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The paper presents resistivity and magnetization measurements on nearly stoichiometric Fe3Si films epitaxially grown on GaAs substrates by electron-beam evaporation in an ultrahigh vacuum chamber. In the low-temperature resistivity a T3 term was found in all samples. A term like that is known to describe the anomalous single-magnon scattering processes in half-metallic materials and confirms so for our samples the hypothesis of half-metallic ferromagnetism in Fe3Si. The films show an anisotropic magnetoresistance in low magnetic fields. In high magnetic fields a negative longitudinal and transverse magnetoresistance (MR) has been observed linearly depending on the field strength. In the vicinity of 200 K the MR shows maximum absolute values up to 1.5% at magnetic fields of about 8 T. From the magnetization measurements a magnetic moment of 0.86μB/atom was obtained, which is close to that of bulk Fe3Si. [ABSTRACT FROM AUTHOR]

This paper concerns with giant magnetoresistance (MR) effects in organic spin valves, which are realized as layered (La,Sr)MnO3 (LSMO)-based junctions with tris-(8, hydroxyquinoline) aluminum (Alq3)-spacer and ferromagnetic top layers. The experimental work was focused on the understanding of the transport behavior in this type of magnetic switching elements. The device preparation was carried out in an ultrahigh vacuum chamber equipped with a mask changer by evaporation and sputtering on SrTiO3 substrates with LSMO stripes deposited by pulsed laser technique. The field and temperature dependences of the MR of the prepared elements are studied. Spin-valve effects at 4.2 K have been observed in a broad resistance interval from 50 Ω to MΩ range, however, without systematic dependence on spacer layer thickness and device area. In some samples, the MR changes sign as a function of the bias voltage. The observed similarity in the bias voltages dependences of the MR in comparison with conventional magnetic tunnel junctions with oxide barriers suggests a description of the found effects within the classical tunneling concept. This assumption is also confirmed by a similar switching behavior observed on ferromagnetically contacted carbon nanotube devices. The proposed model implies the realization of the transport via local Co chains embedded in the Alq3 layer and spin dependent tunneling over barriers at the interface Co grains/Alq3/LSMO. The existence of conducting Co chains within the organics is supported by transmission electron microscopic/electron energy loss spectroscopic studies on cross-sectional samples from analogous layer stacks. [ABSTRACT FROM AUTHOR]

Canine atopic dermatitis ( CAD) is an inflammatory skin disorder that is characterized by pruritus and associated cutaneous changes. Treatment interventions include allergen avoidance, allergen-specific immunotherapy as well as a symptomatic therapy using glucocorticoids and antihistamines. In addition, a dietary intervention using polyunsaturated fatty acids ( PUFA) has been shown to alleviate symptoms in some dogs. Although the beneficial effects of PUFA in the treatment of CAD have been known for several years, their mode of action remains unclear. This review discusses the evidential basis of the therapeutic use of dietary PUFA in the treatment of CAD. Particular emphasis will be placed on the role of cutaneous mast cells. In addition, recent evidence from in vitro studies on the regulation of mast cell exocytosis will be used to build a mechanistic model of the active principle of PUFA. It is proposed that dietary PUFA are integrated into mast cell membranes resulting in a reorganization of membrane microdomains. This may then be accompanied by functional changes of membrane-associated proteins such as the phospholipases D ( PLD), enzymes having an important impact on mast cell exocytosis processes. [ABSTRACT FROM AUTHOR]

Abstract: Thin films of the Heusler alloy Co2Cr0.6Fe0.4Al have been prepared by means of magnetron sputtering under varying conditions (sputter power, sputter pressure and substrate temperature). All the films are polycrystalline with the cubic B2 structure. The extent of Co–Al antisite defects, lattice constants, internal stress states are influenced by the sputter conditions which is related to differences in the saturation magnetization. The magnetic moment can be increased by additional annealing up to an optimum temperature of 400 °C, but does not reach the theoretically predicted value. Above 600 °C the metastable B2 phase transforms into either (ε)-Co/Cr or (α)-Co/Cr. [Copyright &y& Elsevier]

In modern materials science the characterisation of nanostructures is becoming increasingly important. For measurement of the quality of nanoscale multilayer arrangement with high spatial resolution a method is described that is based on the broadening of the spots in the Fourier transformation of transmission electron microscopic images of multilayer cross-sections. Using this method on Si/Ge superlattices with periodic lengths between 4 and 12 nm it could be quantitatively shown that the layer perfection decreases with increasing periodic length. The transition from elastic to plastic deformation between the Si and Ge layers at larger periodic lengths can be the reason for this behaviour. [ABSTRACT FROM AUTHOR]

