Random Magnetic Field
Mostrando 1-12 de 25 artigos, teses e dissertações.
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1. Efeito de substituiÃÃo atÃmica no calor especÃfico da L-arginina fosfatada monohidratada e do FexZn1-xF2
A Physical Properties Measurement System â PPMS was assembled to perform heat capacity (Cp) measurements in the temperature range 1.8 â 390 K. The system was used to investigate the temperature dependence of Cp in samples of L-arginine phosphate monohydrated (LAP) at low temperatures. The measurements were carried out in pure LAP and in doped samples: Cu(0
Publicado em: 2009
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2. Propriedades magnÃticas do nanocompÃsito (Fe1-xCox)y(MnO)1-y
In the present work were investigated the magnetic properties of ferromagnetic nanocomposites (Fe1−xCox)y(MnO)1−y, x = 0.4 and 0.6 e y = 0.35, 0.65 and 1, produced by mechanical-alloying. Structural and morphological characterization were made by x-ray diffraction using Scherrer equation, Williamson-Hall plot and Rietveld refinement. The refineme
Publicado em: 2009
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3. EstatÃstica de contagem de carga e efeitos de interferÃncia em sistemas mesoscÃpicos
In this thesis we presented a detailed study about full counting statistics of transmitted charge and accumulated phase and the quantum interference corrections to the average conductance and the average shot-noise power in non-ideal ballistic chaotic cavities. In the theoretical analysis of this mesoscopic system, we obtained analytical expressions for the
Publicado em: 2009
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4. The van Hemmen model in the presence of a random field
The van Hemmen model with a random field is studied to analyze the tricritical behavior in the Ising spin glass phase. The free energy and phase diagram (T versus H and T versus Jo/J, where H is the root mean square deviation of the magnetic field, Jo and J are the ferromagnetic and root mean square deviation exchange, respectively) are calculated for the mo
Brazilian Journal of Physics. Publicado em: 2007-06
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5. 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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6. Fractal conductance fluctuations in electron billiards: a random matrix theory approach
Motivated by recent experiments and theoretical works that contradict the original explanation for fractal conductance fluctuations (FCF) in electron billiards, based on the "mixed" structure of the classical phase space, we propose an alternative approach to investigate FCF using Random Matrix Theory (RMT). By means of a semiclassical estimate for value of
Brazilian Journal of Physics. Publicado em: 2006-06
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7. Remanent magnetization in the antiferromagnetic systems / Magnetização remanente em sistemas antiferromagnéticos"
In the context of low anisotropy, the magnetization measurements to find out the magnetic effects induced by the substitution of Mn+2 by Cu+2 íons in the quaseone-dimensional Heisenberg-like antiferromagnets CsMn1-xCuxA3.2H2O (A = Cl,Br) were made. In the diluted samples of the Br derivative, we observe the appearance of a remanent magnetization (Mr) below
Publicado em: 2006
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8. ConfiguraÃÃo, anisotropia e defeitos em uma rede de vÃrtices na presenÃa de nanoarmadilhas
Since Abrikosov s work in 1957, it. has been clear the vortex lattice existence and stability in specific magnetic fields and temperature values of type ll super- conductors. On external currents and Thermic fluctuations, vortices move through the superconductor salable resulting thermal dissipation. But it is salvage to most. actual technologic applications
Publicado em: 2006
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9. Evolução da microestrutura e textura com a temperatura de acabamento de um aço GNO 1,3% Si
Silicon steels with non-oriented grain are used in a wide variety of applications, from small electrical machines, where high permeability is important, to large machines, where a low magnetic loss is the most important factor. The magnetic properties are determined, in large extent, by the final recrystallization texture produced, which is connected to the
Publicado em: 2005
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10. Numerical study of resistivity scaling in pi junction granular superconductors
Numerical simulations based on Monte Carlo dynamics are used to investigate the resistivity behavior of granular superconductors containing a random distribution of pi junctions, as in superconducting materials with d-wave symmetry. The presence of pi junctions leads to quenched in circulating currents (chiralities) and to chiral glass behavior at low temper
Brazilian Journal of Physics. Publicado em: 2003-12
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11. Estudo da MagnetoimpedÃncia em La0;7Ca0;3MnO3 e La0;6Y0;1Ca0;3MnO3
In the present work, we report high frequency lock-in detection tecniques. The techniques were used to investigate La0:7Ca0:3MnO3 and La0:6Y0:1Ca0:3MnO3 manganites. The measurements were carried out at temperatures ranging from 50 to 300 K, and for applied magnetic fields up to 6 T, using both dc and ac currents. The frequency f of the ac current was varried
Publicado em: 2003
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12. Zero-temperature superconducting transition in frustrated Josephson-junction arrays
The critical behavior of zero-temperature superconducting transitions which can occur in disordered two-dimensional Josephson-junction arrays are investigated by Monte Carlo calculation of ground-state excitation energies and dynamical simulation of the current-voltage characteristics at nonzero temperatures. Two models of arrays in an applied magnetic field
Brazilian Journal of Physics. Publicado em: 2002-09