5,349 research outputs found
Anomalous Hall effect in non-collinear antiferromagnetic antiperovskite MnNiCuN
We report the anomalous Hall effect (AHE) in antiperovskite MnNiN with
substantial doping of Cu on the Ni site (i.e. MnNiCuN),
which stabilizes a noncollinear antiferromagnetic (AFM) order compatible with
the AHE. Observed on both sintered polycrystalline pieces and single
crystalline films, the AHE does not scale with the net magnetization, contrary
to the conventional ferromagnetic case. The existence of the AHE is explained
through symmetry analysis based on the AFM order in Cu doped
MnNiN. DFT calculations of the intrinsic contribution to the AHE reveal
the non-vanishing Berry curvature in momentum space due to the noncollinear
magnetic order. Combined with other attractive properties, antiperovskite
MnAN system offers great potential in AFM spintronics.Comment: Supplemental Materials not include
Stress relief as the driving force for self-assembled Bi nanolines
Stress resulting from mismatch between a substrate and an adsorbed material
has often been thought to be the driving force for the self-assembly of
nanoscale structures. Bi nanolines self-assemble on Si(001), and are remarkable
for their straightness and length -- they are often more than 400 nm long, and
a kink in a nanoline has never been observed. Through electronic structure
calculations, we have found an energetically favourable structure for these
nanolines that agrees with our scanning tunneling microscopy and photoemission
experiments; the structure has an extremely unusual subsurface structure,
comprising a double core of 7-membered rings of silicon. Our proposed structure
explains all the observed features of the nanolines, and shows that surface
stress resulting from the mismatch between the Bi and the Si substrate are
responsible for their self-assembly. This has wider implications for the
controlled growth of nanostructures on semiconductor surfaces.Comment: 4 pages, 4 figures, submitted to Phys. Rev. Let
Anachronistic Grain Growth and Global Structure of the Protoplanetary Disk Associated with the Mature Classical T Tauri Star, PDS 66
We present ATCA interferometric observations of the old (13 Myr), nearby
(86pc) classical T Tauri star, PDS 66. Unresolved 3 and 12 mm continuum
emission is detected towards PDS 66, and upper limits are derived for the 3 and
6 cm flux densities. The mm-wave data show a spectral slope flatter than that
expected for ISM-sized dust particles, which is evidence of grain growth. We
also present HST/NICMOS 1.1 micron PSF-subtracted coronagraphic imaging of PDS
66. The HST observations reveal a bilaterally symmetric circumstellar region of
dust scattering about 0.32% of the central starlight, declining radially in
surface brightness. The light-scattering disk of material is inclined 32
degrees from face-on, and extends to a radius of 170 AU. These data are
combined with published optical and longer wavelength observations to make
qualitative comparisons between the median Taurus and PDS 66 spectral energy
distributions (SEDs). By comparing the near-infrared emission to a simple
model, we determine that the location of the inner disk radius is consistent
with the dust sublimation radius (1400 K at 0.1 AU). We place constraints on
the total disk mass using a flat-disk model and find that it is probably too
low to form gas giant planets according to current models. Despite the fact
that PDS 66 is much older than a typical classical T Tauri star (< 5 Myr), its
physical properties are not much different.Comment: 31 pages, 7 figure
Gaudin Hypothesis for the XYZ Spin Chain
The XYZ spin chain is considered in the framework of the generalized
algebraic Bethe ansatz developed by Takhtajan and Faddeev. The sum of norms of
the Bethe vectors is computed and expressed in the form of a Jacobian. This
result corresponds to the Gaudin hypothesis for the XYZ spin chain.Comment: 12 pages, LaTeX2e (+ amssymb, amsthm); to appear in J. Phys.
- …