Total visitors:3,400 since 13-02-04

Indian Journal of Pure and Applied Physics

 

 

 

ISSN: 0019-5596

 

CODEN: IJOPAU 42 (1) 1-74

VOLUME  42

NUMBER 1

JANUARY 2004

                                                                      

  

CONTENTS

 

General

 

 

Universal time formulation of special relativity

Vachaspati                                                                                                                

5

 

 

Condeused Matter : Structural, Mechanical and Thermal Properties

 

 

 

Growth impedance of pure CdS films. 

L I Soliman,*, H H Abify & J K Battisha    

12

 

 

Sound velocity change in BaxSr1-x Tio3 pevouskites      

Ashok Kumar*, U C Naithani & B S Semwal                                        

18 

 

 

Mossbauer and infrared studies of manganese deoped iron borate glasses                   

Roshan Lal, N D Sharma*, H K Sharma & Kailash Chandra                       

 25

 

 

Thermo-economic analysis of regenerative Reat engines   Santanu Bandhyopadhyay                                                         

 31

 

 

Fe content variation and supervconduching order parameter dimensionality in Er Ba2 Cu3-x Fex O7-d

U C Upreli   

 38

 

 

Condeused Matter : Electronic Structure, Electrical, Magnetic and Optical Properties

 

 

 

Electronic state in α-gallium using Compton scattering technique           

Rajesh Jain*, B L Ahuja & B K Sharma                                              

 43

 

 

Switching responses of ferroelectric liquid crystals          

Samriti Khosla & K K Raina*

 49

 

 

An inpedance model to improve the higher frequency limit of electrical measurements on the capacitor cell made from electrodes of finite resistances      

Ravindra Dhar                   

 56

 

 

Study of low field magneto-resistance in La0.67A0.33Mn03 [A=Ca, Ba, Sr]

Neeraj Khare*, U P Moharil, B Singh & A K Gupta                                                

 62

 

 

Geophysics, Astronomy and Astrophysics

 

 

 

A comparative study of Suzuki and Kumar formulations for thermal expansivity                                      

Munish Kumar

67

 

Indian Journal of Pure & Applied Physics

Vol. 42, January 2004, pp 5-11

 

Universal time formulation of special relativity

Vachaspati

 

Special Relativity is formulated with time, instead of the speed of light, treated as invariant under inertial coordinate transformations. Velocity of light in space is shown to be isotropic and the observed longer lifetimes of unstable particles in flight are explained. The slowing down of cesium clocks carried by Hafele and Keating in circumnavigating the earth, is discussed. An observational test to find out whether or not nature operates according to the universal time, is outlined.

 

Keywords: Special relativity, Transformation equations, Universal time

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 42, January 2004, pp 12-17

 

Growth impedence of pure CdS films

L I Soliman, H H Afify & I K Battisha

 

The effect of Al, Fe and Cu incorporated CdS pure thin films prepared by spray pyrolysis process has been given. It was found that the increase of the element concentration leads to a significant change in pure CdS physical properties. The films have a polycrystalline hexagonal structure as shown from their X-ray diffraction pattern (XRD). The crystallinity of pure CdS film is reasonably decreased by the addition of Al, Fe and Cu. The grain size of the pure CdS films decrease by incorporation of Fe, Al and Cu as revealed by atomic force microscopy (AFM). The roughness of all samples was calculated. The optical constants of the prepared samples were determined. The calculated energy band gap of pure CdS films decreases by increasing Cu contents, while it does not get effected by Al contents.

 

Keywords: Cds films, Growth impedence, Polycrystalline hexagonal structure, Spray pyrolysis process, Optical constants

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 42, January 2004, pp 18-24

 

Sound velocity change in BaxSr1-xTio3 perovskites

Ashok Kumar, U C Naithani & B S Semwal

 

An expression for the sound velocity change in anharmonic BaxSr1-xTiO3 ferroelectric crystal is obtained, by using double time temperature dependent Green’s function technique. We have considered higher order anharmonic terms in modified Silverman Hamiltonian for it. The defect and anharmonic contributions to the change in sound velocity are separately discussed. The sound velocity decreases anomalously in the vicinity of the Curie temperature. The presence of higher order anharmonicity decreases the sound velocity. It varies with temperature and the sound velocity decreases with addition of defect (concentration x) in BaxSr1-xTiO3.

 

Keywords: Sound velocity change, Ferroelectric perovskites, Anharmonicity.

 

 

  

Indian Journal of Pure & Applied Physics

Vol. 42, January 2004, pp 25-30

 

Mössbauer and infrared studies of
manganese doped iron borate glasses

Roshan Lal*, N D Sharma,* H K Sharma** & Kailash Chandra***

 

The infrared absorption spectra of Manganese-doped Iron borate glasses (X=0,10,15,20&30 mol% MnO) have been investigated to find out the role played by Manganese on the structure of these glasses. MnO was gradually introduced to replace Fe2O3 in the series of manganese doped iron borate glasses containing 60% B2O3 . The structural changes induced were consistent with Mn2O3 formulation and were inferred by monitoring the I.R. spectra of these glasses in the range 200-4000 cm-1 by KBr Technique. The similar ionic radii of Fe3+ and Mn3+ cause no structural changes in either series as observed from infrared spectroscopy, which show that the Fe3+ ions concentration at B-site is replaced by Mn3+ ions. Mössbauer Technique was applied to study the effect of manganese doping at the Fe site for all the samples.

