Competing orders, competing anisotropies, and multicriticality: The case of Co-doped YbRh2Si2

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Desenvolvimento de tratamentos térmicos visando ganhos magnéticos em aços com ultra baixa concentração de carbono

The relationship between the microstructure and the magnetic properties of soft magnetic materials, have been studied by different researchers who seek to employ electrical systems, increasing their life span and reduce their energy consumption. Following this same line the Brazilian Synchrotron Light Laboratory developed a new synchrotron light source, the Sirius, where magnetic materials with high magnetic permeability values are being studied for use in accelerator dipoles. The low carbon steel is a ferromagnetic material that has a great relationship between cost and magnetic permeability. Aiming to raise the values of permeability of the material, heat treatments were done and evaluated the magnetic properties, microstructure and mechanical properties to correlate them. It was noted that the thermal annealing were the most effective, and the annealing performed with a small time threshold, which only phenomenon observed was the primary recrystallisation, was the most elevated values of magnetic permeability of the material, due to the average grain size ideal achieved. The heat treatments do not guide the magnetic domains of the material and not influence the mechanical properties of the material due to lack of carbon in the microstructure. The annealing treatments were shown to be an alternative to raising the values of the magnetic permeability of the material and facilitate the implementation of ultra low carbon steel in the dipoles of Sirius

Tomografia por Biosusceptometria de Corrente Alternada (tBAC): desenvolvimento, caracterização, implementação

The Biosusceptometry AC (BAC) is a research tool that has been extensively explored by the group Biomagnetism IBB-UNESP for monitoring of the gastrointestinal tract, its response to a known drug or in vivo performance of solid dosage forms. During this period the BAC, which has the characteristics of high sensitivity and low cost, has been developed primarily for recording signals contraction of activity and traffic human gastrointestinal tract. With the possibility of producing images with this instrumentation, it was possible to evaluate different situations in vitro and in vivo for physiological studies and pharmaceuticals. Considering the good performance of this system to produce planar images, the first aim of the BAC system tomography (TBAC) was to evaluate the system performance of BAC to produce tomographic images of phantoms ferromagnetic for a single channel system. All these applications were only possible because of their sensitivity to materials of high magnetic suscepitibility as ferrite, which allow to produce an electrical signal proportional to the variation of the magnetic flux generated by the presence of magnetic marker next to a first-order gradiometer. Measuring this variation at various points was possible to generate planar images that recently came to be produced in systems with multiple detectors, said multi-channels. From planar images, also producing tomographic images of simulators BAC bars in a system of 13 channels using only the center channel, with good results when applied to simple objects as one and two bars. When testing the resolution of the system with more elaborate forms the quality and resolution of images reconstructed is not satisfactory, which would be solved by increasing the spatial sampling rate and hence the acquisition time. The present system works with an acquisition time of about five hours. Whereas this system will be applied for in vivo experiments, the acquisition time became a ...

Análise estrutural e morfológica de ferrita NiFe2O4 dopada com cromo

This paper reports on the effect of the substitution of Fe3+ for Cr3+ ions in the spinel lattice of the powders was investigated. Nickel ferrite powders with a NiFe2-xCrxO4 nominal composition (x = 0.0; 0.5; 1.0 and 1.5 mol of the chromium) were synthesized by combustion reaction using urea as fuel. The powders resulting were characterized by XRD, nitrogen adsorption by BET, SEM and Mössbauer spectroscopy (57Fe Mössbauer spectra). The results show that the substitution of the Fe3+ for Cr3+ions increased the crystalline degree of the phase, reduced the superficial area and consequently increased the particle size. The Mössbauer spectra of the samples also confirm the distribution of the particles size by the magnetic properties. Analyze of the spectra Mössbauer gives an estimate of the superparamagnetic and ferromagnetic particles behavior in each sample for several chromium concentrations.

Preparação de nanofio via deposição eletroquímica utilizando modelo de membrana porosa

From the last decade of the twentieth century, the rapid growth of nanotechnology has resulted in the discovery of a number of forms of nanoparticles and nanoclusters. We can cite as an example: nanotubes, nanowires, nanobelts, and nanoconesnanoclusters which have a wide range of applications, particularly as catalysts magnetic material nanodevices, chemical sensors, degradation of toxic chemicals, or even as possible carriers for the isotope medical applications.. The first step is the production and characterization of nanowires multithreaded using different types of metals (nickel, silver, gold) and polymers (pyrrole), which are prepared by electrochemical deposition process. Will be held by the characterization of the same images of scanning electron microscopy (SEM) and transmission electron microscopy (TEM)

Mobile vector soliton in a spin-orbit coupled spin-1 condensate

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Origin of spin incommensurability in hole-doped S=1 Y2-xCaxBaNiO5 chains

Spin incommensurability (IC) has been recently experimentally discovered in the hole-doped Ni-oxide chain compound Y2-xCaxBaNiO5 [G. Xu et al., Science 289, 419 (2000)]. Here a two orbital model for this material is studied using computational techniques. Spin IC is observed in a wide range of densities and couplings. The phenomenon originates in antiferromagnetic correlations across holes dynamically generated to improve hole movement, as it occurs in the one-dimensional Hubbard model and in recent studies of the two-dimensional extended t-J model. The close proximity of ferromagnetic and phase-separated states in parameter space is also discussed.

Magnetic properties of YBCO/LCMO superlattices with and without STO interlayers

Superlattices formed of two antagonic characteristics have been broadly studied in literature mainly in order to clarify the effects of proximity and interface interactions. Here, we present a study of superlattice introducing an insulator between each superconducting and ferromagnetic layer. The electrical insulator STO, YBCO and LCMO layer are deposited by PLD method. The samples with STO show more intergrowth surface morphology, which favors the application providing better contacts between the grains. The magnetic measurements indicated higher Tc values and high anisotropy for SLs with STO, which is dependent on the relative thickness of LCMO and YBCO.

Transporte eletrônico em estruturas híbridas: uma aproximação usando funções de green de não-equílibrio

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)