6,334 research outputs found
"Spin-Flop" Transition and Anisotropic Magnetoresistance in Pr_{1.3-x}La_{0.7}Ce_{x}CuO_{4}: Unexpectedly Strong Spin-Charge Coupling in Electron-Doped Cuprates
We use transport and neutron-scattering measurements to show that a
magnetic-field-induced transition from noncollinear to collinear spin
arrangement in adjacent CuO_{2} planes of lightly electron-doped
Pr_{1.3-x}La_{0.7}Ce_{x}CuO_{4} (x=0.01) crystals affects significantly both
the in-plane and out-of-plane resistivity. In the high-field collinear state,
the magnetoresistance (MR) does not saturate, but exhibits an intriguing
four-fold-symmetric angular dependence, oscillating from being positive at
B//[100] to being negative at B//[110]. The observed MR of more than 30% at low
temperatures induced by a modest modification of the spin structure indicates
an unexpectedly strong spin-charge coupling in electron-doped cuprates.Comment: 4 pages, 5 figures, accepted for publication in Phys. Rev. Let
Neutron scattering study of novel magnetic order in Na0.5CoO2
We report polarized and unpolarized neutron scattering measurements of the
magnetic order in single crystals of Na0.5CoO2. Our data indicate that below
T_N=88 K the spins form a novel antiferromagnetic pattern within the CoO2
planes, consisting of alternating rows of ordered and non-ordered Co ions. The
domains of magnetic order are closely coupled to the domains of Na ion order,
consistent with such a two-fold symmetric spin arrangement. Magnetoresistance
and anisotropic susceptibility measurements further support this model for the
electronic ground state.Comment: 4 pages, 4 figure
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Increased Speed Equals Increased Wait: The Impact of a Reduction in Emergency Department Ultrasound Order Processing Time
We exploit an exogenous process change at two emergency departments (EDs) within a health system to test the theory that increasing capacity in a discretionary work setting increases wait times due to additional services being provided to customers as a consequence of reduced marginal costs for a task. We find that an increase in physician’s capacity for ordering ultrasounds (U/S) resulted in an 11.5 percentage point increase in the probability of an U/S being ordered, confirming that resource availability induces demand. Furthermore, we find that the additional U/S demand increased the time to return other radiological tests due to the higher demand placed on radiologists from the additional U/S. Consequently, the average length of stay (LOS) for patients with an abdominal complaint increased by nearly 30 minutes, and the waiting time to enter the ED increased by 26 minutes. We do not find any indications of improved performance on clinical metrics, with no statistical change in the number of admissions to the hospital or readmissions to the ED within 72 hours. Our study highlights an important lesson for process improvement in interdependent service settings: increasing process capacity at one step in the process can increase demand at that step, as well as for a subsequent shared service, and both can result in an overall negative impact on performance
Spin diffusion in geometrically frustrated Heisenberg antiferromagnets
We investigate spin diffusion in geometrically frustrated Heisenberg
antiferromagnets. It is found that the diffusion constant gradually increases
from its high temperature limit as the temperature approaches the peak
temperature of the susceptibility. Below the peak, the exponential decrease in
the susceptibility leads to a rapid increase in the rate of spin diffusion.
Detailed results are presented for the pyrochlore lattice with nearest-neighbor
interactions.Comment: To appear in J. Phys.: Condensed Matte
Skyrme Crystal In A Two-Dimensional Electron Gas
The ground state of a two-dimensional electron gas at Landau level filling
factors near is a Skyrme crystal with long range order in the
positions and orientations of the topologically and electrically charged
elementary excitations of the ferromagnetic ground state. The lowest
energy Skyrme crystal is a square lattice with opposing postures for
topological excitations on opposite sublattices. The filling factor dependence
of the electron spin-polarization, calculated for the square lattice Skyrme
crystal, is in excellent agreement with recent experiments.Comment: 3 pages, latex, 3 figures available upon request from
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Doping evolution of the phonon density of states and electron-lattice interaction in NdCeCuO
We use inelastic neutron scattering to study the evolution of the generalized
phonon density of states (GDOS) of the -type high- superconductor
NdCeCuO (NCCO), from the half-filled Mott-insulator
() to the K superconductor (). Upon doping the CuO
planes in NdCuO (NCO) with electrons by Ce substitution, the
most significant change in the GDOS is the softening of the highest phonon
branches associated with the Cu-O bond stretching and out-of-plane oxygen
vibration modes. However, the softening occurs within the first few percent of
Ce-doping and is not related to the electron doping induced
nonsuperconducting-superconducting transition (NST) at . These
results suggest that the electron-lattice coupling in the -type high-
superconductors is different from that in the -type materials.Comment: 4 pages and 3 figure
Dorsal clitoral nerve injury following transobturator midurethral sling
Transobturator slings can be successfully used to treat stress urinary incontinence and improve quality of life through a minimally invasive vaginal approach. Persistent postoperative pain can occur and pose diagnostic and therapeutic dilemmas. Following a sling procedure, a patient complained of pinching clitoral and perineal pain. Her symptoms of localized clitoral pinching and pain became generalized over the ensuing years, eventually encompassing the entire left vulvovaginal region
Investigation of the Spin Density Wave in NaxCoO2
Magnetic susceptibility, transport and heat capacity measurements of single
crystal NaxCoO2 (x=0.71) are reported. A transition to a spin density wave
(SDW) state at Tmag = 22 K is observable in all measurements, except chi(ac)
data in which a cusp is observed at 4 K and attributed to a low temperature
glassy phase. M(H) loops are hysteretic below 15 K. Both the SDW transition and
low temperature hysteresis are only visible along the c-axis. The system also
exhibits a substantial (~40%) positive magnetoresistance below this
temperature. Calculations of the electronic heat capacity gamma above and below
Tmag and the size of the jump in C indicate that the onset of the SDW brings
about the opening of gap and the removal of part of the Fermi surface. Reduced
in-plane electron-electron scattering counteracts the loss of carriers below
the transition and as a result we see a net reduction in resistivity below
Tmag. Sodium ordering transitions at higher temperatures are observable as
peaks in the heat capacity with a corresponding increase in resistivity.Comment: 14 pages, 6 figure
Emergent Nodal Excitations due to the Coexistence of Superconductivity and Antiferromagnetism: Cases with and without Inversion Symmetry
We argue the emergence of nodal excitations due to the coupling with static
antiferromagnetic order in fully-gapped superconducting states in both cases
with and without inversion symmetry. This line node structure is not
accompanied with the sign change of the superconducting gap, in contrast to
usual unconventional Cooper pairs with higher angular momenta. In the case
without inversion symmetry, the stability of the nodal excitations crucially
depends on the direction of the antiferromagnetic staggered magnetic moment. A
possible realization of this phenomenon in CePtSi is discussed.Comment: 4 pages, 7 figure
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