2,186 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
Direct observation of large temperature fluctuations during DNA thermal denaturation
In this paper we report direct measurement of large low frequency temperature
fluctuations in double stranded (ds) DNA when it undergoes thermal denaturation
transition. The fluctuation, which occurs only in the temperature range where
the denaturation occurs, is several orders more than the expected equilibrium
fluctuation. It is absent in single stranded (ss) DNA of the same sequence. The
fluctuation at a given temperature also depends on the wait time and vanishes
in a scale of few hours. It is suggested that the large fluctuation occurs due
to coexisting denaturated and closed base pairs that are in dynamic equilibrium
due to transition through a potential barrier in the scale of
25-30k_{B}T_{0}(T_{0}=300K).Comment: 4 pages, 5 figures, Replaced with revised versio
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
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