The formation process of the skutterudite phase in both binary and iron-doped films prepared from non-stoichiometric Co20Sb80 targets was investigated by means of DTA, XRD, and transport measurement techniques. The results of the measurements allowed us to determine the influence of iron incorporation on the thermal behavior of the Co–Sb-based skutterudite phase. The films prepared by a DC magnetron technique on substrates kept at room temperature were amorphous in the as-deposited state. The crystallization of the skutterudite structure was found to occur exothermally on heating at temperatures near 145 and 153 °C for iron-containing and binary films, respectively. Antimony as a secondary phase was established from XRD measurements after the crystalline structure formation. The transport properties, resistivity and thermopower, of the as-grown films are highly sensitive to the phase formation process. The temperature behavior of these properties during the first measuring cycle is in good agreement with DTA and XRD data showing that these techniques can be valuable instruments to investigate the phase formation. The transport properties as well as the lattice parameters of as-grown films exhibit a permanent modification during thermocycling. The films are sensitive to oxygen at elevated temperatures. Iron incorporation lowers the thermal stability of the films in air. The mechanisms of formation and stability of the skutterudite phase are discussed. [Copyright &y& Elsevier]

The phase formation, the resistivity and the thermopower of amorphous Cr0.15Si0.85, and nanocrystalline CrSi2-Si thin film composites have been studied. The films were produced by a magnetron sputtering of a composite target onto unheated substrates with subsequent crystallization of the film at high temperatures. As the film composite develops under the heat treatment from the initial amorphous state into the final polycrystalline material, two percolation thresholds were found. At first, the percolating cluster of nanocrystalline CrSi2 is formed. However, this cluster is destroyed with further annealing due to crystallization and redistribution of Si. The composite films which are close to this insulating threshold reveal a strongly nonlinear conductivity. The conductivity increases with the current by two orders of magnitude. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We have studied the effect of the dipolar magnetic coupling (also known as Néel coupling or "orange-peel" coupling) in tunneling magnetoresistive (TMR) elements. With an in situ scanning tunneling microscope we directly accessed the roughness of the films and found a close correspondence between the values for the coupling fields determined by the magneto-optical Kerr effect and the ones computed on the basis of the measured morphology parameters. We confirm an increase of the dipole coupling between the magnetic layers with decreasing barrier thickness as predicted by the model. Deviations from the theoretical predictions are observed for the case of thinner soft magnetic layers, which can be explained by reduced magnetization in very thin films. We demonstrate the importance of dipolar coupling for understanding the magnetic behavior of TMR elements by comparing TMR curves for optimized and nonoptimized structures. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Nonequilibrium photoresponse behavior has been investigated for YBa[sub 2]Cu[sub 3]O[sub 7-x] (YBCO) granular films to 8 mm microwave radiation under various bias currents and magnetic fields. The measurements reveal that the nonequilibrium photoresponse mode occurs only in the tail region of the resistance transition curve R(T) from the normal to the superconducting state, where transportation behavior of the granular superconducting film is found to be characterized by the Kosterlitz-Thouless (KT) phase transition model. Based on the KT model, the photoresponse mechanism has been interpreted in terms of the depinning process of the unbinding vortices, which are generated from the decoupling process of the vortex-antivortex pairs by current, and are held at the intrinsic pinning sites of the granular high-T[sub c] superconducting films at low temperature. Under the co-action of the bias current and the incident microwave photons, these unbinding vortices will be driven out of the pinning center, creating viscous motion in the Josephson junction array system. An analytical result of the unbinding vortices density n(T,I) induced by applied current has been worked out based on the model of two-dimensional Josephson junction arrays that is employed as a model system for the YBCO granular films. The distribution of the n(T,I) is found to be analogous to that of the photoresponse measured in the temperature region of 2/3T[sub KT]

Magnetotransport of individual rolled-up Fe3Si nanomembranes is investigated in a broad temperature range from 4.2 K up to 300 K in pulsed magnetic fields up to 55 T. The observed magnetoresistance (MR) has the following pronounced features: (i) MR is negative in the investigated intervals of temperature and magnetic field; (ii) its magnitude increases linearly with the magnetic field in a low-field region and reveals a gradual trend to saturation when the magnetic field increases; (iii) the MR effect becomes more pronounced with increasing temperature. These dependences of MR on the magnetic field and temperature are in line with predictions of the spin-disorder model of the spin-flip s–d interaction assisted with creation or annihilation of magnons, which is expected above a certain critical temperature. Comparison of the MR features in rolled-up and planar samples reveals a substantial increase of the critical temperature in the rolled-up tube, which is attributed to a new geometry and internal strain arising in the rolled-up nanomembranes, influencing the electronic and magnetic properties of the material. [ABSTRACT FROM AUTHOR]

Abstract: We study thermoelectric properties, crystallization kinetics and stability of amorphous and nanocrystalline state in Cr–Si and Mn–Si composite films. The as-deposited amorphous films are transformed by annealing with in situ thermopower and electrical resistivity measurements into nanocrystalline state with continuous monitoring their state. Depending on the initial film composition, the films are transformed during the annealing into single phase or multi-phase nanocrystalline composites. A clear correlation between structural state and thermoelectric properties of the composites is found. Particularly, the thermoelectric power factor of nanocrystalline films is enhanced in comparison to the power factor of polycrystalline films, obtained by high-temperature re-crystallization of the nanocrystalline films, due to strong energy dependent charge carrier scattering. [Copyright &y& Elsevier]

