experiments using a Bridgman-anvil pressure cell, adapted to trap Daphne oil as pressure medium. Resistivity, ac-magnetic susceptibility, thermopower, and ac-heat capacity of a type-I superconductor, lead, have been studied at low temperature up to 5±0.1 GPa. This is the first report where ac-magnetic susceptibility has been measured in this type of pressure cell and at such a high pressure range. The signature of the superconducting transition temperature, obtained from all these different measurements, agrees well within the experimental errors.
Polymer length distributions for catalytic polymerization within mesoporous materials: Non-Markovian behavior associated with partial extrusion
Authors: Liu Da-Jiang , Chen Hung-Ting , Lin Victor S.-Y. , Evans J. W.
Published: April 2010

We analyze a model for polymerization at catalytic sites distributed within parallel linear pores of a mesoporous material. Polymerization occurs primarily by reaction of monomers diffusing into the pores with the ends of polymers near the pore openings. Monomers and polymers undergo single-file diffusion within the pores. Model behavior, including the polymer length distribution, is determined by kinetic Monte Carlo simulation of a suitable atomistic-level lattice model. While the polymers remain within the pore, their length distribution during growth can be described qualitatively by a Markovian rate equation treatment. However, once they become partially extruded, the distribution is shown to exhibit non-Markovian scaling behavior. This feature is attributed to the long-tail in the “return-time distribution” for the protruding end of the partially extruded polymer to return to the pore, such return being necessary for further reaction and growth. The detailed form of the scaled length distribution is elucidated by application of continuous-time random walk theory.
A global search for the lowest energy isomer of C26
Authors: An Jie , Gan Li-Hua , Zhao Jian-Qiang , Li Rui
Published: April 2010

The complete set of 2333 isomers of C26 fullerene composed of square, pentagonal, hexagonal, and heptagonal faces together with some noncage structures is investigated at the Hartree–Fock and density functional theory (DFT) levels. For the singlet states, a nonclassical isomer C26-10-01 with a square embedded is predicted by the DFT method as the lowest energy isomer, followed by the sole classical isomer C26-00-01. Further explorations reveal that the electronic ground state of C26-10-01 is triplet state in Cs symmetry, while that of C26-00-01 corresponds to its quintet in D3h symmetry. Both the total energies and nucleus independent chemical shift values at DFT level favor the classical isomer. It is found that both C26-00-01 and C26-10-01 possess high vertical electron affinity. The addition of electron(s) to C26-10-01 increases its aromatic character and encapsulation of Li atom into this cage is highly exothermic, indicating that it may be captured in the form of derivatives. To clarify the relative stabilities at elevated temperatures, the entropy contributions are taken into account based on the Gibbs free energy at the B3LYP/6-311+G∗ level. C26-10-01 behaves thermodynamically more stable than the classical isomer over a wide range of temperatures related to fullerene formation. The IR spectra of these two lowest energy isomers are simulated to facilitate their experimental identification.
Mechanism and model of the oscillatory electro-oxidation of methanol
Authors: Sauerbrei S. , Nascimento M. A. , Eiswirth M. , Varela H.
Published: April 2010

A mechanism for the kinetic instabilities observed in the galvanostatic electro-oxidation of methanol is suggested and a model developed. The model is investigated using stoichiometric network analysis as well as concepts from algebraic geometry (polynomial rings and ideal theory) revealing the occurrence of a Hopf and a saddle-node bifurcation. These analytical solutions are confirmed by numerical integration of the system of differential equations.
Pressure effects on relaxor ferroelectricity in disordered Pb(Sc1/2Nb1/2)O3
Authors: Ahart Muhtar , Mao Ho-kwang , Cohen R. E. , Hemley Russell J. , Samara George A. , Bing Yonghong , Ye Zuo-Guang , Kojima Seiji
Published: April 2010

