Manganitlerın yapısal ve manyeto-taşınım özellikleri üzerine katyonik ve anyonik katkılamanın etkisi

Colossal magnetoresistance (CMR) which is defined as the change in resistivity (as much as 1000%) under applied magnetic fields has been a subject of intense theoretical and experimental research since 1990s. The common and the most substantial characteristic of the magnetoresistive materials is that their electrical resistance can be changed significantly by application of an external magnetic field. The most relevant materials showing CMR effect are the compounds that crystallize in the perovskite structure (rare earth-alkaline earth-manganese based R1-xAxMnO3±δ (RAMO; Re: rare earth metal, Ae:divalent alkaline metal)). Due to their fascinating magnetic and electronic properties, rare earth manganites have a variety of potential applications such as magnetic storage cells for magnetoresistive random access memories, low and high field magnetic sensors and infrared bolometers. This thesis on hole-doped RAMO system has two-fold purpose. One is the investigation of the anion substituted polycrystalline bulk system of La0.7Ca0.3MnO3-δFx (x=0.0, 0.2, 0.4 and 0.6). The second purpose is to understand the effect of deficiency/efficiency in the A (=Ca)-site. This class of transition metal oxide under investigation are hole-doped system with La0.7CaxMnO3-δF2x (x=0.2, 0.3 and 0.4). The main objective is the characterization of the structural and physical property and to understand the magneto-transport behavior in these systems. To accomplish this objective, we prepared the samples by solid state reaction method and investigate by means of X-ray powder diffraction, scanning electron microscopy, electrical resistivity and magnetization measurements.