4,239 research outputs found
Magnetoresistance of single-domain ferromagnetic particles
We have performed magnetoresistance measurements on single-domain, submicron
elliptical Ni particles using nonmagnetic probes in a four probe geometry at
liquid helium temperatures. In the smallest particles, the magnetoresistance
shows sharp jumps which are associated with the switching of individual
domains. Using an anisotropic magnetoresistance model, we can reconstruct
hysteresis loops of the normalized magnetization. The remanent magnetization in
zero applied magnetic field is typically 15 percent less than the saturation
magnetization. This relaxation of the magnetization may be due to surface
effects or crystal grain structure in the particles.Comment: 4 pages, 3 figure
Dipole Perturbations of the Reissner-Nordstrom Solution: The Polar Case
The formalism developed by Chandrasekhar for the linear polar perturbations
of the Reissner-Nordstrom solution is generalized to include the case of dipole
(l=1) perturbations. Then, the perturbed metric coefficients and components of
the Maxwell tensor are computed.Comment: 16 pages, LaTeX, no figures. Submitted for publication in Physical
Review
Equilibration, generalized equipartition, and diffusion in dynamical Lorentz gases
We prove approach to thermal equilibrium for the fully Hamiltonian dynamics
of a dynamical Lorentz gas, by which we mean an ensemble of particles moving
through a -dimensional array of fixed soft scatterers that each possess an
internal harmonic or anharmonic degree of freedom to which moving particles
locally couple. We establish that the momentum distribution of the moving
particles approaches a Maxwell-Boltzmann distribution at a certain temperature
, provided that they are initially fast and the scatterers are in a
sufficiently energetic but otherwise arbitrary stationary state of their free
dynamics--they need not be in a state of thermal equilibrium. The temperature
to which the particles equilibrate obeys a generalized equipartition
relation, in which the associated thermal energy is equal to
an appropriately defined average of the scatterers' kinetic energy. In the
equilibrated state, particle motion is diffusive
Summing up Non-anti-commutative Kaehler potential
We offer a simple non-perturbative formula for the component action of a
generic N=1/2 supersymmetric chiral model in terms of an arbitrary number of
chiral superfields in four dimensions, which is obtained by the
Non-Anti-Commutative (NAC) deformation of a generic four-dimensional N=1
supersymmetric non-linear sigma-model described by arbitrary Kaehler
superpotential and scalar superpotential. The auxiliary integrations
responsible for fuzziness are eliminated in the case of a single chiral
superfield. The scalar potential in components is derived by eliminating the
auxiliary fields. The NAC-deformation of the CP(1) Kaehler non-linear
sigma-model with an arbitrary scalar superpotential is calculated as an
example.Comment: 9 pages, LaTeX, no figures; section 5 and references adde
Strong spin-orbit coupling and magnetism in (111) (LaSr)(AlTa/SrTiO
Strong correlations, multiple lattice degrees of freedom, and the ease of
doping make complex oxides a source of great research interest. Complex oxide
heterointerfaces break inversion symmetry and can host a two dimensional
carrier gas, which can display a variety of coexisting and competing phenomena.
In the case of heterointerfaces based on SrTiO, many of these phenomena can
be effectively tuned by using an electric gate, due to the large dielectric
constant of SrTiO. Most studies so far have focused on (001) oriented
heterostructures; however, (111) oriented heterostructures have recently gained
attention due to the possibility of finding exotic physics in these systems due
their hexagonal surface crystal symmetry. In this work, we use
magnetoresistance to study the evolution of spin-orbit interaction and
magnetism in a new system, (111) oriented
(LaSr)(AlTa)/SrTiO. At more positive
values of the gate voltage, which correspond to high carrier densities, we find
that transport is multiband, and dominated by high mobility carriers with a
tendency towards weak localization. At more negative gate voltages, the carrier
density is reduced, the high mobility bands are depopulated, and weak
antilocalization effects begin to dominate, indicating that spin-orbit
interaction becomes stronger. At millikelvin temperatures, and gate voltages
corresponding to the strong spin-orbit regime, we observe hysteresis in
magnetoresistance, indicative of ferromagnetism in the system. Our results
suggest that in the (111)
(LaSr)(AlTa)/SrTiO system, low mobility
carriers which experience strong spin-orbit interactions participate in
creating magnetic order in the system.Comment: 15 pages, 3 figure
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