18 research outputs found
Low-damping transmission of spin waves through YIG/Pt-based layered structures for spin-orbit-torque applications
We show that in YIG-Pt bi-layers, which are widely used in experiments on the
spin transfer torque and spin Hall effects, the spin-wave amplitude
significantly decreases in comparison to a single YIG film due to the
excitation of microwave eddy currents in a Pt coat. By introducing a novel
excitation geometry, where the Pt layer faces the ground plane of a microstrip
line structure, we suppressed the excitation of the eddy currents in the Pt
layer and, thus, achieved a large increase in the transmission of the
Damon-Eshbach surface spin wave. At the same time, no visible influence of an
external dc current applied to the Pt layer on the spin-wave amplitude in the
YIG-Pt bi-layer was observed in our experiments with YIG films of micrometer
thickness
Temperature dependent relaxation of dipole-exchange magnons in yttrium iron garnet films
Low energy consumption enabled by charge-free information transport, which is
free from ohmic heating, and the ability to process phase-encoded data by
nanometer-sized interference devices at GHz and THz frequencies are just a few
benefits of spin-wave-based technologies. Moreover, when approaching cryogenic
temperatures, quantum phenomena in spin-wave systems pave the path towards
quantum information processing. In view of these applications, the lifetime of
magnonsspin-wave quantais of high relevance for the fields of magnonics,
magnon spintronics and quantum computing. Here, the relaxation behavior of
parametrically excited magnons having wavenumbers from zero up to was experimentally investigated in the temperature range
from 20 K to 340 K in single crystal yttrium iron garnet (YIG) films
epitaxially grown on gallium gadolinium garnet (GGG) substrates as well as in a
bulk YIG crystalthe magnonic materials featuring the lowest magnetic damping
known so far. As opposed to the bulk YIG crystal in YIG films we have found a
significant increase in the magnon relaxation rate below 150 Kup to 10.5
times the reference value at 340 Kin the entire range of probed wavenumbers.
This increase is associated with rare-earth impurities contaminating the YIG
samples with a slight contribution caused by coupling of spin waves to the spin
system of the paramagnetic GGG substrate at the lowest temperatures
Double accumulation and anisotropic transport of magneto-elastic bosons in yttrium iron garnet films
Interaction between quasiparticles of a different nature, such as magnons and
phonons in a magnetic medium, leads to the mixing of their properties and the
formation of hybrid states in the areas of intersection of individual spectral
branches. We recently reported the discovery of a new phenomenon mediated by
the magnon-phonon interaction: the spontaneous bottleneck accumulation of
magneto-elastic bosons under electromagnetic pumping of pure magnons into a
ferrimagnetic yttrium iron garnet film. Here, by studying the transport
properties of the accumulated magneto-elastic bosons, we reveal that such
accumulation occurs in two frequency-distant groups of quasiparticles:
quasi-phonons and quasi-magnons. They propagate with different speeds in
different directions relative to the magnetization field. The theoretical model
we propose qualitatively describes the double accumulation effect, and the
analysis of the two-dimensional spectrum of quasiparticles in the hybridization
region allows us to determine the wavevectors and frequencies of each of the
groups
Tunable space-time crystal in room-temperature magnetodielectrics
We report the experimental realization of a space-time crystal with tunable
periodicity in time and space in the magnon Bose-Einstein Condensate (BEC),
formed in a room-temperature Yttrium Iron Garnet (YIG) film by radio-frequency
space-homogeneous magnetic field. The magnon BEC is prepared to have a well
defined frequency and non-zero wavevector. We demonstrate how the crystalline
"density" as well as the time and space textures of the resulting crystal may
be tuned by varying the experimental parameters: external static magnetic
field, temperature, thickness of the YIG film and power of the radio-frequency
field. The proposed space-time crystals provide a new dimension for exploring
dynamical phases of matter and can serve as a model nonlinear Floquet system,
that brings in touch the rich fields of classical nonlinear waves, magnonics
and periodically driven systems
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
Long-distance supercurrent transport in a room-temperature Bose-Einstein magnon condensate
The term supercurrent relates to a macroscopic dissipation-free collective
motion of a quantum condensate and is commonly associated with such famous
low-temperature phenomena as superconductivity and superfluidity. Another type
of motion of quantum condensates is second sound - a wave of the density of a
condensate. Recently, we reported on an enhanced decay of a parametrically
induced Bose-Einstein condensate (BEC) of magnons caused by a supercurrent
outflow of the BEC phase from the locally heated area of a room temperature
magnetic film. Here, we present the direct experimental observation of a
long-distance spin transport in such a system. The condensed magnons being
pushed out from the potential well within the heated area form a density wave,
which propagates through the BEC many hundreds of micrometers in the form of a
specific second sound pulse - Bogoliubov waves - and is reflected from the
sample edge. The discovery of the long distance supercurrent transport in the
magnon BEC further advances the frontier of the physics of quasiparticles and
allows for the application of related transport phenomena for low-loss data
transfer in perspective magnon spintronics devices
Strong magnon-photon coupling with chip-integrated YIG in the zero-temperature limit
The cross-integration of spin-wave and superconducting technologies is a
promising method for creating novel hybrid devices for future information
processing technologies to store, manipulate, or convert data in both classical
and quantum regimes. Hybrid magnon-polariton systems have been widely studied
using bulk Yttrium Iron Garnet (YFeO, YIG) and
three-dimensional microwave photon cavities. However, limitations in YIG growth
have thus far prevented its incorporation into CMOS compatible technology such
as high quality factor superconducting quantum technology. To overcome this
impediment, we have used Plasma Focused Ion Beam (PFIB) technology -- taking
advantage of precision placement down to the micron-scale -- to integrate YIG
with superconducting microwave devices. Ferromagnetic resonance has been
measured at millikelvin temperatures on PFIB-processed YIG samples using planar
microwave circuits. Furthermore, we demonstrate strong coupling between
superconducting resonator and YIG ferromagnetic resonance modes by maintaining
reasonably low loss while reducing the system down to the micron scale. This
achievement of strong coupling on-chip is a crucial step toward fabrication of
functional hybrid quantum devices that advantage from spin-wave and
superconducting components.Comment: 10 pages, 6 figure