The paper describes an operating principle for the electrical measurement of mechanical strain states. This principle gives up the idea of measuring the strain-induced resistance change of single wire conductors and passes on to determining the strain-induced deformation of the electrical field in area conductors. The basic operating principle, sensitivity considerations and the design of a functional prototype are described. Several experimental results in the application fields of transducer technology and strain analysis demonstrate the high capability of this method. The compact design allows simplification of the production process. An interesting additional advantage is the use of science-based temperature compensation, i.e. the conventional, difficult process of foil treatment to attain temperature self-compensation and suitability of each strain gauge for different component materials is superseded. [ABSTRACT FROM AUTHOR]

Abstract: Bismuth Hall probes with an active area in the µm2 and sub-µm2 (down to (100×100)nm2) range have been fabricated on SiO2/Si substrates. The structural and electrical properties of Bi films with a thickness of 20–90nm were investigated. Critical values of the structural characteristics, at which the film resistivity dependences undergo a distinct change were found. The transition to low resistivity, good crystallinity and high degree of texturing were observed at a film thickness of 65nm. The potential use of the Bi Hall sensor as a swell sensor for monitoring the swelling of stimuli-sensitive hydrogels was demonstrated. [Copyright &y& Elsevier]

The goal of the three-tiered response-to-intervention (RtI) model is to catch students who are at risk early and to provide an appropriate level of intervention. Although RtI has been recommended for academic and social behavior, to date there has been little discussion about the differences associated with implementing RtI across these domains. The purpose of this article is to compare similarities and differences in RtI for academic and social behavior. In addition, some of the primary challenges associated with the implementation of RtI for social behavior are discussed. Examples of how RtI has been implemented with social behavior are provided along with recommendations for future research. [ABSTRACT FROM AUTHOR]

Abstract: AlO x tunnel barriers prepared by oxidizing ultra-thin Al films of various thickness by means of a Rf wave resonance plasma beam source were investigated to understand the influence of the plasma oxidation conditions on the junction resistance R j, the magnetoresistance ratio (MR) and the switching characteristics of exchange-biased magnetic tunnel junctions (MTJs) with NiMn pinning layer. The junction properties were characterized as a function of oxidation time, plasma power and distance between plasma source and sample. The MR of the as-deposited junction was about 15%. The highest exchange bias fields (17mT) and pinned layer coercivities (23mT) can be achieved with extended annealing at low temperatures or with a rapid annealing at , respectively. Short-time annealing (1min) at intermediate temperatures (350°C) and field cooling at 1T leads to the highest MR effect of 35% at room temperature and 55% at 4.2K. [Copyright &y& Elsevier]

We investigated temperature and magnetic field dependences of the magnetization of β-FeSi2 single crystals in the temperature range of 5–300 K in magnetic fields up to 15 kOe. The temperature dependence of the magnetic susceptibility of the Cr- and Ni-doped sample can be explained by temperature-dependent contributions due to paramagnetic centres and due to the carriers excited thermally in the extrinsic conductivity region. The values of the paramagnetic Curie temperature as well as activation energy of the donor and acceptor levels are estimated. [Copyright &y& Elsevier]

Examines the electrical conductivity and thermopower of Cr[sub x]Si[sub 1-x] thin films on annealing up to 950 degrees Centigrade. Stages of the crystallization of the amorphous as-deposited films; Reflection of transport behavior; Percolation threshold; Thermoelectric figure of merit.

The article gives a report on resistivity measurements on Mn-doped p-type FeSi2 single crystals and analyzes the data within the framework of different hopping conductivity models. Both the Mott [N. Mott and E. A. Davies, Electron Processes in Non-Crystalline Materials (Clarendon, Oxford, 1979)] and the Shklovskii–Efros [B. I. Shklovskii and A. L. Efros, Electronic Properties o0066 Doped Semiconductors (Springer, Berlin, 1984)] regimes of the variable-range hopping (VRH) conductivity are observed. It is shown that the temperature dependence of the resistivity of Mn-doped β-FeSi2 crystals, which follows a VRH conduction mechanism, can be expressed by a scaling expression of the form ln(ρ/ρ0)=Af(T/Tx). The characteristic and transition temperatures, as well as the complete set of parameters describing the properties of the localized holes (the localization radius, the dielectric permittivity, the width of the Coulomb gap Δ, and the values of the density of states at the Fermi level) are determined. The data above indicate existence of a rigid gap δ in the spectrum of the DOS in addition to Δ and point out to the polaronic nature of the charge carriers in the investigated compound. [ABSTRACT FROM AUTHOR]

