Indian Journal of Pure and Applied Physics

http://www.niscair.res.in

Total visitors: 3,415  since 04-03-08

 

Volume 46

Number 1

JANUARY 2008

CODEN: IJOPAU 46 (1) 1-74

ISSN: 0019-5596

 

 

CONTENTS

 

Review Article

 

Contemporary issues in glass science

7

C S Sunandana

 

Atomic and Molecular Physics

 

FTIR study of hydrogen bonding interactions between alkyl esters and hexanol, p-cresol in
carbon tetrachloride

12

F Liakath Ali Khan*, P Sivagurunathan & J Asghar

 

Vibrational spectroscopy and phonon dispersion of GaSb

20

Bipul Rakshit, Vipul Srivastava, Sankar P Sanyal*, P K Jha, T R Ravindran & A K Arora

 

Electromagnetism, Optics, Acoustics, Heat Transfer, Classical Mechanics and Fluid Dynamics

 

Fabrication and numerical evaluation of the tapered single mode optical fiber: Detection of
change in refractive index

23

Vivek P Kude & R S Khairnar*

 

Condensed Matter: Structural , Mechanical and Thermal Properties

 

Electrical and mechanical properties of samarium barium copper oxalate crystals

30

Soosy Kuryan*, Rosalin Abraham & Jayakumari Isac

 

Effect of substrate-epitaxy interface doping profile on the series resistance and mm wave
performance of Si IMPATT diode

33

P De

 

Role of Cu additive in the density of localized states in a-Ge20Se80 glassy alloy

38

R Singh, S K Tripathi & S Kumar*

 

Controlling the properties of Mn-Zn ferrites at high frequency by substituting In3+and Al3+ ions

42

Atul Thakur, Preeti Mathur* & M Singh

 

Synthesis and characterization of nanosized cobalt- manganese spinel oxide

47

Nisha J Tharayil*, R Raveendran & Alexander Varghese Vaidyan

 

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

 

Dielectric relaxation studies of alkyl acrylates with phenol derivatives in carbon tetrachloride using microwave absorption techniques

54

F Liakath Ali Khan*, P Sivagurunathan & J Asghar

 

Magnetic behaviour of nano-sized and coarse powders of Cd-Ni ferrites synthesized by wet-chemical route

60

M K Rangolia, M C Chhantbar, A R Tanna, K B Modi, G J Baldha & H H Joshi*

 

Interdisciplinary Physics and Related Areas of Science and Technology

 

Gaussian minimum shift keying systems with additive white Gaussian noise

65

A K Saraf & M Tiwari*

 

 

__________

*The corresponding author has been indicated by (*) mark in case of papers with more than one author.


 

 

Indian Journal of Pure & Applied Physics

Vol. 46, January 2008, pp. 7-11

 

 

 

Contemporary issues in glass science*

C S Sunandana

School of Physics, University of Hyderabad, Hyderabad 500 046

E-mail: csssp75@yahoo.co.in

Received 3 January 2007; accepted 10 October 2007

Glasses-including non-oxide glasses-continue to be investigated for basic understanding and potential applications. The inter-related issues: glass formation as a self-organization process, glass transition, fast-ion relaxation in glasses, nanocrystallization and mixed alkali effect  have been presented. Last two issues in the light of relevant experimental work including our own work on tellurite glasses have been focussed.

Keywords: Self-organization, Fast-ion relaxation, Mixed alkali effect, Nanosystems

 

Indian Journal of Pure & Applied Physics

Vol. 46, January 2008, pp. 12-19

FTIR study of hydrogen bonding interactions between alkyl esters and hexanol,
p-cresol in carbon tetrachloride

 

F Liakath Ali Khan*, P Sivagurunathana & J Asghar

Department of Physics, Islamiah College, Vaniyambadi, Tamilnadu 635 752

aDepartment of Physics, Annamalai University, Annamalai Nagar, Tamilnadu 608 002

*Email: shamisardar@yahoo.com

Received 29 September 2006; revised 29 October 2007; accepted 7 November 2007

The effect of hydroxyl group in hexanol and p-cresol on the carbonyl vibration of representative compounds belonging to methyl methacrylate, ethyl methacrylate and butyl methacrylate in carbon tetrachloride has been studied by FTIR spectroscopic method. The integrated intensities and change in dipole moments for O-H and C=O bonds were calculated. Utilizing Nash method, the formation constant and free energy of the 1:1 complexes have been calculated. The formation constant and free energy change values vary with chain length of acrylic esters, which suggests that the strengths of the intermolecular hydrogen bonds (O–H…O=C) are dependent on chain length of acrylic esters. The strength of the intermolecular C=O: HO bonds is shown to be dependent on the basicity of the C=O group of alkyl esters and the acidity of the proton donor.

