247 research outputs found
Thermal relaxation in charge ordered Pr Ca MnO in presence of a magnetic field
We report observation of substantial thermal relaxation in single crystal of
charge ordered system PrCaMnO in an applied magnetic
field of H = 8T. The relaxation is observed when the temperature is scanned in
presence of a magnetic field in the temperature interval
where is the charge ordering temperature and is charge
melting temperature in a field. In this temperature range the system has
coexisting charged ordered insulator (COI) and ferromagnetic metallic (FMM)
phases. No such relaxation is observed in the COI state in H = 0T or in the FMM
phase at in presence of a magnetic field. We conclude that the
thermal relaxation is due to two coexisting phases with nearly same free
energies but separated by a potential barrier. This barrier makes the
transformation from one phase to the other time-dependent in the scale of the
specific heat experiment and gives rise to the thermal relaxation.Comment: 4 pages LaTEX, 3 eps figure
Measurement of the intrinsic damping constant in individual nanodisks of YIG and YIG{\textbar}Pt
We report on an experimental study on the spin-waves relaxation rate in two
series of nanodisks of diameter 300, 500 and 700~nm, patterned out of
two systems: a 20~nm thick yttrium iron garnet (YIG) film grown by pulsed laser
deposition either bare or covered by 13~nm of Pt. Using a magnetic resonance
force microscope, we measure precisely the ferromagnetic resonance linewidth of
each individual YIG and YIG{\textbar}Pt nanodisks. We find that the linewidth
in the nanostructure is sensibly smaller than the one measured in the extended
film. Analysis of the frequency dependence of the spectral linewidth indicates
that the improvement is principally due to the suppression of the inhomogeneous
part of the broadening due to geometrical confinement, suggesting that only the
homogeneous broadening contributes to the linewidth of the nanostructure. For
the bare YIG nano-disks, the broadening is associated to a damping constant
. A 3 fold increase of the linewidth is observed for
the series with Pt cap layer, attributed to the spin pumping effect. The
measured enhancement allows to extract the spin mixing conductance found to be
for our
YIG(20nm){\textbar}Pt interface, thus opening large opportunities for the
design of YIG based nanostructures with optimized magnetic losses.Comment: 4 pages, 3 figure
Inverse Spin Hall Effect in nanometer-thick YIG/Pt system
High quality nanometer-thick (20 nm, 7 nm and 4 nm) epitaxial YIG films have
been grown on GGG substrates using pulsed laser deposition. The Gilbert damping
coefficient for the 20 nm thick films is 2.3 x 10-4 which is the lowest value
reported for sub-micrometric thick films. We demonstrate Inverse spin Hall
effect (ISHE) detection of propagating spin waves using Pt. The amplitude and
the lineshape of the ISHE voltage correlate well to the increase of the Gilbert
damping when decreasing thickness of YIG. Spin Hall effect based
loss-compensation experiments have been conducted but no change in the
magnetization dynamics could be detected
Evidence of non-degenerated, non-reciprocal and ultra-fast spin-waves in the canted antiferromagnet {\alpha}-Fe2O3
Spin-waves in antiferromagnets hold the prospects for the development of
faster, less power-hungry electronics, as well as new physics based on
spin-superfluids and coherent magnon-condensates. For both these perspectives,
addressing electrically coherent antiferromagnetic spin-waves is of importance,
a prerequisite that has so far been elusive, because unlike ferromagnets,
antiferromagnets couple weakly to radiofrequency fields. Here, we demonstrate
the electrical detection of ultra-fast non-reciprocal spin-waves in the
dipolar-exchange regime of a canted antiferromagnet. Using time-of-flight
spin-wave spectroscopy on hematite (alpha-Fe2O3), we find that the magnon wave
packets can propagate as fast as 30 km/s for reciprocal bulk spin-wave modes
and up to 10 km/s for surface-spin waves propagating parallel to the
antiferromagnetic N\'eel vector. The electrical detection of coherent
non-reciprocal antiferromagnetic spin waves holds makes hematite a versatile
platform where most of the magnonic concepts developed for ferromagnet can be
adapted paving the way for the development antiferromagnetic and
altermagnet-based magnonic devices
Hybrid Composition of Web Services and Grid Services
Abstract Web service composition is now seen as a focal point of research, especially as mechanisms for the coordination of distributed tasks are acquiring more importance. Models such as BPEL4WS can cater for local and centralised coordination. There is, however, a need to reconcile different technologies on a wider scale. This requires the development of efficient and flexible frameworks in order to ensure the optimal use and coordination of distributed applications. The work presented in this paper is concerned with the development of a compositional framework, which brings together Grid services, Web services and Semantic Web technology within a BPEL4WS platform. It is aimed at enhancing BPEL4WS by allowing for the hybrid composition of Web services and Grid services, and by incorporating dynamic binding through agent mediation. The efficient management of workflows afforded by BPEL4WS is combined with the versatility of agent technology. An agent-based system, called SOA, was developed to support the framework
Electronic control of the spin-wave damping in a magnetic insulator
It is demonstrated that the decay time of spin-wave modes existing in a
magnetic insulator can be reduced or enhanced by injecting an in-plane dc
current, , in an adjacent normal metal with strong spin-orbit
interaction. The demonstration rests upon the measurement of the ferromagnetic
resonance linewidth as a function of in a 5~m diameter
YIG(20nm){\textbar}Pt(7nm) disk using a magnetic resonance force microscope
(MRFM). Complete compensation of the damping of the fundamental mode is
obtained for a current density of , in
agreement with theoretical predictions. At this critical threshold the MRFM
detects a small change of static magnetization, a behavior consistent with the
onset of an auto-oscillation regime.Comment: 6 pages 4 figure
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