Resistivity ρ(T) of Co-doped n-type FeSi2 single crystals is investigated in the temperature range of 4.2 K<=T<=300 K, and analyzed within the framework of different hopping conductivity models according to the relation ρ(T)=ApT1/p exp[(T0/T)1/p]. Both the Mott regime with p=4 [Metal-Insulator Transitions (Taylor & Francis, London, 1990)] and the Shklovskii-Efros regime with p=2 [Electronic Properties of Doped Semiconductors (Springer, Berlin, 1984)] within the variable-range hopping conductivity are observed, as well as a crossover of them, where the temperature dependence of the resistivity follows a scaling law ln(ρ/ρ0)=Af(T/Tx). The values of the characteristic (T0) and transition temperatures and the width of the soft Coulomb gap in the spectrum of the density of the localized states (DOS) Δ≈0.5–1.6 meV are determined. In addition to Δ, our results suggest existence of the rigid gap in the spectrum of the DOS with the value up to δ≈0.35 meV. The rigid gap is consistent with a polaronic nature of the charge carriers in the investigated compound. [ABSTRACT FROM AUTHOR]

The resistivity of Cr-doped p-type β-FeSi2 single crystals has been investigated in the temperature interval of T=4.2–300 K. The data are analyzed within the framework of the variable-range hopping (VRH) mechanism for both the Mott and the Shklovskii–Efros regimes. With decreasing temperature a crossover between the Mott and the Shklovskii–Efros VRH conductivity regimes is observed. It is shown that the temperature dependence of the resistivity, ρ (T), of Cr-doped β-FeSi2 crystals, that follows a VRH conductivity mechanism, obeys a scaling law ln(ρ/ρ0)=Af(T/Tx). The values of the characteristic (T0) and the transition temperatures (Tv), as well as the width of the soft Coulomb gap Δ in the spectrum of the density of the localized states (DOS) are determined. The observed values of the VRH transition and characteristic temperatures indicate the existence of a rigid gap δ in the spectrum of the DOS in addition to Δ. This points to the polaronic nature of the charge carriers in the investigated compound. [ABSTRACT FROM AUTHOR]

The magnetization, magnetic susceptibility, and resistivity for Cr-doped p type and Ni-doped n type FeSi2 single crystals have been investigated. The values of the paramagnetic Curie temperature as well as the activation energy of the donor levels are estimated. It is also shown that the magnetization behavior of Cr- and Ni-doped samples significantly depends on the cooling regime: cooling in zero external field and cooling with external field. This resembles the properties of spin glasses and indicates the presence of coupling between magnetic centers. The results of resistivity measurements are analyzed within the framework of different hopping conductivity models. Both the Mott and the Shklovskii-Efros regime of the variable-range hopping is observed. The values of the characteristic and transition temperatures and the width of the Coulomb quasigap are determined. [ABSTRACT FROM AUTHOR]

The results of the studies of structural, electrical, and thermoelectric properties of binary skutterudite CoSb[SUB3] thin films are presented. The n-type films were prepared without intentional doping on oxidized Si(100) and ceramic Al[SUB2]O[SUB3] substrates using magnetron dc sputtering technique. The electron probe microanalysis has shown that the composition of the films is strongly affected by the preparation conditions. The x-ray measurements indicate the films to be amorphous if they are deposited on substrates kept at room temperature. On the basis of the differential thermal and x-ray analyses data, the temperature of the transition from the amorphous to crystalline state was established to be (153 ± 1 ) °C. The films are polycrystalline with a preferential orientation of the growth along the (310) direction of the CoSb[SUB3] lattice if grown on substrates kept at 200 °C. The electrical resistivity ρ(T) and the Seebeck coefficient S(T) were measured from room temperature up to about 700 K. The value of ρ(T) decreases with increasing temperature. The maximum absolute value of the Seebeck coefficient is found to be -250 μV/K at around 550 K for both substrates. This is the highest value of the Seebeck coefficient for CoSb[SUB3] films deposited by dc magnetron sputtering. The predominant mechanisms of the scattering in CoSb[SUB3] are discussed on the basis of the temperature dependence of the Hall mobility. The carrier concentration n(T) is found to be around 1.2 × 10[SUP19] cm[SUP-3] at 300 K and is almost constant over the temperature range of (250-400) K. The room temperature measurements of the thermal conductivity carried out by the 3ω method have shown a value of about 3 W/(m K), which is significantly lower than that reported for bulk material. [ABSTRACT FROM AUTHOR]

We investigated the temperature and magnetic field dependence of the Hall effect, the magnetization and the resistivity of Mn-doped β-FeSi[SUB2] single crystals in the temperature range of 4-300 K in magnetic fields up to 5 T. A negative magnetoresistance as well as strong nonlinear magnetic field dependence of the Hall resistivity and magnetization were observed. The anomalous contribution to the Hall resistivity is found to be important. We also observed the value of the anomalous Hall coefficient to increase with decreasing temperature as the square of the resistivity. It was shown that the magnetization of Mn-doped samples cooled in zero-external field and in a field are different. This resembles the properties of spin glasses. The dominant scattering mechanisms are determined by analyzing the Hall mobility data. The value of the valence band deformation potential is estimated. A particularly important role is played by the anomalous Hall effect which is the microscopic mechanism involving the spin dependent scattering on Mn ions and spin-orbit coupling in the Mn-doped β-FeSi[SUB2] single crystals. [ABSTRACT FROM AUTHOR]

