271 research outputs found
Manifestation of geometric frustration on magnetic and thermodynamic properties of pyrochlores (X=Ti, Zr)
We present here magnetization, specific heat and Raman studies on
single-crystalline specimens of the first pyrochlore member of
the rare-earth titanate series. Its analogous compound in the
rare-earth zirconate series is also investigated in the polycrystalline form.
The Sm spins in remain unordered down to at least T = 0.5 K. The
absence of magnetic ordering is attributed to very small values of exchange
() and dipolar interaction ()
between the spins in this pyrochlore. In contrast, the pyrochlore
is characterized by a relatively large value of Sm-Sm spin
exchange (); however, long-range ordering of the
spins is not established at least down to T = 0.67 K, due to
frustration of the spins on the pyrochlore lattice. The ground state
of ions in both pyrochlores is a well-isolated Kramer's doublet. The
higher-lying crystal field excitations are observed in the low-frequency region
of the Raman spectra of the two compounds recorded at T = 10 K. At higher
temperatures, the magnetic susceptibility of shows a broad
maximum at T = 140 K while that of changes monotonically. Whereas
is a promising candidate for investigating spin-fluctuations on a
frustrated lattice as indicated by our data, the properties of
seem to conform to a conventional scenario where geometrical frustration of the
spin exclude their long-range ordering.Comment: 24 pages, 6 figures, Accepted for publication in Phys. Rev.
Gender differences in perceived health related quality of life among persons living with HIV
In the era of HlV/AlDS and in the context of the developing world HIV/AIDS has led to a pandemic. HIV
antiretroviral drugs are inaccessible and unaffordable and the only choice that health care providers have
is to work towards improving the quality of life of individuals as long as they live with this dreaded disease.
This study on 203 seropositive individuals, 102 women and 101 men, was undertaken to find out the
differences in the quality of life perceived by women and men living with HIV/AIDS. The WHOQOL-BREF
scale was used to assess the quality of life.
The findings from this study reveal that men report a poor quality of life in the psychological domain (p<0.01)
while women in the sociological domain (p=0.03). The stage of illness does not seem to influence quality of
life among women and men. The findings emphasize the need for health providers to assess the QOL among
people living with HIV/AIDS. This information would be helpful in planning effective intervention strategies for
men and women living with HlV/AlDS in order to be ensured of a quality of life
Magnetic order in double-layer manganites (La(1-z)Pr(z))1.2Sr1.8Mn2O7: intrinsic properties and role of the intergrowths
We report on an investigation of the double-layer manganite series
(La(1-z)Pr(z))1.2Sr1.8Mn2O7 (0 <= z <= 1), carried out on single crystals by
means of both macroscopic magnetometry and local probes of magnetism (muSR,
55Mn NMR). Muons and NMR demonstrate an antiferromagnetically ordered ground
state at non-ferromagnetic compositions (z >= 0.6), while more moderate Pr
substitutions (0.2 <= z <= 0.4) induce a spin reorientation transition within
the ferromagnetic phase.
A large magnetic susceptibility is detected at {Tc,TN} < T < 250K at all
compositions. From 55Mn NMR spectroscopy, such a response is unambiguously
assigned to the intergrowth of a ferromagnetic pseudocubic phase
(La(1-z)Pr(z))(1-x)Sr(x)MnO3, with an overall volume fraction estimated as
0.5-0.7% from magnetometry. Evidence is provided for the coupling of the
magnetic moments of these inclusions with the magnetic moments of the
surrounding (La(1-z)Pr(z))1.2Sr1.8Mn2O7 phase, as in the case of finely
dispersed impurities. We argue that the ubiquitous intergrowth phase may play a
role in the marked first-order character of the magnetic transition and the
metamagnetic properties above Tc reported for double-layer manganites.Comment: 11 pages, 9 figures. Submitted to Phys. Rev.
Temperature dependent Raman and x-ray studies of spin-ice pyrochlore and non-magnetic pyrochlore
We present here temperature-dependent Raman, x-ray diffraction and specific
heat studies between room temperature and 12 K on single crystals of spin-ice
pyrochlore compound and its non-magnetic analogue .
