bluuebunny/crossref_metadata_2025_split huggingface dataset:
Spin fluctuations in coupled two‐dimensional magnetic trilayers
Authors: Wende H. , Sorg C. , Bernien M. , Scherz A. , Jensen P. J. , Ponpandian N. , Baberschke K. 
Published: November 2005

AbstractMagnetic trilayer systems consisting of two ultrathin ferromagnetic films of Co and Ni separated by a non‐magnetic spacer of Cu are investigated in order to analyze the effect of spin fluctuations in the ultrathin film limit (2D). The element specificity of the X‐ray magnetic circular dichroism technique is applied to study the temperature dependence of the Co and Ni magnetization separately. The effect of (i) the interlayer exchange coupling and (ii) the enhanced 2D spin fluctuations on the shift of the critical temperature of the Ni films is determined by varying both the Cu and the Ni thicknesses. For a detailed understanding of these effects the experimental results are compared to a microscopic many‐body Green's function theory. Both experiment and theory provide clear indications that for nanostructured magnets a static mean field description is insufficient. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Spin transport in disordered single‐wall carbon nanotubes contacted to ferromagnetic leads
Authors: Krompiewski S. , Nemec N. , Cuniberti G. 
Published: November 2005

AbstractRecent conductance measurements on multi‐wall carbon nanotubes (CNTs) reveal an effective behavior similar to disordered single‐wall CNTs. This is due to the fact that electric current flows essentially through the outermost shell and is strongly influenced by inhomogeneous electrostatic potential coming from the inner tubes. Here, we present theoretical studies of spin‐dependent transport through disorder‐free double‐wall CNTs as well as single‐wall CNTs with Anderson‐type disorder. The CNTs are end‐contacted to ferromagnetic electrodes modelled as fcc (111) surfaces. Our results shed additional light on the giant magnetoresistance effect in CNTs. Some reported results concern realistically long CNTs, up to several hundred nanometers. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Spin accumulation, spin currents, and torque, in the problem of motion of a sharp domain wall in magnetic nanowires
Authors: Vieira V. R. , Dugaev V. K. , Sacramento P. D. , Barnaś J. , Araújo M. A. N. , Berakdar J. 
Published: November 2005

AbstractWe consider the motion of a sharp domain wall in magnetic nanowires with electric current. The width of the domain wall is much smaller than the electron wavelength, which is typical for magnetic semiconductors. We calculate the distributions of the spin density and the spin current related to different modes of the scattering states. The accumulated transverse components of the spin density and the spin current oscillate in the vicinity of the wall and they essentially affect its dynamics, whereas the longitudinal part of the spin current is responsible for another component of the spin torque creating a force for the current‐induced motion of the domain wall along the nanowire. We also analyze the dynamics of the sharp domain wall using the standard Landau–Lifshits–Gilbert formalism and the two‐component spin torque calculated for this model. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Orbital Kondo effect and spin polarized transport through quantum dots
Authors: Lipiński S. , Krychowski D. 
Published: November 2005

AbstractThe coherent spin dependent transport through a set of two capacitively coupled quantum dots placed in a magnetic field is considered within the equation of motion method. The magnetic field breaks the spin degeneracy. For special choices of gate voltages the dot levels are tuned to resonance and the orbital Kondo effect results. For different Zeemann splittings at the dots the Kondo resonance can be formed for only one spin channel. In this case the system operates as an efficient spin filter. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Correlation between growth and magnetic properties of Fe/Ti multilayers
Authors: Smardz K. , Smardz L. 
Published: November 2005

AbstractFe/Ti multilayers (MLs) were prepared onto glass substrates at 295 K using UHV RF/DC magnetron sputtering. Planar growth of the Fe and Ti sublayers was confirmed in‐situ by X‐ray photoelectron spectroscopy (XPS). We have observed exponential variation of the XPS Fe‐2p and Ti‐2p integral intensities with increasing sublayer thicknesses. Systematic structural and magnetic studies showed, that iron sublayers grow on Ti in the soft magnetic nanocrystalline phase up to a critical thickness d crit ∼ 2.3 nm. For a thickness greater than d crit, the Fe sublayers undergo a structural transition to the polycrystalline phase with much higher coercivity. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Changes in magnetic and magnetoresistive characteristics of Ni–Fe/Au/Co/Au multilayers induced by annealing
Authors: Szymański B. , Stobiecki F. , Urbaniak M. 
Published: November 2005

