319 research outputs found
Growth and Characterization of Fe0.95Se0.6Te0.4 Single Crystal
In this paper we present the single crystal growth of Fe0.95Se0.6Te0.4 high
TC superconducting sample by the modified Bridgman technique. The x-ray
diffraction pattern shows the single crystal nature of the sample, as only
(00l) peaks are detectable. The stoichiometric composition has been verified by
energy dispersive x-ray analysis. The superconducting transition temperature at
14 K was confirmed through DC magnetization (ZFC-FC) and resistivity
measurements. By analyzing the isothermal M-H curves, we determined the value
of H_c1 (0) ~360 Oe by extrapolating the data. The temperature coefficient of
resistivity obtained using the power law fitting was found to be 0.6. The
obtained Raman spectra at room temperature can be interpreted with the
tetragonal crystal structure and space group P4/nmm.Comment: conference pape
Exploring the possibility of enhancing the figure-of-merit ( 2) of NaCoO: A combined experimental and theoretical study
Search of new thermoelectric (TE) materials with high
\textit{figure-of-merit} (ZT) is always inspired the researcher in TE field.
Here, we present a combined experimental and theoretical study of TE properties
of NaCoO compound in high-temperature region. The experimental
Seebeck coefficient (S) is found to vary from 64 to 118 V/K in the
temperature range K. The positive values of S are indicating the
dominating p-type behaviour of the compound. The observed value of thermal
conductivity () is 2.2 W/m-K at 300 K. In the temperature region
K, the value of increases up to 2.6 W/m-K and then
decreases slowly till 620 K with the corresponding value of 2.4 W/m-K.
We have also carried out the theoretical calculations and the best matching
between experimental and calculated values of transport properties are observed
in spin-polarized calculation within DFT+\textit{U} by chosen \textit{U} = 4
eV. The maximum calculated value of ZT is found to be 0.67 at 1200 K for
p-type conduction. Our computational study suggests that the possibility of
n-type behaviour of the compound which can lead to a large value of ZT at
higher temperature region. Electron doping of 5.110
cm is expected to give rise the high ZT value of 2.7 at 1200 K.
Using these temperature-dependent ZT values, we have calculated the maximum
possible values of efficiency () of thermoelectric generator (TEG) made
by p and n-type NaCoO. The present study suggests that one can
get the efficiency of a TE cell as high as 11 when the cold and hot
end temperature are fixed at 300 K and 1200 K, respectively. Such high values
of ZT and efficiency suggest that NaCoO can be used as a
potential candidate for high-temperature TE applications
Influence of Ni doping on the electronic structure of Ni_2MnGa
The modifications in the electronic structure of Ni_{2+x}Mn_{1-x}Ga by Ni
doping have been studied using full potential linearized augmented plane wave
method and ultra-violet photoemission spectroscopy. Ni 3d related electron
states appear due to formation of Ni clusters. We show the possibility of
changing the minority-spin DOS with Ni doping, while the majority-spin DOS
remains almost unchanged. The total magnetic moment decreases with excess Ni.
The total energy calculations corroborate the experimentally reported changes
in the Curie temperature and the martensitic transition temperature with x.Comment: 4 pages, 4 figures, accepted in Phys. Rev.
Physical Properties of Metallic Antiferromagnetic CaCo{1.86}As2 Single Crystals
We report studies of CaCo{1.86}As2 single crystals. The electronic structure
is probed by angle-resolved photoemission spectroscopy (ARPES) measurements of
CaCo{1.86}As2 and by full-potential linearized augmented-plane-wave
calculations for the supercell Ca8Co15As16 (CaCo{1.88}As2). Our XRD crystal
structure refinement is consistent with the previous combined refinement of
x-ray and neutron powder diffraction data showing a collapsed-tetragonal
ThCr2Si2-type structure with 7(1)% vacancies on the Co sites corresponding to
the composition CaCo{1.86}As2 [D. G. Quirinale et al., Phys. Rev. B 88, 174420
(2013)]. The anisotropic magnetic susceptibility chi(T) data are consistent
with the magnetic neutron diffraction data of Quirianale et al. that
demonstrate the presence of A-type collinear antiferromagnetic order below the
Neel temperature TN = 52(1) K with the easy axis being the tetragonal c axis.
However, no clear evidence from the resistivity rho(T) and heat capacity Cp(T)
data for a magnetic transition at TN is observed. A metallic ground state is
demonstrated from band calculations and the rho(T), Cp(T) and ARPES data, and
spin-polarized calculations indicate a competition between the A-type AFM and
FM ground states. The Cp(T) data exhibit a large Sommerfield electronic
coefficient reflecting a large density of states at the Fermi energy D(EF),
consistent with the band structure calculations which also indicate a large
D(EF) arising from Co 3d bands. At 1.8 K the M(H) data for H|| c exhibit a
well-defined first-order spin-flop transition at an applied field of 3.5 T. The
small ordered moment of 0.3 muB/Co obtained from the M(H) data at low T, the
large exchange enhancement of chi and the lack of a self-consistent
interpretation of the chi(T) and M(H,T) data in terms of a local moment
Heisenberg model together indicate that the magnetism of CaCo{1.86}As2 is
itinerant.Comment: 18 pages, 15 figures, 4 tables, 61 references; v2: extended the fits
of experimental data by additional electronic structure calculations;
published versio
Yield and Economic Viability of Coriander under Frontline Demonstration in Bundi District of Rajasthan
A study was conducted in Bundi district of Rajasthan to analyze yield and economics of coriander under frontline demonstration. Results of the study revealed that yields in coriander were substantially higher over the Local Check (Control), fetching the participating farmers a higher price for their produce. A majority of the respondent farmers expressed high (44.32%) to very high (37.50%) level of satisfaction with extension services and performance of the technology under the demonstration
- …