Spin Glass Phase
Mostrando 1-12 de 17 artigos, teses e dissertações.
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1. Caracterização estrutural, morfológica e magnética da dupla perovsquita Ca2MnReO6
Compounds with structure of ordered double perovskyte, A2BBO6 (A being an alkalineearth and B being a transition-metal in alternate sites) have attracted interest of the researches because their strong correlated structural and magnetic properties. Moreover, they are suitable candidates to produce devices with great application in spin-electronic, named spin
IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia. Publicado em: 25/06/2009
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2. Structural and dielectric properties of ZrO2 added (Na1/2Bi1/2)TiO3 ceramic
Polycrystalline samples of ZrO2 added (Na1/2Bi1/2)TiO3 were prepared using high-temperature solid-state reaction method at 1050ºC and subsequent sintering at 1090ºC in air atmosphere. Rietveld analyses of XRD data indicated the formation of a single-phase hexagonal structure with R3c symmetry. Dielectric studies revealed the relaxor behaviour. The addition
Brazilian Journal of Physics. Publicado em: 2009-06
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3. 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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4. Propriedades magneticas de filmes de ligas GD-Cr / Magnetic properties of Gd-Cr alloy films
Vapor condensation techniques are very useful for preparation of alloys whose components have no mutual solubility under equilibrium conditions In this work, one of these techniques ? sputtering ? has been used to fabricate metastable GdXCr1-X alloys whose magnetic properties were investigated as a function of the Gd concentration, x. Grazing incidence angle
Publicado em: 2008
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5. 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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6. Antiferromagnetic spherical spin-glass model. / Modelo de vidro de spin esférico antiferromagnético
Neste trabalho investigamos as propriedades estáticas de um modelo de vidro de spin esférico antiferromagnético com interação de multi-spins por meio do método das réplicas. O objetivo consiste em modelar materiais antiferromagnéticos diluídos como FexMg1-xCl2 e compostos antiferromagnéticos mistos como FexMn1-xTiO3 que apresentam evidências de co
Publicado em: 2007
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7. FIRST-ORDER TRANSITION IN THE FERMIONIC ISING SPIN GLASS MODEL IN A TRANSVERSE FIELD / TRANSIÇÕES DE PRIMEIRA ORDEM NO MODELO VIDRO DE SPIN ISING FERMIÔNICO EM UM CAMPO TRANSVERSO
The present work analyzes the fermionic Ising spin glass model in a transverse magnetic field. The problem is written in the Grand Canonical ensemble with the spin operators represented by bilinear combinations of fermionic fields. The transverse field is a spin "flip" mechanism and inserts quantum fluctuations, which can lead the transition temperature Tj t
Publicado em: 2006
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8. VIDRO DE SPIN E ANTIFERROMAGNETISMO COM INTERACÃO DE PAREAMENTO BCS LOCAL
In this work the competition among spin glass(SG), antiferromagnetism (AF) and BCS pairs formation (PAIR) in real space is investigated. The model consists of an Ising spin glass term and a local BCS term that favors double site occupation. This model is composed by two sublattices, but only spins in diferent sublattices can interact. The Ising coupling is a
Publicado em: 2005
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9. 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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10. STUDY OF THE STRUCTURAL AND MAGNETIC PROPERTIES OF Zn1-xMnxIn2Se4 SYSTEM / ESTUDO DAS PROPRIEDADES ESTRUTURAIS E MAGNÉTICAS DO SISTEMA Zn1-xMnxIn2Se4
This work reports a systematic study on the crystal growth and magnetic and structural properties of the diluted magnetic semiconductors (SMD) Zn1-xMnxIn2Se4. Crystals with Mn concentrations $0leqslant xleqslant 1.00$ were grown by chemical vapour transport (CVT). Through x-ray powder diffraction patterns and Laue diagrams of single crystal we studied the tr
Publicado em: 2004
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11. Stability of a two-sublattice spin-glass model
We study the stability of the replica-symmetric solution of a two-sublattice infinite-range spin-glass model, which can describe the transition from an antiferromagnetic to a spin-glass state. The eigenvalues associated with replica-symmetric perturbations are in general complex. The natural generalization of the usual stability condition is to require the r
Brazilian Journal of Physics. Publicado em: 2003-12
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12. 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