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ABSTRACT: This study reports the effect of Gd addition on magnetic and structural properties of Bi1.8Pb0.35Sr1.9Ca2.1Cu3Gd
x
O
y
superconductor with x=0, 0.1, 0.2, 0.3, 0.4 and 0.5 by means of ac susceptibility measurements at various ac fields (ranging from 270 to 1352A/m)
and scanning electron microscopy (SEM) images. Critical onset (Tcon)T_{\mathrm{c}}^{\mathrm{on}}) and loss peak temperatures (T
p) were qualitatively estimated from the ac susceptibility curves. The peak temperature at zero ac-magnetic field (T
p0) and intergrain critical current densities (J
c) were theoretically calculated from the ac susceptibility plots via the critical state models. The results show that peak
temperatures and critical current densities were found to decrease with increasing Gd addition. Moreover, using a self-field
approximation together with J
c dependence on temperature, the characteristic length (L
c) associated with the pinning force is estimated to be approximately the same as the average grain size (R
g) of the pinning center because of the linear decrease in J
c with increasing temperature. Surface morphology and grain connectivity of the samples were also obtained to degrade with
increase in the Gd addition from SEM investigations.
KeywordsBi1.8Pb0.35Sr1.9Ca2.1Cu3Gd
x
O
y
–Ac susceptibility–Critical state models–Critical current density–Peak temperature–Scanning electron microscopy
Journal of Superconductivity and Novel Magnetism 05/2012; 24(7):2153-2159. · 0.65 Impact Factor
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ABSTRACT: This study deals with the identification of a title compound, 2,6-dimethyl-4-nitropyridine N-oxide by means of theoretical calculations. The optimized molecular structures, vibrational frequencies, corresponding vibrational assignments, thermodynamic properties and atomic charges of the title compound in the ground state were evaluated using density functional theory (DFT) with the standard B3LYP/6-311G(d,p) method and basis set combination for the first time. Theoretical vibrational spectra were interpreted with the aid of normal coordinate analysis based on scaled density functional force field. The results show that the optimized geometric parameters (bond lengths and bond angles) and vibrational frequencies were observed to be in good agreement with the available experimental results. Based on the results of comparison between experimental results and theoretical data, the chosen calculation level is powerful approach for understanding the molecular structures and vibrational spectra of the 2,6-dimethyl-4-nitropyridine N-oxide. Moreover, we not only simulated frontier molecular orbitals (FMO) and molecular electrostatic potential (MEP) but also determined the transition state and energy band gap. Based on the investigations, the title compound is found to be useful to bond metallically and interact intermolecularly. Infrared intensities and Raman activities were also reported.
Spectrochimica Acta Part A Molecular and Biomolecular Spectroscopy 05/2011; 81(1):104-10. · 2.10 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: This study reports the effect of Gd addition on magnetic and structural properties of Bi1.8Pb0.35Sr1.9Ca2.1Cu3Gd
x
O
y
superconductor with x=0, 0.1, 0.2, 0.3, 0.4 and 0.5 by means of ac susceptibility measurements at various ac fields (ranging from 270 to 1352 A/m)
and scanning electron microscopy (SEM) images. Critical onset ( and loss peak temperatures (T
p) were qualitatively estimated from the ac susceptibility curves. The peak temperature at zero ac-magnetic field (T
p0) and intergrain critical current densities (J
c) were theoretically calculated from the ac susceptibility plots via the critical state models. The results show that peak
temperatures and critical current densities were found to decrease with increasing Gd addition. Moreover, using a self-field
approximation together with J
c dependence on temperature, the characteristic length (L
c) associated with the pinning force is estimated to be approximately the same as the average grain size (R
g) of the pinning center because of the linear decrease in J
c with increasing temperature. Surface morphology and grain connectivity of the samples were also obtained to degrade with
increase in the Gd addition from SEM investigations.
Journal of Superconductivity and Novel Magnetism - J SUPERCOND NOV MAGN.
