bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electronic structure of rare‐earth compounds TmGa3, ErGa3, and CeIn3 studied by positrons
Authors: Samsel‐Czekała M. , Kontrym‐Sznajd G. , Biasini M. 
Published: January 2006

AbstractThe electronic structure of the isostructural rare‐earth systems TmGa3, ErGa3, and CeIn3 has recently been investigated by measurements of two‐dimensional angular correlations of annihilation radiation (2D ACAR). We employ different tomography techniques to reconstruct electron‐positron (e‐p) momentum density ρ (p) from its line projections. In all these compounds we get very specific shape of ρ (p). In order to draw the Fermi surface (FS), we perform conversion from the extended p to reduced k space. In the case of TmGa3 and ErGa3 a nesting feature of the FS consistent with the antiferromagnetic structure is observed. On the other hand, in CeIn3 we cannot detect any link between the FS topology and the vector of the magnetic propagation. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electronic structure calculations and electrical resistivity of Dy(Co1–xMx)2 (M = Ni, Cu)
Authors: Szajek A. , Kowalczyk A. , Ivanov V. , Falkowski M. 
Published: January 2006

Abstract R(Co1–x Mx )2 (R = rare earth; M = transition metal) alloys exhibit interesting magnetic properties because of the differing nature of magnetism (localized and band) of their constituents. Results of measurements of the magnetic susceptibility, electrical resistivity of intermetallic compounds Dy(Co1–x Mx)2 (M = Ni, Cu) are presented. The effect of partial substitution of Co by M is reflected in a change of TC and in the temperature dependence of electrical resistivity. The ab initio calculations show that impurities reduce magnetic moments on Co atoms. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electronic and magnetic properties of cobalt between titanium layers – ab‐initio calculations
Authors: Jezierski A. 
Published: January 2006

AbstractThe influence of the local environment on the electronic and magnetic properties of Co atom between Ti layers is presented., using (i) a layer model and (ii) a chain model. The effect of surface on the electronic and magnetic properties of Co‐Ti system and the magnetic properties of the chain of the cobalt atoms between titanium layers is studied by ab‐initio LMTO method. The results indicate that the cobalt between titanium layers has a small magnetic moment. In the chain of cobalt atoms between titanium layers the magnetic moment of Co is strongly reduced near the titanium layer. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electronic spectra and magnetic properties of RB6, RB12 and RB2C2 borides
Authors: Baranovskiy A. E. , Grechnev G. E. , Logosha A. V. , Svechkarev I. V. , Filippov V. B. , Shitsevalova N. Yu. , Żogał O. J. , Eriksson O. 
Published: January 2006

AbstractThe electronic structures of R B6, R B12 and R B2C2 borides are studied ab initio by using the full‐potential linear muffin‐tin orbital method. This study includes the promising materials for spin electronics with reported high temperature ferromagnetism, namely, doped divalent hexaborides CaB6, SrB6, BaB6, and the CaB2C2 compound, as well as Kondo semiconductors, SmB6 and YbB12. For CaB6 and SrB6 a semiconducting band structure has been obtained, whereas a semimetallic ground state is revealed for CaB2C2 and doped hexaborides. For YB6, LaB6, CaB2C2 and the semimetallic Ba1–x Lax B6 alloys we have performed spin‐polarized band structure calculations in an external field to evaluate the induced spin and orbital magnetic moments. These calculations indicate a feasibility of the field‐induced weak ferromagnetic phase in CaB2C2 and the La doped hexaborides. The LSDA and GGA calculations for different spin configurations of YbB12 point to a possibility of antiferromagnetic coupling between Yb3+ ions. For SmB6 and YbB12 our LSDA, GGA, and LSDA+U calculations have not revealed the hybridization gap for configurations with trivalent Sm3+ and Yb3+. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
First‐principles electronic structure and magnetic properties of M/GaAs/M (001) heterostructures with M = Fe or Co
Authors: Vlaic P. 
Published: January 2006

