3,377 research outputs found
Ab initio studies of the spin-transfer torque in tunnel junctions
We calculate the spin-transfer torque in Fe/MgO/Fe tunnel junctions and
compare the results to those for all-metallic junctions. We show that the
spin-transfer torque is interfacial in the ferromagnetic layer to a greater
degree than in all-metallic junctions. This result originates in the half
metallic behavior of Fe for the states at the Brillouin zone center;
in contrast to all-metallic structures, dephasing does not play an important
role. We further show that it is possible to get a component of the torque that
is out of the plane of the magnetizations and that is linear in the bias.
However, observation of such a torque requires highly ideal samples. In samples
with typical interfacial roughness, the torque is similar to that in
all-metallic multilayers, although for different reasons.Comment: 5 pages, 4 figure
Identification of the dominant precession damping mechanism in Fe, Co, and Ni by first-principles calculations
The Landau-Lifshitz equation reliably describes magnetization dynamics using
a phenomenological treatment of damping. This paper presents first-principles
calculations of the damping parameters for Fe, Co, and Ni that quantitatively
agree with existing ferromagnetic resonance measurements. This agreement
establishes the dominant damping mechanism for these systems and takes a
significant step toward predicting and tailoring the damping constants of new
materials.Comment: 4 pages, 1 figur
A numerical method to solve the Boltzmann equation for a spin valve
We present a numerical algorithm to solve the Boltzmann equation for the
electron distribution function in magnetic multilayer heterostructures with
non-collinear magnetizations. The solution is based on a scattering matrix
formalism for layers that are translationally invariant in plane so that
properties only vary perpendicular to the planes. Physical quantities like spin
density, spin current, and spin-transfer torque are calculated directly from
the distribution function. We illustrate our solution method with a systematic
study of the spin-transfer torque in a spin valve as a function of its
geometry. The results agree with a hybrid circuit theory developed by
Slonczewski for geometries typical of those measured experimentally.Comment: 13 pages, 8 figure
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