Navegação Ciências Exatas e da Terra por Autor "Magalhaes, Sergio Garcia"
Resultados 1-15 de 15
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Anisotropic magnetoconductivity of a three-dimensional disordered electron gas
Theumann, Alba Graciela Rivas de; Magalhaes, Sergio Garcia (1989) [Artigo de periódico]The magnetoconductivity of a three-dimensional disordered electron gas is calculated from first principies with use of the exact electron eigenstates in a magnetic field, thus avoiding the usual semiclassical approximation ... -
Electrical magnetotransport properties in RCo12B6 compounds (R = Y, Gd, and Ho)
Mesquita, Fabiano; Magalhaes, Sergio Garcia; Pureur Neto, Paulo; Diop, Léopold Vincent Birane; Isnard, Olivier (2020) [Artigo de periódico]Remarkable electronic transport and magnetotransport properties are found in the intermetallic compounds RCo12B6 (R=Y, Ho, and Gd). Detailed resistivity, magnetoresistance, and Hall effect measurements are reported in the ... -
Inverse melting and inverse freezing in a three-state spin-glass model with finite connectivity
Erichsen Junior, Rubem; Theumann, Walter Karl; Magalhaes, Sergio Garcia (2013) [Artigo de periódico]The phase diagrams of the three-state Ghatak-Sherrington spin-glass (or random Blume-Capel) model are obtained in mean-field theory with replica symmetry in order to study the effects of a ferromagnetic bias and finite ... -
Ising spin glass in a random network with a Gaussian random field
Erichsen Junior, Rubem; Silveira, Alexandre; Magalhaes, Sergio Garcia (2021) [Artigo de periódico]We investigate thermodynamic phase transitions of the joint presence of spin glass (SG) and random field (RF) using a random graph model that allows us to deal with the quenched disorder. Therefore, the connectivity becomes ... -
Magnetoconductivity of a disordered electron system with n orbitals persite
Magalhaes, Sergio Garcia; Theumann, Alba Graciela Rivas de (1994) [Artigo de periódico]In the absence of a magnetic field, two formally equivalent expressions for the conductivity contribute different sets of Feynman diagrams, due to cancellations. We use this result to calculate the magnetoconductivity of ... -
Multiband and Mass-Anisotropy Effects in the Magnetoconductivity of a Disordered Electron Gas
Magalhaes, Sergio Garcia; Theumann, Alba Graciela Rivas de (1993) [Artigo de periódico]We investigate the magnetoconductance of a two-band electron system and a model with effectivemass anisotropy by means of the method based on the exact electron eigenstates in a magnetic field proposed formerly by us to ... -
Multicritical points and topology-induced inverse transition in the random-field Blume-Capel model in a random network
Erichsen Junior, Rubem; Lopes, Amanda de Azevedo; Magalhaes, Sergio Garcia (2017) [Artigo de periódico]The interplay between quenched disorder provided by a random field (RF) and network connectivity in the Blume-Capel (BC) model is the subject of this paper. The replica method is used to average over the network randomness. ... -
Multicritical points in a model for 5f-electron systems under pressure and magnetic field
Chaura, Julián Alberto Faúndez; Magalhaes, Sergio Garcia; Calegari, Eleonir João; Riseborough, Peter S. (2021) [Artigo de periódico] -
Nonlinear susceptibility of a quantum spin glass under uniform transverse and random longitudinal magnetic fields
Magalhaes, Sergio Garcia; Morais Junior, Carlos Alberto Vaz de; Zimmer, Fábio Mallmann; Lazo, Matheus Jatkoske; Nobre, Fernando Dantas (2017) [Artigo de periódico]The interplay between quantum fluctuations and disorder is investigated in a quantum spin-glass model, in the presence of a uniform transverse field , as well as of a longitudinal random field hi , which follows a Gaussian ... -
Specific heat and nonlinear susceptibility in spin glasses with random fields
Romitti, Marcos Vinicios; Zimmer, Fábio Mallmann; Morais Junior, Carlos Alberto Vaz de; Magalhaes, Sergio Garcia (2019) [Artigo de periódico]We study magnetic properties of spin glass (SG) systems under a random field (RF), based on the suggestion that RFs can be induced by a weak transverse field in the compound LiHo x Y 1 − x F 4 .Weconsideracluster spin model ... -
Spin-glass freezing in Kondo-lattice compounds
Theumann, Alba Graciela Rivas de; Coqblin, Bernard; Magalhaes, Sergio Garcia; Schmidt, Alex Andre (2001) [Artigo de periódico]A theory is presented that describes a spin-glass phase at finite temperatures in Kondo-lattice systems with an additional Ruderman–Kittel–Kasuya–Yosida interaction represented by long range, random couplings among localized ... -
Spin-glass phase transition and behavior of nonlinear susceptibility in the Sherrington-Kirkpatrick model with random fields
Morais Junior, Carlos Alberto Vaz de; Zimmer, Fábio Mallmann; Lazo, Matheus Jatkoske; Magalhaes, Sergio Garcia; Nobre, Fernando Dantas (2016) [Artigo de periódico]The behavior of the nonlinear susceptibility χ3 and its relation to the spin-glass transition temperature Tf in the presence of random fields are investigated. To accomplish this task, the Sherrington-Kirkpatrick model is ... -
Thermo‑magnetic signature of a superconducting multi‑band square with rough surface
Aguirre, Cristhian Andres; Chaura, Julián Alberto Faúndez; Magalhaes, Sergio Garcia; Mosquera Polo, Ariday Samit; Barba-Ortega, J. (2021) [Artigo de periódico]In the present work, we will study the efect that the surface roughness of the sample has on the magnetic and thermodynamic properties in a mesoscopic superconducting meso-square under an external magnetic feld in a zero-feld ... -
Unfolding of antiferromagnetic phases and multicritical points in a two-orbital model for uranium compounds under pressure and magnetic field
Magalhaes, Sergio Garcia; Lausmann, Ana Claudia; Calegari, Eleonir João; Riseborough, Peter S. (2020) [Artigo de periódico]We investigate the occurrence of multicritical points under pressure and magnetic field in a model that describes two 5 f bands (of either α or β characters), which hybridize with a single itinerant conduction band. The 5 ... -
Unusual magnetic field-dependence of a possible hidden order phase
Calegari, Eleonir João; Magalhaes, Sergio Garcia; Riseborough, Peter S. (2017) [Artigo de periódico]URu2Si2 exhibits a second-order phase transition at 17.5 K. Initially it was thought that the transition was to a spin density wave phase, however, subsequent measurements do not support this assignment. Despite the unknown ...