Indian Journal of Pure and Applied Physics

Total visitors: 2,201  since 31-01-07

[This special issue is based on the papers presented at the National Conference on Condensed Matter and Materials Physics (CMMP 06) held at Department of Physics, The Maharaja Sayajirao University of Baroda, Vadodara 390 002 during January 19-21, 2006]

 

Volume 45                                             Number 1                                           JANUARY 2007

CODEN : IJOPAU 45 (1) 1-104                                                                    ISSN : 0019-5596

 

 

CONTENTS

Foreword

5

S K Sikka

 

Preface

6

Prafulla K Jha

 

Papers

 

Silver-zinc oxide electrical contact materials by mechanochemical synthesis route

9

P B Joshi, V J Rao, B R Rehani & Arun Pratap*

 


Size dependent magnetic behaviour of nanocrystalline spinel ferrite Mg0.95Mn0.05Fe2O4

16

S K Sharma*, Ravi Kumar, V V Siva Kumar, S N Dolia, A Gupta, V R Reddy,
M Knobel & M Singh

 


Structural and magnetic properties of Co nanoparticles in Cu/SiO2 matrix

21

P Anil Kumar*, Subarna Mitra & Kalyan Mandal

 


Role of scattering processes in lattice thermal conductivity of Ge

27

M Ataullah Ansari, Nitin P Singh & B D Indu*

 


Multiferroic behaviour of Ti doped Mg0.95Mn0.05Fe2O4

31

Shalendra Kumar*, Ravi Kumar, A Dogra, V R Reddy, A  Banerjee  & Alimuddin

 


Transport, magnetic and thermal properties of La0.88Ca0.12MnO3 single crystal

37

Ashish Bodhaye, Sankar P Sanyal*, G S Okram & Y M Mukovskii

 


Electrical properties of chloroaluminium phthalocyanine thin film sandwich devices

40

M E-Azimaraghi

 


Ion transport study of mechanically-milled amorphous AgI-Ag2O-V2O5 fast ionic conductors

44

Parveen Kumar*, J P Tiwari & K Shahi

 

 


Dielectric study of Cu2+ doped calcium tartrate tetrahydrate crystals

48

S R Suthar, S J Joshi, B B Parekh* & M J Joshi*

 

 


dc Conductivity and dielectric properties of V2O5-Bi2O3-ZnO glass

52

D K Shukla & S Mollah*

 


Ion beam modification and analysis of polymer composites

57

Anjum Qureshi*, N L Singh, Keyur Somani, A K Rakshit, F Singh & D K Avasthi

 

 


Binary composition spread approach for parallel pulsed laser deposition synthesis and
highthroughput characterization of transparent and semiconducting oxide thin films

62

Utpal S Joshi* & Hideomi Koinuma

 

 


Reflectance and magneto-optical Kerr rotation in DyP

66

Sapan Mohan Saini*, Nirpendra Singh, T Nautiyal & S Auluck

 

 


Optical properties of CeSb and LaSb

69

Nirpendra Singh*, Sapan Mohan Saini, Tashi Nautiyal & S Auluck

 

 


Phonons in non-oxide perovskite superconductor MgCNi3

72

M M Sinha

 

 


Ab-initio calculation and B1 to B2 structural phase transformation in CdO at high pressure

75

Vipul Srivastava, Sankar P Sanyal* & M Rajagopalan

 


Phonon dispersion curves of TiN

79

P K Ojha*, Syamendra Pratap Singh & K S Upadhyaya

 


Theoretical study of molecular ordering in p-n-hexyloxybenzylidene-p-toluidine: A nematic liquid crystal

83

S N Tiwari*, M Mishra & R Shukla

 

 


Variation of electrical resistivity with temperature of liquid ternary alloys of Na-K-Rb

89

P N Gajjar, S R Mishra & A R Jani*

 

 


High-pressure P-V relation and Grüneisen parameter for elemental strontium

93

P R Vyas*, V B Gohel, N K Bhatt & A R Jani

 

 


Phonon interaction and deformation potential variation with temperature and concentration in diluted Ga(1-x)MnxN quantum well

96

Ankur Pandya & Prafulla K Jha*

 

 


 