AbstractThe electronic structure and magnetic properties of M/GaAs/M/ multilayer systems with M = Fe or Co have been studied by means of a first‐principles Green's function technique. The results show that the magnetic behaviour of interface Fe atoms is sensitive to the terminations of the GaAs semiconducting spacer. Thus, in case of Ga terminations the iron magnetic moment increases over its bulk value while for As terminations it remains almost unchanged. At the Co/GaAs interfaces the cobalt magnetic moment is reduced compared with corresponding bulk value and it seems to be less sensitive to the terminations. The exchange coupling between M magnetic slabs is also influenced by terminations. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ab‐initio electronic structure calculations for Pr3Co13B2 and Pr5Co19B6 compounds
Authors: Szajek A. 
Published: January 2006

Abstract Recently synthesized compounds Pr3Co13B2 and Pr5Co19B6 belong to the Rm+nCo5m+3nB2n family with (m = 2, n = 1) and (m = 2, n = 3), respectively. They are studied because of their possible use as permanent magnets. The electronic structure is investigated by the tight binding version of the linear muffin‐tin orbital method in the atomic sphere approximation (TB‐LMTO ASA). The cobalt atoms occupying distinct sites have different types and number of neighbouring atoms and as a consequence the magnetic moments are different. The calculated values are compared with the results of bulk measurements. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Superfluidity in condensed excitons below 20 K
Authors: Wachter P. , Bucher B. 
Published: January 2006

AbstractIn the condensed excitonic phase of intermediate valent TmSe0.45Te0.55 the heat conductivity and the thermal diffusivity have been obtained between 300 K and 1.5 K and between ambient pressure and 17 kbar (1.7 GPa), as a first experiment of its kind. Pressure and temperature are used to navigate in three different phases of the material, the intermediate valent semiconducting phase, the condensed excitonic phase and the intermediate valent metallic phase. In the condensed excitonic phase the heat conductivity λ increases strongly below about 20 K, suggesting a superfluid phase for the lowest temperatures. In a solid under equilibrium conditions this has never been seen before. Also the thermal diffusivity a strongly increases below 20 K, giving evidence for second sound. The quotient λ/ρa represents the specific heat, which thus can be calculated, for the first time as a function of pressure and for a large temperature range. When entering the condensed excitonic phase under pressure and from high temperatures (100 K–250 K), the Dulong‐Petit value of the specific heat drops precipitously to about half its value. Also this phenomenon is unprecedented. In addition the longitudinal sound velocity has been measured under pressure and as a function of temperature. Entering the excitonic phase the sound velocity drastically increases by about a factor two. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Monte Carlo study of the spinless Falicov‐Kimball model in the perturbative regime: preliminary results
Authors: Wojtkiewicz Jacek , Musiał Grzegorz , Dębski Lech 
Published: January 2006

AbstractFinite‐temperature properties of the Falicov‐Kimball model on the square lattice have been studied in the perturbative regime, i.e. in the case: t = U ≪ 1, where t is the hopping constant and U denotes the Coulomb interaction strength. In our study, we have determined the phase diagram of the model in the second‐order of the perturbation theory, where the antiferromagnetic Ising model in the magnetic field emerges, and partially in the fourth‐order, where it constitutes the Ising model with more complicated frustrated antiferromagnetic interactions. The Monte Carlo method was employed, which proved its accuracy in recent analyses of other spin models, like Ashkin‐Teller model. To determine the type of ordering and phase boundaries, the behavior of Binder cumulants, based on the order parameters under consideration, was analyzed. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electron‐quasiparticle interaction in van Heusler alloy Cu2MnAl
Authors: Pristáš G. , Reiffers M. , Šebek J. , Šantavá E. , Courtois P. , Andersen K.H. , Hamelin B. 
Published: January 2006

AbstractElectron‐quasiparticle interaction in single crystal van Heusler ferromagnetic alloy Cu2MnAl (TC = 630 K) has been studied. The temperature dependence of the electrical resistivity ρ (T ) shows normal metallic behaviour with a shoulder at T ≈ 10 K. Point‐contact measurements were carried out at the temperature 4.2 K and in magnetic fields up to 1 T. d 2V/dI 2 (eV ) dependences in spectroscopic regime show the characteristic energies of the electron‐quasiparticle interaction in Cu2MnAl. Moreover, an asymmetric behaviour of dV/dI (eV ) has been detected. The observed behaviour is probably due to partial spin polarisation at the Fermi energy or thermopower effect. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Imaging magnetic microstructures with the use of electrons
Authors: Szmaja Witold , Balcerski Józef , Makita Ken 
Published: January 2006

