【摘 要】
：
Several samples of manganese oxides La(1-x)2/3Ca1/3MnO3(V-LCMO)and(La0.7-xY0.3)2/3Ca1/3MnO3(x＜0.15) (V-LYCMO)with vacancies at La-site (La-vacancy) were prepared
【机 构】
：
School of Materials Science and Engineering,Laboratory of Solid State Microstructures
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Several samples of manganese oxides La(1-x)2/3Ca1/3MnO3(V-LCMO)and(La0.7-xY0.3)2/3Ca1/3MnO3(x＜0.15) (V-LYCMO)with vacancies at La-site (La-vacancy) were prepared by solid-state reaction method. The X-ray diffraction(XRD) patterns refined by Rietveld confirm that these compounds exhibit single phase structure with orthorhombic symmetry (Pnma). The lattice parameters,Mn-O bond length and Mn-O-Mn bond angle vary with La-vacancy concentration, as an indication of the occurrence of the local Jahn-Teller effect. The measurement result of V-LCMO compounds shows that the maximum magnetoresistance(MR) is about 220% at TIM=268 K and La-vacancy content x=0.04. For V-LYCMO compounds, there exists metal-insulator transition at about 50 K,and a very large MR (over 106%) is observed at the temperature ranging from 40 K to 50 K.
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