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The double-doped La2/3+4x/3Sr1/3-4x/3Mn1-xMgxO3 samples with fixed Mn^3+/Mn^4+ ratio equal to 2/1 are investigated by means of magnetism and transport measurements. Phase separation is observed at temperature higher than T^onset c for x = 0.10 and 0.15. For x = 0.10, rather strong phase separation induces drastic magnetic random potential and results in the localization of carriers. Thus, the varlable-range hopping process dominates. For other samples, there is no or only weak phase separation above T^onset c. Thus, thermal activation mechanism is responsible for the high temperature transport behaviour. For x = 0.20 and 0.25, unexpected AFM behaviour is observed at low temperature. All these results are well understood by considering the special role of the "double-doping". 相似文献
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双掺杂La0.67+1.33xSr0.33-1.33xMn1-xMgxO3体系的磁性和输运行为 总被引:1,自引:1,他引:0
用标准的固相反应法制备了双掺杂La0.67 1.33xSr0.33-1.33xMn1-xMgxO3(x=0.00,0.05,0.10,0.15,0.20,0.25)多晶样品,研究了它们的磁性和输运行为。对x=0.10和0.15,在温度高于Tc^cnset时出现相分离;对x=0.20和0.25,在低温区出现反铁磁行为。低掺杂样品ρ-T关系存在金属.绝缘体相变,高掺杂样品在测量温区内仅显示绝缘体行为。这些奇异现象用M-H关系、ESR曲线和拉曼光谱给予了很好的解释。 相似文献
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