Phase Ferromagnetic
Mostrando 25-36 de 48 artigos, teses e dissertações.
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25. ESTUDO MICROANALÍTICO DA PRECIPITAÇÃO DE MICRO E NANOPARTÍCULAS MAGNÉTICAS EM LIGAS DILUÍDAS DE CU-CO / MICROANALYTICAL STUDY OF MAGNETIC MICRO AND NANOPARTICLES PRECIPITATED IN DILUTE CU-CO ALLOYS
The isothermal decomposition processes of dilute Cu-Co bulk alloys have been investigated by means of analytical transmission electron microscopy. The precipitation of ferromagnetic Co particles in non-magnetic Cu matrix after aging treatments was revealed by a variety of electron-microscopy techniques: TEM diffraction contrast, high resolution electron micr
Publicado em: 2007
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26. Propriedades físicas de bicamadas magnéticas
The magnetic order of bylayers composed by a ferromagnetic film (F) coupled with an antiferromagnetic film (AF) is studied. Piles of coupled monolayers describe the films and the interfilm coupling is described by an exchange interaction between the magnetic moments at the interface. The F has a cubic anisotropy while the AF has a uniaxial anisotropy. We ana
Publicado em: 2007
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27. Monte Carlo study of the metamagnet Ising model in a random and uniform field
Monte Carlo simulation has been used to determine the phase diagram of a metamagnet Ising model in the presence of a random and uniform magnetic field. The model consists of a spin-1/2 metamagnet in which the nearest neighbor and next nearest neighbor spin interactions are antiferromagnetic (J1 < 0) and ferromagnetic (J2 > 0), respectively. We used a bimodal
Brazilian Journal of Physics. Publicado em: 2006-09
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28. Phase diagrams of the Blume-Emery-Griffiths thin films
We study the spin-1 Blume-Emery-Griffiths model with bilinear and biquadratic exchange interactions and single-ion crystal field, using the mean field theory. In addition to the four usual phases: The disordered phase D, the ferromagnetic phase F, the staggered quadrupolar phase SQ and The ferrimagnetic phase I, we found two new phases, in the case of a thin
Brazilian Journal of Physics. Publicado em: 2006-06
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29. The study of the magnetocaloric effect in compounds of MnAs1-xAx, A = P, Sb, Te e Mn1-xFexAs / Estudo do efeito magnetocalorico em compostos de MnAs1-xAx, A = P, Sb, Te e Mn1-xFexAs
In this work we describe the obtaining processes of the MnAs1-x Ax (A= Te, P, Sb) and Mn1-xFexAs series for several concentrations. We divided this work in two stages: in the first one the samples were obtained using a high pressure furnace and in the second one using a resistive furnaces with the samples sealed in quartz tubes. The first stage, can be split
Publicado em: 2006
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30. Fluctuations, classical activation, quantum tunneling, and phase transitions
We study two broad classes of physically dissimilar problems, each corresponding to stochastically driven escape from a potential well. The first class, often used to model noise-induced order parameter reversal, comprises Ginzburg-Landau-type field theories defined on finite intervals, perturbed by thermal or other classical spatiotemporal noise. The second
Brazilian Journal of Physics. Publicado em: 2005-06
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31. Kinetic phase transition in the mixed-spin Ising model
In this work we studied a ferromagnetic mixed-spin Ising model including a single ion crystal-field term. The model system consists of two interpenetrating sublattices with spins sigma = 1/2 and S = 1. The spins sigma = 1/2 occupy the sites of one sublattice, their nearest-neighbours are spins S on the other sublattice, and vice versa. The system is in conta
Brazilian Journal of Physics. Publicado em: 2004-06
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32. Monte Carlo study of the anisotropic three-dimensional Heisenberg model in a crystal field
We study the phase diagram of the three-dimensional classical ferromagnetic Heisenberg model with an easy-plane crystalline anisotropy and an easy-axis exchange anisotropy through Monte Carlo simulations. We employ the Metropolis algorithm together with single-histogram techniques in order to characterize the transitions in each region of the phase diagram.
Brazilian Journal of Physics. Publicado em: 2004-06
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33. On the possibility of quasi small-world nanomaterials
The possibility of materials that are governed by a fixed point related to small world networks is discussed. In particular, large-scale Monte Carlo simulations are performed on Ising ferromagnetic models on two different small-world networks generated from a one-dimensional spin chain. One has the small-world bond strengths independent of the length, and ex
Brazilian Journal of Physics. Publicado em: 2004-06
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34. Epitaxial hybrid ferromagnet-semiconductor structures: growth, structural and magnetic properties
Ferromagnet-semiconductor heterostructures are promising materials for the integration of magnetic or spin related functions into semiconductor materials and devices. Fe-on-GaAs and MnAs-on-GaAs are canditates for potential room temperature applications. We review our recent results on growth, structural and magnetic properties of these materials, and their
Brazilian Journal of Physics. Publicado em: 2004-06
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35. Reentrant spin glass behavior in polycrystalline La0.7Sr0.3Mn1-X FeX O 3
The magnetic and transport properties of the compound La0.7Sr0.3Mn1-xFe xO 3 (0.1 < x <0.4) have been studied by means of electrical resistivity, AC magnetic susceptibility, and DC magnetization. At low concentrations (x <0.1), the system displays essentially para-to-ferromagnetic transitions as the temperature is decreased, although a decrease in the magnet
Materials Research. Publicado em: 2004-06
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36. First-principles materials study for spintronics: MnAs and MnN
We report ab-initio all electrons density- functional calculations for the electronic structure of the compounds MnAs and MnN, in the zinc-blende phase. They are potential materials for use in fabrication of new functional semiconductors taking advantage of the spin degree of freedom. The aim is the establishing of the semiconductor spin electronics (spintro
Brazilian Journal of Physics. Publicado em: 2004-06