AbstractIn this contribution the influence of annealing on magnetization reversal and on the giant magnetoresistance effect of [Ni80Fe20/Au(t Au)/Co(t Co)/Au(t Au)]10 multilayers with t Co = 0.6, 0.8 nm and t Au = 1.5, 2.2 nm was studied. Measurements performed for as‐deposited samples and after subsequent annealing at T a (423 K < T a < 523 K) show that the GMR effect is stable under annealing below 475 K. It even slightly increases, for T a above 450 K, opening a path for a GMR value control and therefore is important for applications. The most pronounced changes were observed in the saturation field H CoS‖ which is a measure of perpendicular anisotropy. The significant variations were also noticed in the central part of the M (H ) and R (H ) curves. They are characterized by the nucleation field H N and the saturation field H S⊥ which are related to the appearance and disappearance of stripe domains in Co layers, respectively. The influence of T a on values of H CoS‖, H S⊥ and H N will be discussed. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Role of inter‐dot Coulomb repulsion and exchange interactions on transport in double quantum dot
Authors: Michałek Grzegorz , Bułka Bogdan R. 
Published: November 2005

AbstractEffects of inter‐dot many‐body electronic correlations on the coherent transport through double quantum dots (DQD) connected in series are studied. Conductance as well as another physical quantities are calculated by means of Green's functions. The many‐body electronic correlations are treated in the slave‐boson (SB) mean‐field approach, developed by Kotliar and Ruckenstein. The conductance in the model is characterized by competition between the dot–dot tunnelling coupling and the level broadening (dot–lead coupling). In the case, when the inter‐dot coupling is weaker than the dot–lead coupling each dot accommodates one electron and forms the Kondo resonant state with conducting electrons in a lead. In the opposite limits, when the inter‐dot coupling exceeds level broadening, the conductance vanishes for sufficiently low gate voltages, which means the Kondo effect disappeared. The resonance region is broadened with increasing inter‐dot Coulomb repulsion as well as with decreasing exchange interactions. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Spin and orbital magnetism of Au3Co: Density functional calculations
Authors: Sargolzaei Mahdi , Opahle Ingo , Richter Manuel 
Published: November 2005

AbstractThe metastable L12 compound Au3Co has been considered as a model for high Co impurity concentration in gold. The spin and orbital moments of this compound have been calculated in the framework of local spin density approximation (LSDA) with and without orbital polarization corrections, using the relativistic version of the full‐potential local orbital minimum basis code. We also calculated the magnetocrystalline anisotropy energy. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Magnetic properties of Cu‐flux‐grown UCu2Si2 single crystals
Authors: Troć R. , Bukowski Z. 
Published: November 2005

AbstractIn order to solve a serious problem of understanding the magnetic properties of UCu2Si2, we have grown single crystals of this compound from Cu‐flux. Here we focus primarily on the magnetic behavior of this compound. In contrast to some previous polycrystalline and single‐crystalline reports on UCu2Si2 no signs of the transition into antiferromagnetic behavior have been observed below T C = 104(1) K. The magnetic properties of this compound are highly anisotropic, with an easy axis of magnetization along the [001] direction. The saturation moment has been determined at 4.2 K to be 1.55μ B. In the paramagnetic region the effective moments for the easy and hard directions are both about 3.0μ B. An extensive discussion of the obtained data, compared to those recently published by Fisk et al. and Matsuda et al., also based on single crystalline materials, has been presented. No an antiferromagnetic phase above T C has been detected. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Thermal properties of U3Al2Si3 single crystal
Authors: Mihalik Marián , Flachbart Karol , Gabáni Slavomír , Maťaš Slavomír , Mihalik Matúš , Rogl Peter , Troć Robert 
Published: November 2005

AbstractHeat capacity data of U3Al2Si3 single crystal exhibit a maximum at 38 K connected with a transition to a magnetically ordered state. For a full description of the electron part we used γ 0 = 145 mJ/mol K2 and for the phonon part of the specific heat we used the harmonic approximation of the phonon spectrum including both the Debye model with T D = 296 K and the Einstein model with T E = 136, 249 and 438 K. The heat capacity data below the magnetic transition down to 2 K fit very well within the model introducing the energy gap Δ = 39 K in the dispersion relation of magnons. An upturn of the C /T (T ) curve, found below T = 2 K, can not be fully attributed to the nuclear Schottky contribution. The electronic heat capacity coefficient (γ ≈ 230 mJ/mol K2 is enhanced and varies between 0.15 K and 12 K as the square root of T . (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electronic structure studies of DyNi4Cu
Authors: Pugaczowa‐Michalska M. , Chełkowska G. , Toliński T. , Kowalczyk A. 
Published: November 2005

