Investigations on synthesis characterization and properties measurements of nano and bulk manganites and new Oxypnictide superconductors

Abstract

Oxides comprise a wide class of materials exhibiting rich crystal structures newlineand physical properties that make them ideal candidates for a plethora of applications. newlineThere has been a recent resurgence of interest in oxides in general and complex newlineoxides in particular due to their piezoelectric, ferroelectric, ferromagnetic, newlineferrimagnetic, multiferroic and superconducting properties as well as, in many cases, newlinelarge dielectric constants (imperative for scaled Si metal-oxide-semiconductor field newlineeffect transistors [MOSFET]). Among all these many oxide materials, manganites and newlinenew oxypnictide superconductors are important not only from application point of newlineview but also due to the rich physics behind their unusual properties. This thesis deals newlinewith synthesis, characterization of these two particular types of oxide materials and to newlinetailor the properties of these materials by doping/admixing so as to make it amenable newlinefor device purposes. First the brief introduction of manganites is described followed newlineby basics about oxypnictide superconductors. newlineIn 1993 Jin et al. observed about thousand-fold change in resistance in newlineepitaxial thin film of perovskite La2/3Ca1/3MnO3 at a high magnetic field of 6 Tesla newlineand, christened it as Colossal Magnetoresistance (CMR). The growth of interest in newlinetheir properties stems in large part, from the prospect of creating metal oxide devices newlinewhose performance exceeds GMR devices. In addition, it is now recognized that the newlinelarge magnetoresistivity in these oxides is the result of a unique type of metal newlineinsulator transition, the understanding of which complements the drive for newlineapplications.