___________

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


Indian Journal of Pure & Applied Physics

Vol. 45, January 2007, pp. 9-15

 

 

Silver-zinc oxide electrical contact materials by mechanochemical synthesis route

P B Joshi1, V J Rao1, B R Rehani1 & Arun Pratap2

1Department of Metallurgical Engineering, M S University of Baroda, Vadodara 390 001

2Department of Applied Physics, M S University of Baroda, Vadodara 390 001

2E-mail: apratapmsu@yahoo.com

Received 1 March 2006; revised 27 October 2006; accepted 1 November 2006

Mechanochemical synthesis or reactive milling (RM) is a well-established high-energy milling process for production of a wide range of nanocomposite powders using oxides, carbonates, sulphates or hydroxides as the starting precursors. It ensures chemical reactions such as oxidation/reduction, decomposition or phase transformation in solid-state conditions during room temperature milling, which otherwise require high temperatures. The silver-zinc oxide nanocomposite powders by reactive milling of silver oxide and zinc powder particles have been produced. The resultant Ag-ZnO nanocomposite powders are further processed to bulk solid pieces by conventional powder metallurgy route as electrical contact materials for switchgear applications.

Keywords: Mechanochemical synthesis, Reactive milling, Nanocomposite powders, Silver-zinc oxide composites

IPC Code: H01F41/30

 

Indian Journal of Pure & Applied Physics

Vol. 45, January 2007, pp. 16-20

 

 

Size dependent magnetic behaviour of nanocrystalline spinel ferrite Mg0.95Mn0.05Fe2O4

S K Sharma1,*, Ravi Kumar2, V V Siva Kumar2, S N Dolia3,

A Gupta4, V R Reddy4, M Knobel5 & M Singh1

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

2Inter-University Accelerator Center, New Delhi, 110 067

3Department of Physics, University of Rajasthan, Jaipur 302 004

4IUC-DAEF, Khandwa Road, University campus Indore 452 017

5Instituto de Fisica, Gleb Wataghin, Universidade Estadual de Campinas (UNICAMP) Campinas, 13.083-970, SP, Brazil

Received 1 March 2006; accepted 26 October 2006

Mg0.95Mn0.05Fe2O4 ferrite nanoparticles having dimensions varying from 4.7-12 nm, have been synthesized by using solid-state reaction technique followed by high-energy ball milling for different times. An X-ray diffraction study indicates the presence of single-phase cubic spinel structure. The particle sizes were estimated from the X-ray line broadening of the (311) reflection using Debye-Scherrer’s formula. The size-dependent magnetic properties of Mg0.95Mn0.05Fe2O4 nanoparticles were studied using SQUID magnetometry techniques. The saturation magnetization Ms at 5 K obtained by extrapolating M versus 1/H plot to 1/H = 0 were decreased with the decrease in the particle size. The coercive force of the nanoparticles has a clear size-dependence below the blocking temperature. The calculated anisotropy constant was found to be rather large for nanoparticle samples. All these results can be explained on the basis of single-domain superparamagnetic effects.

Keywords: Mg0.95Mn0.05Fe2O4, Ferrite nanoparticles, Spinel structure, Debye-Sherrer’s formula

IPC Code: H01F 41/30

 

Indian Journal of Pure & Applied Physics

Vol. 45, January 2007, pp. 21-26

 

Structural and magnetic properties of Co nanoparticles in Cu/SiO2 matrix

P Anil Kumar*, Subarna Mitra & Kalyan Mandal

Magnetism Laboratory, S N Bose National Centre for Basic Sciences, Salt Lake, Kolkata 700 098

Received 1 March 2006; revised 6 September 2006; accepted 7 October 2006

The magnetic properties of Co nanoparticles embedded in SiO2 and Cu matrices separately, have been presented in the paper. The size of the cobalt nanoparticles is varied between 15-35 nm. Co forms a usual hcp structure in SiO2 matrix whereas it forms fcc structure when embedded in Cu matrix. This fact is also supported by the higher coercivity of Co nanoparticles in SiO2 matrix. A large coercivity value (~ 855 Oe) for Co nanoparticles embedded in SiO2 matrix and considerably high value (~ 465 Oe) for Co nanoparticles embedded in Cu matrix have been reported. The Law of Approach to Saturation is used in the case of Co-Cu composite to calculate the magnetocrystalline anisotropy constant and saturation magnetization.

