18,229 research outputs found
Direct observation of pinned/biased moments in magnetic superlattices
We report the \QTR{it}{pinned/biased} \QTR{it}{moment} in the superlattices
consisting of ferromagnetic (FM) SrRuO and antiferromgnetic (AFM)
SrMnO. This superlattice system shows anisotropy and oriented
pinning/biasing in the field-cooled (FC) hysteresis loop. The in-plane
cooling-field provides antiferromagnetic orientations while out-of-plane
cooling-field provides ferromagnetic orientations to the pinned/biased moments.
The spacer layer thickness, strength and orientation of magnetic field, cooling
field, and driving current influence the pinning strength. We propose that the
magnetic structure is a repetition of ()/ unit below a
critical field to explain its magnetic and transport properties. The transport
behavior is discussed using the spin-dependent conduction.Comment: to be published in Physical Review
Nucleon strange quark content from two-flavor lattice QCD with exact chiral symmetry
Strange quark content of the nucleon is calculated in dynamical lattice QCD
employing the overlap fermion formulation. For this quantity, exact chiral
symmetry guaranteed by the Ginsparg-Wilson relation is crucial to avoid large
contamination due to a possible operator mixing with . Gauge
configurations are generated with two dynamical flavors on a 16^3 x 32 lattice
at a lattice spacing a \simeq 0.12fm. We directly calculate the relevant
three-point function on the lattice including a disconnected strange quark loop
utilizing the techniques of all-to-all quark propagator and low-mode averaging.
Our result f_{T_s} = 0.032(8)(22), is in good agreement with our previous
indirect estimate using the Feynman-Hellmann theorem.Comment: 31 pages, 22 figures; version published in PR
Anomalous low temperature state of CeOs4Sb12: Magnetic field and La-impurity study
Specific heat for single crystalline samples of Ce1-xLaxOs4Sb12 at zero-field
and magnetic fields to 14 T is reported. Our results confirm enhanced value of
the electronic specific heat coefficient in the paramagnetic state. They
provide arguments for the intrinsic origin of the 1.1 K anomaly. This
transition leads to opening of the gap at the Fermi surface. This low
temperature state of CeOs4Sb12 is extremely sensitive to chemical impurities.
2% of La substituted for Ce suppresses the transition and reduces the
electronic specific heat coefficient. The magnetic field response of the
specific heat is also anomalous.Comment: 4 pages, 3 figure
Helicoidal ordering in iron perovskites
We consider magnetic ordering in materials with negative charge transfer
energy, such as iron perovskite oxides. We show that for a large weight of
oxygen holes in conduction bands, the double exchange mechanism favors a
helicoidal rather than ferromagnetic spin ordering both in metals, e.g. SrFeO_3
and insulators with a small gap, e.g. CaFeO_3. We discuss the magnetic
excitation spectrum and effects of pressure on magnetic ordering in these
materials.Comment: 4 pages, 5 figure
In-situ growth of superconducting NdFeAs(O,F) thin films by Molecular Beam Epitaxy
The recently discovered high temperature superconductor F-doped LaFeAsO and
related compounds represent a new class of superconductors with the highest
transition temperature (Tc) apart from the cuprates. The studies ongoing
worldwide are revealing that these Fe-based superconductors are forming a
unique class of materials that are interesting from the viewpoint of
applications. To exploit the high potential of the Fe-based superconductors for
device applications, it is indispensable to establish a process that enables
the growth of high quality thin films. Efforts of thin film preparation started
soon after the discovery of Fe-based superconductors, but none of the earlier
attempts had succeeded in an in-situ growth of a superconducting film of
LnFeAs(O,F) (Ln=lanthanide), which exhibits the highest Tc to date among the
Fe-based superconductors. Here, we report on the successful growth of
NdFeAs(O,F) thin films on GaAs substrates, which showed well-defined
superconducting transitions up to 48 K without the need of an ex-situ heat
treatment
Application of LANDSAT MSS data to the study of oceanographical environment
The author has identified the following significant results. LANDSAT MSS data of a three year time lapse indicate change of sea surface condition in Seto Inland Sea and coastal region. The red tide which formerly concentrated in the bay or inland sea now extends into an open sea. A small ocean vortex similar to mesoscale atmospheric vortex is revealed by the band 4 image of the satellite data. A manual photographic method applied to a single band image of MSS is effective in detecting sea surface pollution
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