1,542 research outputs found
Direct evidence for the magnetic ordering of Nd ions in NdMnSi and NdMnGe by high resolution inelastic neutron scattering
We have investigated the low energy nuclear spin excitations in
NdMnSi and NdMnGe by high resolution inelastic neutron
scattering. Previous neutron diffraction investigations gave ambiguous results
about Nd magnetic ordering at low temperatures. The present element-specific
technique gave direct evidence for the magnetic ordering of Nd ions. We found
considerable difference in the process of the Nd magnetic ordering at low
temperature in NdMnSi and NdMnGe. Our results are consistent
with those of magnetization and recent neutron diffraction measurements
Polarisation dependence of magnetic Bragg scattering in YMnO
The polarisation dependence of the intensity of elastic magnetic scattering
from \ymno\ single crystals has been measured at 25 K in magnetic fields
between 1 and 9 T. A significant polarisation dependence was observed in the
intensities of magnetic satellite reflections, propagation vector
\pv=0.5,0,0.25 measured with both the [100] and [010] axes parallel to the
common polarisation and applied field direction. The intensity asymmetries
observed in sets of orthorhombicly equivalent reflections show systematic
relationships which allow the phase relationship between different components
of their magnetic interaction vectors to be determined. They fix the
orientation relationships between the small and moments on the \mnfp\
and \mntp\ sub-lattices and lend support to the structure reported by Kim et
al. It was found that that which suggests
that there is a small modulation of the nuclear structure which has the same
wave-vector as the magnetic modulation leading to a small nuclear structure
factor for the satellite reflections. The differences observed indicate shifts in the atomic positions of order 0.005 \AA
Magnetoelastic effects in Jahn-Teller distorted CrF and CuF studied by neutron powder diffraction
We have studied the temperature dependence of crystal and magnetic structures
of the Jahn-Teller distorted transition metal difluorides CrF and CuF
by neutron powder diffraction in the temperature range 2-280 K. The lattice
parameters and the unit cell volume show magnetoelastic effects below the
N\'eel temperature. The lattice strain due to the magnetostriction effect
couples with the square of the order parameter of the antiferromagnetic phase
transition. We also investigated the temperature dependence of the Jahn-Teller
distortion which does not show any significant effect at the antiferromagnetic
phase transition but increases linearly with increasing temperature for CrF
and remains almost independent of temperature in CuF. The magnitude of
magnetovolume effect seems to increase with the low temperature saturated
magnetic moment of the transition metal ions but the correlation is not at all
perfect
Multiferroic coupling in nanoscale BiFeO3
Using the results of x-ray and neutron diffraction experiments, we show that
the ferroelectric polarization, in ~22 nm particles of BiFeO3, exhibits a jump
by ~30% around the magnetic transition point T_N (~635 K) and a suppression by
~7% under 5T magnetic field at room temperature (<<T_N). These results confirm
presence of strong multiferroic coupling even in nanoscale BiFeO3 and thus
could prove to be quite useful for applications based on nanosized devices of
BiFeO3.Comment: 4 pages including 4 figures and supplementary data; accepted for
publication in Appl. Phys. Let
Weak ferromagnetism and magnetic phase transitions in GdCuO
We report a polarised neutron study of the magnetic structures and phase
trasitions in \gdc\ in low magnetic fields. These experiments have been
complemented by integrated intensity measurements with unpolarised neutrons in
zero field. Polarised neutron flipping ratio measurements have been made with
magnetic fields , 0.10 and 0.5 T in the temperature range 4-20 K.
These have enabled us to deduce that the anomalous temperature behaviour of the
coherent magnetic scattering from the Cu sublattice, which shows sharp
intensity minima at \Tcn1 K and \Tcn2 K, is due to
cross-overs in the sign of the interaction between strongly coupled, weakly
ferromagnetic, CuO layers. At \Tcn1\ the coupling changes from
ferromagnetic to anti-ferromagnetic and long-range order between layers is
temporarily lost. \Tcn2\ is the temperature at which the Gd moments order and a
further reorganisation of the interlayer order takes place. The weak
ferromagnetism of the CuO layers is found to be due to a small rotation of the
Cu moments in the same direction as that in which their coordinating oxygen
squares rotate in the tetragonal to orthorhombic distortion of the crystal
structure. Further analysis of the flipping ratio measurements has enabled us
to model the magnetic structures of the zero-field and the field-induced phases
of GdCuO
Identification of candidate categories of the International Classification of Functioning Disability and Health (ICF) for a Generic ICF Core Set based on regression modelling
Background: The International Classification of Functioning, Disability and Health (ICF) is the framework developed by WHO to describe functioning and disability at both the individual and population levels. While condition-specific ICF Core Sets are useful, a Generic ICF Core Set is needed to describe and compare problems in functioning across health conditions. Methods: The aims of the multi-centre, cross-sectional study presented here were: a) to propose a method to select ICF categories when a large amount of ICF-based data have to be handled, and b) to identify candidate ICF categories for a Generic ICF Core Set by examining their explanatory power in relation to item one of the SF-36. The data were collected from 1039 patients using the ICF checklist, the SF-36 and a Comorbidity Questionnaire. ICF categories to be entered in an initial regression model were selected following systematic steps in accordance with the ICF structure. Based on an initial regression model, additional models were designed by systematically substituting the ICF categories included in it with ICF categories with which they were highly correlated. Results: Fourteen different regression models were performed. The variance the performed models account for ranged from 22.27% to 24.0%. The ICF category that explained the highest amount of variance in all the models was sensation of pain. In total, thirteen candidate ICF categories for a Generic ICF Core Set were proposed. Conclusion: The selection strategy based on the ICF structure and the examination of the best possible alternative models does not provide a final answer about which ICF categories must be considered, but leads to a selection of suitable candidates which needs further consideration and comparison with the results of other selection strategies in developing a Generic ICF Core Set
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