High-pressure Brillouin and Raman scattering spectroscopy and x-ray diffraction measurements were carried out on disordered Pb(Sc1/2Nb1/2)O3, considered to be a model system for phase transitions in relaxor ferroelectrics and related materials. The observed pressure-dependent Raman spectra are unusual, with the relaxor state distinguished by broad Raman bands. Raman spectra as a function of pressure reveal a new peak at 370 cm−1, with two peaks near 550 cm−1 merge above 2–3 GPa, indicating a structural phase transition in this pressure range consistent with earlier dielectric measurements. A significant softening in the longitudinal acoustic mode is observed by Brillouin scattering. Both the temperature and pressure dependencies of the linewidth reveal that the longitudinal acoustic mode softening arises from electrostrictive coupling between polar nanoregions and acoustic modes. X-ray diffraction indicates that the pressure-volume compression curve changes near 2 GPa.
Two-dimensional freezing criteria for crystallizing colloidal monolayers
Authors: Wang Ziren , Alsayed Ahmed M. , Yodh Arjun G. , Han Yilong
Published: April 2010

Video microscopy was employed to explore crystallization of colloidal monolayers composed of diameter-tunable microgel spheres. Two-dimensional (2D) colloidal liquids were frozen homogenously into polycrystalline solids, and four 2D criteria for freezing were experimentally tested in thermal systems for the first time: the Hansen–Verlet freezing rule, the Löwen–Palberg–Simon dynamical freezing criterion, and two other rules based, respectively, on the split shoulder of the radial distribution function and on the distribution of the shape factor of Voronoi polygons. Importantly, these freezing criteria, usually applied in the context of single crystals, were demonstrated to apply to the formation of polycrystalline solids. At the freezing point, we also observed a peak in the fluctuations of the orientational order parameter and a percolation transition associated with caged particles. Speculation about these percolated clusters of caged particles casts light on solidification mechanisms and dynamic heterogeneity in freezing.
Direct imaging of current induced magnetic vortex gyration in an asymmetric potential well
Authors: Bisig Andre , Rhensius Jan , Kammerer Matthias , Curcic Michael , Stoll Hermann , Schütz Gisela , Van Waeyenberge Bartel , Chou Kang Wei , Tyliszczak Tolek , Heyderman Laura J. , Krzyk Stephen , von Bieren Arndt , Kläui Mathias
Published: April 2010

Employing time-resolved x-ray microscopy, we investigate the dynamics of a pinned magnetic vortex domain wall in a magnetic nanowire. The gyrotropic motion of the vortex core is imaged in response to an exciting ac current. The elliptical vortex core trajectory at resonance reveals asymmetries in the local potential well that are correlated with the pinning geometry. Using the analytical model of a two-dimensional harmonic oscillator, we determine the resonance frequency of the vortex core gyration and, from the eccentricity of the vortex core trajectory at resonance, we can deduce the stiffness of the local potential well.
Direct determination of state-to-state rotational energy transfer rate constants via a Raman-Raman double resonance technique: ortho-acetylene in v2=1 at 155 K
Authors: Doménech José L. , Martínez Raúl Z. , Ramos Ángel , Bermejo Dionisio
Published: April 2010

A new technique for the direct determination of state-to-state rotational energy transfer rate constants in the gas phase is presented. It is based on two sequential stimulated Raman processes: the first one prepares the sample in a single rotational state of an excited vibrational level, and the second one, using the high resolution quasi-continuous stimulated Raman-loss technique, monitors the transfer of population to other rotational states of the same vibrational level as a function of the delay between the pump and the probe stages. The technique is applied to the odd-J rotational states of v2=1 acetylene at 155 K. The experimental layout, data acquisition, retrieval procedures, and numerical treatment are described. The quantity and quality of the data are high enough to allow a direct determination of the state-to-state rate constant matrix from a fit of the experimental data, with the only conditions of detailed balance and of a closed number of states. The matrix obtained from this direct fit is also compared with those obtained using some common fitting and scaling laws.
Determination of the ionization and dissociation energies of the deuterium molecule (D2)
Authors: Liu Jinjun , Sprecher Daniel , Jungen Christian , Ubachs Wim , Merkt Frédéric
Published: April 2010

