420 research outputs found
Cross country defence management:a case study into the management of defences in the pipeline industry
Magnons versus electrons in thermal spin transport through metallic interfaces
We develop a theory for spin transport in magnetic metals that treats the
contribution of magnons and electrons on equal footing. As an application we
consider thermally-driven spin injection across an interface between a magnetic
metal and a normal metal, i.e., the spin-dependent Seebeck effect. We show that
the ratio between magnonic and electronic contribution scales as
, with the Fermi temperature and the Curie
temperature . Since, typically, , the magnonic contribution
may dominate the thermal spin injection, even though the interface is more
transparent for electronic spin current.Comment: Contribution to the Special issue on Spincaloritronics in Journal of
Physics D: Applied Physic
Phenomenology of current-induced skyrmion motion in antiferromagnets
We study current-driven skyrmion motion in uniaxial thin film
antiferromagnets in the presence of the Dzyaloshinskii-Moriya interactions and
in an external magnetic field. We phenomenologically include relaxation and
current-induced torques due to both spin-orbit coupling and spatially
inhomogeneous magnetic textures in the equation for the N\'eel vector of the
antiferromagnet. Using the collective coordinate approach we apply the theory
to a two-dimensional antiferromagnetic skyrmion and estimate the skyrmion
velocity under an applied DC electric current.Comment: 14 pages, 3 figures, 1 tabl
Modeling ultrafast demagnetization and spin transport: the interplay of spin-polarized electrons and thermal magnons
We theoretically investigate laser-induced spin transport in metallic
magnetic heterostructures using an effective spin transport description that
treats itinerant electrons and thermal magnons on an equal footing.
Electron-magnon scattering is included and taken as the driving force for
ultrafast demagnetization. We assume that in the low-fluence limit the magnon
system remains in a quasi-equilibrium, allowing a transient nonzero magnon
chemical potential. In combination with the diffusive transport equations for
the itinerant electrons, the description is used to chart the full spin
dynamics within the heterostructure. In agreement with recent experiments, we
find that in case the spin-current-receiving material includes an efficient
spin dissipation channel, the interfacial spin current becomes directly
proportional to the temporal derivative of the magnetization. Based on an
analytical calculation, we discuss that other relations between the spin
current and magnetization may arise in case the spin-current-receiving material
displays inefficient spin-flip scattering. Finally, we discuss the role of
(interfacial) magnon transport and show that, a priori, it cannot be neglected.
However, its significance strongly depends on the system parameters
Probing optical spin-currents using THz spin-waves in noncollinear magnetic bilayers
Optically induced spin currents have proven to be useful in spintronics
applications, allowing for sub-ps all-optical control of magnetization.
However, the mechanism responsible for their generation is still heavily
debated. Here we use the excitation of spin-current induced THz spin-waves in
noncollinear bilayer structures to directly study optical spin-currents in the
time domain. We measure a significant laser-fluence dependence of the spin-wave
phase, which can quantitatively be explained assuming the spin current is
proportional to the time derivative of the magnetization. Measurements of the
absolute spin-wave phase, supported by theoretical calculations and
micromagnetic simulations, suggest that a simple ballistic transport picture is
sufficient to properly explain spin transport in our experiments and that the
damping-like optical STT dominates THz spin-wave generation. Our findings
suggest laser-induced demagnetization and spin-current generation share the
same microscopic origin.Comment: Supplementary information include
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