1,953 research outputs found
Polarization Dependent Switching of Asymmetric Nanorings with a Circular Field
We experimentally investigated the switching from onion to vortex states in asymmetric cobalt nanorings by an applied circular field. An in-plane field is applied along the symmetric or asymmetric axis of the ring to establish domain walls (DWs) with symmetric or asymmetric polarization. A circular field is then applied to switch from the onion state to the vortex state, moving the DWs in the process. The asymmetry of the ring leads to different switching fields depending on the location of the DWs and direction of applied field. For polarization along the asymmetric axis, the field required to move the DWs to the narrow side of the ring is smaller than the field required to move the DWs to the larger side of the ring. For polarization along the symmetric axis, establishing one DW in the narrow side and one on the wide side, the field required to switch to the vortex state is an intermediate value
Towards an understanding of nucleon spin structure: from hard to soft scales
The workshop "The Helicity Structure of the Nucleon" (BNL June 5, 2006) was
organized as part of the 2006 RHIC & AGS Users' Meeting to review the status of
the spin problem and future directions. The presentations can be found at
http://www.phenix.bnl.gov/WWW/publish/caidala/UsersHelicityWorkshop2006/ .
Recent data suggests small polarized glue and strangeness in the proton. Here
we present a personal summary of the main results and presentations. What is
new and exciting in the data, and what might this tell us about the structure
of the proton ?Comment: 20 pages, to appear in Int. J. Mod. Phys.
Quantum Number Density Asymmetries Within QCD Jets Correlated With Lambda Polarization
The observation of jets in a variety of hard-scattering processes has allowed
the quantitative study of perturbative quantum chromodynamics (PQCD) by
comparing detailed theoretical predictions with a wide range of experimental
data. This paper examines how some important, nonperturbative, facets of QCD
involving the internal dynamical structure of jets can be studied by measuring
the spin orientation of Lambda particles produced in these jets. The
measurement of the transverse polarization for an individual Lambda within a
QCD jet permits the definition of spin-directed asymmetries in local quantum
number densities in rapidity space (such as charge, strangeness and baryon
number densities) involving neighboring hadrons in the jet. These asymmetries
can only be generated by soft, nonperturbative dynamical mechanisms and such
measurements can provide insight not otherwise accessible into the color
rearrangement that occurs during the hadronization stage of the fragmentation
process.Comment: The replacement manuscript contains a new abstract, five pages of
additional material and a revised version of Fig.
Switching of +/-360deg domain wall states in a nanoring by an azimuthal Oersted field
We demonstrate magnetic switching between two domain wall vortex
states in cobalt nanorings, which are candidate magnetic states for robust and
low power MRAM devices. These domain wall (DW) or "twisted onion"
states can have clockwise or counterclockwise circulation, the two states for
data storage. Reliable switching between the states is necessary for any
realistic device. We accomplish this switching by applying a circular Oersted
field created by passing current through a metal atomic force microscope tip
placed at the center of the ring. After initializing in an onion state, we
rotate the DWs to one side of the ring by passing a current through the center,
and can switch between the two twisted states by reversing the current, causing
the DWs to split and meet again on the opposite side of the ring. A larger
current will annihilate the DWs and create a perfect vortex state in the rings.Comment: 5 pages, 5 figure
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