The transition wave numbers from selected rovibrational levels of the EF Σ1g+(v=0) state to selected np Rydberg states of ortho- and para-D2 located below the adiabatic ionization threshold have been measured at a precision better than 10−3 cm−1. Adding these wave numbers to the previously determined transition wave numbers from the X Σ1g+(v=0, N=0,1) states to the EF Σ1g+(v=0, N=0,1) states of D2 and to the binding energies of the Rydberg states calculated by multichannel quantum defect theory, the ionization energies of ortho- and para-D2 are determined to be 124 745.394 07(58) cm−1 and 124 715.003 77(75) cm−1, respectively. After re-evaluation of the dissociation energy of D2+ and using the known ionization energy of D, the dissociation energy of D2 is determined to be 36 748.362 86(68) cm−1. This result is more precise than previous experimental results by more than one order of magnitude and is in excellent agreement with the most recent theoretical value 36 748.3633(9) cm−1 [K. Piszczatowski, G. Łach, M. Przybytek et al., J. Chem. Theory Comput. 5, 3039 (2009)]. The ortho-para separation of D2, i.e., the energy difference between the N=0 and N=1 rotational levels of the X Σ1g+(v=0) ground state, has been determined to be 59.781 30(95) cm−1.
Fabrication of silicon nanopillar-based nanocapacitor arrays
Authors: Chang Shih-wei , Oh Jihun , Boles Steven T. , Thompson Carl V.
Published: April 2010

We report the fabrication of silicon nanopillar-based nanocapacitor arrays using metal-assisted etching in conjunction with electrodeposition. The high aspect ratio made possible by the catalyzed etching provides for an increased effective electrode area and hence a significant improvement in the capacitance density. Electroplated Ni electrode forms a conformal layer over the silicon nanopillars. Capacitance measurements show the expected trend as a function of pillar height and array period. The fabrication approach is simple, compatible with integration into standard silicon technology, and easily scalable.
Solvent flow patterns fluctuating largely around a protein and correlation with solvent density fluctuations: A molecular dynamics study
Authors: Umezawa Koji , Morikawa Ryota , Nakamura Haruki , Higo Junichi
Published: April 2010

The authors demonstrated recently that translational motions of water molecules around a protein are collective in a short (approximately 10 ps) time scale. The patterns can be regarded as “flows” of three specific patterns—fair current, drying/wetting, and vortex—although the patterns disappear eventually over a longer time scale. Our earlier study suggested a hypothesis that the solvent flows are related to the intersolute interaction. However, the connection between the flows and the interaction was left unexamined. The current simulation study analyzed flow patterns around a protein, human lysozyme, revealing that the drying flows correlate with decreased solvent density. The decrease in solvent density has been known to enhance intersolute attractive interactions. The drying flows can therefore induce the intersolute attractive interactions. Human lysozyme has a catalytic cleft on the protein surface. Large fluctuations of drying/wetting patterns were observed only around the cleft because the large fluctuations occur selectively around convex residues on the protein surface, to which large side-chain fluctuations of the protein are also assigned. The emergence of fair current patterns correlated well with the emergence of drying/wetting patterns. This correlation was found only near the protein surface. Near the protein surface, the vortex flow plane of rotation tended to be parallel to the surface. Current study suggests that the drying flows enhance the substrate approach to the catalytic cleft.
Space-resolved vacuum ultraviolet spectrometer system for edge impurity and temperature profile measurement in HL-2A
Authors: Cui Zhengying , Morita Shigeru , Fu Bingzhong , Huang Yuan , Sun Ping , Gao Yadong , Xu Yuan , Dong Chunfeng , Lu Ping , Wang Quanming , Ding Xuantong , Yang Qingwei , Duan Xuru
Published: April 2010