Keywords: Co nanoparticles, Cu/SiO2 matrix, Magnetic properties, Magnetocrystalline anisotropy constant

IPC Code: H01F41/30

 

Indian Journal of Pure & Applied Physics

Vol. 45, January 2007, pp. 27-30

 

Role of scattering processes in lattice thermal conductivity of Ge

 

M Ataullah Ansari, Nitin P Singh & B D Indu*

Physics Department, Gurukul Kangri Vishvavidyalaya, Haridwar 249 404

 *Physics Department, Indian Institute of Technology, Roorkee 247 667

Received 1 March 2006; revised 25 July 2006; accepted 16 October 2006

The various objections raised against Callaway’s classic paper on the model of phonon heat conductivity such as (i) unresolved problem of additivity of inverse relaxation times (inadequate use of Mathiessen’s rule), (ii) absence of dispersion relation and (iii) lack of sufficient information pertaining to phonon modes (phonon velocities), have been amicably removed in this paper. The problem is solved by the use of phonon frequency spectrum and phonon group velocity formulation via the method of double time thermodynamic Green’s functions developed via an almost realistic Hamiltonian (second quantized) containing the effects of impurities, anharmonicities and their interactions. The lattice thermal conductivity of two samples of germanium has been analyzed on the basis of this modified model and a fairly good agreement between theory and experimental observations has been reported. The involvement of different scattering events has been discussed via a new approach, which is capable to explore the various temperature regimes of their effectiveness. The role of interference mode is an additive feature of this work.

Keywords: Lattice thermal conductivity, Phonons, Dispersion relation

IPC Code: G01N25/18

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 45, January 2007, pp. 31-36

Multiferroic behaviour of Ti doped Mg0.95Mn0.05Fe2O4

Shalendra Kumar1, Ravi Kumar2, A Dogra2, V R Reddy3, A Banerjee3 & Alimuddin1

1Department of Applied Physics, Aligarh Muslim University, Aligarh 202 002

2Inter-University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110 067

3IUC-DAE-CSR, Khandwa Road, University Campus, Indore 452 017

1E-mail: shailuphy@gmail.com

Received 1 March 2006; revised 18 September 2006; accepted 9 October 2006

Multiferroic behaviour of Ti doped Mg0.95Mn0.05Fe2O4 has been studied using X-ray diffraction, isothermal magnetization hysteresis, dc magnetization and dielectric measurements. X-ray diffraction analysis shows a structural transformation from cubic spinel to tetragonal. On the other hand, the presence of paramagnetic doublet within the sextet shows the presence of electric field gradient (EFG) due the structural transformation. Isothermal hysteresis loop shows ferromagnetic behaviour of Mg0.95Mn0.05Fe2-2xTi2xO4 and decrease in saturation magnetization with increase in the substitution of the Ti+4. The decrease in the saturation magnetization is due to the dilution of the sublattice by the non-magnetic Ti+4 ions and which is explained by the weakening of exchange interaction in the system. The dc magnetization shows that the Curie temperature is decreasing with increasing in the substitution of non-magnetic ions. The presence of the peak in the dielectric constant measured as a function of temperature at 100 kHz indicates the presence of ferroelectric transition in the materials.

Keywords:   Multiferroic behaviour, Mg0.95Mn0.05Fe2O4, X-ray diffraction, Isothermal magnetization hysteresis, dc Magnetization

IPC Code: H01G 7/06

 

Indian Journal of Pure & Applied Physcs

Vol. 45, January 2007, pp. 37-39

 

Transport, magnetic and thermal properties of La0.88Ca0.12MnO3 single crystal

Ashish Bodhaye1, Sankar P Sanyal1,*, G S Okram2 & Y M Mukovskii3

1Department of Physics, Barkatullah University, Bhopal 462 026

2 UGC-DAE-Consortiums for Scientific Research, Indore 452 017

3Moscow State Steel and Alloys Institute, Moscow 117936, Russia

Received  1 March 2006; revised 2 August 2006; accepted 9 October 2006

The transport, magnetic and thermal properties of La0.88Ca0.12MnO3 single crystals have been studied using various experimental techniques. The resistivity measurement shows the characteristics of semiconducting behaviour having the resistivity 6.9 MWcm at 90K and 31.5 Wcm at 296K. There is no resistivity peak or electronic transition over the whole temperature range studied. However, there is a notable change of resistivity at about 115 K, seemingly related to paramagnetic insulator to ferromagnetic insulator transition. The ac susceptibility measurement confirms that this material shows paramagnetic insulator to ferromagnetic insulator transition with Tc = 117.5 K. The sharp peak around the same temperature in the heat capacity measurement indicates the onset of long range ordering.

