http://nopr.niscair.res.in/handle/123456789/8749 Search the Channel search http://nopr.niscair.res.in/simple-search http://nopr.niscair.res.in/handle/123456789/8913 Title: Study of depression of critical temperature of praseodymium doped high <i>T</i>_ccuprates <br/> <br/>Authors: Gill, R; Singh, P <br/> <br/>Abstract: The recent experimental observation of the substitution of praseodymium (Pr) in high transition temperature (<i style="">T</i>_c) superconducting Y123 compounds gives rise to very interesting properties, such as monotonic decrease of <i style="">T</i>_cwith increase in Pr concentration which is not satisfactorily explained yet. The depression of <i style="">T</i>_c is due to hole filling/hole localization, magnetic pair breaking or some kind of disorder/dislocation is still not clear. The depression of <i style="">Tc </i>in Y_1-xPr_xBa₂Cu₃O_7-x has been explained using magnetic pair breaking, hole filling and disorder. It has been argued that the disorder along with hole filling is responsible for suppression of <i style="">T</i>_c and subsequently to lower order parameter (∆). <br/> <br/>Page(s): 977-979 Mon, 28 Nov 2005 22:58:59 GMT http://nopr.niscair.res.in/handle/123456789/8912 Title: Carbon nanotubes field effect transistors : A review <br/> <br/>Authors: Alvi, P A; Lal, K M; Siddiqui, M J; Naqvi, Alim H <br/> <br/>Abstract: Carbon nanotubes field effect transistors (CNTFETs) are one of the most promising candidates for future nanoelectronics. In this paper, the review of CNTFETs is presented. The structure, operation and the characteristics of carbon nanotubes metal-insulator-semiconductor capacitors have been discussed. The operation and <i style="">dc</i> characteristics of CNTFETs have been presented. In future, we expect the performance of CNTFETs will be better by improving CNT quality and on optimizing device structures. <br/> <br/>Page(s): 899-904 Mon, 28 Nov 2005 22:58:59 GMT http://nopr.niscair.res.in/handle/123456789/8911 Title: Excitation energy transfer between Eu³⁺ and Tm³⁺ ions in zinc phosphate glass <br/> <br/>Authors: Joshi, B C; Dhondiyal, Charu Ch <br/> <br/>Abstract: Non-radiative energy transfer from Eu³⁺to Tm³⁺has been studied by observing the steady state emission of Eu³⁺ with varying concentration of Tm³⁺in zinc phosphate glass. It has been observed that Eu³⁺ion emission intensity decreases with increasing Tm³⁺ concentration resulting in a non-radiative energy transfer from Eu³⁺ to Tm³⁺ whereas energy transfer from Tm³⁺ to Eu³⁺ was not observed between donor and acceptor ions. This energy transfer has been explained on the basis of cross-relaxation of energy. The energy transfer mechanism and other parameters related to energy transfer between Eu³⁺ and Tm³⁺have been computed. <br/> <br/>Page(s): 918-920 Mon, 28 Nov 2005 22:58:59 GMT http://nopr.niscair.res.in/handle/123456789/8910 Title: Dielectric tensor theory of electric field gradient in dilute transition metal based alloys: Application to vanadium alloys <br/> <br/>Authors: Pal, B; Singh, J <br/> <br/>Abstract: The electric field gradient (EFG) in dilute alloys consists of two contributions valence effect and size effect EFGs. In the estimation of valence effect EFG an electrostatic screening approach is used to evaluate impurity scattering potential in transition metal (TM) based alloys. The dielectric tensor is inverted using the mixed band scheme where <i style="">s</i>-electrons are represented in free electron approximation and <i style="">d</i>-electrons in simple tight binding approximation. In this scheme the exact expression is obtained for the excess impurity potential <img src='/image/spc_char/delta.gif' border=0><i style="">V</i>(<b style="">r</b>) which consists of isotropic and anisotropic parts. The latter is the manifestation of local field (LF) effects in TM based alloys. The numerical results for <img src='/image/spc_char/delta.gif' border=0><i style="">V</i>(<b style="">r</b>) are obtained for vanadium (V) alloys with Ti, Cr, Mn, Fe, Mo and W impurities using non-interacting model band structure. The size effect contribution to EFG is evaluated in the elastic continuum approach. The EFG is calculated for the above mentioned V-alloys including the LF effects. The calculated results for EFG are consistent with experimental predictions and suggest that both the valence and size effects are equally important to explain the experimental results. <br/> <br/>Page(s): 972-976 Mon, 28 Nov 2005 22:58:59 GMT