15 research outputs found
Magnonic crystal based forced dominant wavenumber selection in a spin-wave active ring
Spontaneous excitation of the dominant mode in a spin-wave active ring -- a
self-exciting positive-feedback system incorporating a spin-wave transmission
structure -- occurs at a certain threshold value of external gain. In general,
the wavenumber of the dominant mode is extremely sensitive to the properties
and environment of the spin-wave transmission medium, and is almost impossible
to predict. In this letter, we report on a backward volume magnetostatic
spin-wave active ring system incorporating a magnonic crystal. When mode
enhancement conditions -- readily predicted by a theoretical model -- are
satisfied, the ring geometry permits highly robust and consistent forced
dominant wavenumber selection.Comment: 4 pages, 3 figure
Strong coupling of magnons in a YIG sphere to photons in a planar superconducting resonator in the quantum limit
We report measurements of a superconducting coplanar waveguide resonator
(CPWR) coupled to a sphere of yttrium-iron garnet. The non-uniform CPWR field
allows us to excite various magnon modes in the sphere. Mode frequencies and
relative coupling strengths are consistent with theory. Strong coupling is
observed to several modes even with, on average, less than one excitation
present in the CPWR. The time response to square pulses shows oscillations at
the mode splitting frequency. These results indicate the feasibility of
combining magnonic and planar superconducting quantum devices.Comment: 5 pages, 4 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
Microwave magnon damping in YIG films at millikelvin temperatures
Magnon systems used in quantum devices require low damping if coherence is to
be maintained. The ferrimagnetic electrical insulator yttrium iron garnet (YIG)
has low magnon damping at room temperature and is a strong candidate to host
microwave magnon excitations in future quantum devices. Monocrystalline YIG
films are typically grown on gadolinium gallium garnet (GGG) substrates. In
this work, comparative experiments made on YIG waveguides with and without GGG
substrates indicate that the material plays a significant role in increasing
the damping at low temperatures. Measurements reveal that damping due to
temperature-peak processes is dominant above 1 K. Damping behaviour that we
show can be attributed to coupling to two-level fluctuators (TLFs) is observed
below 1 K. Upon saturating the TLFs in the substrate-free YIG at 20 mK,
linewidths of 1.4 MHz are achievable: lower than those measured at room
temperature.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