http://nopr.niscair.res.in/handle/123456789/9011 Search the Channel search http://nopr.niscair.res.in/simple-search http://nopr.niscair.res.in/handle/123456789/9569 Title: A comparative study of Suzuki and Kumar formulations for thermal expansivity <br/> <br/>Authors: Kumar, Munish <br/> <br/>Abstract: The Suzuki formulation for the determination of volume as a function of temperature, widely used in the literature is differentiated to give the relation for the coefficient of volume thermal expansion. The formulation is compared with the other relations claimed to be new by Shanker <i>et al.</i> <i>Physica B, </i>233 (1997) 78 as well as Pandey <i>J Phys Chem Solids</i>, 59 (1998) 1157. It is found that the relations advocated by these authors are same, which are well known from the theory of high pressure-high temperature reported by Kumar. It is concluded that the results based on Kumar formulation are better as compared with Suzuki formulation. <br/> <br/>Page(s): 67-70 Mon, 29 Dec 2003 22:58:59 GMT http://nopr.niscair.res.in/handle/123456789/9568 Title: Study of low field magneto-resistance in La_0.67A_0.33MnO₃ [A ≡ Ca, Ba, Sr] screen printed films <br/> <br/>Authors: Khare, Neeraj; Moharil, U P; Singh, B; Gupta, A K <br/> <br/>Abstract: Screen printed polycrystalline films of La_0.67A_0.33MnO₃[A ≡ Ca, Ba, Sr] have been found to exhibit substantially large magneto-resistance at low fields and low temperature as compared to an epitaxial La_0.67Ba_0.33MnO₃ film prepared by laser ablation technique. A value of magneto-resistance ratio (MRR) of 6 % has been achieved even at a dc field of 600 Oe at 77 K. Temperature dependence of MRR of the screen-printed films show that MRR increases with decrease of the temperature. This MRR-T behaviour shows that magneto-resistance in screen printed films has its origin in grain boundaries. The variation of MRR of these films with magnetic field at 77 K shows sharp increase in the field 0-1 kOe and slower increase for the field 1-3 kOe. Sharp increase in the MRR has been attributed to spin polarized tunnelling occurring across the grain boundaries, where as the slower increase in MRR for a field variation of 1-3 kOe is due to suppression of spin disorders present in the grain boundary region in the polycrystalline films. <br/> <br/>Page(s): 62-66 Mon, 29 Dec 2003 22:58:59 GMT http://nopr.niscair.res.in/handle/123456789/9567 Title: Switching responses of ferroelectric liquid crystals <br/> <br/>Authors: Khosla, Samriti; Raina, K K <br/> <br/>Abstract: The switching time of the FLC material has been calculated by using dielectric and electro-optic techniques. The electro-optic measurements have been carried out by direct pulse technique using different resistances and capacitors. The results obtained from these methods are compared. It is observed that measurement of response time using capacitor gives more reliable results as compared to those given by resistor method in the direct pulse technique. <br/> <br/>Page(s): 49-55 Mon, 29 Dec 2003 22:58:59 GMT http://nopr.niscair.res.in/handle/123456789/9566 Title: Electronic state in <img src='/image/spc_char/alpha.gif' border=0>-gallium using Compton scattering technique <br/> <br/>Authors: Jain, Rajesh; Ahuja, B L; Sharma, B K <br/> <br/>Abstract: <smarttagtype namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="State"><smarttagtype namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="City"><smarttagtype namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="place"> Study of the electronic state in <img src='/image/spc_char/alpha.gif' border=0>-Ga using Compton scattering technique is reported in this paper. The isotropic Compton profile has been measured using a <img src='/image/spc_char/gamma.gif' border=0>-ray Compton spectrometer, which employs a 5 Ci annular ²⁴¹Am source. The measurement is compared with the available augmented plane-wave (APW) and non-local model potential calculations. Comparison with the present calculations based on renormalised-free-atom (RFA) model for 4s and 4p electrons is also made. It is seen that APW (with Lam-Platzman electron-electron correlation) calculation is in better agreement with the experiment. The Fourier transform of experimental Compton profile confirms the free-electron like behaviour of Ga. </smarttagtype></smarttagtype></smarttagtype> <br/> <br/>Page(s): 43-48 Mon, 29 Dec 2003 22:58:59 GMT