Keywords: CMR, La0.88Ca0.12MnO3, Metal-insulator transition

IPC Code: G 01 R 27/14, 33/16

 

 

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 45, January 2007, pp. 40-43

 

Electrical properties of chloroaluminium phthalocyanine thin film sandwich devices

M E- Azimaraghi

Advanced Materials and Photonics Group, Applied Physics Division, Physics Department,

Teacher Training University, 49 Shahid Mofateh Avenue, Tehran, Iran

Received 1 March 2006; revised 18 September 2006; accepted 18 October 2006

Spectroscopic measurements in the range 10 kHz - 6 MHz at different temperatures are reported for Au/ClAlPc/Au thin film sandwich devices. The ac conductivity was found to vary with the angular frequency ω. In the high frequency region, the ac conductivity is proportional to ωn. The capacitance and loss tangent decrease with increasing frequency and the capacitance increases with increasing temperature. The results show that the relative importance of the hopping model and band theory in describing the film conduction with regard to the operating conditions. The band theory is dominant at high temperatures and low frequencies, whereas hopping model is dominant at high frequencies and low temperatures.

Keywords: Electrical properties, Chloroaluminium phthalocyanine,Thin film, Sandwich devices

IPC Code: G01R

 

Indian Journal of Pure & Applied Physics

Vol. 45, January 2007, pp. 44-47

Ion transport study of mechanically-milled amorphous AgI-Ag2O-V2O5
fast ionic conductors

Parveen Kumar J P Tiwari & K Shahi٭

Solid State Ionics Laboratory, Advanced Center for Materials Science, Indian Institute of Technology Kanpur, India 208 016

٭Department of Physics Indian Institute of Technology Kanpur 208016

E-mail: parveen.kumar.2006@alumni.iitk.ac.in

Received 1 March 2006; revised 21 September 2006; accepted 9 October 2006

The structural and electrical characterizations of mechanically-milled (MM) amorphous fast ionic conductors (a-FICs), viz. xAgI (100-x)[0.67 Ag2O-0.33V2O5] ( x = 40, 50, 55 and 70 ) have been reported. The amorphisation is restricted only to the compositions which are well within the glass forming region and all samples are found to be highly agglomerated and X-ray amorphous in nature. The frequency dependent ac conductivity , , of the amorphous samples investigated in the frequency range 5Hz -13 MHz and temperature range 100- 350 K shows a dc conductivity regime at low frequencies and a dispersive regime at higher frequencies. The  spectra can be described by the Jonscher power law (JPL),  However, the values σdc(T) and A(T) both show two distinct Arrhenius regions and n ( < 1 ) is found to be temperature dependent, i.e., decreasing with increasing temperature.

Keywords: Mechanically-milled, Jonscher power law, Fast ionic conductors

IPC Code: G01R

 

Indian Journal of Pure & Applied Physics

Vol. 45, January 2007, pp. 48-51

 

Dielectric study of Cu2+ doped calcium tartrate tetrahydrate crystals

S R Suthar, S J Joshi, B B Parekh* & M J Joshi#

Crystal Growth Laboratory, Physics Department, Saurashtra University, Rajkot, 360 005

*Presently, Institute of Diploma Studies, Nirma University of Science and Technology, Ahmedabad 382 481

# E-mail : mshilp24@rediffmail.com

Received 1 March 2006; accepted 12 September 2006

Calcium tartrate crystals are well-known for their ferroelectric properties. In the present study, copper doped calcium tartrate tertrahydrate crystals were grown by the single diffusion gel growth technique. The amount of copper doping was confirmed by Induced Condensed Plasma (ICP). The single phase nature was identified by powder XRD. The dielectric measurements were made on pelletized samples in the temperature range 40-160°C and the frequency range 1- 500 kHz. The dielectric constant was determined from the value of capacitance. The copper doping showed significant influence on the value of dielectric constant and the transition temperature.

