1,100 research outputs found
Spin torque driven dynamics of a coupled two layer structure: interplay between conservative and dissipative coupling
In this manuscript the general concepts of spin wave theory are adapted to
the dynamics of a self-polarized system based on two layers coupled via
interlayer exchange (conservative coupling) and mutual spin torque (dissipative
coupling). An analytical description of the non-linear dynamics is proposed and
validated through numerical simulations. In contrast to the single layer model,
the phase equation of the coupled system has a contribution coming from the
dissipative part of the LLGS equation. It is shown that this is a major
contribution to the frequency mandatory to describe well the most basic
features of the dynamics of coupled systems. Using the proposed model a
specific feature of coupled dynamics is addressed: the redshift to blueshift
transition observed in the frequency current dependence of this kind of
exchange coupled systems upon increasing the applied field. It is found that
the blueshift regime can only occur in a region of field where the two linear
eigenmodes contribute equally to the steady state mode (i.e. high mode
hybridization). Finally, a general perturbed Hamiltonian equation for the
coupled system is proposed.Comment: 16 pages, 7 figue
Inertial terms to magnetization dynamics in ferromagnetic thin films
Inertial magnetization dynamics have been predicted at ultrahigh speeds, or
frequencies approaching the energy relaxation scale of electrons, in
ferromagnetic metals. Here we identify inertial terms to magnetization dynamics
in thin NiFe and Co films near room temperature. Effective
magnetic fields measured in high-frequency ferromagnetic resonance (115-345
GHz) show an additional stiffening term which is quadratic in frequency and
80 mT at the high frequency limit of our experiment. Our results extend
understanding of magnetization dynamics at sub-picosecond time scales.Comment: 11 pages, 3 figure
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