Thin semiconducting thermoelectric films with narrow energy band gaps are considered to be very promising for future microdevice applications (sensors and generators). The polycrystalline BiSbTe alloys (V-VI semiconductors) are examples. In this report, the detailed temperature dependence of electrical resistivity [ρ(T)], n- and p-type carrier concentration [n(T) and p(T)], and Hall mobility [μ(T)] of n-type Bi[sub 2]Te[sub 3], p-type Sb[sub 2]Te[sub 3], and p-type (Bi[sub 1-x]Sb[sub x])[sub 2]Te[sub 3] (x=0.73 and 0.77) alloy films prepared by metalorganic chemical vapor deposition are presented in the range of 100-500 K. From the room temperature measurement of the Seebeck coefficient (α), the values of α for Bi[sub 2]Te[sub 3], Sb[sub 2]Te[sub 3], and (Bi[sub 1-x]Sb[sub x])[sub 2]Te[sub 3] with x=0.73 and 0.77 are found to be -220, +110, +240, and +210 μV/K, respectively, which are optimal in these types of film materials. The carrier concentration of these films at 300 K is found to be around (10[sup 19]-10[sup 20]) cm[sup -3]. The ρ(T) data show an exponential increase with increasing temperature irrespective of the carrier types. For the temperature dependence of the Hall mobility, the lattice contribution is found to be predominant for all the films. Also, we have fabricated a simple micromodule Peltier device (MMP) using the n-type Bi[sub 2]Te[sub 3] and the p-type (Bi[sub 1-x]Sb[sub x])[sub 2]Te[sub 3] (x=0.77) films where a maximum cooling of 2.6 °C was obtained with a low input current of 2.5 mA. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The superconducting characteristics of the spin-valve Co2Cr1 - xFexAly/Cu/Ni/Cu/Pb heterostructures are studied. It is found that the difference in the plots characterizing superconducting transitions at the parallel and perpendicular orientations of magnetizations in the ferromagnetic Heusler alloy layer (HA = Co2Cr1 - xFexAly) with a high degree of spin polarization and in the nickel (Ni) layer can be as large as 0.5 K. For all samples, the dependence of Tc on the angle between the magnetization directions of the ferromagnetic layers exhibits a deep minimum near the orthogonal orientation. This minimum results from the long-range triplet components of the superconducting condensate in a ferromagnetic material. At the perpendicular orientation of the magnetizations, the Heusler alloy layer with the high degree of spin polarization absorbs the spin-polarized Cooper pairs from the spacing between the Heusler alloy and Ni layers. [ABSTRACT FROM AUTHOR]

The thermoelectric properties and crystallization kinetics of Cr0.26Si0.74 thin films with the thicknesses 11, 14, 21, 31, 56, 74, and 115 nm are studied. The films are produced by magnetron-assisted sputtering onto a cold substrate and, in the initial state, are amorphous in structure. During thermal annealing, the amorphous mixture transforms into a two-phase nanocrystalline composite consisting of chromium disilicide and silicon. In-situ measurements of the thermoelectric properties of the films during annealing show that the temperature of the onset of crystallization decreases, as the film thickness is decreased, whereas the crystallization rate increases. The thermopower of the nanocrystalline films decreases, as the film thickness is increased, and the thermoelectric-power factor reaches its maximum in films with a thickness of 31 nm. [ABSTRACT FROM AUTHOR]

We have studied the superconducting spin-valve effect in a F1/F2/S heterostructure containing a Heusler alloy layer standing for an F2 layer. The Heusler alloy layer was grown at the substrate temperature T sub = 300 K . According to our previous data in such preparation conditions this layer is a weak ferromagnet. For the samples with the Heusler layer thickness d Heusler = 1 and 4 nm the full switching between the normal and superconducting states is realized with the dominant aid of the long-range triplet component of the superconducting pair condensate which occurs at the perpendicular mutual orientation of magnetizations. [ABSTRACT FROM AUTHOR]

Using synchrotron x-ray diffraction and reflectivity, we studied the transition from the paramagnetic NiMn phase to the chemically ordered, antiferromagnetic L10 phase of NiMn/Fe19Ni81 thin films deposited on a Si/SiO2 substrate as a function of the annealing temperature. The transformation to a dominating L10-ordered NiMn film takes place between 300 and 400 °C irrespective of the irradiation. This is also consistent with magnetization reversal measurements of the corresponding permalloy layers. The benefit of the ion irradiation is a reduction of the mosaicity for both the NiMn and the permalloy film, and a smoothening of internal interfaces. [ABSTRACT FROM AUTHOR]