Keywords: Methyl methacrylate, Ethyl methacrylate, Butyl methacrylate, p-cresol, 1-hexanol, Hydrogen bonding

 

 

Indian Journal of Pure & Applied Physics

Vol. 46, January 2008, pp. 20-22

 

 

Vibrational spectroscopy and phonon dispersion of GaSb

 

Bipul Rakshit, Vipul Srivastava, Sankar P Sanyal*, P K Jha1, T R Ravindran2 & A K Arora2

Department of Physics, Barkatullah University Bhopal, Bhopal 462 026

1Department of Physics, The M S University of Baroda, Vadodara 390 002

2Material Science Division, Indira Gandhi Centre for Atomic Research, Kalpakkam

*E-mail: spsanyal@sancharnet.in

Received 11 September 2006; revised 22 August 2007; accepted 30 October 2007

The lattice vibrational properties of III-V semiconductor compound, GaSb have been investigated experimentally using Raman scattering and Fourier Transform Infrared spectroscopic techniques. The experimental results by both the techniques show a sharp peak around 222 cm-1. The experimental results have been analyzed using deformable bond approximation (DBA), whose formalism is a simplified version of deformation dipole model (DDM). The calculated phonon dispersion curves for GaSb, are in excellent agreement with the available inelastic neutron scattering data. The results will be useful to characterize the nano-structured GaSb.

Keywords: Raman scattering, Fourier Transform IR spectrum, Phonon dispersion

 

Indian Journal of Pure & Applied Physics

Vol. 46, January 2008, pp. 23-29

 

Fabrication and numerical evaluation of the tapered single mode optical fiber: Detection of change in refractive index

 

Vivek P Kude & R S Khairnar*

Department of Applied Physics, MGM College of Engineering, Nanded, Maharashtra

*School of Physical Sciences, SRTM University, Vishnupuri, Nanded, Maharashtra

*E- mail:rk2kin@yahoo.com.

Received 9 October 2006; revised 18 September 2007; accepted 5 November 2007

The fabrication of the tapered single mode fiber has been carried out. The tapered fiber is numerically evaluated for propagation behaviour of light by means of bound rays and tunneling rays in tapered portion. The nature of bound and tunneling rays as a function of refractive index is observed numerically, which shows that tapered portion of the fiber is suitable for sensor application. To make the fiber sensitive to refractive index of the medium other than core medium, it is etched up to fiber core using hydrofluoric acid (HF). The sensitivity of the sensor has been studied by varying the diameter of the etched portion in the fiber. The tapered portion is dipped in the DMSO solution having various molarity thereby exhibiting different refractive indices. The optical signal is passed through the fiber and output signal intensity has been measured with a wide wavelength photo-detector. The output intensity measured in voltage is found to be linearly dependent on the refractive indices surrounding the etched portion of the fiber. The result shows that the tapered single mode optical fiber is sensitive to refractive index of liquid at short (1 meter) as well as long (1.8 km) length of optical fiber. It also reveals that a distant detection and sensing can be carried out by a single mode tapered fiber sensors.

Keywords: Single mode fiber, Refractive index sensor, Evanescent waves, Signal attenuation

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 46, January 2008, pp. 30-32

 

Electrical and mechanical properties of samarium barium copper oxalate crystals

Soosy Kuryana, Rosalin Abrahamb & Jayakumari Isacc

aSt Stephen’s College, Kollam, Kerala

b St Dominics College, Kanjirapally, Kottayam, Kerala

cCenter for Condensed Matter, C.M.S College, Kottayam, Kerala

Received 28 March 2007; revised 3 September 2007; accepted 1 November 2007

Samarium barium copper oxalate (SmBaCuOx) crystals were grown using silica gel technique by the diffusion of a mixture of samarium chloride, barium chloride and cuprous nitrate into the test tube having the set gel containing oxalic acid. The grown crystals were characterized by X-ray diffraction analysis, Inductively Coupled Plasma Atomic Emission analysis and microhardness measurements. The variation of dielectric constant εr and dielectric loss D in the frequency range100Hz - 1MHz has been studied and reported. The electrical conductivity of SmBaCuOx crystals was found to increase with increase of frequency.

Keywords: Samarium barium copper oxalate crystals, Inductively coupled plasma emission system, Electrical conductivity, Microhardness

 

 

Indian Journal of Pure & Applied Physics

Vol. 46, January 2008, pp. 33-37

 

 

Effect of substrate-epitaxy interface doping profile on the series resistance and mm wave performance of Si IMPATT diode

P De

Department of Physics, Gobardanga Hindu College, University of Calcutta, P O Khantura, 743 273

E-mail: pdeghc@yahoo.co.in

Received 26 August 2006; accepted 22 August 2007

The effect of abrupt and exponential type of doping profiles in the transition region of epitaxy-substrate interfaces
(nn++ and pp++) on the parasitic resistance and mm wave properties of double drift region low-high-low (n++nn+npp+pp++) Si IMPATT diode suitable for 35 GHz window frequency have been simulated. The results show that the negligible width of the nn++ (0.016
mm) and pp++ (0.015 mm) substrate-epitaxy interface regions over the total depletion layer width of 2.0 mm with realistic exponential doping gradient rather than its hypothetical abrupt nature, severely degrade the maximum avalanche region breakdown field at the junction, negative resistance, negative conductance as well as the power conversion efficiency; in other way increasing simultaneously the value of drift region electric field, punch through condition and the series resistance of the diode.

