188 research outputs found
Current-driven destabilization of both collinear configurations in asymmetric spin-valves
Spin transfer torque in spin valves usually destabilizes one of the collinear
configurations (either parallel or antiparallel) and stabilizes the second one.
Apart from this, balance of the spin-transfer and damping torques can lead to
steady precessional modes. In this letter we show that in some asymmetric
nanopillars spin current can destabilize both parallel and antiparallel
configurations. As a result, stationary precessional modes can occur at zero
magnetic field. The corresponding phase diagram as well as frequencies of the
precessional modes have been calculated in the framework of macrospin model.
The relevant spin transfer torque has been calculated in terms of the
macroscopic model based on spin diffusion equations.Comment: 4 pages, 4 figure
Spin effects in single-electron tunneling in magnetic junctions
Spin dependent single electron tunneling in ferromagnetic double junctions is
analysed theoretically in the limit of sequential tunneling. The influence of
discrete energy spectrum of the central electrode (island)on the spin
accumulation, spin fluctuations and tunnel magnetoresistance is analysed
numerically in the case of a nonmagnetic island. It is shown that spin
fluctuations are significant in magnetic as well as in nonmagnetic junctions.Comment: 14 pages, 3 eps-figures include
Nonlinear magnetotransport in dual spin valves
Recent experimental measurements of magnetoresistance in dual spin valves [A.
Aziz et al., Phys. Rev. Lett. 103, 237203 (2009)] reveal some nonlinear
features of transport, which have not been observed in other systems. We
propose a phenomenological model describing current-dependent resistance (and
giant magnetoresistance) in double spin valves. The model is based on a
modified Valet-Fert approach, and takes into account the dependence of
bulk/interface resistance and bulk/interface spin asymmetry parameters for the
central magnetic layer on spin accumulation, and consequently on charge
current. Such a nonlinear model accounts for recent experimental observations
Gate-controlled spin polarized current in ferromagnetic single electron transistors
We theoretically investigate spin dependent transport in ferromagnetic/normal
metal/ferromagnetic single electron transistors by applying master equation
calculations using a two dimensional space of states involving spin and charge
degrees of freedom. When the magnetizations of ferromagnetic leads are in
anti-parallel alignment, the spins accumulate in the island and a difference of
chemical potentials of the two spins is built up. This shift in chemical
potential acts as charge offset in the island and alternates the gate
dependence of spin current. Taking advantage of this effect, one can control
the polarization of current up to the polarization of lead by tuning gate
voltages.Comment: 5 pages, 4 figure
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