A 1 m normal incidence vacuum ultraviolet (VUV) spectrometer has been developed for spatial distribution measurement of edge impurity line emission in the wavelength range of 300–3200 Å on HL-2A tokamak. A vertical profile of the impurity line emission is measured with a space-resolved slit placed between an entrance slit and a grating of the spectrometer. Two concave 1200 grooves/mm gratings blazed at 800 and 1500 Å are set on a rotatable holder in the spectrometer, which gives wavelength dispersion of 0.12 mm/Å. A back-illuminated charge-coupled device is used as a detector with an image size of 6.7×26.6 mm2 (26×26 μm2/pixel). An excellent spatial resolution of 2 mm is obtained with good spectral resolution of 0.15 Å when the space-resolved slit of 50 μm in width is used. The space-resolved spectra thus provide three radial profiles of emission line intensity, ion temperature, and poloidal rotation. The electron temperature can be measured by the intensity ratio, e.g., CIII 2s2-2s3p (386 Å)/2s2-2s2p (977 Å). The sensitivity of the spectrometer is calibrated in situ by using the VUV bremsstrahlung continuum radiation emitted from the tokamak plasma. A good performance of the spectrometer system for the edge impurity and temperature profile measurements is presented with results on Ohmic and H-mode discharges.
Induction annealing and subsequent quenching: Effect on the thermoelectric properties of boron-doped nanographite ensembles
Authors: Xie Ming , Lee Chee Huei , Wang Jiesheng , Yap Yoke Khin , Bruno Paola , Gruen Dieter , Singh Dileep , Routbort Jules
Published: April 2010

Boron-doped nanographite ensembles (NGEs) are interesting thermoelectric nanomaterials for high temperature applications. Rapid induction annealing and quenching has been applied to boron-doped NGEs using a relatively low-cost, highly reliable, laboratory built furnace to show that substantial improvements in thermoelectric power factors can be achieved using this methodology. Details of the design and performance of this compact induction furnace as well as results of the thermoelectric measurements will be reported here.
Transport of spherical gyrotactic organisms in general three-dimensional flow fields
Authors: Thorn Graeme J. , Bearon Rachel N.
Published: April 2010

In this paper we consider spherical organisms whose orientations are determined by the combination of viscous torque with a self-righting torque (either due to bottom-heaviness, shape, or through preferential swimming due to active sensing): a phenomenon known as gyrotaxis. We restate the stable equilibrium orientation of such an organism in a homogeneous shear flow, which exists for all shear values if the two torques are not parallel, and only when the nondimensional shear is below a critical value if the torques are parallel. We calculate the long-term trajectories of such an organism in a flow, which consists of linear motion in the direction of the vorticity and a conic section in the plane of shear, giving, for instance, helical motion in the case of pure rotation. We compute the orientation probability density function when the reorientation is coupled with rotational diffusion and show that including rotational diffusion reduces the mean swimming speed and rotates the mean equilibrium orientation toward the vertical. Numerical simulation of stochastic gyrotactic cells in synthetic turbulence demonstrates the interaction between swimming and more general flow fields. The calculation of the mean drift and diffusion demonstrates that the expected transition between swimming-dominated transport (for low kinetic energy dissipation rate ϵ) and turbulence-dominated transport (for large ϵ) occurs over dissipation rates such motile organisms experience in nature (ϵ∼10−10–10−3 m2 s−3).
A consistent and accurateab initioparametrization of density functional dispersion correction (DFT-D) for the 94 elements H-Pu
Authors: Grimme Stefan , Antony Jens , Ehrlich Stephan , Krieg Helge
Published: April 2010