Raman data show a "new" band not predicted by factor group analysis of
Raman-active modes for the pyrochlore structure in , appearing
below a temperature of 110 K with a concomitant contraction of the cubic
unit cell volume as determined from the powder x-ray diffraction analysis. Low
temperature Raman experiments on O-isotope substituted
confirm the phonon origin of the "new" mode. These findings, absent in
, suggest that the room temperature cubic lattice of the
pyrochlore undergoes a "subtle" structural transformation near
. We find anomalous \textit{red-shift} of some of the phonon modes in both
the and the as the temperature decreases, which is
attributed to strong phonon-phonon anharmonic interactions.Comment: 28 pages, 9 figures (Accepted for publication in Physical Review B
Use of cetylpyridinium chloride for the storage of sputum samples and isolation of M. tuberculosis
Of 220 sputum specimens collected
from pulmonary tuberculosis patients, 85 were culture
positive when the sputum aliquots were stored
with cetypyridinium chloride (CPC) and processed
on 7th day (CPC method), whereas only 70 were
culture positive when the aliquots of the same specimens
were stored without CPC and processed by
sodium hydroxide (NaOH) method. The difference in
the culture positivity was statistically significant. The
number of positive, cultures obtained by the CPC
method (85) was comparable to that obtained by the
NaOH method before storage (95) and the difference
was not statistically significant
Structural, magnetic, electrical and supraconducting properties of the high temperature superconductor Nd(SrBa)Cu3O6+z Effect of argon annealing
We have studied the structural and superconducting properties of two samples superconductors Nd(SrBa)Cu3O6+z. One was a conventionally annealed sample at 450°C in oxygen (0) and the other was heated in argon at 850°C followed by oxygen annealing (A0). The Tc of the sample (O) was 68 K and that of (AO) sample was 78 K. This was confirmed by our AC susceptibility, resistivity and Seebeck effect measurements. Further, there was an enhancement in the shielding and the intergranular critical current. The X-ray and neutron data showed a tetragonal structure, and that the (O) sample had a higher impurity level arising from Nd entering the Sr/Ba sites that may result in a decrease in the carrier density (p) which also was confirmed by our thermopower measurements. A combination of several factors such as changes in the Cu (1) apical oxygen distance, chain oxygen ordering, increase in p and in-phase purity for the (AO) sample may qualitatively account for the observed data.We have studied the structural and superconducting properties of two samples superconductors Nd(SrBa)Cu3O6+z. One was a conventionally annealed sample at 450°C in oxygen (0) and the other was heated in argon at 850°C followed by oxygen annealing (A0). The Tc of the sample (O) was 68 K and that of (AO) sample was 78 K. This was confirmed by our AC susceptibility, resistivity and Seebeck effect measurements. Further, there was an enhancement in the shielding and the intergranular critical current. The X-ray and neutron data showed a tetragonal structure, and that the (O) sample had a higher impurity level arising from Nd entering the Sr/Ba sites that may result in a decrease in the carrier density (p) which also was confirmed by our thermopower measurements. A combination of several factors such as changes in the Cu (1) apical oxygen distance, chain oxygen ordering, increase in p and in-phase purity for the (AO) sample may qualitatively account for the observed data
Magneto-optical investigation of the field-induced spin-glass insulator to ferromagnetic metallic transition of the bilayer manganite (LaPr)SrMnO
We measured the magneto-optical response of
(LaPr)SrMnO in order to investigate the
microscopic aspects of the magnetic field driven spin-glass insulator to
ferromagnetic metal transition. Application of a magnetic field recovers the
ferromagnetic state with an overall redshift of the electronic structure,
growth of the bound carrier localization associated with ferromagnetic domains,
development of a pseudogap, and softening of the Mn-O stretching and bending
modes that indicate a structural change. We discuss field- and
temperature-induced trends within the framework of the Tomioka-Tokura global
electronic phase diagram picture and suggest that controlled disorder near a
phase boundary can be used to tune the magnetodielectric response. Remnants of
the spin-glass insulator to ferromagnetic metallic transition can also drive
300 K color changes in (LaPr)SrMnO.Comment: 9 pages, 8 figure
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