Indian Journal of Pure and Applied Physics

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Volume 47

Number 3

MARCH 2009

CODEN: IJOPAU 47 (3)157-236

ISSN: 0019-5596

 

 

   CONTENTS

Atomic and Molecular Physics

 

ESR, IR, Raman and optical absorption studies of 60B2O3 + 10Te2O2 + 5TiO2 + 24R2O: 1CuO
(where R= Li, Na, K) quarternary glasses

163

S Suresh , M Prasad, G Upender, V Kamalakar & V Chandra Mouli*

 

Condensed Matter: Structural, Mechanical and Thermal Properties

 

Annealing behaviour of GaAs implanted with 70 MeV 120Sn ions

170

Yousuf P Ali, Geeta Nair, A M Narsale*, K S Chandrasekaran   &  B M Arora

 

Thermal expansivity and isothermal bulk modulus of ionic materials at high temperatures

175

S K  Srivastava*, Pallavi Sinha & Monika Panwar

 

Low temperature synthesis of nanosized Mn1-xCdxFe2O4 ferrites

180

Rajesh Iyer*, Rucha Desai & R V Upadhyay

 

Supersymmetric structure of fractional quantum Hall effect in graphene 

186

S Sahoo* & S Das

 

Effect of horizontal thermal gradient on double-diffusive ferroconvection

192

R Sekar*, G Vaidyanathan & R Hemlatha

 

Growth characterization and etching studies of calcium tartrate single crystal grown
using tamarind extract

199

P P Pradyumnan* & Shini C

 

Microstructure based model for effective thermal conductivity of snow

206

Ashok K Singh* & K S Wasankar

 

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

 

Structural and dielectric behaviour of barium substituted lead zinc niobate ceramics at
low temperature

212

A K Himanshu*, D C Gupta, Alo Dutta, T P Sinha & S K Bandopadhayay

 

Electric field dependent attenuation constant in BaxSr1-xTiO3 perovskites

220

Ashish Kukreti*, Ashok Kumar & U C Naithani

 

 

 

__________

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

 

 

 

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 47, March 2009, pp. 163-169  

 

 

ESR, IR, Raman and optical absorption studies of 60 B2O3 + 10 TeO2 +5TiO2
+24 R2O: 1CuO (where R=Li, Na, K) quaternary glasses

S Suresh, M Prasad, G Upender, V Kamalaker & V Chandra Mouli

Glassy Materials Research Laboratory (GMRL), Department of Physics, Osmania University, Hyderabad 500 007

E-mail: vorucm90@yahoo.com

Received 22 November 2007, revised 1 December 2008; accepted 2 February 2009

ESR, IR, Raman and optical absorption spectra of 60 B2O3 + 10 TeO2 +5TiO2+24 R2O (where R = Li, Na and K) quaternary glasses containing Cu2+ spin probe have been studied. IR results show the BO3-BO4- ring structure interconnected by TeO3- and TeO4- groups, where the BO4- groups are neighbours of the TeO3-groups. BO3 → BO4 transition is also observed, which correlates with the conversion of TeO4 →TeO3. From Raman spectra, a weak band recorded at 805 cm-1 clearly indicates the presence of boroxol rings for potassium boro-tellurite glass alone. From ESR spectra, the three weak parallel components are observed in the low field region. However, the perpendicular components are not resolved leading to an intensive line in the high field region. When one kind of alkali oxide is replaced by another, the Spin Hamiltonian parameters have been found to vary drastically. The spin Hamiltonian parameter values indicate that the ground state of Cu2+ is dx2- y2 and the site symmetry around the Cu2+ ion is tetragonally distorted octahedral coordination. Optical absorption peak of Cu2+ is found to be a maximum at around 794 nm for Li2O containing borate rich glasses. This peak shifts towards the lower wavelength side as Li2O is replaced with Na2O, K2O. Bonding parameters indicate a slight covalency for the in-plane σ bonding as compared to in-plane and out-of-plane π bonds.

           Keywords: Boro-tellurite, Spectroscopic studies, Quaternary glasses

 

 

Indian Journal of Pure & Applied Physics

Vol. 47, March 2009, pp. 170-174

 

 

  Annealing behaviour of GaAs implanted with 70 MeV 120Sn ions

Yousuf P Ali1, Geeta Nair2, A M Narsale3, K S Chandrasekaran4 & B M Arora4

1Department of Physics, Hadaramout University of Science and Technology, Mukalla – Yemen

2Physics Department, K J Somoiyya College, Vidyavihar, Mumbai 400 078

3Western Regional Instrumentation Centre, Mumbai University, Vidyanagri, Mumbai 400 098

4Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400 005

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

Received 2 September 2008; accepted 7 January 2009

Single crystal GaAs substrates implanted with 70 MeV 120Sn have been investigated by X-ray diffraction (XRD) and electrical resistance measurements after annealing in the temperature range 373-823 K. XRD measurements for the samples annealed up to 723 K show two peaks, one due to the substrate and another due to the implant damaged layer. The strain parameter from the measured separation between the substrate and layer peaks of several symmetric and asymmetric reflections after each annealing step has been calculated. Strain recovery occurs in two predominant annealing stages, one at about 500 K and the other at about 700 K. Temperature dependence (100-300 K) of resistance of these samples indicates that electrical conduction in the samples annealed up to 723 K, is dominated by variable range hopping. Localized states density at the Fermi level N(EF), estimated from temperature dependence of sample resistance after each annealing step, shows two annealing stages similar to those observed from XRD measurements. Isothermal annealing carried out at two different annealing temperatures (523 and 573 K) indicates the activation energy Ea = 0.16 eV for the first annealing stage.

