414 research outputs found
Enhanced domain wall velocity near a ferromagnetic instability
Assuming a Fermi liquid behavior for -conduction electrons, we rewrite the
extended Landau-Lifshitz-Gilbert (LLG) equation renormalized by interactions
through the Landau parameters () in an explicit
form to describe the dynamic of a domain wall (DW) due to spin transfer torque
phenomenon. The interaction between spins of the \textit{s}-conduction
electrons explains qualitatively the DW velocity experimental observations in
(Permalloy) recalculated by us without
defects or impurity hypothesis. Close to Stoner ferromagnetic instability point
where , the DW velocity becomes high
( ) and critical spin current density becomes
reduced ( ) when compared to that
calculated by nonadiabatic approach. At the critical point, the DW velocity
diverges while critical spin current density at the same point goes to zero.
Our theory also provides a prediction to looking for materials in which is
possible applies a smallest critical spin current density and observes higher
DW velocity.Comment: 7 pages, 5 figure
One-dimensional Gapless Magnons In A Single Anisotropic Ferromagnetic Nanolayer.
Gapless magnons in a plane ferromagnet with normal axis anisotropy are shown to exist besides the usual gapped modes that affect spin dependent transport properties only above a finite temperature. These magnons are one-dimensional objects, in the sense that they are localized inside the domain walls that form in the film. They may play an essential role in the spin dependent scattering processes even down to very low temperatures.9122680
Produção de carboximetilcelulase e poligalacturonase sólido pelo fungo Trichoderma polysporum por fermentação em estado sólido, utilizando bagaço de laranja com substrato.
Monitoring the phenolics compounds of the 2G ethanol process.
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Isolamento de fungos visando à produção de enzimas celulolíticas para aplicação na hidrólise da biomassa.
Nonequilibrium interacting electrons in a ferromagnet
Dynamics of the magnetization in ferromagnets is examined in the presence of
transport electrons allowing the latter to interact. It is found that the
existence of inhomogeneities such as domain wall (DW) structures, leads to
changes that affect the dynamical structure of the equations of motion for the
magnetization. Only in the limit of uniform magnetizations or sufficiently wide
DW's, the equations of motion maintain the form they have in the noninteracting
case. In this limit, results like the spin torques, the Gilbert parameter, and
the DW velocities become renormalized. However the length scale that defines
such a limit depends on the strength of the interaction. It is shown that if
large ferromagnetic fluctuations exist in the metallic band then the range for
which conformity with the noninteracting case holds extends to the limit of
arbitrarily narrow DW's.Comment: 4 pages, no figures, revised version, accepted for publication in the
PRB's Rapid Communication sectio
Produção e celulases e xilanases por duas linhagens de Trichoderma visando a aplicação na produção de Etanol celulósico.
Produção e caracterização de (hemi)celulases de Aspergillusniger obtidas por diferentes sistemas de cultivo.
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