 

Keywords: Mössbauer study, Infrared spectra, iron borate glasses, glasses

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 42, January 2004, pp 31-37

 

Thermo-economic analysis of regenerative heat engines

Santanu Bandyopadhyay

 

Analysis of ideal internally reversible regenerative heat engines is presented in this paper, from finite resources point of view. Thermo-economic performances of a regenerative heat engine depend on the nature of polytropic processes and on the efficiency of regeneration. The study of the effects of regeneration efficiency, on the resource allocation for optimal performance of generalized regenerative engine, is also presented in this paper. Thermo-economic performances of an internally reversible regenerative heat engine, with perfect regeneration, are equivalent to those of internally reversible Carnot, Otto and Joule-Brayton engines. Concurrent employment of the first and the second laws ensure the optimal allocation of finite resources simultaneously with minimization of entropy generation. The operating regions both for operation and design of such regenerative engines are identified from the power-efficiency characteristic. The results are derived without assuming any particular equation of state associated with the working fluid.

 

[Keywords: Heat engines; Regenerative heat engines; Reversible heat engines; Reversible regenerative heat engines; Thermo-economic analysis; Carnot engine; Otto engine; Joule-Braydon engine]

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 42, January 2004, pp 38-42

 

Fe content variation and superconducting order parameter dimensionality in ErBa2Cu3-xFexO7-d

U C Upreti

 

The effects of predominantly chain-site dopant, Fe, concen­tration variation on superconducting order parameter fluctuations (SCOPF) in ErBa2Cu3-xFe xO7-d polycrystalline bulk samples are presented and compared. A large reduction in OPD near the dynamic critical region is seen, suggesting an anomalous crossover and indicating a much slower suppression of superconductivity. Near to Tc the SCOPF behaviour suggests Cu-O network cou­pling deterioration. It is also observed that the SCOPF are invariant to Fe low concentrations and with Fe concentration increase these show marked dimensionality variation and increased oxygen content dependence. Higher Fe concentration is seen to promote a dimensionality reversal.

 

Keyword : ErBa2Cu3-xFexO7-d  Superconducting order parameter High Tc superconductors

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 42, January 2004, pp 43-48

 

Electronic state in a-gallium using
Compton scattering technique

Rajesh Jaina, B L Ahujab & B K Sharmac

 

Study of the electronic state in a-Ga using Compton scattering technique is reported in this paper. The isotropic Compton profile has been measured using a g-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.

 

Keywords: APW band structure calculation; Compton scattering; Electron momentum density; Electron-electron correlation effects; Gallium

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 42, January 2004, pp 49-55

 

Switching responses of ferroelectric liquid crystals

Samriti Khosla & K K Raina*

 

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.

 

Keywords: Liquid crystal, Ferroelectric liquid crystal, Switching

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 42, January 2004, pp 56-61

 

An impedance model to improve the higher frequency limit of electrical measurements on the capacitor cell made from electrodes of finite resistances

Ravindra Dhar

 

Measurement of the frequency dependent dielectric permittivity () and loss () of the materials filled in parallel plate capacitors are highly affected above 100 kHz due to the presence of the electrodes resistance and leads inductance. An impedance model has been used to improve the higher frequency limit of the dielectric measurements on the isotropic liquids and anisotropic liquid crystal materials filled in parallel plate capacitors made from the electrodes having finite resistance (specially indium tin oxide coated electrodes). By using this model it has been possible to extend the upper frequency limit of the correct measurement of capacitance and conductance (and hence and ) at least by a decade of the frequency.

 

[Keywords: High frequency impedance model, Dielectric spectroscopy, Permittivity and loss, Liquid crystals]

 

 

Indian Journal of Pure & Applied Physics

Vol. 42, January 2004, pp 62-66

 

Study of low field magneto-resistance in
La0.67A0.33MnO3 [A º Ca, Ba, Sr] screen printed films

Neeraj Khare1, U P Moharil1,2, B Singh2 & A K Gupta1

 

Screen printed polycrystalline films of La0.67A0.33MnO3 [A º Ca, Ba, Sr] have been found to exhibit substantially large magneto-resistance at low fields and low temperature as compared to an epitaxial La0.67Ba0.33MnO3 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.

 

[Keywords: Magneto-resistance, Polycrystalline films, Epitaxial films, Laser ablation technique, spin Polarized tunneling]

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 42, January 2004, pp 67-70

 

A comparative study of Suzuki and Kumar formulations
for thermal expansivity

Munish Kumar

 

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 et al. Physica B, 233 (1997) 78 as well as Pandey J Phys Chem Solids, 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.