Ferromagnetism
Mostrando 13-24 de 33 artigos, teses e dissertações.
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13. Propriedades estruturais, eletronicas e magneticas de filmes finos de materiais magneticos / Structural, electronic and magnetic thin film properties of magnetic materials
A Física de superfícies, interfaces e filmes finos vem se desenvolvendo muito rapidamente nas últimas décadas com o aparecimento de inúmeras técnicas experimentais para estudo das propriedades de superfície. Por outro lado, tem ocorrido um grande avanço dos equipamentos de informática e dos métodos computacionais, com o desenvolvimento de novos alg
Publicado em: 2008
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14. Structural and magnetic properties of the half-ferromagnetic Co2+x+yMn1-xAl1-y alloys
Co2+x+yMn1-xAl1-y intermetallic compounds have been prepared by arc melting and studied with X-ray diffraction and magnetization measurements to ascertain the effect of deviations of composition from the stoichiometry on the ferromagnetism of this system. Hysteresis loops registered at room temperature show a soft ferromagnetic behavior in excess Co. In off-
Brazilian Journal of Physics. Publicado em: 2007-12
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15. Parameter symmetry in ferromagnetic superconductors / Simetria do parametro de ordem em supercondutores ferromagneticos
In this dissertation, we present a study of the order-parameter symmetry in ferromagnetic superconductors. Our approach is inspired on the Landau Theory of Phase Trasition or, more precisely, on the idea that a second order phase transition is a symmetry breaking process where the ordered phase of the system is described by a subgroup of the highly symmetric
Publicado em: 2007
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16. Studies of the magnetic properties on Mn-doped GaAs and Zn1-xCoxO thin films / Estudos das propriedades magneticas dos filmes finos de GaAs diopado com Mn e de Zn1-xCoxO
Ferromagnetic semiconductors (FM) are compounds of technological interest due to the possibility of combining their charge and spin degrees of freedom when producing electronic devices. In particular, semiconductor thin films doped with transition metal have become focus of intense scientific investigation since ferromagnetism with reasonably high Curie temp
Publicado em: 2007
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17. Influência de vacâncias de spin na dinâmica de vórtices em sistemas magnéticos bidimensionais / Influence of spin vacancies in the vortex dynamics in two-dimensional magnetic systems
Neste trabalho estudamos a dinâmica de spins no modelo XY 2D clássico, incluindo impurezas não-magnéticas. Os resultados analíticos, testados por simulações, indicam duas formas de "aprisionar" um vórtice por meio de duas vacâncias de spin. Além disso, revelam uma interação efetiva do tipo atrativa entre estes defeitos. Analisamos também a funç
Publicado em: 2006
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18. 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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19. "Novos materiais magnéticos para imãs de alta performance" / New magnetic materials for high performance magnets
O objetivo do presente trabalho foi desenvolver novos materiais magnéticos para ímãs de alta performance. Duas classes de materiais foram estudadas: materiais a base de (Nd,Sm)5(Fe,MT)17, onde MT é um metal de transição, e materiais nanocristalinos a base de (Nd,Pr)FeB com adições de TiC. As ligas (Nd,Sm)5(Fe,MT)17 foram preparadas por fusão em forn
Publicado em: 2005
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20. Tunelamento e transporte quantico em sistemas mesoscopicos : fundamentos e aplicações
O interesse atual e crescente nos sistemas mesoscópicos se deve à miniaturização cada vez maior dos dispositivos eletrônicos e à produção de materiais com possibilidade de armazenar informação em altas densidades (Gbits e Terabits/pol 2 ). A Física Mesoscópica descreve fenômenos que ocorrem em uma escala de tamanhos intermediária entre o macros
Publicado em: 2005
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21. Manipulation with spin ordering in ferromagnetic semiconductors
A short overview is given of recent advances in the field of carrier-controlled ferromagnetism in Mn-based III-V and II-VI diluted magnetic semiconductors and their nanostructures. The tailoring of domain structures and magnetic anisotropy by strain engineering and confinement is described. Experiments demonstrating the tunability of T C by light and electri
Brazilian Journal of Physics. Publicado em: 2004-06
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22. 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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23. Magnetotransport and Hall ferromagnetism in magnetic semiconductor heterostructures / Magneto-transporte e ferromagnetismo Hall em heteroestruturas semicondutoras magnéticas
Digital magnetic heterostructures (DMHs) are semiconductor structures with magnetic impurities (Mn) restricted to some planar arrangements (monolayers) regularly spaced. In the presence of an external magnetic field, the sp-d exchange interaction between the localized magnetic moments and the itinerant carriers is responsible for a giant spin splitting, of t
Publicado em: 2004
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24. Local superconductivity and ferromagnetism interplay in graphite-sulfur composites
The superconductivity of graphite-sulfur composites is highly anisotropic and associated with the graphite planes. The superconducting state coexists with the ferromagnetism of pure graphite, and a continuous crossover from superconducting to ferromagnetic-like behavior could be achieved by increasing the magnetic field or the temperature. The angular depend
Brazilian Journal of Physics. Publicado em: 2003-12