The method of dispersion correction as an add-on to standard Kohn–Sham density functional theory (DFT-D) has been refined regarding higher accuracy, broader range of applicability, and less empiricism. The main new ingredients are atom-pairwise specific dispersion coefficients and cutoff radii that are both computed from first principles. The coefficients for new eighth-order dispersion terms are computed using established recursion relations. System (geometry) dependent information is used for the first time in a DFT-D type approach by employing the new concept of fractional coordination numbers (CN). They are used to interpolate between dispersion coefficients of atoms in different chemical environments. The method only requires adjustment of two global parameters for each density functional, is asymptotically exact for a gas of weakly interacting neutral atoms, and easily allows the computation of atomic forces. Three-body nonadditivity terms are considered. The method has been assessed on standard benchmark sets for inter- and intramolecular noncovalent interactions with a particular emphasis on a consistent description of light and heavy element systems. The mean absolute deviations for the S22 benchmark set of noncovalent interactions for 11 standard density functionals decrease by 15%–40% compared to the previous (already accurate) DFT-D version. Spectacular improvements are found for a tripeptide-folding model and all tested metallic systems. The rectification of the long-range behavior and the use of more accurate C6 coefficients also lead to a much better description of large (infinite) systems as shown for graphene sheets and the adsorption of benzene on an Ag(111) surface. For graphene it is found that the inclusion of three-body terms substantially (by about 10%) weakens the interlayer binding. We propose the revised DFT-D method as a general tool for the computation of the dispersion energy in molecules and solids of any kind with DFT and related (low-cost) electronic structure methods for large systems.
Microcavity enhanced silicon light emitting pn-diode
Authors: Potfajova J. , Schmidt B. , Helm M. , Gemming T. , Benyoucef M. , Rastelli A. , Schmidt O. G.
Published: April 2010

An electrically driven silicon light emitting diode with two distributed Bragg reflectors is reported. The active material is a Si pn-junction fabricated by boron ion implantation into an n-type silicon-on-insulator wafer. The cavity with a thickness of a few wavelengths is formed by amorphous Si/SiO2 multilayer stacks. A strong narrowing and enhancement of the electroluminescence at a resonant wavelength of λ=1146 nm is observed with a quality factor of Q=143 and a finesse of F=11.
Ultrasensitive near-infrared cavity ring-down spectrometer for precise line profile measurement
Authors: Gao Bo , Jiang Wei , Liu An-Wen , Lu Yan , Cheng Cun-Feng , Cheng Guo-Sheng , Hu Shui-Ming
Published: April 2010

A cavity ring-down (CRD) spectrometer is built with a continuous-wave Ti:sapphire ring laser. Using a pair of R∼0.999 95 high-reflective mirrors, the noise-equivalent minimum detectable absorption loss reaches 7×10−11/cm over the spectral range of 780–830 nm. A thermal-stabilized Fabry-Perot interferometer is applied to calibrate the CRD spectrum with an accuracy of 1×10−4 cm−1. The quantitative measurement is carried out for the line profile measurements of some overtone absorption lines of C2H2 near 787 nm. Doppler determined line shape has been observed with milli-Torr acetylene gas in the ring-down cavity. The instrumental line width is estimated from the line profile fitting to be <1×10−4 cm−1. It demonstrates that the CRD spectrometer with extremely high sensitivity is also very suitable for quantitative measurements including precise line profile studies in the near-infrared.
Photoelectric performance of TiO2 nanotube array photoelectrodes cosensitized with CdS/CdSe quantum dots
Authors: Gao Xian-Feng , Sun Wen-Tao , Ai Guo , Peng Lian-Mao
Published: April 2010

The photoresponse of TiO2 nanotube-array films in the visible region is shown to have been significantly improved by sensitizing them with CdS and CdSe semiconductor quantum dots using a sequential chemical bath deposition method. These quantum dots served as cosensitizers, and the performance of corresponding photoelectrode was measured in a photoelectrochemical solar cell. A 13.0 mA/cm2 short circuit current density is achieved with the TiO2/CdS/CdSe photoelectrode under AM 1.5G illuminations, which is higher than the direct sum of CdS and CdSe sensitized TiO2.
Current driven discontinuous insulator-metal transition and low-field colossal magnetoresistance in Sm0.6Sr0.4MnO3
Authors: Rebello A. , Mahendiran R.
Published: April 2010

