470 research outputs found
Thermal Control of the Magnon-Photon Coupling in a Notch Filter coupled to a Yttrium-Iron-Garnet/Platinum System
We report thermal control of mode hybridization between the ferromagnetic
resonance (FMR) and a planar resonator (notch filter) working at 4.74 GHz. The
chosen magnetic material is a ferrimagnetic insulator (Yttrium Iron Garnet:
YIG) covered by 6 nm of platinum (Pt). A current induced heating method has
been used in order to enhance the temperature of the YIG/Pt system. The device
permits us to control the transmission spectra and the magnon-photon coupling
strength at room temperature. These experimental findings reveal potentially
applicable tunable microwave filtering function.Comment: 5 pages, 4 figure
Observation of the spin Peltier effect
We report the observation of the spin Peltier effect (SPE) in the
ferrimagnetic insulator Yttrium Iron Garnet (YIG), i.e. a heat current
generated by a spin current flowing through a Platinum (Pt)|YIG interface. The
effect can be explained by the spin torque that transforms the spin current in
the Pt into a magnon current in the YIG. Via magnon-phonon interactions the
magnetic fluctuations modulate the phonon temperature that is detected by a
thermopile close to the interface. By finite-element modelling we verify the
reciprocity between the spin Peltier and spin Seebeck effect. The observed
strong coupling between thermal magnons and phonons in YIG is attractive for
nanoscale cooling techniques.Comment: 5 pages, 3 figures, 4 pages supplementary information, 4
supplementary figure
Coherent long-range transfer of angular momentum between magnon Kittel modes by phonons
We report ferromagnetic resonance in the normal configuration of an
electrically insulating magnetic bilayer consisting of two yttrium iron garnet
(YIG) films epitaxially grown on both sides of a 0.5-mm-thick nonmagnetic
gadolinium gallium garnet (GGG) slab. An interference pattern is observed and
it is explained as the strong coupling of the magnetization dynamics of the two
YIG layers either in phase or out of phase by the standing transverse sound
waves, which are excited through a magnetoelastic interaction. This coherent
mediation of angular momentum by circularly polarized phonons through a
nonmagnetic material over macroscopic distances can be useful for future
information technologies
Optimizing the magnon-phonon cooperativity in planar geometries
Optimizing the cooperativity between two distinct particles is an important
feature of quantum information processing. Of particular interest is the
coupling between spin and phonon, which allows for integrated long range
communication between gates operating at GHz frequency. Using local light
scattering, we show that, in magnetic planar geometries, this attribute can be
tuned by adjusting the orientation and strength of an external magnetic field.
The coupling strength is enhanced by about a factor of 2 for the out-of-plane
magnetized geometry where the Kittel mode is coupled to circularly polarized
phonons, compared to the in-plane one where it couples to linearly polarized
phonons. We also show that the overlap between magnon and phonon is maximized
by matching the Kittel frequency with an acoustic resonance that satisfies the
half-wave plate condition across the magnetic film thickness. Taking the
frequency dependence of the damping into account, a maximum cooperativity of
about 6 is reached in garnets for the normal configuration near 5.5 GHz
Morbidity of 200 Consecutive Cases of Hand-Assisted Laparoscopic Living Donor Nephrectomies: A Single-Center Experience
Background. Recipients of laparoscopically procured kidneys have been reported to have delayed graft function, a slower creatinine nadir, and potential significant complications. As the technique has evolved laparoscopic donor nephrectomy technique is becoming the gold standard for living donation. Study Design. We retrospectively reviewed the data of the first 200 hand-assisted laparoscopic living donor nephrectomies performed between January 2003 and February 2009. The initial 41 donors and their recipients (Group 1) were compared to the next 159 donors and their recipients (Group 2). The estimated blood loss, serum creatinine at discharge and 6 months, and the incidence of delayed graft function and perioperative complications were analyzed. Results. The median donor serum creatinine at discharge and 6 months was 1.2 mg/dL in each group. None of the laparoscopic procedures required conversion to an open procedure, and none of the donors required perioperative blood transfusion. The median recipient serum creatinine at 6 months after transplant was 1.2 mg/dL for each group. No ischemic ureteral complications related to the laparoscopic technique were seen. Conclusions. HALDN with meticulous surgical technique allows kidney procurement with very low morbidity and no mortality. This improved safety and decreased invasiveness from laparoscopic approach may further decrease morbidity of the procedure and increase organ donation
Electrically induced strong modulation of magnon transport in ultrathin magnetic insulator films
Magnon transport through a magnetic insulator can be controlled by
current-biased heavy-metal gates that modulate the magnon conductivity via the
magnon density. Here, we report nonlinear modulation effects in 10nm thick
yttrium iron garnet (YIG) films. The modulation efficiency is larger than
40\%/mA. The spin transport signal at high DC current density (2.2A/m) saturates for a 400nm wide Pt gate, which indicates
that even at high current levels a magnetic instability cannot be reached in
spite of the high magnetic quality of the films
Giant magnon spin conductivity approaching the two-dimensional transport regime in ultrathin yttrium iron garnet films
Conductivities are key material parameters that govern various types of
transport (electronic charge, spin, heat etc.) driven by thermodynamic forces.
Magnons, the elementary excitations of the magnetic order, flow under the
gradient of a magnon chemical potential in proportion to a magnon (spin)
conductivity . The magnetic insulator yttrium iron garnet (YIG) is
the material of choice for efficient magnon spin transport. Here we report an
unexpected giant in record-thin YIG films with thicknesses down to
3.7 nm when the number of occupied two-dimensional (2D) subbands is reduced
from a large number to a few, which corresponds to a transition from 3D to 2D
magnon transport. We extract a 2D spin conductivity ( S) at room
temperature, comparable to the (electronic) spin conductivity of the
high-mobility two-dimensional electron gas in GaAs quantum wells at millikelvin
temperatures. Such high conductivities offer unique opportunities to develop
low-dissipation magnon-based spintronic devices
Large time existence for 3D water-waves and asymptotics
We rigorously justify in 3D the main asymptotic models used in coastal
oceanography, including: shallow-water equations, Boussinesq systems,
Kadomtsev-Petviashvili (KP) approximation, Green-Naghdi equations, Serre
approximation and full-dispersion model. We first introduce a ``variable''
nondimensionalized version of the water-waves equations which vary from shallow
to deep water, and which involves four dimensionless parameters. Using a
nonlocal energy adapted to the equations, we can prove a well-posedness
theorem, uniformly with respect to all the parameters. Its validity ranges
therefore from shallow to deep-water, from small to large surface and bottom
variations, and from fully to weakly transverse waves. The physical regimes
corresponding to the aforementioned models can therefore be studied as
particular cases; it turns out that the existence time and the energy bounds
given by the theorem are always those needed to justify the asymptotic models.
We can therefore derive and justify them in a systematic way.Comment: Revised version of arXiv:math.AP/0702015 (notations simplified and
remarks added) To appear in Inventione
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