AbstractElectronic structure of the DyNi4Cu compound, crystallising in the hexagonal CaCu5‐type of structure has been studied using the XPS method as well as the self‐consistent spin‐polarised TB‐LMTO (tigh‐binding linear muffin‐tin orbital) method. Our calculations show that DyNi4Cu is ferromagnetically ordered at 0 K. The analysis of the valence band shape in vicinity of the Fermi level shows that this part of the spectrum comes mainly from 3d electrons of Ni and Cu atoms. The features of the experimental XPS valence band spectra near the Fermi level are reproduced in our calculations. Peaks below –7.5 eV are connected with the contribution of the f ‐electrons of Dy. The obtained peak positions in the valence band are in good agreement with the binding energies of metallic dysprosium, copper and nickel. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Andreev reflection at ferromagnetic metal‐triplet superconductor junction
Authors: Kowalewski L. , Wojciechowski R. J. , Wojtuś P. 
Published: November 2005

AbstractProperties of tunneling conductance spectra of a ferromagnetic‐insulator‐anisotropic spin triplet superconductor junction are theoretically investigated. The Andreev reflection and transmission of quasiparticles at the interfaces, parallel to the c ‐axis of the superconductor Sr2RuO4, for unitary p ‐wave and non‐unitary states are discussed. Asymmetry of the Andreev reflection amplitude with respect to the boundary normal is analyzed. Discussion of the resonance peak in this reflection is also performed. The essential influence of the magnitude and direction of the exchange field on the conduction spectrum is investigated. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Orbital‐selective Mott transitions in the 2‐band Jz‐model: a high‐precision quantum Monte Carlo study
Authors: van Dongen P. G. J. , Knecht C. , Blümer N. 
Published: November 2005

AbstractUsing high‐precision quantum Monte Carlo (QMC) simulations within the framework of dynamical mean field theory (DMFT), we show that the anisotropic degenerate two‐orbital Hubbard model contains two consecutive orbital‐selective Mott transitions (OSMTs) even in the absence of spin‐flip terms and pair‐hopping processes. In order to reveal the second transition we carefully analyze the low‐frequency part of the self‐energy and the local spectral functions. This paper extends our previous work to lower temperatures. We discuss the nature – in particular the order – of both Mott transitions and list various possible extensions. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dynamic response of magnetic ions in the colossal magnetoresistance manganites La1–xCaxMnO3
Authors: Deac I. G. , Tetean R. V. , Miron M. , Burzo E. 
Published: November 2005

AbstractWe present a detailed study of the nonlinear dynamic susceptibility of the polycrystalline perovskite manganites La1–x Cax MnO3 (0.30 ≤ x ≤ 0.66), below and above the transition temperature as functions of frequency and temperature. Near to x = 0.5 the system changes from ferromagnetic and conducting to antiferromagnetic and insulating with a large hysteretic behavior in M (T ) and ρ (T ). The Curie temperatures determined from dynamic susceptibility analysis were compared to the data obtained previously by electrical and static magnetic measurements, and a new phase diagram was drawn. The data suggest the presence of correlated magnetic clusters near to the magnetic transition. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Non‐collinear magnetic states in Ni–Fe/Au/Co/Au multilayers investigated by magnetoresistance measurements
Authors: Stobiecki F. , Urbaniak M. , Szymański B. , Schmidt M. , Luciński T. 
Published: November 2005

AbstractSputtered Ni80Fe20/Au/Co/Au multilayers (MLs) exhibit perpendicular anisotropy of Co layers and easy‐plane anisotropy of Permalloy layers. In these samples the changes of relative orientation of magnetization between Co and NiFe layers, with magnetic field, can be determined by magnetoresistance measurements. The magnetic structure is discussed for two types of Ni80Fe20/Au/Co/Au MLs characterized by a weak coupling between ferromagnetic layers: (i) MLs with rectangular hysteresis loops and small coercive field, (ii) MLs with dense stripe domain structure in Co layers. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Sample size of 12 per group rule of thumb for a pilot study
Authors: Julious Steven A. 
Published: November 2005

AbstractWhen designing a clinical trial an appropriate justification for the sample size should be provided in the protocol. However, there are a number of settings when undertaking a pilot trial when there is no prior information to base a sample size on. For such pilot studies the recommendation is a sample size of 12 per group. The justifications for this sample size are based on rationale about feasibility; precision about the mean and variance; and regulatory considerations. The context of the justifications are that future studies will use the information from the pilot in their design. Copyright © 2005 John Wiley & Sons, Ltd.
Cost‐efficient higher‐order crossover designs for two‐treatment clinical trials
Authors: Yuan Ying , Zhou Jihao 
Published: November 2005