We show that with increasing magnitude of current (I), insulator-metal (I-M) transition in Sm0.6Sr0.4MnO3 becomes discontinuous and shifts down in temperature, which is accompanied by an abrupt decrease in temperature of the sample while cooling. The I-M transition exhibits a hysteresis while warming. A magnetic field of μ0H=0.5 T results in −99% magnetoresistance for I=11 mA compared to −32% for I=1 mA. Our results underscore the importance of inhomogeneous Joule heating that leads to coexistence of the high temperature paramagnetic phase with the low temperature ferromagnetic phase over a wide temperature range.
Fermi level depinning at the germanium Schottky interface through sulfur passivation
Authors: Thathachary Arun V. , Bhat K. N. , Bhat Navakanta , Hegde M. S.
Published: April 2010

We demonstrate the depinning of Fermi level on both p- and n-type germanium after sulfur passivation by aqueous (NH4)2S treatment. Schottky contacts realized using metals with a wide range of work functions produce nearly ideal behavior confirming that the Fermi level is depinned. Examination of the passivated surface using x-ray photoelectron spectroscopy reveals bonding between Ge and sulfur. It is shown that good Ohmic contacts to n-type Ge and a hole barrier height (ϕBp) of 0.6 eV to p-type Ge can be achieved after this passivation treatment, with Zr Schottky contacts. This is the highest ϕBp reported so far.
Embedded indium-tin-oxide nanoelectrodes for efficiency and lifetime enhancement of polymer-based solar cells
Authors: Yu Peichen , Chang Chia-Hua , Su Ming-Shin , Hsu Min-Hsiang , Wei Kung-Hwa
Published: April 2010

In this paper, distinctive indium-tin-oxide (ITO) nanorods are employed to serve as buried electrodes for polymer-based solar cells. The embedded nanoelectrodes allow three-dimensional conducting pathways for low-mobility holes, offering a highly scaffolded cell architecture in addition to bulk heterojunctions. As a result, the power conversion efficiency of a polymer cell with ITO nanoelectrodes is increased to about 3.4% and 4.4% under one-sun and five-sun illumination conditions, respectively, representing an enhancement factor of up to ∼10% and 36% compared to a conventional counterpart. Also, the corresponding device lifetime is prolonged twice as much to about 110 min under five-sun illumination.
Crystal symmetry breaking in few-quintuple Bi2Te3 films: Applications in nanometrology of topological insulators
Authors: Shahil K. M. F. , Hossain M. Z. , Teweldebrhan D. , Balandin A. A.
Published: April 2010

The authors report results of micro-Raman spectroscopy investigation of mechanically exfoliated single-crystal bismuth telluride films with thickness ranging from a few-nanometers to bulk limit. It is found that the optical phonon mode A1u, which is not-Raman active in bulk Bi2Te3 crystals, appears in the atomically-thin films due to crystal-symmetry breaking. The intensity ratios of the out-of-plane A1u and A1g modes to the in-plane Eg mode grow with decreasing film thickness. The evolution of Raman signatures with the film thickness can be used for identification of Bi2Te3 crystals with the thickness of few-quintuple layers important for topological insulator and thermoelectric applications.
Improved light extraction efficiency of white organic light-emitting devices by biomimetic antireflective surfaces
Authors: Li Yunfeng , Li Feng , Zhang Junhu , Wang Chunlei , Zhu Shoujun , Yu Huijun , Wang Zhanhua , Yang Bai
Published: April 2010

One simple method to increase the light extraction from white organic light-emitting devices by using biomimetic silica antireflective surfaces is demonstrated. A silica cone array was directly etched on the opposite side of the indium–tin–oxide coated fused silica substrate. The antireflective surfaces can dramatically suppress the reflection loss and increase the transmission of light over a large range of wavelength and a large field of view. Using such surfaces, the luminance efficiency of the device in the normal direction is increased by a factor of 1.4 compared to that of the device using flat silica substrate.
Optimization of silica–silver–gold layered nanoshell for large near-field enhancement
Authors: Wu D. J. , Liu X. J.
Published: April 2010