           Keywords: MeV implantation, Radiation defects, GaAs

 

 

Indian Journal of Pure & Applied Physics

Vol. 47, March 2009, pp. 175-179

 

 

Thermal expansivity and isothermal bulk modulus of ionic materials at high temperatures

S K Srivastava*1, Pallavi Sinha1 & Monika Panwar2

1Computational Intelligence Laboratory, Institute of Science and Technology, Klawad, Yamunanagar 133 105, Haryana

2M.M.Engineering College, Mullana, Ambala, Haryana

*E-mail: sanjeevsrivastava1980@rediffmail.com

Received: 22 April 2008; revised 1 December 2008; accepted 3 February 2009

The volume expansion and bulk modulus data due to Anderson have been extrapolated by modification of previously used relationships for ionic materials viz. NaCl, KCl, MgO and CaO. The empirically modified relationships provide the non-linear models for the variation of both thermal expansivity and bulk modulus with temperature. The results are found to be in close agreement with the experiment which in turn reveals the validity of present work.

           Keywords: Thermal expansivity, Isothermal bulk modulus, Ionic materials

 

 

Indian Journal of Pure & Applied Physics

Vol. 47, March 2009, pp. 180-185

 

 

Low temperature synthesis of nanosized Mn1-xCdxFe2O4 ferrites

Rajesh Iyer, Rucha Desai* & R V Upadhyay*

Department of Physics, St.Xavier’s College, Ahmedabad 380 009

*Department of Physics, Bhavnagar University, Bhavnagar 364 002

Received 24 April 2008; revised 14 November 2008; accepted 10 December 2008

Nanosized Mn1-xCdxFe2O4 mixed ferrite samples were synthesized using the co-precipitation technique. The Cd2+ ion was employed as the dopant and the values of x = 0, 0.1 0.3 and 0.5. The X-ray and IR spectra analysis were carried out to confirm the spinel phase formation as well as to ascertain the cation distribution in the ferrite samples. The magnetic study was carried out to ascertain the effect of the cadmium doping on the Ms Value.

          Keywords:Mixed nanosized ferrites, Cation distribution, Sub lattice interaction

 

 

Indian Journal of Pure & Applied Physics

Vol. 47, March 2009, pp. 186-191

 

 

Supersymmetric structure of fractional quantum Hall effect in graphene

 

S Sahoo & S Das

Department of Physics, National Institute of Technology,
Durgapur 713209, West Bengal

Received 24 June 2008; accepted 5 November 2008

Graphene shows unusual low-energy electronic excitations described in terms of Dirac fermions. The fractional quantum Hall effect in a bilayer graphene in different Landau levels within the supersymmetric formalism has been studied. The quantized Hall conductivity is found to be

 , where n = 0, 1, 2, 3 …

Keywords: Supersymmetry, Fractional quantum Hall effect, Graphene, Landau levels

 

 

Indian Journal of Pure & Applied Physics

Vol. 47, March 2009, pp. 192-198

 

 

Effect of horizontal thermal gradient on double-diffusive ferroconvection

 

R Sekara, G Vaidyanathanb & R Hemalathac

aDepartment of Mathematics, bDepartment of Physics, Pondicherry Engineering College, Puducherry 605 014

cDepartment of Mathematics, Avvaiyar Govt College for Women, Karaikal 609 603

cE-mail: hemalatha53@yahoo.co.in

Received 8 July 2008; revised 12 December 2008; accepted 4 February 2009

The effect of horizontal thermal and salinity gradients on ferroconvection of a double diffusive system subjected to two dimensional magnetic fields with compensating horizontal thermal and solutal gradients has been investigated. Assuming that the fluid layer is bounded by free boundaries, the conditions for the onset of stationary and oscillatory instabilities are established using linear theory and normal mode technique. Wide range of values of the ratios of horizontal and vertical gradients with respect to temperature, salinity and the cell size are considered. It has been found that the system stabilizes only through oscillatory mode for ratios of the temperature and salinity gradients which tend to make the cell size greater than 1. Stationary instability is found to occur for the ratios of the temperature and salinity gradients which tend to make the cell shape smaller than 1.

