44,043 research outputs found
The perfect spin injection in silicene FS/NS junction
We theoretically investigate the spin injection from a ferromagnetic silicene
to a normal silicene (FS/NS), where the magnetization in the FS is assumed from
the magnetic proximity effect. Based on a silicene lattice model, we
demonstrated that the pure spin injection could be obtained by tuning the Fermi
energy of two spin species, where one is in the spin orbit coupling gap and the
other one is outside the gap. Moreover, the valley polarity of the spin species
can be controlled by a perpendicular electric field in the FS region. Our
findings may shed light on making silicene-based spin and valley devices in the
spintronics and valleytronics field.Comment: 6 pages, 3 figure
Hysteresis and Anisotropic Magnetoresistance in Antiferromagnetic
The out-of-plane resistivity () and magnetoresistivity (MR) are
studied in antiferromangetic (AF) single crystals, which
have three types of noncollinear antiferromangetic spin structures. The
apparent signatures are observed in measured at the zero-field and
14 T at the spin structure transitions, giving a definite evidence for the
itinerant electrons directly coupled to the localized spins. One of striking
feature is an anisotropy of the MR with a fourfold symmetry upon rotating the
external field (B) within ab plane in the different phases, while twofold
symmetry at spin reorientation transition temperatures. The intriguing thermal
hysteresis in and magnetic hysteresis in MR are observed at spin
reorientation transition temperatures.Comment: 4 pages, 4 figure
Nature of eclipsing pulsars
We present a model for pulsar radio eclipses in some binary systems, and test
this model for PSRs B1957+20 and J2051-0827. We suggest that in these binaries
the companion stars are degenerate dwarfs with strong surface magnetic fields.
The magnetospheres of these stars are permanently infused by the relativistic
particles of the pulsar wind. We argue that the radio waves emitted by the
pulsar split into the eigenmodes of the electron-positron plasma as they enter
the companion's magnetosphere and are then strongly damped due to cyclotron
resonance with the ambient plasma particles. Our model explains in a natural
way the anomalous duration and behavior of radio eclipses observed in such
systems. In particular, it provides stable, continuous, and frequency-dependent
eclipses, in agreement with the observations. We predict a significant
variation of linear polarization both at eclipse ingress and egress. In this
paper we also suggest several possible mechanisms of generation of the optical
and -ray emission observed from these binary systems.Comment: 12 pages, 5 figures, submitted to Ap
Charge redistribution in the formation of one-dimensional lithium wires on Cu(001)
We describe the formation of one-dimensional lithium wires on a Cu(001) substrate, providing an atomic-scale description of the onset of metallization in this prototypical adsorption system. A combination of helium atom scattering and density-functional theory reveals pronounced changes in the electronic charge distribution on the formation of the c(5√2×√2)R45° Li/Cu(001) structure, as in-plane bonds are created. Charge donation from Li-substrate bonds is found to facilitate the formation of stable, bonded, and depolarized chains of Li adatoms that coexist with an interleaved phase of independent adatoms. The resultant overlayer has a commensurate charge distribution and lattice modulations but differs fundamentally from structurally similar charge-density wave systems
Evidence of s-wave pairing symmetry in layered superconductor LiNbO from the specific heat measurement
A high quality superconducting LiNbO polycrystalline sample was
synthesized by deintercalation of Li ions from LiNbO. The field
dependent resistivity and specific heat were measured down to 0.5 K. The upper
critical field is deduced from the resistivity data and
is estimated to be T. A notable specific heat jump is
observed at the superconducting transition temperature K at zero
field. Below , the electronic specific heat shows a thermal activated
behavior and agrees well with the theoretical result of the BCS s-wave
superconductors. It indicates that the superconducting pairing in
LiNbO has s-wave symmetry.Comment: 4 pages, 5 figure
Integer quantum Hall effect and topological phase transitions in silicene
We numerically investigate the effects of disorder on the quantum Hall effect
(QHE) and the quantum phase transitions in silicene based on a lattice model.
It is shown that for a clean sample, silicene exhibits an unconventional QHE
near the band center, with plateaus developing at and
a conventional QHE near the band edges. In the presence of disorder, the Hall
plateaus can be destroyed through the float-up of extended levels toward the
band center, in which higher plateaus disappear first. However, the center
Hall plateau is more sensitive to disorder and disappears at a
relatively weak disorder strength. Moreover, the combination of an electric
field and the intrinsic spin-orbit interaction (SOI) can lead to quantum phase
transitions from a topological insulator to a band insulator at the charge
neutrality point (CNP), accompanied by additional quantum Hall conductivity
plateaus.Comment: 7 pages, 4 figure
Jahn-Teller Distortion and Ferromagnetism in the Dilute Magnetic Semiconductors GaN:Mn
Using first-principles total-energy methods, we investigate Jahn-Teller
distortions in III-V dilute magnetic semiconductors, GaAs:Mn and GaN:Mn in the
cubic zinc blende structure. The results for an isolated Mn impurity on a Ga
site show that there is no appreciable effect in GaAs, whereas, in GaN there is
a Jahn-Teller effect in which the symmetry around the impurity changes from
T to D or to C. The large effect in GaN occurs because of
the localized d character, which is further enhanced by the distortion. The
lower symmetry should be detectable experimentally in cubic GaN with low Mn
concentration, and should be affected by charge compensation (reductions of
holes and conversion of Mn ions to d with no Jahn-Teller effect).
Jahn-Teller effect is greatly reduced because the symmetry at each Mn site is
lowered due to the Mn-Mn interaction. The tendency toward ferromagnetism is
found to be stronger in GaN:Mn than in GaAs:Mn and to be only slightly reduced
by charge compensation.Comment: 6 pages, 3 figure
Performance of nano-structured multilayer PVD coating TiAlN/VN in dry high speed milling of aerospace aluminium 7010-T7651
A low-friction and wear resistant TiAlN/VN multilayer coating with TiAlN/VN bilayer thickness 3 nm has been grown by using the combined cathodic arc etching and unbalanced magnetron sputtering deposition on high speed steel tools for dry cutting of aluminium alloys. In this paper, in-lab and industrial high speed milling tests have been performed on an aerospace aluminium alloy 7010-T7651. The results show that the TiAlN/VN coated tools achieved lower cutting forces, lower metal surface roughness, and significantly longer tool lifetime by three times over the uncoated tools as a result of the low friction and eliminated tool-metal adhesion. Under the same conditions, a TiAlN based multicomponent coating TiAlCrYN also increased the tool lifetime by up to 100% despite the high cutting forces measured
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