55 research outputs found
Room temperature and low-field resonant enhancement of spin Seebeck effect in partially compensated magnets
Resonant enhancement of spin Seebeck effect (SSE) due to phonons was recently
discovered in Y3Fe5O12 (YIG). This effect is explained by hybridization between
the magnon and phonon dispersions. However, this effect was observed at low
temperatures and high magnetic fields, limiting the scope for applications.
Here we report observation of phonon-resonant enhancement of SSE at room
temperature and low magnetic field. We observed in Lu2BiFe4GaO12 and
enhancement 700 % greater than that in a YIG film and at very low magnetic
fields around 10-1 T, almost one order of magnitude lower than that of YIG. The
result can be explained by the change in the magnon dispersion induced by
magnetic compensation due to the presence of non-magnetic ion substitutions.
Our study provides a way to tune the magnon response in a crystal by chemical
doping with potential applications for spintronic devices.Comment: 17 pages, 4 figure
Field-induced transition from parallel to perpendicular parametric pumping for a microstrip transducer
Microstrip transducers used for the excitation of spin waves in magnetic
films possess two characteristic properties: high spatial localization of the
microwave magnetic field and the presence of field components parallel and
perpendicular to the bias field.
Here, the effects of these features on the process of parametric pumping are
presented. By microwave measurements of the spin-wave instability threshold a
transition from parallel pumping to perpendicular pumping at the critical field
with the minimal threshold is observed. This transition is
accompanied by a sharp threshold increase above the critical field due to the
spatial confinement of the pump region.Comment: 4 pages, 2 figure
Reverse Doppler effect in backward spin waves scattered on acoustic waves
We report on the observation of reverse Doppler effect in backward spin waves
reflected off of surface acoustic waves. The spin waves are excited in a
yttrium iron garnet (YIG) film. Simultaneously, acoustic waves are also
generated. The strain induced by the acoustic waves in the magnetostrictive YIG
film results in the periodic modulation of the magnetic anisotropy in the film.
Thus, in effect, a travelling Bragg grating for the spin waves is produced. The
backward spin waves reflecting off of this grating exhibit a reverse Doppler
shift: shifting down rather than up in frequency when reflecting off of an
approaching acoustic wave. Similarly, the spin waves are shifted up in
frequency when reflecting from receding acoustic waves.Comment: 4 pages, 3 figure
Oscillatory Energy Exchange Between Waves Coupled by a Dynamic Artificial Crystal
We describe a general mechanism of controllable energy exchange between waves
propagating in a dynamic artificial crystal. We show that if a spatial
periodicity is temporarily imposed on the transmission properties of a
wave-carrying medium whilst a wave is inside, this wave is coupled to a
secondary counter-propagating wave and energy oscillates between the two. The
oscillation frequency is determined by the width of the spectral band gap
created by the periodicity and the frequency difference between the coupled
waves. The effect is demonstrated with spin waves in a dynamic magnonic
crystal.Comment: 5 pages, 4 figure
Temporal behavior of the inverse spin Hall voltage in a magnetic insulator-nonmagnetic metal structure
It is demonstrated that upon pulsed microwave excitation, the temporal
behavior of a spin-wave induced inverse spin Hall voltage in a magnetic
insulator-nonmagnetic metal structure is distinctly different from the temporal
evolution of the directly excited spin-wave mode from which it originates. The
difference in temporal behavior is attributed to the excitation of long-lived
secondary spin-wave modes localized at the insulator-metal interface
Probing of a parametrically pumped magnon gas with a non-resonant packet of traveling spin waves
The magnon gas created by spatially localized longitudinal parametric pumping
in an yttrium-iron-garnet film is probed by a traveling packet of spin waves
non-resonant with the pumping field. The analysis of the influence of the
magnon gas on the amplitude and phase of the propagating spin waves allows to
determine characteristic properties of the parametrically pumped magnon gas. A
simple theoretical model is proposed from which the magnon density in the
pumping region is calculated.Comment: 3 pages, 3 figure
Resonant scattering of spin waves from a region of inhomogeneous magnetic field in a ferromagnetic film
The transmission of a dipole-dominated spin wave in a ferromagnetic film
through a localised inhomogeneity in the form of a magnetic field produced by a
dc current through a wire placed on the film surface was studied experimentally
and theoretically. It was shown that the amplitude and phase of the transmitted
wave can be simultaneously affected by the current induced field, a feature
that will be relevant for logic based on spin wave transport.
The direction of the current creates either a barrier or well for spin wave
transmission. The main observation is that the current dependence of the
amplitude of the spin wave transmitted through the well inhomogeneity is
non-monotonic. The dependence has a minimum and an additional maximum. A theory
was constructed to clarify the nature of the maximum. It shows that the
transmission of spin waves through the inhomogeneity can be considered as a
scattering process and that the additional maximum is a scattering resonance
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