1,712 research outputs found
Interlayer Couplings Mediated by Antiferromagnetic Magnons
Collinear antiferromagnets (AFs) support two degenerate magnon excitations
carrying opposite spin polarizations, by which magnons can function as
electrons in various spin-related phenomena. In an insulating
ferromagnet(F)/AF/F trilayer, we explore the magnon-mediated interlayer
coupling by calculating the magnon thermal energy in the AF as a function of
the orientations of the Fs. The effect manifests as an interlayer exchange
interaction and a perpendicular magnetic anisotropy; they both depend on
temperature and the AF thickness. In particular, the exchange interaction turns
out to be antiferromagnetic at low temperatures and ferromagnetic at high
temperatures, whose magnitude can be eV for nanoscale
separations, allowing experimental verification.Comment: Physical Review Letters 121, 207202 (2018
Synthesizing and characterization of hole doped nickel based layer superconductor (LaSr)ONiAs
We report the synthesizing and characterization of the hole doped Ni-based
superconductor (. By substituting La with Sr, the
superconducting transition temperature is increased from 2.75 K of the
parent phase to 3.7 K at the doping levels x= 0.1 - 0.2. The curve
versus hole concentration shows a symmetric behavior as the electron
doped samples . The normal state resistivity in Ni-based
samples shows a good metallic behavior and reveals the absence of an anomaly
which appears in the Fe-based system at about 150 K, suggesting that this
anomaly is not a common feature for all systems. Hall effect measurements
indicate that the electron conduction in the parent phase is
dominated by electron-like charge carriers, while with more Sr doping, a
hole-like band will emerge and finally prevail over the conduction, and
accordingly the superconducting transition temperature increases.Comment: 4 pages, 5 figure
Effect of Earth's rotation on the trajectories of free-fall bodies in Equivalence Principle Experiment
Owing to Earth's rotation a free-fall body would move in an elliptical orbit
rather than along a straight line forward to the center of the Earth. In this
paper on the basis of the theory for spin-spin coupling between macroscopic
rotating bodies we study violation of the equivalence principle from
long-distance free-fall experiments by means of a rotating ball and a
non-rotating sell. For the free-fall time of 40 seconds, the difference between
the orbits of the two free-fall bodies is of the order of 10^{-9}cm which could
be detected by a SQUID magnetometer owing to such a magnetometer can be used to
measure displacements as small as 10^{-13} centimeters.Comment: 6 pages, 4 figure
Transmission resonance in a composite plasmonic structure
The design, fabrication, and optical properties of a composite plasmonic
structure, a two-dimentional array of split-ring resonators inserted into
periodic square holes of a metal film, have been reported. A new type of
transmission resonance, which makes a significant difference from the
conventional peaks, has been suggested both theoretically and experimentally.
To understand this effect, a mechanism of ring- resonance induced dipole
emission is proposed.Comment: 14 pages, 4 figure
Transition of stoichiometricSr2VO3FeAs to a superconducting state at 37.2 K
The superconductor Sr4V2O6Fe2As2 with transition temperature at 37.2 K has
been fabricated. It has a layered structure with the space group of p4/nmm, and
with the lattice constants a = 3.9296Aand c = 15.6732A. The observed large
diamagnetization signal and zero-resistance demonstrated the bulk
superconductivity. The broadening of resistive transition was measured under
different magnetic fields leading to the discovery of a rather high upper
critical field. The results also suggest a large vortex liquid region which
reflects high anisotropy of the system. The Hall effect measurements revealed
dominantly electron-like charge carriers in this material. The
superconductivity in the present system may be induced by oxygen deficiency or
the multiple valence states of vanadium.Comment: 5 pages, 4 figure
Superconductivity at 15.6 K in Calcium-doped Tb_{1-x}Ca_xFeAsO: the structure requirement for achieving superconductivity in the hole-doped 1111 phase
Superconductivity at about 15.6 K was achieved in Tb_{1-x}Ca_xFeAsO by
partially substituting Tb^{3+} with Ca^{2+} in the nominal doping region x =
0.40 \sim 0.50. A detailed investigation was carried out in a typical sample
with doping level of x = 0.44. The upper critical field of this sample was
estimated to be 77 Tesla from the magnetic field dependent resistivity data.
The domination of hole-like charge carriers in the low-temperature region was
confirmed by Hall effect measurements. The comparison between the calcium-doped
sample Pr_{1-x}Ca_xFeAsO (non-superconductive) and the Strontium-doped sample
Pr_{1-x}Sr_xFeAsO (superconductive) suggests that a lager ion radius of the
doped alkaline-earth element compared with that of the rare-earth element may
be a necessary requirement for achieving superconductivity in the hole-doped
1111 phase.Comment: 7 pages, 7 figure
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