AbstractHigher‐order crossover designs have drawn considerable attention in clinical trials, because of their ability to test direct treatment effects in the presence of carry‐over effects. The important question, when applying higher‐order crossover designs in practice, is how to choose a design with both statistical and cost efficiencies from various alternatives. In this paper, we propose a general cost function and compare five statistically optimal or near‐optimal designs with this cost function for a two‐treatment study under different carry‐over models. Based on our study, to achieve both statistical and cost efficiencies, a four‐period, four‐sequence crossover design is generally recommended under the simple carry‐over or no carry‐over models, and a three‐period, two‐sequence crossover design is generally recommended under the steady‐state carry‐over models. Copyright © 2005 John Wiley & Sons, Ltd.
Multiple imputation compared with restricted pseudo‐likelihood and generalized estimating equations for analysis of binary repeated measures in clinical studies
Authors: Lipkovich Ilya , Duan Yuyan , Ahmed Saeeduddin 
Published: November 2005

AbstractNon‐likelihood‐based methods for repeated measures analysis of binary data in clinical trials can result in biased estimates of treatment effects and associated standard errors when the dropout process is not completely at random. We tested the utility of a multiple imputation approach in reducing these biases. Simulations were used to compare performance of multiple imputation with generalized estimating equations and restricted pseudo‐likelihood in five representative clinical trial profiles for estimating (a) overall treatment effects and (b) treatment differences at the last scheduled visit. In clinical trials with moderate to high (40–60%) dropout rates with dropouts missing at random, multiple imputation led to less biased and more precise estimates of treatment differences for binary outcomes based on underlying continuous scores. Copyright © 2005 John Wiley & Sons, Ltd.
The formation of neutral CCCO2H and HCCCO2 molecules from anionic precursors in the gas phase: a joint experimental and theoretical study
Authors: Fitzgerald Mark , Bowie John H. , Schröder Detlef , Schwarz Helmut 
Published: November 2005

AbstractCalculations at the CCSD(T)/aug‐cc‐pVDZ//B3LYP/6‐31G(d) level of theory indicate that the anions −CCCO2H and HCCCO are stable species in their singlet states. Upon collision‐induced, vertical one‐electron oxidation under neutralisation‐reionisation (−NR+) conditions, they produce the neutral molecules CCCO2H and HCCCO2, respectively. Some of the CCCO2H neutrals should be stable for the duration of the neutralisation‐reionisation experiment (10−6 s), while others will dissociate to CCCO and OH (requires 125 kJ mol−1). In contrast, neutral HCCCO2 is expected to be much less stable, and dissociate to HCC and CO2 (37 kJ mol−1). Neither CCCO2H nor HCCCO2 is expected to interconvert, or to rearrange to other isomers. The anions −CCCO2H and HCCCO have been formed in the ion source of the mass spectrometer by the reactions between (CH3)3SiCCCO2H and F− and HCCCO2Si(CH3)3 and F−, respectively. The −NR+ spectrum of −CCCO2H shows a recovery signal and also indicates that the lowest energy dissociation pathway of neutral CCCO2H corresponds to the loss of OH. The −NR+ spectrum of HCCCO2 displays little or no recovery signal, and the spectrum is dominated by the [CO2]+ ion. The experimental observations are in agreement with the predictions of the extensive theoretical studies. Copyright © 2005 John Wiley & Sons, Ltd.
High precision measurements of 17O/16O and 18O/16O ratios in H2O
Authors: Barkan Eugeni , Luz Boaz 
Published: November 2005

AbstractWe have optimized the method of water fluorination using the solid reagent CoF3 to produce O2. This allows isotope ratio measurements by dual‐inlet mass spectrometry with very high precision of 0.01 to 0.03‰ for both δ17O and δ18O. Using this method, δ17O and δ18O of atmospheric O2 were determined as 12.08 and 23.88‰ vs. VSMOW, respectively. Likewise, δ17O and δ18O of GISP were −13.12 and −24.73‰, and for SLAP they were −29.48 and −55.11‰ vs. VSMOW, respectively. Analysis of these data in a ln(δ17O + 1) vs. ln(δ18O + 1) plot yields a line with a regression coefficient (λ) of 0.5279 ± 0.0001 (R2 = 0.999999). We also determined the fractionation factors 17α and 18α in liquid‐vapor equilibrium, and found that the ratio ln17α/ln18α is constant (0.529 ± 0.001) over the temperature range 11.4 to 41.5°C. Copyright © 2005 John Wiley & Sons, Ltd.
Study of fragmentation pattern and adsorption of 9‐O‐(triphenylsilyl)‐10,11‐dihydrocinchonidine on platinum by hydrogen/deuterium exchange using electrospray ionization ion‐trap tandem mass spectrometry
Authors: Szöllősi György , Bucsi Imre , Cserényi Szabolcs , Bartók Mihály 
Published: November 2005