We have studied the proximity effect in thin-film heterostructures composed of the superconducting Pb (S) and of the ferromagnetic Heusler alloy Co2Cr1-xFexAl(F) with different degrees of the spin polarization of the conduction band. A thin Cu interlayer is inserted in between the S and F layers to ensure the stability of the S/F interface. The analysis of the dependences of the superconducting transition temperatures in such heterostructures on the thickness of the Pb or of the Heusler alloy using the theory by Fominov et al. [Ya. V. Fominov, N. M. Chtchelkatchev, and A. A. Golubov, Phys. Rev. B 66, 014507 (2002)] shows that, with increasing the exchange splitting of the conduction band of a ferromagnet and, respectively, of the degree of the spin polarization, the probability of transmission of the superconducting Cooper pairs through the S/F interface decreases. We conclude that the spin imbalance plays a key role in the processes taking place at the interface between a superconductor and a ferromagnet with spin-polarized conduction electrons. [ABSTRACT FROM AUTHOR]

We report on thermoelectric properties of nanocrystalline Cr 1−x Si x composite films. As-deposited amorphous films were transformed into a nanocrystalline state with the average grain size of 10–20 nm by annealing during in-situ thermopower and electrical resistivity measurements. Partially crystallized films, i.e. films consisting of crystalline grains dispersed in an amorphous matrix, are a new type of a heterogeneous material where the nanocrystalline phase plays the role of scattering centers giving rise to a large contribution to the thermopower. We show that the thermopower enhancement is related to the energy dependent scattering (energy filtering) of the charge carriers on the nanograin interfaces. [ABSTRACT FROM AUTHOR]

We report magnetic and superconducting properties of the modified spin-valve system CoOx/Fe1/Cu/Fe2/Cu/Pb. Introduction of a Cu interlayer between Fe2 and Pb layers prevents material interdiffusion process, increases the Fe2/Pb interface transparency, stabilizes and enhances properties of the system. This allowed us to perform a comprehensive study of such heterostructures and to present theoretical description of the superconducting spin-valve effect and of the manifestation of the long-range triplet component of the superconducting condensate. [ABSTRACT FROM AUTHOR]

A review of our recent results on the spin valve effect is presented. We have used a theoretically proposed spin switch design F1/F2/S comprising a ferromagnetic bilayer (F1/F2) as a ferromagnetic component, and an ordinary superconductor (S) as the second interface component. Based on it we have prepared and studied in detail a set of multilayers CoO x /Fe1/Cu/Fe2/S (S=In or Pb). In these heterostructures we have realized for the first time a full spin switch effect for the superconducting current, have observed its sign-changing oscillating behavior as a function of the Fe2-layer thickness and finally have obtained direct evidence for the long-range triplet superconductivity arising due to noncollinearity of the magnetizations of the Fe1 and Fe2 layers. [ABSTRACT FROM AUTHOR]

The spin valve effect for the superconducting current based on the superconductor/ferromagnet proximity effect has been studied for a CoO/Fe1/Cu/Fe2/Cu/Pb multilayer. The magnitude of the effect Δ T = T − T, where T and T are the superconducting transition temperatures for the parallel (P) and antiparallel (AP) orientation of magnetizations, respectively, has been measured for different thicknesses of the Fe1 layer d. The obtained dependence of the effect on d reveals that Δ T can be increased in comparison with the case of a half-infinite Fe1 layer considered by the previous theory. A maximum of the spin valve effect occurs at d ∼ d. At the optimal value of d almost full switching from the normal to the superconducting state when changing the mutual orientation of magnetizations of the iron layers Fe1 and Fe2 from P to AP is demonstrated. [ABSTRACT FROM AUTHOR]

Quantum coherent transport of surface states in a mesoscopic nanowire of the three-dimensional topological insulator Bi2Se3 is studied in the weak-disorder limit. At very low temperatures, many harmonics are evidenced in the Fourier transform of Aharonov-Bohm oscillations, revealing the long phase coherence length of spin-chiral Dirac fermions. Remarkably, from their exponential temperature dependence, we infer an unusual \/T power law for the phase coherence length Lφ(T). This decoherence is typical for quasiballistic fermions weakly coupled to their environment. [ABSTRACT FROM AUTHOR]

We have studied the dependence of the superconducting (SC) transition temperature on the mutual orientation of magnetizations of Fel and Fe2 layers in the spin valve system CoOx/Fe1/Cu/Fe2/Pb. We find that this dependence is nonmonotonic when passing from the parallel to the antiparallel case and reveals a distinct minimum near the orthogonal configuration. The analysis of the data in the framework of the SC triplet spin valve theory gives direct evidence for the long-range triplet superconductivity arising due to noncollinearity of the two magnetizations. [ABSTRACT FROM AUTHOR]

Abstract: Bismuth thin films were grown on oxidized Si substrates by electron beam evaporation. The films showed clear tendency to form hillocks inducing large surface roughness. The evolution of hillocks with film thickness and deposition rate was studied. In order to improve the surface quality of the Bi films a nanoscale mechanical polishing was performed. Upon polishing, hillocks-free Bi thin films were obtained without influencing the crystalline structure and the resistivity of the films. The achieved film surface quality allows to prepare high quality Bi Hall probes with an active area down to the nm2 range promising for advanced device performance. [Copyright &y& Elsevier]

