Zobrazeno 1 - 10 of 27 pro vyhledávání: '"Gusmao, Miguel Angelo Cavalheiro"'
1
Quasi-one-dimensional magnetic properties of NiNb2−xVxO6 compounds synthesized at high pressure in a nonstandard columbite-type structure
Autor: Peña Pacheco, Jully Paola, Gusmao, Miguel Angelo Cavalheiro, Isnard, Olivier
Publikováno v: Repositório Institucional da UFRGS
Universidade Federal do Rio Grande do Sul (UFRGS)
instacron:UFRGS
We report on the low-dimensional magnetic behavior of the series of compounds NiNb2−xVxO6 (0 x 2), with a columbite-type crystal structure stabilized at high pressure and temperature. Based on susceptibility, magnetization, and specific-heat measur
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3
Band-filling and disorder effects in the ordered phase of the Falicov-Kimball model
Autor: Carvalho, Rubens Diego Barbosa de, Gusmao, Miguel Angelo Cavalheiro
Publikováno v: Repositório Institucional da UFRGS
Universidade Federal do Rio Grande do Sul (UFRGS)
instacron:UFRGS
We investigate the stability of “magnetic” ordering against band-filling changes and Anderson-like disorder in the Falicov-Kimball model, within dynamical mean-field theory (DMFT). The one-particle density of states is obtained by both arithmetic
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4
Effects of band filling in the Anderson-Falicov-Kimball model
Autor: Carvalho, Rubens Diego Barbosa de, Gusmao, Miguel Angelo Cavalheiro
Publikováno v: Repositório Institucional da UFRGS
Universidade Federal do Rio Grande do Sul (UFRGS)
instacron:UFRGS
In this work, we study the Anderson-Falicov-Kimball model within the dynamical mean field theory for the Bethe lattice, restricting our analysis to the nonmagnetic case. The one-particle density of states is obtained by both arithmetic and geometric
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5
Magnetic behavior of the NixFe1−xNb2O6 quasi-one-dimensional system : isolation of Ising chains by frustration
Autor: Sarvezuk, Paulo Willian Carvalho, Gusmao, Miguel Angelo Cavalheiro, Cunha, Joao Batista Marimon da, Isnard, Olivier
Publikováno v: Repositório Institucional da UFRGS
Universidade Federal do Rio Grande do Sul (UFRGS)
instacron:UFRGS
Physical properties of the NixFe1−xNb2O6 compounds are investigated combining x-ray and neutron powder diffraction with magnetic and calorimetry measurements as well as 57Fe Mössbauer spectroscopy. This system is known to present quasi-one-dimensi
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6
Suppression of magnetic ordering in quasi-one-dimensional FexCo1−xNb2O6 compounds
Autor: Sarvezuk, Paulo Willian Carvalho, Kinast, Eder Julio, Colin, C. V., Gusmao, Miguel Angelo Cavalheiro, Cunha, Joao Batista Marimon da, Isnard, Olivier
Publikováno v: Repositório Institucional da UFRGS
Universidade Federal do Rio Grande do Sul (UFRGS)
instacron:UFRGS
We present a systematic investigation of the series of compounds FexCo1−xNb2O6 by means of x-ray and neutron powder diffraction combined with magnetic measurements, carried out in the paramagnetic as well as in the ordered state, to probe the stabi
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7
Generic model of the colossal magnetoresistance pyrochlore Tl/sub 2/Mn/sub 2/O/sub 7
Autor: Ventura, Cecilia Ileana, Gusmao, Miguel Angelo Cavalheiro
Publikováno v: Repositório Institucional da UFRGS
Universidade Federal do Rio Grande do Sul (UFRGS)
instacron:UFRGS
The colossal magnetoresistance (CMR) exhibited by the pyrochlore compound Tl₂Mn₂O₇ was discovered in 1996. Important differences with CMR Mn-perovskite compounds regarding crystal structure and electronic properties were soon realized, indicati
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8
Fluctuation magnetoconductivity in YBa/sub 2/Cu/sub 3/O/sub 7/ : Gaussian, three-dimensional XY, beyond three-dimensional XY, and lowest-Landau-level scaling
Autor: Costa, Rosangela Menegotto, Pureur Neto, Paulo, Gusmao, Miguel Angelo Cavalheiro, Senoussi, Sadok, Behnia, K.
Publikováno v: Repositório Institucional da UFRGS
Universidade Federal do Rio Grande do Sul (UFRGS)
instacron:UFRGS
Systematic measurements of the in-plane fluctuation magnetoconductivity in a YBa₂Cu₃O₇ single crystal are presented. Fields between 0 and 14 T were applied either parallel or perpendicular to the Cu-O atomic planes. The data reveal the occurren
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9
Specific heat and magnetic order in LaMnO/sub 3+[delta]
Autor: Ghivelder, Luis, Abrego-Castillo, Ildeman, Gusmao, Miguel Angelo Cavalheiro, Alonso, José Antônio, Cohen, Lesley F.
Publikováno v: Repositório Institucional da UFRGS
Universidade Federal do Rio Grande do Sul (UFRGS)
instacron:UFRGS
Magnetic and specific-heat measurements are performed in three different samples of LaMnO₃₊[delta], with δ = 0.11, 0.15, and 0.26, presenting important disorder effects, such as carrier localization, due to high amounts of La and Mn vacancies. F
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10
Eletronic and phonomic states of the Holstein-Hubbard dimer of variable length
Autor: Acquarone, C., Iglesias, Jose Roberto, Gusmao, Miguel Angelo Cavalheiro, Noce, A., Romano, Alfonso
Publikováno v: Repositório Institucional da UFRGS
Universidade Federal do Rio Grande do Sul (UFRGS)
instacron:UFRGS
We consider a model Hamiltonian for a dimer of length a including all the electronic one- and two-body terms consistent with a single orbital per site, a free Einstein phonon term for a frequency V, and an electronphonon coupling g0 of the Holstein t
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