常压下的Ca(Mn_(3-x)Cu_x)Mn_4O_(12)样品的制备及其导电机制的研究

钙钛矿结构ＣａＣｕ３Ｍｎ４Ｏ１２的传统制备方法是热压法（几万个大气压，１０００℃）。人们发现它的居里点Ｔｃ＝３５５ Ｋ，磁电阻ＭＲ值比相同条件下的Ｌａ０．６Ｙ０．０７Ｃａ０．３３ＭｎＯａ大得多，并且从低温到高于居里点的温度范围内都存在较大的磁电阻值。另外，Ｃａ（Ｍｎ３－ｘ Ｃｕｘ） Ｍｎ４Ｏ１２（ｘ＝３）的饱和磁化场，在室温３００Ｋ时，饱和磁化场仅为０．０３Ｔ。本实验中，在常压和１０７０ Ｋ的条件下合成了Ｃａ（Ｍｎ３－ｘＣｕｘ）Ｍｎ４Ｏ１２，从而大大简化了Ｃａ （Ｍｎ３－ｘＣｕｘ）Ｍｎ４Ｏ１２的制备条件。关于该材料的导电机制，铁磁磁畴再取向饱和场与磁电阻饱和场相同，表明Ｃａ（Ｍｎ３－ｘ Ｃｕｘ）Ｍｎ４Ｏ１２的ＭＲ来源于磁畴间或颗粒间的隧道机制。

The Synthesis of Ca(Wn_(3-x)Cu_x)Wn_4O_12 in Air and Study of its Conducting Mechanism

The conventional fabrication method of perovskite CaCu3Mn4O12 is the high pressure or the hydrothermal synthesis. People have found that its Curie temperature is 355K. The MR is much larger than the MR of La0.06 Y0.07 Ca0.33 MnO3 at the same temperature and fields, and exists from low temperature to over Tc. Additionally, the saturation fields of Ca(Mn3-x Cux)Mn4 O12 is very low. The MR at room temperature is almost saturated at only 0.03 T. Regarding the conducting mechanismo in this material, the similar saturation fields in the FM - domain reorientation and in the MR suggests an interdomain/grain tunneling mechanism origin for the MR. The perovskites Ca(Mn3-xCux)Mn4 O12 have been synthesized in air at 1070 K using conventional ceramic technology in our experiment.