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In this paper we deal with solving robustly and efficiently one-dimensional linear parabolic singularly perturbed systems of convection-diffusion type, where the diffusion parameters can be different at each equation and even they can have different orders of magnitude. The numerical algorithm combines the classical upwind finite difference scheme to discretize in space and the fractional implicit Euler method together with an appropriate splitting by components to discretize in time. We prove that if the spatial discretization is defined on an adequate piecewise uniform Shishkin mesh, the fully discrete scheme is uniformly convergent of first order in time and of almost first order in space. The technique used to discretize in time produces only tridiagonal linear systems to be solved at each time level; thus, from the computational cost point of view, the method we propose is more efficient than other numerical algorithms which have been used for these problems. Numerical results for several test problems are shown, which corroborate in practice both the uniform convergence and the efficiency of the algorithm. [ABSTRACT FROM AUTHOR]

The structure, morphology, composition, magnetism, and magneto-optical (MO) response of FePd films sputter deposited at different temperatures on a monocrystalline V(001) buffer layer is studied. It is observed that the perpendicular magnetic anisotropy (PMA) could be ascribed to the V interdiffusion and the formation of a FeV alloy, being the global sample saturation magnetization also reduced.

Epitaxial Nb thin films deposited onto the same crystalline insulating surface can evolve in very different fashions depending on specific deposition conditions, thereby affecting their microstructure, surface morphology and superconducting properties. Here, we examine and compare the microstructure and ensuing surface morphology from two distinct Nb/MgO series each with its own epitaxial registry-namely Nb(001)/MgO(001) and Nb(110)/MgO(001)-leading to distinct surface anisotropy and we closely examine the dynamical scaling of the surface features during growth. We compare our findings with those in other metal/MgO epitaxial systems and for the first time, general scaling formalism is applied to analyze anisotropic surfaces exhibiting biaxial symmetry. Further, Power Spectral Density is applied to the specific problem of thin film growth and surface evolution to qualify the set of deposition conditions leading to smoother surfaces. We find good correlation between the surface morphology and microstructure of the various Nb films with superconducting properties such as their residual resistance ratio and lower critical field. [ABSTRACT FROM AUTHOR]

We present our investigations on the enhancement of magneto-optical (MO) effects in nanocomposite Au–Co thin films. All the samples in this study were obtained by cosputter deposition varying the relative Au:Co composition and the growth temperature. A strong enhancement of the transverse MO activity is observed when surface plasmons are excited in the Kretschmann configuration. The correlation between the nanocomposite films' microstructure, morphology, composition, and their optical response under surface plasmon resonance excitation and their MO enhancement is discussed. [ABSTRACT FROM AUTHOR]

The morphological and magnetic properties of Co nanoparticles deposited by triode sputtering on Si3N4 at 550 °C are reported. The nominal thickness of Co ranges from 2 up to 15 nm, and two different capping layers, Au and Pt, are used. The nanoparticles were characterized by x-ray diffraction and atomic force microscopy. Morphological and structural studies show that the nanoparticles grow in a well-defined nanostructured pattern and adopt a hexagonal closed packed crystalline structure. Moreover, the average particle size and the particle size dispersion increase as the thickness increases, due to percolation. Experimental characterization of effective anisotropy field was carried out with transverse susceptibility. Transverse susceptibility measurements reveal an in-plane isotropic magnetic behavior. Both the effective anisotropy field and the coercive field increase as the particle size increases, following a D6 dependence, which is typical for three-dimensional structures in the framework of the random anisotropy model. The relationship between the particle size distribution and the anisotropy field distribution is shown, explaining the significant dependence of the magnetic behavior on the Co layer thickness. On the other hand, different capping layers give rise to a change in the magnetic response due to the modification of the interparticle interaction. [ABSTRACT FROM AUTHOR]

We present a study of the optical and magneto-optical (MO) properties of Co nanoparticles embedded in ZrO2 in the spectral range from 1.4 to 4.3 eV. The nanostructured films were prepared by pulsed laser deposition in a wide range of Co nanoparticle concentrations varying from 20% to 80%. For Co concentration lower than x∼0.45 the size of the nanoparticles was found to remain almost constant (D∼2.5 nm), whereas it increases above it. Differences are found between the optical and MO constant of the Co nanoparticles and those of continuous Co films. Those differences are associated with size effects of the intraband contribution inside the nanoparticles. [ABSTRACT FROM AUTHOR]

We present a study of the optical and magneto-optical (MO) properties of Co nanoparticles embedded in ZrO2 in the spectral range from 1.4 to 4.3 eV. The nanostructured films were prepared by pulsed laser deposition in a wide range of Co nanoparticle concentrations varying from 20% to 80%. For Co concentration lower than x∼0.45 the size of the nanoparticles was found to remain almost constant (D∼2.5 nm), whereas it increases above it. Differences are found between the optical and MO constant of the Co nanoparticles and those of continuous Co films. Those differences are associated with size effects of the intraband contribution inside the nanoparticles. [ABSTRACT FROM AUTHOR]

