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Yang G.,Cultivating Base of Anhui Key Laboratory of Spintronic and Nano Metric Materials | Yang G.,Suzhou University | Tang Y.,Cultivating Base of Anhui Key Laboratory of Spintronic and Nano Metric Materials | Tang Y.,Suzhou University | And 8 more authors.
Xiyou Jinshu/Chinese Journal of Rare Metals | Year: 2012

Polycrystalline samples of La 1-x(Ca 1-yAg y) x MnO 3(y=0.0, 0.2, 0.4, 0.6, 0.8) were prepared by the solid-state reaction method. The effects of the radius and disorder degree σ 2 of A-site ions on electric transport property and magnetoresistance of the samples La 1-x(Ca 1-yAg y) x MnO 3 with unchanged value of Mn 3+/Mn 4+ ratio through the introduction of both univalent and bivalent elements at A-site were studied through the measurements of X-ray diffraction (XRD) patterns, resistivity-temperature (ρ-T) curves and magnetoresistance-temperature (MR-T) curves. The results showed that the temperature of insulator-metal transition of all the samples basically kept unchanged, which could be explained by the competition between the effects of the radius of A-site ions and of the disorder degree of A-site ions on electric transport property. The MR of the sample with y=0.0 in the magnetic field of 0.8 T basically kept above 23% in the temperature range of 133~26 K, that of the sample with y=0.6 kept above 23% in the temperature range of 209~131 K, and so large MR appeared in such a wide temperature range, which was in favor of the practical application of MR. The mechanism of the temperature stability of MR was the result of the competition between the intrinsic magnetoresistance and the tunneling magnetoresistance. Source

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