AbstractThe paper presents investigations of magnetic microstructures by techniques which make use of electrons. In this context, we refer to the examples of magnetic microstructure images of cobalt monocrystals, Nd–Fe–B permanent magnet and a thin permalloy film, while the methods used are the type‐I magnetic contrast technique of scanning electron microscopy (SEM), the colloid‐SEM method and the Fresnel mode of transmission electron microscopy (TEM). It is shown that the SEM type‐I magnetic contrast and the colloid‐SEM method have quite different probing depths and consequently provide useful complementary information on the magnetic microstructure at the surface of bulk materials which exhibit an out‐of‐plane component of magnetization. It is also demonstrated that TEM is a powerful tool for investigating the magnetic microstructure of thin magnetic films. Some improvements over previous results are presented. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Structure and magnetic anisotropy evolution in Au/Co/Au sandwiches upon thermal treatment
Authors: Wawro A. , Kurant Z. , Baczewski L.T. , Pankowski P. , Pełka J.B. , Maneikis A. , Bójko A. , Zablotskii V. , Maziewski A. 
Published: January 2006

AbstractThe correlation between structural and magnetic properties of Au(111)/Co(0001)/Au(111) sandwiches with perpendicular magnetic anisotropy, grown by molecular beam epitaxy, has been studied in details. Thermal treatment in the range between room temperature and 300 °C at various stages of samples growth process as well as after its completion is applied as a factor modifying the structure of studied specimens. Annealing at 150 °C does not affect substantially either crystalline structure or perpendicular magnetic anisotropy. At 250 °C the RHEED pattern of Co layers reveals the loss of the lattice coherence with Au underlayer and the analysis of synchrotron radiation reflectometry leads to the conclusion that the continuity of Co layers is lost. Structural evolution upon thermal treatment is well correlated with changes of magnetic anisotropy studied by magnetooptical Kerr effect. After annealing at 250 °C magnetization switches from out‐of‐plane to in‐plane orientation, which is explained in terms of interfacial and magnetoelastic contributions to the sample magnetic anisotropy. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
[Ni(Prixa)2 (pyr)]n – Low‐dimensional S = 1 Heisenberg magnet
Authors: Orendáčová A. , Zorkovská A. , Park J.‐H. , Orendáč M. , Trávníček Z. , Feher A. , Meisel M. W. 
Published: January 2006

Abstract[Ni(Prixa)2(pyr)]n was previously identified as a S = 1 Heisenberg chain with intrachain interaction J /k B ≅ –2.7 K and subcritical single‐ion anisotropy D. Specific heat measurements conducted from 100 mK to 9 K in zero magnetic field revealed the presence of a λ‐like anomaly at T c = 2.2 K, which can be associated with a phase transition to the ordered state. Magnetic entropy removed above T c indicates a low‐dimensional character of the magnetic system. Observed deviations between the specific heat data and predictions from a S = 1 Heisenberg chain model with various D /J ratios can be ascribed to the presence of additional exchange coupling mediated by a set of hydrogen bonds. These interactions together with the intrachain coupling potentially form a two‐dimensional distorted triangular S = 1 Heisenberg lattice which might approximate magnetic behaviour above T c. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Magnetic properties of non‐stoichiometric U1+xNi1+yAl compounds
Authors: Zentko A. , Kováč J. , Kavečanský V. , Maťaš S. , Mihalik M. , Zentková M. , Svoboda P. 
Published: January 2006

AbstractWe have studied the magnetic and electrical properties of non‐stoichiometric U1+x Ni1+y Al compounds. It has been shown that both the positive and negative deviations from the stoichiometry lead to suppression of magnetically ordered state, to the broadening of the phase transition and to the occurrence of a region with high degree of short range magnetic ordering between 20 K and 50 K. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Structure and magnetic properties of Sm‐Ni‐Cu compounds after mechanical treatment
Authors: Szlaferek A. , Andrzejewski B. , Toliński T. , Kowalczyk A. 
Published: January 2006