Keywords: Double diffusive, Magnetic field, Horizontal temperature, Salinity gradients, Linear stability, Cell size

 

 

Indian Journal of Pure & Applied Physics

Vol. 47, March 2009, pp. 199-205

 

 

Growth characterization and etching studies of calcium tartrate single crystal grown using tamarind extract

P P Pradyumnan* & Shini C

Department of Physics, University of Calicut 673 635, Kerala

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

Received 15 January 2007; revised 14 October 2008; accepted 2 January 2009

Calcium tartrate crystals were grown in silica gel by single diffusion method. The reactants used were calcium chloride and extract from tamarind juice. Crude as well as centrifuged tamarind extracts were used. The studies on the growth parameter of the crystal were conducted. The characterization studies such as XRD, FT-IR, TG-DTA of the grown crystals were done and it was then compared with that of calcium tartrate crystals grown using AR grade tartaric acid. The absorption spectral, CHN analysis and etching were also studied.

Keywords: Gel growth, Calcium tartrate, XRD, FTIR, Thermal studies, Etching studies

 

 

Indian Journal of Pure & Applied Physics

Vol. 47, March 2009, pp. 206-211

 

 

Microstructure based model for effective thermal conductivity of snow

 

Ashok K Singh1 & K S Wasankar2

1Defense Institute of Advanced Technology, Pune

2Department of Mechanical Engineering, Govt. College of Engineering, Karad

Received 3 July 2007; revised 17 December 2008; accepted 2 January 2009

The paper presents a model to quantitatively relate macroscopic effective thermal conductivity (ETC) of snow with the microscopic interfacial contact area among the components using micro-structural parameters obtained from surface section images of snow samples. Unit cell model of Jackson and Black, based on stereological concept of contiguity, is expanded to include the effect of microstructure of snow, as well as, other parameters to predict the ETC of snow. The model is described by three dominant thermal conductance that account for the heat transfer across solid-solid, solid-liquid, and solid-air interface. The complex structure of snow is described using the primary microstructure parameters: coordination number, grain size, bond size, dendricity and sphericity. The ETC formulations developed, include the effect of these snow parameters besides the characteristics of the phases and temperature dependence of their conductivities. The model predictions agree closely with the measurements made using transient thermal probe method. The ETC values obtained from the present model are in close agreement with the observed values than the results of other existing models.

Keywords: Microstructure, Thermal conductivity, Snow, Heat transfer

 

 

Indian Journal of Pure & Applied Physics

Vol. 47, March 2009, pp. 212-219

 

 

Structural and dielectric behaviour of barium substituted lead zinc niobate
ceramics at low temperature

 

A K Himanshua,b*, D C Guptab, Alo Duttac, T P Sinhac & S K Bandyopadhayaya

aVariable Energy Cyclotron Centre, DAE, 1/AF Bidhannagar, Kolkata 700 064

bSchool of Physics, Jiwaji University, Gwalior, Madhya Pradesh 474 011

cDepartment of Physics, Bose Institute, 93/1, Acharya Prafulla Chandra Road, Kolkata 700 009

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

Received 14 November 2008; accepted 26 December 2008

The polycrystalline samples of (Pb1-xBax)(Zn1/3Nb2/3)O3 (PBZN) ceramics have been synthesized by the columbite precursor method. X-ray diffraction analysis of PBZN synthesized for x = 0.15, 0.25, 0.35 and 0.50 shows a cubic perovskite phase at room temperature. The changes in the structures are observed with increasing Ba contents in PBZN. The dielectric dispersion of the solid solutions has been studied as a function of temperature in the frequency range 100 Hz-1MHz. The temperature variation of the real components (e¢) at different frequencies of the dielectric permittivity shows a broad maximum. The diffuse peaks in e¢ versus T confirm the relaxor behaviour of PBZN. The changes in the relaxor properties of the compounds are found to be compositional dependent. The frequency dependence of Tm in these compounds with barium substitution is modeled using Vogel-Fulcher relation.

Keywords: Relaxor ferroelectric, Barium substituted lead zinc niobate, Vogel- Fulcher

 

 

Indian Journal of Pure & Applied Physics

Vol. 47, March 2009, pp. 220-227

 

 

Electric field dependent attenuation constant in BaxSr1-xTiO3 perovskites

 

Ashish Kukreti*, Ashok Kumar & U C Naithani

Department of Physics, Garhwal University, Pauri Campus, Pauri(Garhwal), Uttarakhand 246 001

*E-mail: ashishkukreti07@gmail.com

Received 5 March 2008; revised 25 November 2008; accepted 6 January 2009

A theoretical expression is derived for attenuation constant in para-electric phase in anharmonic BaxSr1-xTiO3 ferroelectric crystal, using double time temperature dependent Green’s function technique. Taking electric field as a parameter, the variation of attenuation constant with frequency and temperature has been studied by considering third and fourth order anharmonic interactions. The mass and force constant change due to the presence of impurity atoms in Silverman-Joseph Hamiltonian augmented with higher order anharmonic terms. The effect of electric field, defect and anharmonicity on stabilization of the soft mode frequency has also been studied. The attenuation constant increases with increasing temperature and frequency in the presence of an electric field. In the vicinity of the Curie temperature, the attenuation constant increases anomalously.

Keywords: Attenuation constant, Curie temperature, Anharmonicity, Electric dipole moment, Displacive ferroelectrics

 

 

 

 

Author Index



Keyword Index