2,214 research outputs found
Spin Dynamical Properties of the Layered Perovskite La1.2Sr1.8Mn2O7
Inelastic neutron-scattering measurements were performed on a single crystal
of the layered colossal magnetoresistance (CMR) material La1.2Sr1.8Mn2O7 (Tc ~
120K). We found that the spin wave dispersion is almost perfectly
two-dimensional with the in-plane spin stiffness constant D ~ 151meVA. The
value is similar to that of similarly doped La1-xSrxMnO3 though its Tc is three
times higher, indicating a large renormalization due to low dimensionality.
There exist two branches due to a coupling between layers within a
double-layer. The out-of-plane coupling is about 30% of the in-plane coupling
though the Mn-O bond lengths are similar.Comment: 3 pages, 3 figures J. Phys. Chem. Solids in pres
Zn-induced spin dynamics in overdoped LaSrCuZnO
Spin fluctuations and the local spin susceptibility in isovalently
Zn-substituted LaSrCuZnO (,
) are measured via inelastic neutron scattering techniques. As
Zn is substituted onto the Cu-sites, an anomalous enhancement of
the local spin susceptibility appears due to the
emergence of a commensurate antiferromagnetic excitation centered at wave
vector \textbf{Q} that coexists with the known incommensurate
SDW excitations at \textbf{Q}.
Our results support a picture of Zn-induced antiferromagnetic (AF) fluctuations
appearing through a local staggered polarization of Cu-spins, and the
simultaneous suppression of T as AF fluctuations are slowed in proximity to
Zn-impurities suggests the continued importance of high energy AF fluctuations
at the far overdoped edge of superconductivity in the cuprates.Comment: 10 pages, 8 figure
Successful Strategies for Discharging Medicaid Nursing Home Residents with Mental Health Diagnoses to the Community
The state and federal push to transition Medicaid residents from nursing homes to the community calls for effective discharge strategies targeted to residents’ diverse needs. This exploratory, mixed-methods study utilized the Minimum Data Set to describe demographics, health characteristics, and transition patterns of Kansas Medicaid residents with mental health diagnoses who were discharged from nursing homes from 2005 to 2008. Discharged residents (n = 720) had multiple comorbidities, and more than half remained in the community following their first nursing home event. In-depth interviews with nursing home staff (n = 11) explored successful discharge strategies. Successful strategies support an ecological approach to meeting individual, family, organizational, and community needs. This includes creating/sustaining a culture of discharge, encompassing informal and formal community supports in the discharge process, proactively addressing physical environment needs, and assisting individuals and their family members in managing physical and mental health conditions. Findings suggest that policies in the areas of preadmission screening, caregiver support, and revised Medicaid reimbursement are needed to better support continuity of care and promote discharge for nursing home residents with complex care needs. Future research could examine individual and family perspectives on the discharge process and track outcomes when transitioning between settings
The complex multiferroic phase diagram of MnCoWO
The complete magnetic and multiferroic phase diagram of
MnCoWO single crystals is investigated by means of magnetic,
heat capacity, and polarization experiments. We show that the ferroelectric
polarization in the multiferroic state abruptly changes
its direction twice upon increasing Co content, x. At x=0.075,
rotates from the axis into the plane and at
x=0.15 it flips back to the axis. The origin of the multiple
polarization flops is identified as an effect of the Co anisotropy on the
orientation and shape of the spin helix leading to thermodynamic instabilities
caused by the decrease of the magnitude of the polarization in the
corresponding phases. A qualitative description of the ferroelectric
polarization is derived by taking into account the intrachain (axis) as
well as the interchain (axis) exchange pathways connecting the magnetic
ions. In a narrow Co concentration range (0.1x0.15), an
intermediate phase, sandwiched between the collinear high-temperature and the
helical low-temperature phases, is discovered. The new phase exhibits a
collinear and commensurate spin modulation similar to the low-temperature
magnetic structure of MnWO.Comment: 18 pages, 6 figure
Magnetic Excitations of the Diagonal Incommensurate Phase in Lightly-Doped La2-xSrxCuO4
We present inelastic neutron scattering experiments on a single-domain
crystal of lightly-doped La1.96Sr0.04CuO4. We find that the magnetic excitation
spectrum in this insulating phase with a diagonal incommensurate spin
modulation is remarkably similar to that in the superconducting regime, where
the spin modulation is bond parallel. In particular, we find that the
dispersion slope at low energy is essentially independent of doping and
temperature over a significant range. The energy at which the excitations cross
the commensurate antiferromagnetic wave vector increases roughly linearly with
doping through the underdoped regime.Comment: 4 pages, 5 figure
Upgrade to the Birmingham Irradiation Facility
The Birmingham Irradiation Facility was developed in 2013 at the University of Birmingham using the Medical Physics MC40 cyclotron. It can achieve High Luminosity LHC (HL-LHC) fluences of 1015 (1 MeV neutron equivalent (neq)) cm-2 in 80 s with proton beam currents of 1 μA and so can evaluate effectively the performance and durability of detector technologies and new components to be used for the HL-LHC. Irradiations of silicon sensors and passive materials can be carried out in a temperature controlled cold box which moves continuously through the homogenous beamspot. This movement is provided by a pre-configured XY-axis Cartesian robot scanning system. In 2014 the cooling system and cold box were upgraded from a recirculating glycol chiller system to a liquid nitrogen evaporative system. The new cooling system achieves a stable temperature of -50 °C in 30 min and aims to maintain sub-0 °C temperatures on the sensors during irradiations. This paper reviews the design, development, commissioning and performance of the new cooling system
Magnon Damping by magnon-phonon coupling in Manganese Perovskites
Inelastic neutron scattering was used to systematically investigate the
spin-wave excitations (magnons) in ferromagnetic manganese perovskites. In
spite of the large differences in the Curie temperatures (s) of different
manganites, their low-temperature spin waves were found to have very similar
dispersions with the zone boundary magnon softening. From the wavevector
dependence of the magnon lifetime effects and its correlation with the
dispersions of the optical phonon modes, we argue that a strong magneto-elastic
coupling is responsible for the observed low temperature anomalous spin
dynamical behavior of the manganites.Comment: 11 pages, 4 figure
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