AbstractWe have investigated the influence of mechanical alloying on structural changes and magnetic properties of the SmNi4Cu compound. This compound crystallizes in the hexagonal structure of CaCu5, space group P6/mmm. SmNi4Cu is ferromagnetic with the Curie temperature of 34 K and the saturation magnetic moment of 0.36 µ B at 4.2 K. The decrease of intensity and broadening of the diffraction lines have been detected after milling as a consequence of the grains' size reduction. The analysis of the as‐prepared sample using EDAX has revealed a stable composition without a presence of any additional phases and elements. The obtained results show that the magnetic properties significantly depend on the milling time. The temperature and magnetic field dependences of the magnetization exhibit a presence of antiferromagnetic‐like behavior of the milled samples. The transition temperature does not vary as a function of the milling time. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The RKKY interaction in the presence of an external magnetic field
Authors: Balcerzak T. 
Published: January 2006

AbstractThe Ruderman‐Kittel‐Kasuya‐Yosida (RKKY) interaction has been extended to the case when an external magnetic field is taken into account. It has been shown that the RKKY Hamiltonian should contain the Zeeman‐like term in which the effective gyromagnetic factor occurs. This effective gyromagnetic factor contains a correction term which is linearly dependent on the contact potential between the localized spins and conduction electrons. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Influence of the short range order (SRO) on electrical resistivity of magnetic alloys
Authors: Lipowczan M. , Borgieł W. , Stysiak D. 
Published: January 2006

AbstractThe model of the magnetic binary alloy which contains interacting itinerant electrons and localized spins was considered. The interaction between both kinds of electrons was assumed in the simple local exchange form. The complicated many body problem was reduced to the one particle one with the help of Coherent Potential Approximation (CPA ). Itinerant electron selfenergy was calculated using standard Green's function technique with taking into account short range order (SRO ) within the localized spin system. Electron's states were strongly affected by the correlations (SRO , when T > T C) within localized moments system. The DC electrical conductivity σ in the paramagnetic region expressed by Kubo‐Grennwood alloy formula was calculated. The resistivity ρ = 1/σ and its derivative over the temperature have the structure near T C, which depends on the number of the electrons in the band and the interaction strength between two subsystems. The quantities ρ , $ { {\partial \rho} \over {\partial T} }$ were not constant vs. temperature as it is in the simple models. The influence of the important model parameters on the DC conductivity was also discussed. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Deviation from Matthiessen rule in magnetic disordered alloys–theoretical investigation
Authors: Stysiak D. , Borgieł W. , Deniszczyk J. 
Published: January 2006

AbstractThe model of the magnetic disordered alloys, including the itinerant electrons, localized spins and phonons, was elaborated in details in the paramagnetic region with the use of the Coherent Potential Approximation (CPA) approach. The expression for the DC electrical conductivity was taken from the Kubo‐Greenwood formula for an alloys. The separate (residual, phonon and magnetic) contributions to the resistivity for the temperatures above Curie transition temperature, different sets of the model parameters were calculated. The linear temperature dependence of the phonon contribution to the resistivity was reproduced except from the anomalous behavior observed for the parameters sets for which the Fermi level locates near the band's edges. For the same parameters sets our calculations showed the largest percentage deviations from the Matthiessen's rule. Our model calculations confirmed the Matthiessen's rule generalized to the case of the three, residual, phonon and magnetic contributions to the resistivity of the magnetic disordered alloys with the partially filled band when the Fermi level locates far from the bands edges. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Quasi‐one‐dimensional S = 1/2 magnet Pb[Cu(SO4)(OH)2]: frustration due to competing in‐chain exchange
Authors: Baran M. , Jedrzejczak A. , Szymczak H. , Maltsev V. , Kamieniarz G. , Szukowski G. , Loison C. , Ormeci A. , Drechsler S.‐L. , Rosner H. 
Published: January 2006