Keywords: Substrate-epitaxy interface, Series resistance, IMPATT diode

 

Indian Journal of Pure & Applied Physics

Vol. 46, January 2008, pp. 38-41

 

Role of Cu additive in the density of localized states in a-Ge20Se80 glassy alloy

R Singh, S K Tripathi* & S Kumar

Department of Physics, Christ Church College, Kanpur 208 001

Centre of Advanced Study in Physics, Panjab University, Chandigarh 160014

Received 5 December 2006; revised 19 June 2007; accepted 29 October 2007

The dc conductivity at high electric fields in vacuum evaporated amorphous thin films of Ge20Se80 and (Ge20Se80)98Cu2 glassy alloys has been measured. Current-voltage (I-V) characteristics have been measured at various fixed temperatures. In these samples, ohmic behaviour is observed at low electric fields. However, at high electric fields (E~104V/cm), non ohmic behaviour is observed. An analysis of the experimental data confirms the presence of space charge limited conduction (SCLC) in the glassy materials studied in the present case. From the fitting of the data to the theory of SCLC, the density of defect states (DOS) near Fermi level has been calculated. An increase in DOS has been found when we incorporate Cu in the pure binary Ge20Se80 glassy system. The peculiar role of Cu as a third element in the binary Ge20Se80 glassy alloy is also discussed.

Keywords: Thin films, Chalcogenide glasses, Space charge limited conduction, Density of defect states

 

Indian Journal of Pure & Applied Physics

Vol. 46, January 2008, pp. 42-46

 

Controlling the properties of Mn-Zn ferrites at high frequency
by substituting In3+ and Al3+ ions

Atul Thakur1, Preeti Mathur*1 & M Singh1,2

1Department of Physics, H P University, Summer Hill, Shimla, 171 005

2Department of Physics, University of Dundee, Dundee, DD 14HN, UK

*E-mail: at_phy_hpu@yahoo.co.in

Received 27 November 2006; revised 18 September 2007; accepted 4 October 2007

The effect of substitution of In3+ and Al3+ ions on the electrical and magnetic properties of Mn-Zn spinel ferrites has been investigated. The substitution of In3+ ions in place of Fe3+ ions resulted in an increase of lattice parameter, because of the larger size of the substituted ions, whereas lattice parameter decreased on substituting Al3+ ions in place of the Fe3+ ions, owing to their smaller size. The dc resistivity was found to increase with the substitution of In3+ and Al3+ ions in the Mn-Zn ferrite system. The improvement in the dc resistivity has been observed at the expense of deterioration in the magnetic properties of Al3+ substituted Mn-Zn Ferrites. A significant reduction in the value of initial permeability, saturation magnetization and Curie temperature was observed with successive increase of Al3+ ions. The saturation magnetization and initial permeability were found to increase with incorporation of In3+ ions. A marked increase in the value of initial permeability was found for the Mn0.4Zn0.6In0.5Fe1.5O4 ferrites. The Curie temperature was found to decrease with an increase of In3+ ion concentration. Possible mechanisms contributing to these processes have been discussed.

Keywords: Mn-Zn ferrite, Lattice parameter, Saturation magnetization, Curie temperature

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 46, January 2008, pp. 47-53

 

