Geometrical multilayers: coercivity in magnetic 3-D nanostructures

Electrodeposition of magnetic metals through self-assembly templates from polystyrene spheres is used for fabrication of magnetic nanostructures with 3-D architectures. These arrays demonstrate unusual properties including an oscillatory dependence of the coercive field on film thickness. Numerical simulations reveal that the ratio between the array period and the hole diameter in anti-dot array is a crucial parameter giving rise to qualitatively distinct magnetization reversal regimes

Electrodeposition of Ni-Si Schottky barriers

Electrodeposition is being used to fabricate magnetic microstructures directly on patterned n-type Si wafers of various substrate resistivities. The Ni-Si Schottky barrier is characterized and found to be of high quality for relatively low Si resistivities (1-2 Omega(.)cm), with extremely low reverse leakage. It is shown that a direct correlation exists among the electrodeposition potential, the roughness, and the coercivity of the films. A conductive seed layer or a back contact is not compulsory for electrodeposition on Si with resistivities up to 15 Omega(.)cm. This shows that electrodeposition of magnetic materials on Si might be a viable fabrication technique for magnetoresistance and spintronics applications

Relaxation and Simplex mathematical algorithms applied to the study of steady-state electrochemical responses of immobilized enzyme biosensors: Comparison with experiments

AbstractA description of the implementation of the relaxation method with automatic mesh point allocation for immobilized enzyme electrodes is presented. The advantages of this method for the solution of coupled reaction–diffusion problems are discussed. The relaxation numerical simulation technique is combined with the Simplex fitting algorithm to extract kinetic parameters from experimental data. The results of the simulations are compared to experimental data from self-assembled multilayered electrodes comprised of glucose oxidase (GOx) and an Os modified redox mediator and found to be in excellent agreement

Self-assembly routes towards creating superconducting and magnetic arrays

Using self-assembly from colloidal suspensions of polystyrene latex spheres we prepared well-ordered templates. By electrochemical deposition of magnetic and superconducting metals in the pores of such templates highly ordered magnetic and superconducting anti-dot nano-structures with 3D architectures were created. Further developments of this template preparation method allow us to obtain dot arrays and even more complicated structures. In magnetic anti-dot arrays we observe a large increase in coercive field produced by nanoscale (50–1000nm) holes. We also find the coercive field to demonstrate an oscillatory dependence on film thickness. In magnetic dot arrays we have explored the genesis of 3D magnetic vortices and determined the critical dot size. Superconducting Pb anti-dot arrays show pronounced Little-Parks oscillations in Tc and matching effects in magnetization and magnetic susceptibility. The spherical shape of the holes results in significantly reduced pinning strength as compared to standard lithographic samples. Our results demonstrate that self-assembly template methods are emerging as a viable, low cost route to prepare sub-micron structures

Shape-induced anisotropy in antidot arrays from self-assembled templates

Using self-assembly of polystyrene spheres, well-ordered templates have been prepared on glass and silicon substrates. Strong guiding of self-assembly is obtained on photolithographically structured silicon substrates. Magnetic antidot arrays with three-dimensional architecture have been prepared by electrodeposition in the pores of these templates. The shape anisotropy demonstrates a crucial impact on magnetization reversal processes

Glasses in hard spheres with short-range attraction

We report a detailed experimental study of the structure and dynamics of glassy states in hard spheres with short-range attraction. The system is a suspension of nearly-hard-sphere colloidal particles and non-adsorbing linear polymer which induces a depletion attraction between the particles. Observation of crystallization reveals a re-entrant glass transition. Static light scattering shows a continuous change in the static structure factors upon increasing attraction. Dynamic light scattering results, which cover 11 orders of magnitude in time, are consistent with the existence of two distinct kinds of glasses, those dominated by inter-particle repulsion and caging, and those dominated by attraction. Samples close to the `A3 point' predicted by mode coupling theory for such systems show very slow, logarithmic dynamics.Comment: 22 pages, 18 figure

Electrodeposition of Ni-Si Schottky barriers

Electrodeposition is being used to fabricate magnetic microstructures directly on patterned n-type Si wafers of various substrate resistivities. The Ni-Si Schottky barrier is characterized and found to be of high quality for relatively low Si resistivities (1-2 Omega(.)cm), with extremely low reverse leakage. It is shown that a direct correlation exists among the electrodeposition potential, the roughness, and the coercivity of the films. A conductive seed layer or a back contact is not compulsory for electrodeposition on Si with resistivities up to 15 Omega(.)cm. This shows that electrodeposition of magnetic materials on Si might be a viable fabrication technique for magnetoresistance and spintronics applications

Integrated microsphere planar lightwave circuits

Multicomponent glass microspheres self-assembled on optical waveguides combine tailored optical properties with strong light/material interaction potentially leading to compact low-power photonic devices. Progress and prospects for microsphere/waveguide integration will be described

Search for Higgs bosons decaying to tautau pairs in ppbar collisions at sqrt(s) = 1.96 TeV

We present a search for the production of neutral Higgs bosons decaying into tautau pairs in ppbar collisions at a center-of-mass energy of 1.96 TeV. The data, corresponding to an integrated luminosity of 5.4 fb-1, were collected by the D0 experiment at the Fermilab Tevatron Collider. We set upper limits at the 95% C.L. on the product of production cross section and branching ratio for a scalar resonance decaying into tautau pairs, and we then interpret these limits as limits on the production of Higgs bosons in the minimal supersymmetric standard model (MSSM) and as constraints in the MSSM parameter space.Comment: 7 pages, 5 figures, submitted to PL