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 School of Physics :Research




Materials Science

1. X-ray Spectroscopy {XANES & EXAFS}

[Dr. Ashutosh Mishra]

X-ray spectroscopic studies are of significant importance in understanding the crystal structure, environment of atoms, electronic structure, presence of defects and impurities. In recent years X-ray spectroscopy for chemical analysis (XSCA) has emerged as a powerful tool for the study of coordination compounds and can provide an unambiguous answer to the vexed question of Valence State. At present study, plans are on to prepare new quasi-crystals of Cu and Co metal with some other metal elements. These quasi-crystals need systematic study and plans are to look for different Al-Cu-Fe alloys in the powder form having chemical compositions close to Al65Cu23Fe12. As a next step, X-ray diffraction technique and scanning electron microscope (SEM) will characterize these materials. Resistivity and magnetic susceptibility measurements in collaboration with IUC-DAEF, Indore will also be made.

The main scope of the present work is the X-ray absorption spectroscopic investigations of the prepared quasi-crystals. This technique points to the accurate and reliable method for elucidating certain important features of the general electronic structure of solids. Both absorption and emission processes are involved in this method and we need to have RXAF facility. Measurements on Cu K-edge and Co K-edge shall be made to obtain chemical shift, edge width, and shift of principal absorption maximum for these quasi-crystals. The extended X-ray absorption fine structure (EXAFS) and X-ray absorption near edge structure (XANES) of these compounds will also be studied to explore the average bond length. Chemical shift and other X-ray absorption parameters, magnetic susceptibility, resistivity measurements etc. shall be used in knowing detailed structure of the samples. The data obtained from the various measurements shall be interpreted to yield useful information about the quasi-crystalline samples. Attempts will be made to correlate various results with earlier ones.

2. Correlated Electron systems

[Dr. Dinesh Varshney]

Metal oxides constitute the most amazing class of materials with a wide range of properties exhibit a variety of phenomena such as ferroelectricity, ferromagnetism, superconductivity, and so on. In the last few years, a new aspect of metal oxide has come to the fore. This has to do with colossal magneto resistance (CMR) exhibited by certain manganese oxides, in particular rare earth manganites of perovskite structure. Investigations of the transport phenomenon like, heat capacity, thermal conductivity, resistivity, etc., and anomalies associated with them are in progress. Further the role of Jahn Teller distortion and other charge transfer mechanism of the substituted manganites followed by preparation and characterization is to be explored.

The material C60 behaves as a semiconductor on reacting with donors like ‘Alkali metals’ form a new class of molecular solids with general formula A3C60 (A = K, Rb, Cs, Na, Li). An approach with nonadiabatic channels as vertex corrections in the self-energy, within the framework of strong coupling theory that consists of dynamical matrix of force constants for C60 molecules is being worked out. The developed effective interaction potential shall allow for a fair estimation of the physical properties of these materials.

Diluted magnetic semi conductors, also known as semimagnetic semiconductor, have attracted the attention of the scientific and industrial community. These materials have some unique properties that enhance their potential for use in a wise range of electronic, laser and magneto-optic devices. Efforts to study the thermodynamical properties and their pressure derivative, specific heat and high pressure induced phase transition from Zincblende (B3) to Rocksalt (B1) structures with the general formula, A1-x MnxX (A = Zn, Cd; X = Se, Te) for hole composition range are being made. The high pressure and anharmonic properties with and without incorporation of TBI and other effective potential term will guided to reconcile the DMS materials for technological excellence.

Superconductivity in cuprates is well known with layered structure possesses one or more CuO2 planes which are responsible for the conduction process. An effective two- dimensional dynamic interaction potential, which includes screening of holes as carriers by spin and charge density fluctuations, is being developed. It seems that the general problem of explaining the superconductivity lies actually in understanding the nature of layered interactions, with variable number of conducting layers, thickness of layers, doping concentration, metal-insulator transition and pairing symmetry, anomalies in physical properties. The challenge for theorists is to construct, solve, and interpret models that express these interplay and still waiting for adequate theoretical reasoning of the phenomena.

3. Structural and magnetic measurements of metallic glasses and nano crystalline materials [Dr. S. N. Kane]

The experimental and theoretical modeling of structural, magnetic, magnetoelastic, hysteresis and giant magneto-impedance properties of conventional metallic glass ribbons, wires, glass covered microwires, bulk metallic glasses and gradually devitrified nano-crystalline materials are of technological importance. These thrust areas are being investigated using experimental techniques such as Mössbauer spectroscopy, magnetic measurements, Curie temperature measurement, X-ray Diffraction, Differential Scanning Calorimetery, Atomic Force Microscopy etc..

4. Synthesis and characterization of nano particles and polymers
[Dr. M. Banerjee]

Nanoparticles and polymers constitute the frontline areas of contemporary research in Materials Science/Condensed Matter Physics. One of the major applications of nanomaterials is in the field of catalysts. Hence, some mixed ferrite nanoparticles were synthesized through low temperature Co-precipitation method that could produce nanoparticles of size ranging from  10-14 nm. These nanomaterials showed good catalytic activity in alkylation reaction used to produce some life saving drugs. The procedure can be used to produce bulk amounts of ferrite. It is planned to test this method to produce other systems and study their properties.

