91 research outputs found
Current perpendicular to plane Giant Magnetoresistance (GMR) in laminated nanostructures
We theoretically studied spin dependent electron transport
perpendicular-to-plain (CPP) in magnetic laminated multilayered structures by
using Kubo formalism. We took into account not only bulk scattering, but the
interface resistance due to both specular and diffuse reflection and also spin
conserving and spin-flip processes. It was shown that spin-flip scattering at
interfaces substantially reduces the value of GMR. This can explain the
experimental observations that the CPP GMR ratio for laminated structures only
slightly increases as compared to non-laminated ones despite lamination induces
a significant increase in CPP resistance.Comment: 4 pages, 2 figure
Density-of-states picture and stability of ferromagnetism in the highly-correlated Hubbard model
The problem of stability of saturated and non-saturated ferromagnetism in the
Hubbard model is considered in terms of the one-particle Green's functions.
Approximations by Edwards and Hertz and some versions of the self-consistent
approximations based on the 1/z-expansion are considered. The account of
longitudinal fluctuations turns out to be essential for description of the
non-saturated state. The corresponding pictures of density of states are
obtained. "Kondo" density-of-states singularities owing to spin-flip processes
are analyzed. The critical electron concentrations for instabilities of
saturated ferromagnetism and paramagnetic state are calculated for various
lattices. Drawbacks of various approximations are discussed. A comparison with
the results of previous works is performed.Comment: 16 pages, 7 eps figure
Localization corrections to the anomalous Hall effect in a ferromagnet
We calculate the localization corrections to the anomalous Hall conductivity
related to the contribution of spin-orbit scattering into the current vertex
(side-jump mechanism). We show that in contrast to the ordinary Hall effect,
there exists a nonvanishing localization correction to the anomalous Hall
resistivity. The correction to the anomalous Hall conductivity vanishes in the
case of side-jump mechanism, but is nonzero for the skew scattering. The total
correction to the nondiagonal conductivity related to both mechanisms, does not
compensate the correction to the diagonal conductivity.Comment: 7 pages with 7 figure
Spin-dependent transport in nanocomposite C:Co films
The magneto-transport properties of nanocomposite C:Co (15 and 40 at.% Co)
thin films are investigated. The films were grown by ion beam co-sputtering on
thermally oxidized silicon substrates in the temperature range from 200 to 500
degC. Two major effects are reported: (i) a large anomalous Hall effect
amounting to 2 \mu ohm cm, and (ii) a negative magnetoresistance. Both the
field-dependent resistivity and Hall resistivity curves coincide with the
rescaled magnetization curves, a finding that is consistent with spin-dependent
transport. These findings suggest that C:Co nanocomposites are promising
candidates for carbon-based Hall sensors and spintronic devices.Comment: 13 pages, 7 figure
Dipolar interactions and anisotropic magnetoresistance in metallic granular systems
We revisit the theory of magnetoresistance for a system of nanoscopic
magnetic granules in metallic matrix. Using a simple model for the spin
dependent perturbation potential of the granules, we solve Boltzmann equation
for the spin dependent components of the non equilibrium electronic
distribution function. For typical values of the geometric parameters in
granular systems, we find a peculiar structure of the distribution function of
conduction electrons, which is at variance with the two-current model of
conduction in inhomogeneous systems. Our treatment explicitly includes the
effects of dipolar correlations yielding a magnetoresistance ratio which
contains, in addition to the term proportional to the square of uniform
magnetization (), a weak anisotropic contribution
depending on the angle between electric and magnetic fields, and arising from
the anisotropic character of dipolar interactions.Comment: 9 pages, 2 figures, accepted in PR
Magnetic modulation of inverse Spin Hall Effect in lateral spin-valves
International audienceWe analytically investigated the spin-dependent transport properties in a lateral spin-valve device comprising pinned ferromagnetic electrodes allowing to inject a spin current in a spin conducting channel where spin orbit scattering takes place. This produces an Inverse Spin Hall voltage (ISHE) across the thickness of the spin conducting channel. It is shown that by adding an extra soft ferromagnetic electrode with rotatable magnetization along the spin conducting channel, the ISHE generated voltage can be magnetically modulated by changing the magnetization orientation of this additional electrode. The dependence of the ISHE voltage on the direction of magnetization of the ferromagnetic electrode with rotatable magnetization was calculated in various configurations. Our results suggest that such structures could be considered as magnetic field sensors in situations where the total thickness of the sensor is constrained such as in hard disk drive readers
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