We present a structural, morphological, magnetic, and magneto-optical study of cobalt nanoparticles deposited on 50 Å AlN/c-sapphire substrates and embedded in an AlN matrix. The dependence of the properties of Co nanoclusters deposited on AlN with growth temperature and amount of deposited Co are studied and discussed. Also we directly compare the properties of as grown and AlN embedded Co nanoclusters and show that the AlN matrix has a strong impact on their magnetic and magneto-optical properties. [ABSTRACT FROM AUTHOR]

Several studies are conducted to explain the localized surface plasmon resonance enhanced magneto-optical activities of the core-shell Fe-Ag nanoparticles. The exploitation of these properties is shown to be extremely beneficial in enhancing the sensitivity of these nanoparticles.

The morphological and magnetic properties of Co nanoparticles deposited by triode sputtering on [Si.sub.3][N.sub.4] are described. The relationship between the particle size distribution and the anisotropy field distribution has shown the dependence of the magnetic behavior on the Co layer thickness.

The optical and magneto-optical (MO) properties of Co nanoparticles embedded in ZrO2 in the spectral range from 1.4 to 4.3 eV are studied. For Co concentration lower than x~0.45 the size of the nanoparticles is found to remain almost constant, whereas it increases above it.

In this work, we are interested in approximating the solution of 2D parabolic singularly perturbed problems of convection–diffusion type. The convective term of the differential equation, associated to the initial and boundary value problem, is such that each one of its components has an interior simple turning point, which can be of attractive or repulsive type. We describe a numerical method to discretize the continuous problem, which combines the fractional implicit Euler method, defined on a uniform mesh, to discretize in time, and the classical upwind finite difference scheme, defined on a nonuniform mesh of Shishkin type, to discretize in space. The fully discrete algorithm has a low computational cost. From a numerical point of view, we see that the method is efficient and uniformly convergent with respect to the diffusion parameter in both cases when the source term is a continuous function or it has a first kind discontinuity at the turning points. Some numerical results for different test problems are showed; from them, we deduce the good properties of the numerical method. [ABSTRACT FROM AUTHOR]

In this paper we analyze the uniform convergence of a numerical method designed to approximate efficiently the solution of 2D parabolic singularly perturbed problems of reaction diffusion type. The method combines a modified fractional implicit Euler method to discretize in time, and the classical central finite difference scheme, on a special nonuniform mesh, to discretize in space. The resulting fully discrete scheme is uniformly convergent with respect to the diffusion parameter. The analysis of the convergence is made by using a two step technique, which discretizes first in time and later on in space. We show the order reduction phenomenon associated to the fractional implicit Euler method, which typically appears if the boundary conditions are time dependent and a natural evaluation of them is done. An appropriate choice for the boundary conditions is proposed and analyzed in detail, proving that the order reduction can be removed. Some numerical tests show the practical effects of our method; as well, we compare it with the classical choice for the boundary data in terms of the uniform consistency and the order of uniform convergence of the numerical scheme. [ABSTRACT FROM AUTHOR]

The grid approximation of an initial-boundary value problem is considered for a singularly perturbed parabolic convection-diffusion equation with a convective flux directed from the lateral boundary inside the domain in the case when the convective flux degenerates inside the domain and the right-hand side has the first kind discontinuity on the degeneration line. The high-order derivative in the equation is multiplied by ε2, where ε is the perturbation parameter, ε ∊ (0, 1]. For small values of ε, an interior layer appears in a neighbourhood of the set where the right-hand side has the discontinuity. A finite difference scheme based on the standard monotone approximation of the differential equation in the case of uniform grids converges only under the condition N-1 = o(ε), No-1 = o(1), where N +1 and No+1 are the numbers of nodes in the space and time meshes, respectively. A finite difference scheme is constructed on a piecewise-uniform grid condensing in a neighbourhood of the interior layer. The solution of this scheme converges ε- uniformly at the rate O(N-1 ln N +No-1). Numerical experiments confirm the theoretical results. [ABSTRACT FROM AUTHOR]

NbN thin films have the potential to be incorporated into radio frequency cavities in a multilayer coating to overcome the fundamental field gradient limit of 50 MV m-1 for the bulk niobium based technology that is currently implemented in particle accelerators. In addition to having a larger critical field value than bulk niobium, NbN films develop smoother surfaces which are optimal for cavity performance and lead to fewer losses. Here, we present a study on the correlation of film deposition parameters, surface morphology, microstructure, transport properties and superconducting properties of NbN thin films. We have achieved films with bulk-like lattice parameters and superconducting transition temperatures. These NbN films have a lower surface roughness than similarly grown niobium films of comparable thickness. The potential application of NbN thin films in accelerator cavities is discussed. [ABSTRACT FROM AUTHOR]