Synthesis and characterization of nanosized cobalt-manganese spinel oxide

Nisha J Tharayil+, R Raveendran « & Alexander Varghese Vaidyan§

+, « Department of Physics, Sree Narayana College, Kollam, Kerala

§ Department of Chemistry, St Stephen’s College, Pathanapuram, Kerala

+ E-mail: nishajohntharayil @yahoo.co.in

Received 25 October 2006; revised 23 August 2007; accepted 15 October 2007

Nanoparticles of cobalt-manganese oxide were prepared by chemical co-precipitation method by decomposition of their respective metal chlorides, sodium carbonate and ethylene diamene tetra acetic acid (EDTA). The heat treatment of the ground precursor powders at their respective decomposition temperature and beyond, results in the evolution of heat from the combustion of the residual carbonaceous material. This facilitates the reaction among the constituent metal ions and the formation of the desired oxide phase at low temperature. The average crystallization size was determined from X-ray diffraction line broadening and the diffractogram was compared with JCPDS data to identify the crystallographic phase of the particle. The shift in d--value due to the nano nature was also analyzed.The internal elastic micro strain was calculated and it was seen that as the particle size increases strain decreases. The effect of sintering on the particle size was also analyzed. The nano nature of the mixed oxide was also analyzed from the TEM and AFM studies. The FTIR studies have been used to confirm the formation of metal oxide. The characteristic stretching and bending frequencies of the sample were also analyzed. The absorption spectra of the material in the UV-Vis –NIR range were recorded. Strong absorption bands are observed to occur at 550 nm and a weak band around 730nm. From the analysis of absorption spectra, the cobalt-manganese oxide (sintered at 5000, 7000 and 9000 C) have been found to have direct band gaps ranging from 2.07 to 1.59 eV.

Keywords: Nanoparticles, Arrested precipitation, Calcination temperature, SEM TEM, AFM, Fourier Transform Infrared Spectrum, Absorption spectra, Optical band gap

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 46, January 2008, pp. 54-59

 

Dielectric relaxation studies of alkyl acrylates with phenol derivatives in carbon tetrachloride using microwave absorption techniques

F Liakath Ali Khan* , P Sivagurunathana & J Asghar

Department of Physics, Islamiah College, Vaniyambadi, Tamilnadu 635 752

aDepartment of Physics, Annamalai University, Annamalai Nagar, Tamilnadu 608 002

Received 12 October 2006; revised 29 October 2007; accepted 19 November 2007

The dielectric relaxation of alkyl acrylates (methyl acrylate, ethyl acrylate and butyl acrylate) with phenol derivatives (p-cresol, p-chlorophenol, 2,4-dichlorophenol and p-bromophenol) has been measured at microwave frequency 9.37 GHz in dilute solution of carbon tetrachloride at 308K. Different dielectric parameters like dielectric constant e¢ and dielectric loss e² at microwave frequency, static dielectric constant eo and dielectric constant e¥ at optical frequency have been determined. The relaxation time and activation energy have been determined using the measured dielectric data. The results show a linear dependence of relaxation time on alkyl chain length of acrylic esters and acidity of phenol derivatives. Comparative study of free energy of activation for the dielectric relaxation and viscous flow suggests that the process of viscous flow involves greater interference by neighbours than does dielectric relaxation, as the latter takes place by rotation only whereas the viscous flow involves both rotational and translational motion. The validity of the single frequency equation of Higasi et al. Bull Chem Soc Japan, 44(1971)988. For multiple relaxation time t1 is found to be function of the hydrogen bonding strength of phenolic hydrogen whereas the group rotation relaxation time t2 is a function of the steric interaction of proton donor. The relaxation time is maximum at 50:50 mol% ratio.

Keywords: Acrylic esters, Phenol derivatives, Dielectric relaxation

 

Indian Journal of Pure & Applied Physics

Vol. 46, January 2008, pp. 60-64

 

 

Magnetic behaviour of nano-sized and coarse powders of Cd-Ni ferrites synthesized by wet-chemical route

M K Rangolia, M C Chhantbar, A R Tanna, K B Modi, G J Baldha & H H Joshi

Department of Physics, Saurashtra University, Rajkot 360 005

Received 1 March 2006; accepted 2 August 2007

Nano particles having particle size in the range (80 -100Å) for compositions (x = 0.2, 0.4, 0.6, 0.8) of CdxNi1-xFe2O4 spinel ferrite system are prepared by chemical co-precipitation route. The structural and magnetic properties have been studied by X-ray diffraction, magnetization, susceptibility and 57Fe Mössbauer spectroscopy measurements, before and after high temperature annealing. The magnetic behaviour is explained by invoking the concept of superparamagnetism assuming core-shell structure of the nano-particles.

Keywords: Nano particles, Ferrites, Mössbauer spectroscopy

 

 

Indian Journal of Pure & Applied Physics

Vol. 46, January 2008, pp. 65-70

 

 

Gaussian minimum shift keying systems with additive white Gaussian noise

 

A K Saraf & M Tiwari

Department of Physics and Electronics, Dr Harisingh Gour Vishwavidyalaya, Sagar

Received 9 May 2006; revised 16 May 2007; accepted 28 September 2007

In this paper, the basic properties of an I-Q Gaussian minimum shift keying (GMSK) with additive white Gaussian noise have been investigated. The probability of error for non-fading and fading channels of communication has been analyzed and discussed. The hardware realization is simple and straight forward like minimum shift keying (MSK) system. Some analytical results have been achieved and compared with machine computed GMSK results of others. The modular circuits are available for VLSI design. Thus, the system developed is suitable for VLSI design of GMSK.

Keywords: Gaussian minimum shift keying, Spectral density, Probability of error, Additive white Gaussian noise