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Polycrystalline nano BiFeO3 powders were synthesized by auto-combustion method using urea as fuel and metal nitrates (Fe(NO3)(3).9H(2)O, Bi(NO3)(3)-5H(2)O) as oxidizers. In order to optimize the single-phase synthesis condition of BiFeO3, different fuel to oxidizer ratios have been investigated. The preliminary structural investigation using X-ray diffraction shows the samples were of single phase and crystallize in rhombohedral structure (R3c). The ferroelectric and antiferromagnetic ordering temperatures of BiFeO3 were found to be 832 degrees C and 364 degrees C respectively, from differential thermal analysis. The temperature dependent dielectric study shows an anomaly around 215 degrees C which corresponds to magneto-electric coupling in the material. Field-emission scanning electron micrographs show effect of fuel to oxidizer ratio on grain size evolution. The ferroelectric hysteresis loops for all the samples were measured at a frequency of 100 Hz confirming the ferroelectric nature. An evidence of magneto-electric coupling was also observed at room temperature from magneto-capacitance measurements. (C) 2013 Elsevier B.V. All rights reserved.

This work presents a new approach towards resonant interaction between light and matter . An investigation of electromagnetic wave propagation in random media is presented .Numerical simulations of the extinction rate of electromagnetic radio wave propagation in the presence of large number of point scatterers distributed randomly is presented and is based on the multiple scattering theory. The results obtained shows, the attenuation rate increases as realizations increases but remains independent for large no of point scatterers in the cluster.

Magnetoelectric multiferroics have triggered the attention of scientific community because of their intriguing fundamental physics and novel multifunctional device applications. BiFeO3 has been established as a prototype multiferroic materials having perovskite structure. However, the potentials of this material are yet to be realized due to several difficulties in synthesis, characterization and attaining the desired value of magnetoelectric coupling. The physical properties and the phase transition of this material vary as a function of intensive parameters (i.e., temperature, frequency, pressure, electric field and magnetic field). In the present dissertation, we have fabricated nanoceramic solid solution of (1-x)BiFeO3-xRMnO3 (R: Y3+, Gd3+, Dy3+) and Bi1-xBaxFe1-xZrxO3 with an aim to demonstrate enhanced magnetoelectric multiferroic properties. These modifications have induced a compositional driven structural phase transition and morphotropic phase boundary in the solid solution. The field emission scanning electron micrographs shows polycrystalline nature of microstructure. Temperature dependent dielectric study of BiFeO3 shows anomaly near antiferromagnetic transition temperature, 364 °C suggesting the signature of mgnetoelectric coupling in the material. The antiferromagnetic ordering temperature decreases towards room temperature with increase in composition. Improved ferroelectric hysteresis loops at room temperature have been observed. The grain and grain boundary contributions from the overall electrical properties have been separated using complex impedance spectroscopic analysis. The temperature variation of the bulk and grain boundary electrical conductivity obeyed the Arrhenius behavior suggesting the thermally activated conduction mechanism. The magnetization versus magnetic field curve for YMnO3 modified BiFeO3 samples has exhibited a switching behavior at low fields. Enhanced magnetization properties have been observed in GdMnO3 and DyMnO3 modifie

We have studied in detail the structural and transport aspect of the series of manganites Eu1-xSrxMnO3. Starting with the parent composition in this family of compounds EuMnO3 which is rather an antiferromagnetic insulator, we have investigated how the electronic transport varies with higher concentration of Sr in these compounds vis-a-vis with structures. A series of samples have been prepared through solid state reaction route from the high purity constituent materials. The structural characterization is carried out by XRD with Retieveld analysis. Most of the samples in the series crystallises under orthorhombic structures with Pnma space group. With increasing concentration of Sr, the sample tends to more symmetric in nature. The SEM imaging renders the proper granular structures of the samples in the series. Moreover, a detail investigation is carried out for the transport features of the materials. The temperature dependence of resistivity shows unique features with varied concentrations of the Sr. With a lower concentrations favours the insulating state of the materials to that of semiconducting with increasing the content of Sr on the rare earth side of the parent manganite. The features are described in terms of the double exchange model with the support of structural parameters calculated for each material.

We have studied in detail the structural and transport aspect of the series of manganites Eu1-xSrxMnO3. Starting with the parent composition in this family of compounds EuMnO3 which is rather an antiferromagnetic insulator, we have investigated how the electronic transport varies with higher concentration of Sr in these compounds vis-a-vis with structures. A series of samples have been prepared through solid state reaction route from the high purity constituent materials. The structural characterization is carried out by XRD with Retieveld analysis. Most of the samples in the series crystallises under orthorhombic structures with Pnma space group. With increasing concentration of Sr, the sample tends to more symmetric in nature. The SEM imaging renders the proper granular structures of the samples in the series. Moreover, a detail investigation is carried out for the transport features of the materials. The temperature dependence of resistivity shows unique features with varied concentrations of the Sr. With a lower concentrations favours the insulating state of the materials to that of semiconducting with increasing the content of Sr on the rare earth side of the parent manganite. The features are described in terms of the double exchange model with the support of structural parameters calculated for each material.

Magnetoelectric multiferroics have triggered the attention of scientific community because of their intriguing fundamental physics and novel multifunctional device applications. BiFeO3 has been established as a prototype multiferroic materials having perovskite structure. However, the potentials of this material are yet to be realized due to several difficulties in synthesis, characterization and attaining the desired value of magnetoelectric coupling. The physical properties and the phase transition of this material vary as a function of intensive parameters (i.e., temperature, frequency, pressure, electric field and magnetic field). In the present dissertation, we have fabricated nanoceramic solid solution of (1-x)BiFeO3-xRMnO3 (R: Y3+, Gd3+, Dy3+) and Bi1-xBaxFe1-xZrxO3 with an aim to demonstrate enhanced magnetoelectric multiferroic properties. These modifications have induced a compositional driven structural phase transition and morphotropic phase boundary in the solid solution. The field emission scanning electron micrographs shows polycrystalline nature of microstructure. Temperature dependent dielectric study of BiFeO3 shows anomaly near antiferromagnetic transition temperature, 364 °C suggesting the signature of mgnetoelectric coupling in the material. The antiferromagnetic ordering temperature decreases towards room temperature with increase in composition. Improved ferroelectric hysteresis loops at room temperature have been observed. The grain and grain boundary contributions from the overall electrical properties have been separated using complex impedance spectroscopic analysis. The temperature variation of the bulk and grain boundary electrical conductivity obeyed the Arrhenius behavior suggesting the thermally activated conduction mechanism. The magnetization versus magnetic field curve for YMnO3 modified BiFeO3 samples has exhibited a switching behavior at low fields. Enhanced magnetization properties have been observed in GdMnO3 and DyMnO3 modifie

This work presents a new approach towards resonant interaction between light and matter . An investigation of electromagnetic wave propagation in random media is presented .Numerical simulations of the extinction rate of electromagnetic radio wave propagation in the presence of large number of point scatterers distributed randomly is presented and is based on the multiple scattering theory. The results obtained shows, the attenuation rate increases as realizations increases but remains independent for large no of point scatterers in the cluster.