AbstractWe have studied the adsorption on a platinum (Pt) catalyst of two compounds utilizable as a chiral basic catalyst and a chiral modifier, dihydrocinchonidine (DHCD), and a new cinchona alkaloid derivative containing a bulky group, the Ph3SiO‐DHCD molecule. The method of choice was the detection by electrospray ionization (ESI) ion‐trap tandem mass spectrometry (MS/MS) of hydrogen/deuterium (H/D) exchange at room temperature, in tetrahydrofuran, at a D2 pressure of 1 bar. Based on the ESI‐MS/MS spectrum of the new compound, we propose a mechanism for the formation of the silatropylium cation containing a SiO bond. From the fragmentation pattern of Ph3SiO‐DHCD it was confirmed that ESI‐ion‐trap MS/MS can be used to study the adsorption processes of complicated carbon compounds by investigating their H/D exchange reactions. In the case of Ph3SiO‐DHCD, the results demonstrate that H/D exchange takes place mainly on the quinoline skeleton. However, the strong π‐bonded adsorption of the quinoline skeleton parallel with the imaginary plane of Pt is not preferred because the bulky Ph3Si group inhibits the multiple π‐bonded adsorption of the Ph3SiO‐DHCD. Because of this hindrance the molecule was adsorbed tilted via the nonbonding electron pair of the N atom and C2′ atom of the quinoline skeleton; consequently, mainly alkaloid‐d1 and alkaloid‐d2 are formed. Copyright © 2005 John Wiley & Sons, Ltd.
Detection limits of matrix‐assisted laser desorption/ionisation mass spectrometry coupled to chromatography – a new application of solvent‐free sample preparation
Authors: Falkenhagen Jana , Weidner Steffen M. 
Published: November 2005

AbstractThe detection limits of matrix‐assisted laser desorption/ionisation mass spectrometry (MALDI‐MS) by semi‐online coupling with chromatography were investigated using various mixtures of polyethylene oxides (PEOs) with different end groups. In contrast to the common ‘dried‐droplet’ sample preparation technique, which results in an inhomogeneous sample‐to‐matrix ratio within the MALDI spot, the used coupling technique offers a very high reproducibility combined with surpassing sensitivity of a few femtograms over a broad range of sample‐to‐matrix ratios. These results are in correlation with the results of the recently established solvent‐free MALDI‐TOFMS method utilising the grinding approach and are also of assistance towards the more theoretical aspect of MALDI that suggests that there is no necessity for an analyte incorporation into a matrix crystal for excellent matrix‐assistance. Copyright © 2005 John Wiley & Sons, Ltd.
Identification of a trace colored impurity in drug substance by preparative liquid chromatography and mass spectrometry
Authors: Wang Peng , Shi Y.‐J. , Helmy Roy , Reamer Robert , Vailaya Anant 
Published: November 2005

Abstract6‐(Nitrooxy)hexyl‐(2z)‐4‐(acetyloxy)‐3‐[4‐(methylsulfonyl)phenyl]‐2‐phenylbut‐2‐enoate (enoate 1) was investigated as a novel therapy for pain relief. In a recent manufacturing run at the pilot plant scale, the enoate drug substance was found to have a yellowish color not observed previously. An unknown impurity at trace level was detected by high‐performance liquid chromatographic (HPLC) analysis and found to be the primary cause for the color of the drug substance. The colored impurity was enriched by preparative HPLC and structurally elucidated by liquid chromatography/tandem mass spectrometry (LC/MS/MS). It was found that the colored impurity was derived from the product of oxidative dimerization of rofecoxib, an impurity present in the enoic acid intermediate. It was further revealed by the photodiode array and LC/MS/MS data that the colored impurity exists in the drug substance as a pair of double‐bond isomers with one isomer at majority. These findings were also confirmed by synthesizing the colored impurity through the proposed pathway. Copyright © 2005 John Wiley & Sons, Ltd.