AbstractZero‐field susceptibility and specific heat of Pb[Cu(SO4)(OH)2] (linarite) single crystal were measured. In order to verify that linarite is a quasi‐one‐dimensional system with competing nearest‐neighbour and next‐nearest‐neighbour in‐chain exchange interaction (J1 ≈ –30 K, J2 ≈ 15 K), theoretical results based on electronic structure calculations within the LDA and a phenomenological modelling using the finite‐temperature transfer‐matrix method are taken into account. The possibility of various ground states is discussed in terms of the screened onsite repulsion U s: commensurate Neel or spin‐Peierls phases versus incommensurate spiral states with acute or obtuse pitch angles. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the performance of turbo equalization for precoded ISI channels
Authors: Ghrayeb Ali , El‐Tarhuni Mohamed 
Published: January 2006

AbstractIn this paper, we present a semi‐analytical approach for analyzing the serial concatenation (SCC) of a high rate convolutional code and a precoded intersymbol interference (ISI) channel. The significance of the proposed approach is that it can be used to identify, for a given outer high rate code and fixed ISI channel, the precoder that results in the lowest error rate floor. In estimating the bit error performance in the floor region, we use analytical techniques developed for trellis codes to compute the overall system minimum squared Euclidean distance, and then use a semi‐analytical approach to find the corresponding multiplicity. We also demonstrate via simulations that the proposed technique may be extended to fading ISI channels with favorable results. We give examples that support our analysis. Copyright © 2006 John Wiley & Sons, Ltd.
Probabilistic Subset Conjunction
Authors: Kohli Rajeev , Jedidi Kamel 
Published: January 2006

The authors introduce subset conjunction as a classification rule by which an acceptable alternative must satisfy some minimum number of criteria. The rule subsumes conjunctive and disjunctive decision strategies as special cases.Subset conjunction can be represented in a binary-response model, for example, in a logistic regression, using only main effects or only interaction effects. This results in a confounding of the main and interaction effects when there is little or no response error. With greater response error, a logistic regression, even if it gives a good fit to data, can produce parameter estimates that do not reflect the underlying decision process. The authors propose a model in which the binary classification of alternatives into acceptable/unacceptable categories is based on a probabilistic implementation of a subset-conjunctive process. The satisfaction of decision criteria biases the odds toward one outcome or the other. The authors then describe a two-stage choice model in which a (possibly large) set of alternatives is first reduced using a subset-conjunctive rule, after which an alternative is selected from this reduced set of items. They describe methods for estimating the unobserved consideration probabilities from classification and choice data, and illustrate the use of the models for cancer diagnosis and consumer choice. They report the results of simulations investigating estimation accuracy, incidence of local optima, and model fit.
Clinical trials update from the American Heart Association: REPAIR‐AMI, ASTAMI, JELIS, MEGA, REVIVE‐II, SURVIVE, and PROACTIVE
Authors: Cleland John G.F. , Freemantle Nick , Coletta Alison P. , Clark Andrew L. 
Published: December 2005

AbstractThis article provides information and a commentary on trials presented at the American Heart Association meeting held in November 2005, relevant to the pathophysiology, prevention and treatment of heart failure. All reports should be considered as preliminary data, as analyses may change in the final publication. In REPAIR‐AMI an improvement in ejection fraction was observed in post‐MI patients following infusion of bone marrow stem cells. However, the ASTAMI study showed no benefit of stem cell implantation in a similar patient cohort. The JELIS study reported a reduction in major coronary events in patients receiving statins plus fish oil compared to statins alone. MEGA showed that low dose statins in a low risk population reduce the incidence of major cardiovascular events. Two studies of levosimendan in acute heart failure gave conflicting results, in the REVIVE‐II study levosimendan was reported to have a superior effect on the composite primary outcome compared to placebo, however, in SURVIVE despite a trend to early benefit with levosimendan, there was no difference in effect on long‐term outcome versus dobutamine. The PROACTIVE study showed encouraging results for the use of pioglitazone in post‐myocardial infarction patients with concomitant type 2 diabetes.