This paper describes the methods and techniques used to verify the POWER7® microprocessor and systems. A simple linear extension of the methodology used for POWER4®, POWER5®, and POWER6® was not possible given the aggressive design point and schedule of the POWER7 project. In addition to the sheer complexity of verifying an eight-core processor chip with scalability to 32 sockets, central challenges came from the four-way simultaneous multithreading processor core, a modular implementation structure with heavy use of asynchronous interfaces, aggressive memory subsystem design with numerous new reliability, availability, and serviceability (RAS) advances, and new power management and RAS mechanisms across the chip and the system. Key aspects of the successful verification project include a systematic application of IBM's random-constrained unit verification, unprecedented use of formal verification, thread-scaling support in core verification, and a consistent use of functional coverage across all verification disciplines. Functional coverage instrumentation, which is combined with the use of the newest IBM hardware simulation accelerator platform, enabled coverage-driven development of postsilicon exercisers in preparation of bring-up, a foundation for the desired systematic linkage of presilicon and postsilicon verification. RAS and power management verification also required new approaches, extending these disciplines to span all the way from the unit level to the end-to-end scenarios using the hardware accelerators. [ABSTRACT FROM AUTHOR]

The ability to precisely control the thermal conductivity (κ) of a material is fundamental in the development of on-chip heat management or energy conversion applications. Nanostructuring permits a marked reduction of κ of single-crystalline materials, as recently demonstrated for silicon nanowires. However, silicon-based nanostructured materials with extremely low κ are not limited to nanowires. By engineering a set of individual phonon-scattering nanodot barriers we have accurately tailored the thermal conductivity of a single-crystalline SiGe material in spatially defined regions as short as ∼15 nm. Single-barrier thermal resistances between 2 and 4×10−9 m2 K W−1 were attained, resulting in a room-temperature κ down to about 0.9 W m−1 K−1, in multilayered structures with as little as five barriers. Such low thermal conductivity is compatible with a totally diffuse mismatch model for the barriers, and it is well below the amorphous limit. The results are in agreement with atomistic Green’s function simulations. [ABSTRACT FROM AUTHOR]

The error detection and correction capability of the IBM POWER6™ processor enables high tolerance to single-event upsets. The soft-error resilience was tested with proton beam- and neutron beam-induced fault injection. Additionally, statistical fault injection was performed on a hardware-emulated POWER6 processor simulation model. The error resiliency is described in terms of the proportion of latch upset events that result in vanished errors, corrected errors, checkstops, and incorrect architected states. [ABSTRACT FROM AUTHOR]

Abstract: An innovative staged chemical vapor deposition (SCVD) approach providing flexible control over the feedstock type during single wall carbon nanotube (SWNTs) growth is proposed. The efficiency of staged growth by means of a cyclohexane/methane system using thin film catalysts is here illustrated. The mechanism involves the nucleation stage efficiently triggered by cyclohexane, followed by methane assisting a growth stage yielding high purity SWNTs vertically aligned with lengths of several hundred μm. In addition, SCVD also facilitates catalyst free SWNT detachment enabling repeated growth. [Copyright &y& Elsevier]

Abstract: We have investigated the magnetic properties of the Heusler phase in the composition regime in the disordered B2 phase. Both bulk and surface static and dynamic magnetic aspects were addressed by employing alternating gradient magnetometry (AGM), magneto-optical Kerr effect (MOKE) and Brillouin light scattering (BLS). All samples show ferromagnetic hysteresis loops and a tendency of increasing saturation magnetization with the iron content. With BLS the behavior of bulk spin waves and the Damon Eshbach (DE) surface spin wave mode have been studied. The spectra are typical for opaque bulk ferromagnetic samples with strong exchange. The measured spin wave frequencies as a function of magnetic field are in good agreement with the calculated values. Saturation magnetization and gyromagnetic ratio g have been determined from the field-dependent peak positions of the bulk and the DE modes. The -factor extracted from the DE mode shows a clear tendency of increase with increasing Fe-content. However, we could not find any peculiarities of the alloy with , which had been proposed as a Heusler phase on the basis of electronic structure calculations [T. Block, C. Felser, G. Jakob, J. Ensling, B. Mühling, P. Gütlich, R.J. Cava, J. Solid State Chem. 176 (2003) 646]. [Copyright &y& Elsevier]

Abstract: Carbon nanotubes are grown from a nanometer thin iron film as catalyst by chemical vapor deposition of cyclohexane. We observe growth of carbon nanotubes in a temperature window between 720 and 845°C. The low synthesis temperature of 720°C results from the catalyst thickness which lowers the iron–carbon eutectic temperature as compared to bulk iron. At this temperature very little amorphous carbon is deposited on the substrate due to the absence of self pyrolysis of cyclohexane. This points out the importance of the interplay between catalyst thickness and carbon source. The synthesized nanotubes are investigated by resonance Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy. [Copyright &y& Elsevier]