Keywords: Gel growth, Doping, Single crystal, Calcium tartrate, Dielectric study, Induced condensed plasma

IPC Code: G01R 27/26

 

Indian Journal of Pure & Applied Physics

Vol. 45, January 2007, pp. 52-56

 

 

dc Conductivity and dielectric properties of V2O5-Bi2O3-ZnO glass

D K Shukla & S Mollah*

Department of Physics, Aligarh Muslim University, Aligarh 202 002

*E-mail: smollah@rediffmail.com

Received 1 March 2006; accepted 26 October 2006

Semiconducting oxide glass with composition 40V2O5-40Bi2O3-20ZnO is prepared by rapid quenching method. The glassy phase is confirmed from X-ray diffraction (XRD) pattern which shows a broad hump around 2q = 30o. The dc conductivity of the glass has been measured in the temperature range 300 – 600 K and compared with that of other vanadium and copper based zinc oxide containing glasses. The dc conductivity is due to non-adiabatic small polaron hopping conduction which is confirmed from the fitting of the conductivity data with different polaronic hopping models. The frequency (75 kHz - 30 MHz) dependent dielectric constant of the glass decreases first and then increases with the increase of frequency at room temperature. The anomaly in frequency dependent dielectric constant at ~ 5 MHz may be due to the displacement and/or orientational motion of BiO3 and BiO6 structural units present in the glass.

Keywords: Glass, dc Conductivity, Polaronic hopping models, Dielectric properties, V2O5-Bi2O3-ZnO, Semiconducting
                     oxide glass

IPC Code:  G01R

 

 

Indian Journal of Pure & Applied Physics

Vol. 45, January 2007, pp. 57-61

 

Ion beam modification and analysis of polymer composites

Anjum Qureshi1, N L Singh1*, Keyur Somani2, A K Rakshit2, F Singh3 & D K Avasthi3

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

2Chemistry Department, M S University of Baroda, Vadodara 390 002

3 Nuclear Science Centre, Aruna Asaf Ali Marg, New Delhi110 067

Received 1 March 2006; accepted 6 October 2006

Thin films of ferric oxalate dispersed in polyvinyl chloride (PVC) were synthesized. Ferric oxalate was dispersed in PVC films at various concentrations. These films were irradiated with 80MeV O6+ ions at a fluence of 1´ 1011 ions/cm2.The radiation induced changes in dielectric properties, microhardness and surface roughness have been studied in the paper. It is observed that hardness and dielectric properties of the film increase with the concentration of dispersed ferric oxalate and also with the fluence. This suggests that ion beam irradiation promotes the metal to polymer adhesion, and converts the polymeric structure into hydrogen depleted carbon network, which make polymer harder and more conductive. Atomic force microscopy shows that the average roughness of the irradiated films is lower than that of un-irradiated films.

Keywords: Ion beam modification, Polymer composites, Polyvinyl chloride, Dielectric properties, Microhardness, AFM

IPC code: G01R 27/26

 

 

Indian Journal of Pure & Applied Physics

Vol. 45, January 2007, pp. 62-65

 

Binary composition spread approach for parallel pulsed laser deposition
synthesis and highthroughput characterization of transparent
and semiconducting oxide thin films

Utpal S Joshi1 & Hideomi Koinuma2,3

1Department of Physics, School of Sciences, Gujarat University, Ahmedabad 380 009, India

2Institute of Solid State Physics, University of Tokyo, Kashiwanoha, Chiba 277-8581, Japan

3National Institute of Materials Sciences, 1-1, Namiki, Tsukuba, Ibaragi 305-0044, Japan

