Antiferromagnet
Mostrando 1-7 de 7 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. Persistence of order on ferromagnetic models in the presence of quasi random auto-similar fields / Persistência de ordem em modelos ferromagnéticos na presença de campos auto-similares quase aleatórios"
In this work we study the existence of long range order for ferromagnetic models in the presence of an external field whose configuration has a pattern typically random. We prove, via the Peierlsargument modified by Griffiths in his study of an antiferromagnet, that the two dimensional ferromagnetic Ising model for a staggered field exhibits long-range order
Publicado em: 2007
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3. 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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4. Histerese e irreversibilidade em vidro de spin ising prÃximo ao limiar de percolaÃÃo: FexZn1-xF2
Na presente dissertaÃÃo realizamos estudos atravÃs de simulaÃÃo computacional, utilizando o mÃtodo Monte Carlo (MC) do antiferromagneto (AF) diluÃdo FexZn1−xF2, prÃximo da regiÃo de percolaÃÃo (x = 0.24) e na presenÃa de um campo magnÃtico externo H. O sistema AF FexZn1−xF2 mostra-se para x = 0.25 com caracterÃsticas tÃpicas de um
Publicado em: 2003
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5. The two-dimensional quantum Heisenberg antiferromagnet with Ising-like anisotropy
We study the two dimensional quantum Heisenberg antiferromagnet on the square lattice with easy-axis exchange anisotropy by the semiclassical method called pure-quantum self-consistent harmonic approximation. In particular, we focus on the problem of the existence of a nite-temperature transition in such a model, and study the corresponding critical temperat
Brazilian Journal of Physics. Publicado em: 2000-12
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6. Instability of long-range order in a d = 3 random-field Ising model system: Fe xZn1-xF2
Instabilities of long-range order are observed in samples of the d = 3 dilute uniaxial antiferromagnet Fe xZn1-xF2 with x = 0:56 and 0.41, under strong random fields. The onset of instability, mapped in the (H, T) phase diagrams of the samples, reveals that the H, T and x dependence of the effective random field is in qualitative agreement with a mean-field
Brazilian Journal of Physics. Publicado em: 2000-12
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7. Spinons and holons for the one-dimensional three-band Hubbard models of high-temperature superconductors.
The one-dimensional three-band Hubbard Hamiltonian is shown to be equivalent to an effective Hamiltonian that has independent spinon and holon quasiparticle excitations plus a weak coupling of the two. The spinon description includes both copper sites and oxygen hole sites leading to a one-dimensional antiferromagnet incommensurate with the copper lattice. T