741 research outputs found
Ferromagnetism Induced by Uniaxial Pressure in the Itinerant Metamagnet Sr3Ru2O7
We report a uniaxial-pressure study on the magnetisation of single crystals
of the bilayer perovskite Sr3Ru2O7, a metamagnet close to a ferromagnetic
instability. We observed that the application of a uniaxial pressure parallel
to the c-axis induces ferromagnetic ordering with a Curie temperature of about
80 K and critical pressures of about 4 kbar or higher. This value for the
critical pressure is even higher than the value previously reported (~ 1 kbar),
which might be attributed to the difference of the impurity level. Below the
critical pressure parallel to the c-axis, the metamagnetic field appears to
hardly change. We have also found that uniaxial pressures perpendicular to the
c-axis, in contrast, do not induce ferromagnetism, but shift the metamagnetic
field to higher fields.Comment: Accepted for publication in Proc of 24th Int. Conf. on Low
Temperature Physics (LT24); 2 page
Multiple superconducting transitions in the Sr3Ru2O7 region of Sr3Ru2O7-Sr2RuO4 eutectic crystals
We report superconducting properties of Sr3Ru2O7-Sr2RuO4 eutectic crystals,
consisting of the spin-triplet superconductor Sr2RuO4 with a monolayer stacking
of RuO2 planes and the metamagnetic normal metal Sr3Ru2O7 with a bilayer
stacking. Although Sr3Ru2O7 has not been reported to exhibit superconductivity
so far, our AC susceptibility measurements revealed multiple superconducting
transitions occurring in the Sr3Ru2O7 region of the eutectic crystals. The
diamagnetic shielding essentially reached the full fraction at low AC fields
parallel to the c axis. However, both the shielding fraction and the onset
temperature are easily suppressed by AC fields of larger than 0.1 mT-rms and no
anomaly was observed in the specific heat. Moreover, the critical field curves
of these transitions have a positive curvature near zero fields, which is
different from the upper critical field curve of the bulk Sr2RuO4. These facts
suggest that the superconductivity observed in the Sr3Ru2O7 region is not a
bulk property. To explain these experimental results, we propose the scenario
that stacking RuO2 planes, the building block of superconducting Sr2RuO4, are
contained in the Sr3Ru2O7 region as stacking faults.Comment: 8 pages, 10 figures, accepted for publication in Phys. Rev.
Superconductivity in Sr2RuO4-Sr3Ru2O7 eutectic crystals
Superconducting behavior has been observed in the Sr2RuO4-Sr3Ru2O7 eutectic
system as grown by the flux-feeding floating zone technique. A supercurrent
flows across a single interface between Sr2RuO4 and Sr3Ru2O7 areas at distances
that are far beyond those expected in a conventional proximity scenario. The
current-voltage characteristics within the Sr3Ru2O7 macrodomain, as extracted
from the eutectic, exhibit signatures of superconductivity in the bilayered
ruthenate. Detailed microstructural, morphological and compositional analyses
address issues on the concentration and the size of Sr2RuO4 inclusions within
the Sr3Ru2O7 matrix. We speculate on the possibility of inhomogeneous
superconductivity in the eutectic Sr3Ru2O7 and exotic pairing induced by the
Sr2RuO4 inclusions.Comment: Pages 4, figures 3, submitted to Phys. Rev. Let
Charge Screening Effect in Metallic Carbon Nanotubes
Charge screening effect in metallic carbon nanotubes is investigated in a
model including the one-dimensional long-range Coulomb interaction. It is
pointed out that an external charge which is being fixed spatially is screened
by internal electrons so that the resulting object becomes electrically
neutral. We found that the screening length is given by about the diameter of a
nanotube.Comment: 11 pages, 6 figure
Influence of off-cut angle of (0001) 4H-SiC on the crystal quality of InN grown by RF-MBE
AbstractThe effect of the off-cut angle of a 4H-SiC (0001) substrate on the growth of InN thick layer by RF-plasma assisted molecular beam epitaxy (RF-MBE) has been investigated. The off-cut angle used in this study was inclined from 0° (just surface) toward the [11–20] direction of 4° and 8°. Crystalline quality and surface morphology were remarkably sensitive to the value of off-angle. Higher off-cut angles result in a reduction of the full-widths at half-maximum of HRXRD (0002) ω-scans, compared to that of the layer on the (0001)-just surface. In addition, the full-widths at halfmaximum of μ-Raman scattering spectra at 490cm-1, which is attributed to E2 (high) phonon mode, was decreased with increase in off-cut angle. Furthermore, In-droplets, which are commonly observed on the (0001) InN grown surface under In rich-growth condition, were found to be suppressed owing to an improvement of a nucleation on the off-cut angle surface. In our case, the use of 8°-off substrate increased film density and growth rate, while a surface roughness was reduced. These results clearly demonstrate that the larger off-cut angles improve the crystalline quality of InN film with reducing the In-droplets due to a higher step surface density on the off-cut angle surface
Describing Sr2RuO4 superconductivity in a generalized Ginzburg--Landau theory
We propose a simple explanation of unconventional thermodynamical and
magnetic properties observed for Sr2RuO4. Actually, our two-phase model of
superconductivity, based on a straight generalization of the Ginzburg-Landau
theory, does predict two jumps in the heat capacity as well as a double curve
for the dependence of the critical temperature on an external magnetic field.
Such theoretical previsions well agree with the currently available
experimental data for Sr2RuO4Comment: revtex, 9 pages, 1 eps figur
Tunneling properties at the interface between superconducting Sr2RuO4 and a Ru micro-inclusion
We have investigated the magnetic field and temperature dependence of the
tunneling spectra of the eutectic system Sr2RuO4-Ru. Electric contacts to
individual Ru lamellae embedded in Sr2RuO4 enable the tunneling spectra at the
interface between ruthenate and a Ru microinclusion to be measured. A zero bias
conductance peak (ZBCP) was observed in the bias voltage dependence of the
differential conductance, suggesting that Andreev bound states are present at
the interface. The ZBCP starts to appear at a temperature well below the
superconducting transition temperature. The onset magnetic field of the ZBCP is
also considerably smaller than the upper critical field when the magnetic field
is parallel to the ab-plane. We propose that the difference between the onset
of the ZBCP and the onset of superconductivity can be understood in terms of
the existence of the single-component state predicted by Sigrist and Monien.Comment: 4 pages, 4 figures, to appear in J. Phys. Soc. Jpn. vol. 74 no.
Enzootic bovine leukosis accompanied by splenomegaly in an 8-month-old calf
ΔΕΝ ΔΙΑΤΙΘΕΤΑΙ ΠΕΡΙΛΗΨΗIn this report, an 8-month-old calf (crossbred, Holstein × Japanese Black) developed fever and accompanied abomasum displacement. Blood chemical test showed remarkably high values of white blood cell count and heteromorphic lymphocytes. In pathological appraisal, enlarged splenomegaly and swelling of the lymph nodes were observed. Histopathological examination revealed invasion of tumor cells derived from B1 cells into systemic lymph nodes, liver and spleen. The provirus loads of bovine leukemia virus (BLV) was 1,439 copies per 10 ng DNA by using real time PCR. In conclusion, this case was diagnosed as bovine leukemia caused by BLV infection with a huge splenomegaly
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