1E-mail: usjoshi@sgu.ernet.in

Received 1 March 2006; accepted 9 October 2006

Conventional ‘one by one’ synthesis approach has been a major rate limiting step in the systematic exploration of increasingly complex materials for the demanding new technologies. Derived from the new concepts of combinatorial chemistry, recently introduced continuous binary composition spread technique based on the non-uniformity of the deposition rate typically observed in pulsed laser deposition (PLD) is applied to the parallel growth of transparent and semiconducting oxides LixNi1-xO. A large variation of x in LixNi1-xO was achieved on a single MgO(100) substrate. Details of the synthesis technique are discussed. Microstructural, transport and optical studies were done to optimize the Li concentration in the film. XRD and AFM confirmed an epitaxial growth and smooth surface for all the Li contents. SIMS data revealed a non-linear Li variation along the film with a minimum of 0.01% of Li content. High conductivity of 1.42 ohm-1 cm-1 was obtained in sufficiently high Li concentration regions. Optical transparency beyond 80% was obtained in the 40 nm thick films. The combinatorial binary composition spread technique results in significant time and energy savings for rapidly optimizing the thin film growth parameters to explore new TCOs for future optoelectronic applications.

Keywords: Pulsed laser deposition, Semiconducting oxide thin films, Thin films

IPC Code: H01L21/00

Indian Journal of Pure & Applied Physics

Vol. 45, January 2007, pp. 66-68

 

Reflectance and magneto-optical Kerr rotation in DyP

Sapan Mohan Saini*, Nirpendra Singh, T Nautiyal & S Auluck

Department of Physics, Indian Institute of Technology Roorkee, Roorkee 247 667, Uttranchal

Received 1 March 2006; accepted 18 September 2006

The rare-earth compounds are distinguished by their unique magnetic, electric and optical properties. These are strongly correlated materials. Their highly localized 4f electrons are responsible for their large magnetic moment. Optical properties of a material can be utilized in different applications such as reflectors, filters, and X-ray masks. On the other hand, magneto-optical properties of materials are used in storage devices. The calculations of optical properties of rare-earth compound DyP using the full potential linear augmented plane wave (FPLAPW) method with inclusion of spin orbit coupling have been reported. The Coulomb-corrected local spin density approximation, i.e. LSDA+U, which is known to treat the highly correlated 4f electrons properly have been employed. The calculated optical properties are in good agreement with the measured value. The magneto-optical Kerr rotation has been reported and the values expected for DyP in the low energy range have been predicted.

Keywords: Rare earth compound, Optical properties, Reflectivity

IPC Code:  C30B

 

Indian Journal of Pure & Applied Physics

Vol. 45, January 2007, pp. 69-71

 

 

Optical properties of CeSb and LaSb

Nirpendra Singh*, Sapan Mohan Saini, Tashi Nautiyal & S Auluck

Department of Physics, Indian Institute of Technology Roorkee, Roorkee 247 667

Received 1 March 2006; revised 25 August 2006; accepted 16 October 2006

The calculations of the electronic and the optical properties of CeSb and LaSb, using the full potential augmented plane wave (FP-LAPW) method including spin orbit coupling within local spin density (LSDA) approximation as implemented in WIEN2K code have been performed. The reflectivity and the real part of the optical conductivity of CeSb and LaSb have been calculated. The real part of the optical conductivity of these compounds is deduced from Kramers-Kronig transformation. The calculated spectra of the real part of the optical conductivity and reflectivity of LaSb and CeSb are in the agreement with the available experimental data. Our calculations give the value of specific heat constant of CeSb and LaSb 23.4 mJmol-1K-2 and 0.37 mJmol-1K-2, respectively, which are very close to experimental value.

Keywords: Rare earth compound, Optical properties, Reflectivity

IPC Code: B05D 5/06

 

Indian Journal of Pure & Applied Physics

Vol. 45, January 2007, pp. 72-74

 

Phonons in non-oxide perovskite superconductor MgCNi3

M M Sinha

Department of Physics, Sant Longowal Institute of Engineering and Technology, Longowal, Distt. Sangrur (Punjab) 148 106