Polymers are macromolecules, which are lightweight and versatile material as can be visualized from their application. These are used to produce articles of everyday use on one side and highly sophisticated articles like, medical implants and light combat aircraft. Polymers and polymer blends can be insulator or conductor depending on their structure. Hence structure and conductivity relation of polymers is very important. Insulating polymers can be used for encapsulation and the conducting ones can be used as electrolytes for making light weight solid state batteries. Polymer blends have been studied for correlating their conductivity with charge in structure, to be used as encapsulation. Lithium doped polymeric blends of PEO and PEG showed good electrical conductivity. Its feasibility as electrolyte in solid state battery especially in pacemakers makes an interesting and challenging problem and will be investigated. These materials have been characterized using WAXD, DSC, SEM, Mossbauer etc. Further investigations include XASFS, Photoemission, TEM, and SAXS.

Nuclear Physics

1. Nuclear mass formula [Theory]

[Prof. A. K. Dutta]

A considerable effort continues to be devoted to the construction of nuclear mass formulas. Much of the motivation behind the search for improved parameters of the nuclear binding energy lies in the fact that the evolution of stellar nucleosynthesis, and in particular the r-process, depends critically on the binding energies of nuclei that lie so close to the neutron drip line that there is no possibility of being able to observe them in the laboratory. It is therefore of greatest importance to construct mass formulas that can make reliable extrapolations to regions close to the neutron drip line. A mass formula has been developed which is based on the macroscopic-microscopic model called the “Extended Thomas-Fermi-Strutinsky Integral (ETFSI)” method. Future plans are to make improvements in the already developed ETFSI mass formula so that reliable calculations of fission barriers are also possible. Interest will also lie in the exploration and possible existence of superheavy nuclei and the study of nuclei close to the proton-drip line.

Plasma Physics

1. Relativistic plasma microwave Electronics

[Prof. K. P. Maheshwari & Dr. Y. Choyal]

Active research in the department is pursued in the field of gyrotrons, and relativistic backward wave oscillators. At present the development of a IREB driven backward wave oscillator (BWO) to generate high power microwaves is in progress and a 20- stage Marx generator leading to a 400 kV, 100 ns voltage output pulse has already been constructed. This voltage pulse has been used to generate an intense relativistic electron beam needed for basic experiments on backward wave oscillator, vircators and to generate high power microwave pulse. In near future plans are to upgrade the BWO laboratory by adding a guide magnetic field of magnitude ~ 0.9 Tesla so as to facilitate the transport of intense relativistic electron beam and to develop a BWO to deliver a microwave power output of ~ 1 MW at 8.9 GHz. Investigation on the effect of background plasma in enhancing the efficiency of conversion directed e-beam energy in microwave output is in progress.

Laser Physics

1. Free electron lasers

[Dr. G. Mishra and Prof. A. K. Dutta]

A number of new novel concepts on insertion devices and free electron lasers over the past few years have been investigated by the group. The group activities have been focussed on theoretical studies of new concepts on undulators as insertion devices and a key component in free electron laser device. At present the activities include primarily in long wavelength free electron lasers. Success has been achieved in explaining the effects of non-relativistic correction and off-axis field effects on spectral characteristics of undulator radiation. The analysis predicts deep insight into the physics of free electron lasers where imperfect initial conditions brings out additional constraints on FEL performance and limits the gain. Additional schemes have been suggested to overcome these restrictions and to compensate for the gain reduction .The free electron laser in a waveguide operation has been another topic of our activity. Operating a free electron laser in a waveguide is particularly interesting and attracting for its two resonant frequencies and slippage control. The velocity mismatch between the electron and the radiation is referred to as slippage in free electron lasers and is a sensitive factor in reducing the gain in free electron lasers. The waveguide free electron laser removes this restriction and gain improves quite substantially.

Planned activities for the future include to high gain regime of the free electron laser. The high gain regime of FEL operation is particularly attractive for its exponential gain characteristics and wavelength scaling down upto the x-ray range. Two schemes are most promising in these directions. With a very bright electron beam in a long undulator, the single pass gain may be so high that the noise signal present in the beam is amplified to intense coherent radiation. This is called the self-amplified-spontaneous emission (SASE) scheme. Another scheme applicable for generating very short wavelength radiation is based on the harmonic generation mechanism in a high gain FEL starting from available coherent input radiation. The scheme called the high-gain-high-harmonic generation (HGHG) is the basis of the recent free electron laser activities. These schemes are quite promising, as they have been experimentally demonstrated at selected International laboratories. Nevertheless many important issues such as effect of wakefields, imperfect beam trajectories and off-axis and angular off-set have to be incorporated into high gain FEL scheme in order to extract meaningful understanding of the free electron laser operating in the high gain regime. The aim of the group is to strengthen the activities on these issues with both analytical skills and with the aid of simulation codes such as GENESIS and GINGER, RADIA.

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