Thesis/Project Reports

Study of Swift Heavy Ion Irradiation Induced effects in Nanostructured Zinc Ferrite” submitted Ph. D. Thesis under guidance of Dr. R.C. Srivastava (Assoc Prof. Department of Physics, G. B. Pant Univ. Ag. & Tech. Pantnagar, Uttarakhand)

Modification of material properties by swift heavy ion for their possible technological and industrial applications, and to understand the underlying phenomena is an active research topic. The dominant process responsible for the energy loss by the swift heavy ions in any medium is electronic stopping. This process produces point like defects/clusters of defects and the columnar defects depending upon the amount of energy lost by this process. Present work aims to investigate the effects of point/cluster defects induced by 100 MeV O7+ beam in nanosized zinc ferrite. Beside this we have also investigated the size dependent structural, magnetic and optical behaviour of the nanosized zinc ferrite. The crystallite size of the sample increases with the sintering temperature of the system. The specific area of the samples decreases almost linearly with the sintering temperature. TEM shows almost spherical shape of the nanoparticles and the particle size are in accordance of the XRD results. EPR and Mössbauer spectroscopy shows the presence of superparamagnetic domains in the samples, which were further confirmed by recording the hysteresis loop. It was also observed that sample having largest crystallite size shows the paramagnetic nature. The saturation magnetization at room temperature decreases from 26.1 to 11.4 emu/g as the crystallite size increases from 10 nm to 62 nm and has almost constant value of 46.2 emu/g at 10 K. The blocking temperature and irreversibility temperature decreases with the increase in crystallite size. The increase in value of magnetization is attributed to the cation inversion. Further, the irradiation of the zinc ferrite nanoparticles of different crystallite size was done by 100 MeV oxygen beam at two different fluence of 1×1013 and 5×1013 ions/cm2. The irradiated samples exhibit the presence of cubic spinel phase, however the attributes of ZnO phase was also found. All the specimens show the decrease in crystallite with the fluence of irradiation with the dominant decrease in the sample having sintering temperature of 1000oC. The variations of peak broadening with sintering temperature show deviation form phonon confinement. The EPR shape analyses indicate the presence of spin-lattice relaxation process present in both the pristine and irradiated specimen. The magnetization measurements performed at 10K and room temperature on these samples show the decrease in magnetization except the irradiated counterparts of sample sintered at 1000oC (10K). The decrease in the value of magnetization is attributed to the decrease in cation inversion and increase in canting angle as determined from in-field Mössbauer spectroscopy. Further, the decrease/increase in the blocking and irreversibility temperature with fluence shows the attributes of the size dependence of pristine samples.

“Study of Copper doped Calcium and Barium titanates Ceramics” thesis submitted to the G. B. Pant Univ. of Agriculture & Technology under guidance of Dr. U. C. Johri. The structure characterization and dielectric properties were studied for a series of copper-doped Calcium titanates CuxCa1-xTiO3 and copper doped Barium titanates prepared by the conventional solid sate reaction method. X-ray diffraction and EPR analyses indicate that all samples belong to the orthorhombic system. Cu addition results in non-linear variation of lattice parameters and density of sample. The EPR spectra confirms that the copper ions are in divalent state. The dielectric constant decreases for CuxCa1-xTiO3 and increases for CuxBa1-xTiO3 copper concentration.

“To make current sensor for the TF power supply of the BETA machine using Hall Effect” project report submitted to the Institute for Plasma Research, Gandhinagar under the guidance of Dr. Amit Circar.