E-mail: mm_sinha@rediffmail.com

Received 1 March 2006; revised 25 July 2006; accepted 23 October 2006

The new intermetallic non-oxide perovskite superconductor MgCNi3 was discovered by He et al, Nature, 411(2001) 54, following on from the breakthrough of the finding of the MgB2 superconductor at the beginning of 2001. MgB2 has subsequently been intensively studied; however, less attention has been paid to MgCNi3 due to its much lower superconducting transition temperature (Tc ~8 K), as compared to that of MgB2 (Tc ~39 K). But it has many interesting properties, which need to be focused on to obtain an understanding of its complicated physics. Being a perovskite superconductor like Ba1-xKxBiO3 and cuprate superconductors, MgCNi3 is special it is neither an oxide nor does it contains any copper. Meanwhile, MgCNi3 can be regarded as fcc Ni with only one quarter of Ni replaced by Mg and with C sitting on the octahedral sites. The fact that superconductivity rather than ferromagnetism occurs in a compound where so much nickel is present is surprising and suggest that MgCNi3 is a candidate for exhibiting unconventional superconductivity. In this work, a de Launey angular force constant model has been used to study the phonons in MgCNi3. The phonon dispersion curves in the symmetric directions are plotted and compared with available results.

Keywords: Lattice dynamics, Phonon spectra, Zone center phonons, Intermetalic compound

IPC Code: H01L 39/00

 

 

Indian Journal of Pure & Applied Physics

Vol. 45, January 2007, pp. 75-78

Ab-initio calculation and B1 to B2 structural phase transformation
in CdO at high pressure

Vipul Srivastava, Sankar P Sanyal & M Rajagopalan*

Department of Physics, Barkatullah University, Bhopal 462 026

*Department of Physics, Anna University, Chennai 600 025

Received 1 March 2006 ;accepted 9 October 2006

The electronic and structural properties of CdO at high pressure have been studied by using the self-consistent tight binding linear muffin tin orbital method. The relative stabilities of CdO at high pressure in the rock salt and CsCl structures have been examined. The rock-salt structure is found to be the ground state structure of CdO. The phase transition from NaCl (B1)- to CsCl (B2)-type structure for CdO is found to occur at 81.7 GPa, which is close to experimental value 90.6 GPa. Calculated lattice parameter and bulk modulus in both the phases are in good agreement with experimental results. The calculated band structure shows a small overlap between the conduction and valence bands with a direct band-gap of ~1.37 eV. A broadening of the upper Cd-4d and O-2p bands with some intermixing between them is observed in total DOS histogram of CdO.

Keywords: Ab-initio calculation, Structural phase transformation, CdO, High pressure, Band structure

IPC Code: H01L, B30B

 

Indian Journal of Pure & Applied Physics

Vol. 45, January 2007, pp. 79-82

 

Phonon dispersion curves of TiN

 

P K Ojha*, Syamendra Pratap Singh** & K S Upadhyaya+

Physics Department, K N Govt P G College, Gyanpur, S R N Bhadohi, U P

*Physics Department, Maa Khandwari Devi Degree College, Chahania, Chandauli, U P

**Physics Department, M M Town Inter College, Ballia, U P

Received 1 March 2006; revised 14 September 2006; accepted 4 October 2006

A lattice dynamical model which includes the effect of three-body interactions (TBI) in the framework of second neighbour rigid shell model (SNTRSM) and second neighbour rigid ion model (SNTRIM) has been developed. The models, thus obtained, have been applied to study the phonon dispersion curves (PDCs) of TiN along the principal symmetry directions. It is found that SNTRSM explains well the phonon anomalies in the experimental PDCs of TiN as compared to SNTRIM and other models.

Keywords: Phonon dispersion, TiN, Rigid shell model, Rigid ion model

IPC Code: H01L39/00

 

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 45, January 2007, pp. 83-88

 

Theoretical study of molecular ordering in p-n-hexyloxybenzylidene-p-toluidine: A nematic liquid crystal

S N Tiwari, M Mishra & R Shukla

Department of Physics, DDU Gorakhpur University, Gorakhpur 273 009

E-mail: sntiwari123@rediffmail.com

Received 1 March 2006; revised 21 August 2006; accepted 9 October 2006

Anisotropy in the pair potential primarily governs the mesomorphic behaviour of the liquid crystalline molecules. The intermolecular interactions between a pair of HBT molecules have been evaluated using modified second order perturbation treatment along with multicentred-multipole expansion technique. An all valence electron method, CNDO/2, has been employed to compute the net atomic charge and corresponding dipole moments located at each atomic centre of the liquid crystal molecule. Using the results of stacking and in-plane interaction energy studies, probability calculations at varied angular and positional configurations in a molecular pair of HBT, have been carried out using Maxwell-Boltzmann formula. An attempt has been made to elucidate the nematogenic behaviour of p-n-hexyloxybenzylidene-p-toluidine (HBT) molecules.