The near-field enhancement of silica–silver–gold (SSG) nanoshells has been investigated by using Mie theory. If the thickness of Au shell is smaller than 5 nm, the maximum of near-field for SSG increases first and then decreases with increasing Ag layer thickness. Thus, the near-field for SSG can be modified by Ag layer and can possess more excellent near-field enhancement. If the thickness of Au shell is larger than 10 nm, the maximum of near-field of SSG nanoshell decreases with increasing Ag layer thickness. We further discuss the influence of Au shell thickness on the near-field of SSG nanoshell.
Physical origin of dipole formation at high-k/SiO2 interface in metal-oxide-semiconductor device with high-k/metal gate structure
Authors: Wang Xiaolei , Han Kai , Wang Wenwu , Chen Shijie , Ma Xueli , Chen Dapeng , Zhang Jing , Du Jun , Xiong Yuhua , Huang Anping
Published: April 2010

A physical model on dipole formation at high-k/SiO2 interface is proposed to study possible mechanism of flatband voltage (VFB) shift in metal-oxide-semiconductor device with high-k/metal gate structure. Dielectric contact induced gap states (DCIGS) on high-k or SiO2 side induced by high-k and SiO2 contact are assigned to dominant origin of dipole formation. DCIGS induced interface dipole is considered to cause VFB shift through charge transfer effect. Based on the proposed model, directions of dipoles at several high-k/SiO2 interfaces are predicted, and magnitudes of dipoles are approximately calculated. Both directions and magnitudes are in agreement with the reported results.
Origin and passivation of fixed charge in atomic layer deposited aluminum oxide gate insulators on chemically treated InGaAs substrates
Authors: Shin Byungha , Weber Justin R. , Long Rathnait D. , Hurley Paul K. , Van de Walle Chris G. , McIntyre Paul C.
Published: April 2010

We report experimental and theoretical studies of defects producing fixed charge within Al2O3 layers grown by atomic layer deposition (ALD) on In0.53Ga0.47As(001) substrates and the effects of hydrogen passivation of these defects. Capacitance-voltage measurements of Pt/ALD-Al2O3/n-In0.53Ga0.47As suggested the presence of positive bulk fixed charge and negative interfacial fixed charge within ALD-Al2O3. We identified oxygen and aluminum dangling bonds (DBs) as the origin of the fixed charge. First-principles calculations predicted possible passivation of both O and Al DBs, which would neutralize fixed charge, and this prediction was confirmed experimentally; postmetallization forming gas anneal removed most of the fixed charge in ALD-Al2O3.
Study on the electrical conduction mechanism of bipolar resistive switching TiO2 thin films using impedance spectroscopy
Authors: Lee Min Hwan , Kim Kyung Min , Kim Gun Hwan , Seok Jun Yeong , Song Seul Ji , Yoon Jung Ho , Hwang Cheol Seong
Published: April 2010

The electrical conduction mechanism within a resistive switching TiO2 film in its bipolar high resistance state was examined by ac impedance spectroscopy and dc current-voltage measurements. Bipolar switching, which can be initiated from a unipolar high resistance state, was attributed to both modulation of the Schottky barrier height at the film-electrode interface and the electronic energy state in the film. Numerical fittings of the impedance data revealed two distinct RC domains in series, which were attributed to an interfacial barrier (activation energy ∼0.1 eV) and a nonconducting layer (activation energy ∼0.5 eV), respectively.
Improvement of electron injection in inverted bottom-emission blue phosphorescent organic light emitting diodes using zinc oxide nanoparticles
Authors: Lee Hyunkoo , Park Insun , Kwak Jeonghun , Yoon Do Y. , Lee Changhee
Published: April 2010

We fabricated highly efficient iridium(III) bis[(4,6-di-fluorophenyl)-pyridinato-N,C2′] picolinate doped inverted bottom-emission blue phosphorescent organic light-emitting diodes, with an electron injection layer of zinc oxide (ZnO) nanoparticles (NPs). The ZnO NPs layer lowers the turn-on voltage by about 4 V and significantly enhances the efficiency. The device with ZnO NPs shows peak efficiencies of 16.5 cd/A and 8.2%, about three times higher than those of the device without ZnO NPs. Since the ZnO NPs layer has a wide band gap, good electron transporting properties and low work function, it can be utilized as an effective electron injection layer with good transparency.