7,030 research outputs found
A structure marker study for Pd_2Si formation: Pd moves in epitaxial Pd_2Si
A sample with the configuration Si (111)/single crystalline Pd_2Si/polycrystalline Pd_2Si/Pd is used to study the dominant moving species during subsequent Pd_2Si formation by annealing at 275 °C. The interface between monocrystalline and polycrystalline Pd_2Si is used as a marker to monitor the dominant moving species. The result shows that Pd is the dominant moving species in the monocrystal
Determination of the Spin-Hall-Effect-Induced and the Wedged-Structure-Induced Spin Torque Efficiencies in Heterostructures with Perpendicular Magnetic Anisotropy
We report that by measuring current-induced hysteresis loop shift versus
in-plane bias magnetic field, the spin Hall effect (SHE) contribution of the
current-induced effective field per current density, , can be
estimated for Pt and Ta-based magnetic heterostructures with perpendicular
magnetic anisotropy (PMA). We apply this technique to a Pt-based sample with
its ferromagnetic (FM) layer being wedged-deposited and discover an extra
effective field contribution, , due to the asymmetric nature of
the deposited FM layer. We confirm the correlation between and
the asymmetric depinning process in FM layer during magnetization switching by
magneto-optical Kerr (MOKE) microscopy. These results indicate the possibility
of engineering deterministic spin-orbit torque (SOT) switching by controlling
the symmetry of domain expansion through the materials growth process
Model reduction in power systems using Krylov subspace methods
This paper describes the use of Krylov subspace methods in the model reduction of power systems. Additionally, a connection between the Krylov subspace model reduction and coherency in power systems is proposed, aiming at retaining some physical relationship between the reduced and the original system
Density wave and supersolid phases of correlated bosons in an optical lattice
Motivated by the recent experiment on the Bose-Einstein condensation of
Cr atoms with long-range dipolar interactions (Werner J. et al., Phys.
Rev. Lett., 94 (2005) 183201), we consider a system of bosons with repulsive
nearest and next-nearest neighbor interactions in an optical lattice. The
ground state phase diagram, calculated using the Gutzwiller ansatz, shows,
apart from the superfluid (SF) and the Mott insulator (MI), two modulated
phases, \textit{i.e.}, the charge density wave (CDW) and the supersolid (SS).
Excitation spectra are also calculated which show a gap in the insulators,
gapless, phonon mode in the superfluid and the supersolid, and a mode softening
of superfluid excitations in the vicinity of the modulated phases. We discuss
the possibility of observing these phases in cold dipolar atoms and propose
experiments to detect them
Genericity and Singularities of Robot Manipulators
The kinematic singularities of robot manipulators are studied from the point of view of the theory of singularities. The notion of a generic\u27\u27 kinematic map, whose singularities form smooth manifolds of prescribed dimension in the joint space of the manipulator, is examined. For three-joint robots, an equivalent algebraic condition for genericity using the Jacobian determinants is derived. This condition lends itself to symbolic computation and is sufficient for the study of decoupled manipulators. Orientation and translation singularities of manipulators are studied in detail. A complete characterization of orientation singularities of robots with any number of joints is given. The translation singularities of the eight possible topologies of three-joint robots are studied and the conditions on the link parameters for nongenericity are determined
Zero Temperature Insulator-Metal Transition in Doped Manganites
We study the transition at T=0 from a ferromagnetic insulating to a
ferromagnetic metallic phase in manganites as a function of hole doping using
an effective low-energy model Hamiltonian proposed by us recently. The model
incorporates the quantum nature of the dynamic Jahn-Teller(JT) phonons strongly
coupled to orbitally degenerate electrons as well as strong Coulomb correlation
effects and leads naturally to the coexistence of localized (JT polaronic) and
band-like electronic states. We study the insulator-metal transition as a
function of doping as well as of the correlation strength U and JT gain in
energy E_{JT}, and find, for realistic values of parameters, a ground state
phase diagram in agreement with experiments. We also discuss how several other
features of manganites as well as differences in behaviour among manganites can
be understood in terms of our model.Comment: To be published in Europhysics Letter
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