Keywords: Nematic, Perturbation, Mesogen, CNDO, Multicentred-multipole, Liquid crystal, Molecular ordering,
                      Anisotropy

IPC Code:  C09K 19/10

 

 

Indian Journal of Pure & Applied Physics

Vol. 45, January 2007, pp. 89-92

 

Variation of electrical resistivity with temperature of liquid ternary alloys
of Na-K-Rb

P  N  Gajjar, S  R  Mishra* & A  R  Jani*

Department of Physics, University School of Sciences, Gujarat University, Ahmedabad 380 009

*Department of Physics, Sardar Patel University, Vallabh Vidyanagar 388 120

Received 1 March 2006; revised 11 September 2006: accepted 16 October 2006

A model potential and Ziman formulation is employed to study the temperature sensitiveness of electrical resistivity of liquid ternary alloys of Na-K-Rb. The calculated structure factors and form factors are employed for the numerical investigation of electrical resistivity for temperatures in the range 100-500°C. The binary combinations Na-K, Na-Rb show the Nordheim parabola for increasing temperatures, but there is an exception to K-Rb alloy system. The good agreement for electrical resistivity for pure liquid metals and their binary combination is achieved.  The results of electrical resistivity for the ternary combination Na-K-Rb rise with temperatures.

Keywords: Pseudopotential, Electrical resistivity, Alloys, Liquid ternary alloys

IPC Code: G01L

 

 

 

 

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 45, January 2007, pp. 93-95

 

 

High-pressure P-V relation and Grüneisen parameter for elemental strontium

P R Vyas, V B Gohel, N K Bhatt* & A R Jani

Department of Physics, Gujarat University, Ahmedabad 380 009, Gujarat

*D J Shah Parivar Science College, Dholka 387 810, Gujarat

*E-mail: bhattnisarg@hotmail.com

Department of Physics, Sardar Patel University, Vallabh Vidyanagar, 388 120, Gujarat

Received 1 March 2006; revised 4 September 2006; accepted 30 October 2006

The functional relationship among the thermodynamical variables for a system in equilibrium, equation of state (EOS), provides an insight to the dependence of the microscopic internal structure of the material. In this regard, we have calculated static and dynamic P-V curve for divalent fcc-Sr. Vibrational contribution to the Helmholtz free energy is evaluated within recently proposed mean-field potential (MFP) approximation with the local pseudopotential. Temperature dependence of thermodynamic Grüneisen parameter (gth), a quantity that enters the Mie-Grüneisen form of EOS, is also obtained. Results so obtained are in good agreement with the experimental and other theoretical estimates. Use of present coupling scheme (i.e. MFP + pseudopotential) is thus justified; which has an added benefit of computational simplicity.

Keywords: Equations of states, Grüneisen parameter, Mean-field potential, Strontium

IPC Code: G01L

Indian Journal of Pure & Applied Physics

Vol. 45, January 2007, pp. 96-99

 

Phonon interaction and variation of deformation potential with temperature and concentration in diluted Ga(1-x)MnxN quantum well

Ankur Pandya & Prafulla K Jha

Computational Condensed Matter Physics Laboratory, Department of Physics, Faculty of Science
The M S University of Baroda, Vadodara 390 002

Received 1March 2006; accepted 19 September 2006

The carrier transport properties for two dimensional diluted Ga(1-x)MnxN have been calculated via electron acoustical phonon interaction on the basis of deformation potential coupling mechanism for the different concentrations of Mn
(x £10%) at different temperatures. The acoustic phonon scattering rate increases with the energy and decreases with the manganese concentration. The contribution of acoustic phonons in the variation of resistivity for different manganese concentrations and threshold thermal energy have also been determined. The temperature and concentration both affect the acoustic phonon scattering rate. Therefore, the resistivity varies due to the effect of these on the acoustical deformation potential (ADP).

Keywords: Phonons interaction, Diluted magnetic semiconductor

IPC Code: G10K11/00