5,943 research outputs found
Spin accumulation and dynamics in inversion-symmetric van der Waals crystals
Inversion symmetric materials are forbidden to show an overall spin texture
in their band structure in the presence of time-reversal symmetry. However, in
van der Waals materials which lack inversion symmetry within a single layer, it
has been proposed that a layer-dependent spin texture can arise leading to a
coupled spin-layer degree of freedom. Here we use time-resolved Kerr rotation
in inversion symmetric WSe and MoSe bulk crystals to study this
spin-layer polarization and unveil its dynamics. Our measurements show that the
spin-layer relaxation time in WSe is limited by phonon-scattering at high
temperatures and that the inter-layer hopping can be tunned by a small in-plane
magnetic field at low temperatures, enhancing the relaxation rates. We find a
significantly lower lifetime for MoSe which agrees with theoretical
expectations of a spin-layer polarization stabilized by the larger spin-orbit
coupling in WSe
Thickness dependence of spin-orbit torques generated by WTe2
We study current-induced torques in WTe2/permalloy bilayers as a function of
WTe2 thickness. We measure the torques using both second-harmonic Hall and
spin-torque ferromagnetic resonance measurements for samples with WTe2
thicknesses that span from 16 nm down to a single monolayer. We confirm the
existence of an out-of-plane antidamping torque, and show directly that the
sign of this torque component is reversed across a monolayer step in the WTe2.
The magnitude of the out-of-plane antidamping torque depends only weakly on
WTe2 thickness, such that even a single-monolayer WTe2 device provides a strong
torque that is comparable to much thicker samples. In contrast, the
out-of-plane field-like torque has a significant dependence on the WTe2
thickness. We demonstrate that this field-like component originates
predominantly from the Oersted field, thereby correcting a previous inference
drawn by our group based on a more limited set of samples.Comment: 8 pages, 8 figure
Disorder is not always bad for charge-to-spin conversion in WTe2
The Wang group at Stanford University demonstrates disordered WTex films for efficient charge-to-spin conversion phenomena. The deposition of these films by sputtering and the charge-to-spin conversion resilience against disorder make them attractive for applications in new magnetic memory devices
Pneumocephalus Following Unidentified Dural Puncture: A Case Report with an Unusual Neurological Presentation
Pneumocephalus is a rare consequence of epidural anesthesia, which may occur following inadvertent or unidentified dural puncture when the loss of resistance to air technique is applied to identify the epidural space. Headache is the most common symptom presented in this condition, usually with sudden onset. This case report describes an unusual presentation of diffuse pneumocephalus after an unidentified dural puncture. The patient (male, 67 years old) was submitted to epidural catheter placement for the treatment of acute exacerbation of ischemic chronic pain using loss of resistance to air technique. No cerebrospinal fluid or blood flashback was observed after needle withdrawal. Shortly after the intervention, the patient presented symptoms of lethargy, apathy, and hypophonia, which are not commonly associated with pneumocephalus. No motor or sensory deficits were detected. Cranial computed tomography showed air in the frontal horn of the left ventricle, subarachnoid space at interhemispheric fissure and basal cisterns, confirming the diagnosis of diffuse pneumocephalus. The patient remained under vigilance with oxygen therapy and the epidural catheter left in place. After 24 hours, cranial computed tomography showed air in the temporal and frontal horns of the left ventricle, with no air in the subarachnoid space. The patient presented no neurological signs or symptoms at this time. Although headache is the most common symptom presented in reported cases of pneumocephalus, this case shows the need for the clinician to be aware of other signs and symptoms that may be indicative of this condition, in order to properly diagnose and treat these patients.info:eu-repo/semantics/publishedVersio
Anomalous metamagnetic-like transition in a FeRh/FePt interface occurring at T120 K in the field-cooled-cooling curves for low magnetic fields
We report on the magnetic properties of a special configuration of a FeRh
thin film. An anomalous behavior on the magnetisation vs. temperature was
observed when low magnetic fields are applied in the plane of a thin layer of
FeRh deposited on ordered FePt. The anomalous effect resembles a
metamagnetic transition and occur only in the field-cooled-cooling
magnetisation curve at temperatures near 120 K in samples without any heat
treatment.Comment: 7 pages, 5 figures. arXiv admin note: text overlap with
arXiv:1008.195
Large interfacial spin-orbit torques in layered antiferromagnetic insulator NiPS3/ferromagnet bilayers
Finding efficient ways of manipulating magnetic bits is one of the core goals
in spintronic research. Electrically-generated spin-orbit torques (SOTs) are
good candidates for this and the search for materials capable of generating
highly-efficient SOTs has gained a lot of traction in the recent years. While
antiferromagnet/ferromagnet bilayer structures have been employed extensively
for passive applications, e.g. by using exchange bias fields, their active
properties are not yet widely employed. Here we show the presence of large
interfacial SOTs in bilayer of a ferromagnet and the two-dimensional layered
antiferromagnetic insulator NiPS. We observe a large in-plane damping-like
interfacial torque, showing a torque conductivity of even at room
temperature, comparable to the best devices reported in the literature for
standard heavy-metal-based and topological insulators-based devices.
Additionally, our devices also show an out-of-plane field-like torque arising
from the NiPS/ferromagnet interface, further indicating the presence of an
interfacial spin-orbit coupling in our structures. Temperature-dependent
measurements reveal an increase of the SOTs with a decreasing temperature below
the N\'eel temperature of NiPS (), pointing to
a possible effect of the magnetic ordering on our measured SOTs. Our findings
show the potential of antiferromagnetic insulators and two-dimensional
materials for future spintronic applications.Comment: 19 pages, 3 figures, 1 table. Changed units of the torque normalized
by the electric field from to $\mathrm{nm \, T/V}
Neutron Transfer reactions induced by 8Li on 9Be
Angular distributions for the elastic scattering of 8Li on 9Be and the
neutron transfer reactions 9Be(8Li,7Li)10Be and 9Be(8Li,9Li)8Be have been
measured with a 27 MeV 8Li radioactive nuclear beam. Spectroscopic factors for
8Li|n=9Li and 7Li|n=8Li bound systems were obtained from the comparison between
the experimental differential cross section and finite-range DWBA calculations
with the code FRESCO. The spectroscopic factors obtained are compared to shell
model calculations and to other experimental values from (d,p) reactions. Using
the present values for the spectroscopic factor, cross sections for the direct
neutron-capture reactions 7Li(n,g)8Li and 8Li(n,g)9Li were calculated in the
framework of a potential model.Comment: 24 pages, 8 Figures, submitted as regular article to PR
Control of polarization and mode mapping of small volume high Q micropillars
We show that the polarization of the emission of a single quantum dot embedded within a microcavity pillar of elliptical cross section can be completely controlled and even switched between two orthogonal linear polarizations by changing the coupling of the dot emission with the polarized photonic modes. We also measure the spatial profle of the emission of a series of pillars with
different ellipticities and show that the results can be well described by simple theoretical modeling
of the modes of an infinite length elliptical cylinder
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