328 research outputs found
Artificial ferroelectricity due to anomalous Hall effect in magnetic tunnel junctions
We theoretically investigated Anomalous Hall Effect (AHE) and Spin Hall
Effect (SHE) transversally to the insulating spacer O, in magnetic tunnel
junctions of the form F/O/F where F are ferromagnetic layers and O represents a
tunnel barrier. We considered the case of purely ballistic (quantum mechanical)
transport, taking into account the assymetric scattering due to spin-orbit
interaction in the tunnel barrier. AHE and SHE in the considered case have a
surface nature due to proximity effect. Their amplitude is in first order of
the scattering potential. This contrasts with ferromagnetic metals wherein
these effect are in second (side-jump scattering) and third (skew scattering)
order on these potentials. The value of AHE voltage in insulating spacer may be
much larger than in metallic ferromagnetic electrodes. For the antiparallel
orientation of the magnetizations in the two F-electrodes, a spontaneous Hall
voltage exists even at zero applied voltage. Therefore an insulating spacer
sandwiched between two ferromagnetic layers can be considered as exhibiting a
spontaneous ferroelectricity
Greenhouse effect in the atmosphere of Venus
Greenhouse effect in lower layers of Venus atmospher
Analytical description of ballistic spin currents and torques in magnetic tunnel junctions
In this work we demonstrate explicit analytical expressions for both charge
and spin currents which constitute the 2x2 spinor in magnetic tunnel junctions
with noncollinear magnetizations under applied voltage. The calculations have
been performed within the free electron model in the framework of the Keldysh
formalism and WKB approximation. We demonstrate that spin/charge currents and
spin transfer torques are all explicitly expressed through only three
irreducible quantities, without further approximations. The conditions and
mechanisms of deviation from the conventional sine angular dependence of both
spin currents and torques are shown and discussed. It is shown in the thick
barrier approximation that all tunneling transport quantities can be expressed
in an extremely simplified form via Slonczewski spin polarizations and our
effective spin averaged interfacial transmission probabilities and effective
out-of-plane polarizations at both interfaces. It is proven that the latter
plays a key role in the emergence of perpendicular spin torque as well as in
the angular dependence character of all spin and charge transport considered.
It is demonstrated directly also that for any applied voltage, the parallel
component of spin current at the FM/I interface is expressed via collinear
longitudinal spin current components. Finally, spin transfer torque behavior is
analyzed in a view of transverse characteristic length scales for spin
transport.Comment: 10 pages, 6 figure
RAILWAY NATURAL INDUSTRIAL COMPLEXES AND THEIR IMPACT ON WATERBODIES
The paper aims to investigate objects located in railway natural industrial complexes, e.g. the Kuybyshevskaya Railway within the boundaries of Samara region. The authors analyse its following characteristic properties: geometric (proximity to water bodies); intercepted (crossings with bridges or waterbodies); watercut (proximity to subsurface water outlets and high groundwater); hilly-mountainous terrain (washouts and washaways); violation of surface (water drainage from the walls, washaways of flood-prone slopes). The researchers studied a schematic map of the Kuybyshevskaya Railway and came to the conclusion that there is a considerable number of railways crossings with water objects in Samara region, Ulyanovsk region and the Republic of Tatarstan. Some of these railways crossings are located in close proximity to waterbodies. The average value of the crossings is 0.549 km for every 1 km, i.e. approximately every 500 m railway tracks cross at least one water object. It means that there is a surface run-off coming from railroad tracks and near-by territories into a waterbody every 500 m. Systematic monitoring of water pollution is performed by a considerable number (up to 20) of gauging stations located within all railroad tracks in Samara region
Does Giant Magnetoresistance Survive in Presence of Superconducting Contact?
The giant magnetoresistance (GMR) of ferromagnetic bilayers with a
superconducting contact (F1/F2/S) is calculated in ballistic and diffusive
regimes. As in spin-valve, it is assumed that the magnetization in the two
ferromagnetic layers F1 and F2 can be changed from parallel to antiparallel. It
is shown that the GMR defined as the change of conductance between the two
magnetic configurations is an oscillatory function of the thickness of F2 layer
and tends to an asymptotic positive value at large thickness. This is due to
the formation of quantum well states in F2 induced by Andreev reflection at the
F2/S interface and reflection at F1/F2 interface in antiparallel configuration.
In the diffusive regime, if only spin-dependent scattering rates in the
magnetic layers are considered (no difference in Fermi wave-vectors between
spin up and down electrons) then the GMR is supressed due to the mixing of spin
up and down electron-hole channels by Andreev reflection.Comment: 7 pages, 4 figures, submitted to Phys.Rev.Let
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