Macrospin in ferromagnetic nanojunctions

We study the passage of transverse current through a ferromagnetic nanojunctions, viz., a layered nanostructure of the spin-valve type containing two ferromagnetic layers separated by a spacer that prevents exchange coupling between the layers in the absence of current, but does not affect spin pola...

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Bibliographic Details
Published in:Journal of experimental and theoretical physics 2008-12, Vol.107 (6), p.1027-1038
Main Authors: Gulyaev, Yu. V., Zilberman, P. E., Panas, A. I., Epshtein, E. M.
Format: Article
Language:English
Subjects:
APPROXIMATIONS
Classical and Quantum Gravitation
Electronic Properties of Solids
Elementary Particles
EQUATIONS OF MOTION
EQUILIBRIUM
LAYERS
MAGNETIC FIELDS
MAGNETIZATION
NANOSCIENCE AND NANOTECHNOLOGY
NANOSTRUCTURES
Particle and Nuclear Physics
PHASE TRANSFORMATIONS
Physics
Physics and Astronomy
Quantum Field Theory
Relativity Theory
Solid State Physics
SPIN
SPIN ORIENTATION
TORQUE
VALVES
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Summary:We study the passage of transverse current through a ferromagnetic nanojunctions, viz., a layered nanostructure of the spin-valve type containing two ferromagnetic layers separated by a spacer that prevents exchange coupling between the layers in the absence of current, but does not affect spin polarization of the current. The conditions for a high level of injection of spins by current are derived at which the concentration of injected nonequilibrium spins can reach or even exceed their equilibrium concentration. In such conditions, a number of new effects are observed. The threshold of exchange switching by current is lowered by several orders of magnitude due to matching of spin resistances of the layers. The application of an external magnetic field in the vicinity of the orientation phase transition additionally lowers this threshold. This leads to multistability, in which one value of the current corresponds to two (or more) stable noncollinear orientations of magnetization, and switching itself becomes irreversible. A methodical feature of this research is that the calculation is performed in the so-called macrospin approximation, which is in good agreement with most of known experiments. In this approximation, the equations of motion taking into account the torque as well as spin injection are derived for the first time and solved.
ISSN:1063-7761
1090-6509
DOI:10.1134/S1063776108120121