Thermoelectric efficiency of semiconducting ruthenium silicide Ru2Si3 has been systematically studied both experimentally and theoretically. Pure and Mn-doped Ru2Si3 single crystals were grown by zone melting with optical heating. Temperature dependences of the resistivity, Hall factor, Seebeck coefficient, and thermal conductivity were studied in the range of 100–900 K. For Mn-doped Ru2Si3 crystals, the Seebeck coefficient is positive in the whole temperature range under study, it reaches its maximum value of 400 μV/K at about 500 K. At room temperature, the Seebeck coefficient of these crystals is about 300 μV/K, which is twice as high as in the undoped material. The theoretical study of transport and thermoelectric properties includes the ab initio calculation of band structure, estimation of the carrier effective masses, modeling of the electron and hole mobilities in terms of classical scattering mechanisms, and calculation of the Seebeck coefficient and thermoelectric figure of merit, ZT. The results of theoretical modeling show a good qualitative and quantitative agreement with the experimental data. [ABSTRACT FROM AUTHOR]

All-optical control of the magnetization of polycrystalline exchange bias bilayer systems is achieved using short picosecond laser pulses. Due to the photoexcitation, the spin temperature across the interface between the ferromagnetic and antiferromagnetic layer is elevated, resulting in a collapse of the interfacial exchange coupling. Thus, within the first 10 ps, a fast reduction of both the exchange bias field and the coercive field is observed for three different exchange bias systems comprising both different ferromagnets and antiferromagnets. The fast thermal unpinning is followed by a slower heat diffusion dominated relaxation process, which strongly depends on the thermal conductivity of the used buffer layers and substrates. The fast optical unpinning can be understood in terms of an internal anisotropy pulse field capable of triggering ultrafast precessional magnetization dynamics of the ferromagnetic layer, which makes heat-assisted coherent magnetization rotation feasible. [ABSTRACT FROM AUTHOR]

The properties of multi-walled carbon nanotubes filled with iron, which is assembled in nanowires inside the nanotubes, were studied with electron spin resonance and conductivity methods. The low-temperature decrease of magnetization in zero-field cooled samples was found depending on the relative orientation of magnetization and the nanotube axes. The azimuthal variation of magnetization can be ascribed to inhomogeneous arrangement of Fe inside the nanotubes, that can be also concluded from the conductivity and spectroscopy measurements. [ABSTRACT FROM AUTHOR]

The transport and thermoelectric properties of semiconducting rhenium silicide ReSi1.75 are comprehensively studied both experimentally and theoretically. Single-crystal samples of undoped and aluminum-doped ReSi1.75 are grown by floating-zone melting using optical heating. The temperature dependences of the resistivity, Hall coefficient, and Seebeck coefficient (thermoelectric power) are measured in the range 77–800 K. At room temperature, the charge-carrier concentration for the undoped rhenium silicide is 1019cm–3 and the carrier mobility is 30cm2/(Vs). The theoretical study of the transport and thermoelectric properties includes ab initio calculation of the band structure; estimation of the carrier effective masses; simulation of the electron and hole mobility, taking into account classical scattering mechanisms; and calculation of the Seebeck coefficient. The results of the simulation and the experimental data are in good agreement. © 2005 Pleiades Publishing, Inc. [ABSTRACT FROM AUTHOR]

Abstract: We present results for magnetotransport measurements on multiwall-carbon nanotubes (MWCNT) contacted by cobalt electrodes. By measuring the V(I) characteristics at constant magnetic fields and different orientation of the magnetization directions in the Co electrodes, we were able to determine both current and voltage dependences of the magnetoresistance (MR) effects. These tunneling MR values are compared with the directly measured MR at constant current with sweeping magnetic field. The V(I) curves show an ohmic behavior at 295K and a non-linear tunneling behavior at 4.2K. With decreasing bias current the MR increased up to 60% at 4.2K, and with decreasing bias voltages even up to 175%. The MR disappears at high bias current (voltages) and temperatures higher than 40K. For most of the samples the current dependences of the MR were found to be nearly symmetric upon reversing the current direction. However, in some cases we also observed a sign change of the MR as function of the applied current, which suggests an inversion of the spin polarization in one of the Co interfaces. [Copyright &y& Elsevier]

Structure and electrical properties of magnetron sputtered and subsequently annealed CrSi2/Si multilayers were investigated in dependence on the annealing temperature and the single layer thickness. Transmission electron microscopy proves the as-deposited layer stacks to consist of amorphous silicide and silicon layers. After annealing at temperatures from 450 to 650 °C the stacks consist of crystalline CrSi2 and amorphous Si layers. The layered structure is well developed and stable for annealing temperatures up to 650 °C and single layer thicknesses down to about 3 nm. For small single layer thicknesses the electrical properties of the stacks are essentially different from those of thin polycrystalline CrSi2 films. Analyzing Hall coefficient and conductivity measurements a decrease of the carrier mobility and a strong increase of the carrier density with decreasing single layer thickness have been observed. This behavior can be described by the influence of the CrSi2/Si interfaces on the electrical properties of the stacks. [Copyright &y& Elsevier]