| Doping perovskite manganites have been researched for over fifty years, the discovery of the colossal magnetoresistance(CMR) in such oxide has brought many interests. The rich diversities displayed in the electrical and magnetic transport property and structure in these oxides have indicated the intricate interplay between spin, charge, orbital and lattice degrees of freedom. Additionally, the fascinating potential of this material has been shown in magnetic storage technology. In this thesis, we devote to the study of the physical property and the phenomenon of charge ordering in this material by different doping concentration in A side.In the chapter one, we mainly summarized the study results of the maganetoresistance, and introduced the research progress of perovskite mangantes.In chapter two, we gave an overview of the physical phenomena in perovskite manganites such as lattice structure and electron structure. We interpreted the physical mechanism including double exchange, super exchange, charge ordering, Jahn-Teller effect and variable range hoping to understand the relevant concepts.Chapter three gave the experimental method.In chapter four, we prepared the samples Nd1/2(Sr1-xCax)3/2MnO4(x=0.0.0.1.0.3,0.5,0.7,0.8,0.9). By using the neutron powder diffraction measurements and Rietveld refinements, we confirmed the obtained samples are single phase(I4/mmm) at room temperature. The curves of the temperature variation of the susceptibility and the resistivity of samples were investigated and that showed an increase of TCO with the increase of the doping concentration x, meanwhile the octahedral MnO6has been flatened at direction c. we have also measured the physical properties of the sanple Nd1/2(Sr0.3Ca0.7)3/2Mn04and observed TN=180K and TCO=258K respectively. The electrical transport properties of Nd1/2(Sr1-xCax)3/2MnO4below TCO meet well with the variable range hopping model. |
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