【摘要】 利用金属有机物分解法在石英衬底上制备了多晶Ｌａ０．６７Ｃａ０．３３ＭｎＯｘ薄膜。研究了薄膜输运特性及其与温度的关系，发现薄膜的金属一半导体转变温度Ｔｐ（约１７２Ｋ）远低于其居里温度（约２４７Ｋ）；在平行于膜面的ＩＴ磁场下，７７Ｋ～３０２Ｋ温度范围内，没有磁电阻（ＭＲ）峰，而是在Ｔｐ温度以下，有一定的平台，平台处ＭＲ值约为２１％～２４％，在Ｔｐ温度以上，ＭＲ随温度上升而迅速降低；在７７Ｋ温度下，薄膜具有显著的低场磁电阻效应。上述磁输运特性与载流子在晶界附近的输运行为如强的自旋相关散射和晶粒间自旋极化隧道效应等有关。在７７Ｋ温度下，还观察到了退磁效应引起的磁电阻垂直各向导性。更多还原

【Abstract】 Polycrystalline La0.67Ca0.33MnOz thin films were successfully synthesized on amorphous quartz substrates by metal-organic decomposition. The temperature dependence of magnetotransport of the film was investigated. The results showed that the metalinsulator transition temperature Tp (about 172K) of the film was far below its Curie temperature (about 247K). Under 1T field parallel to the film plane, a broad plateau of magnetoresistance (MR) was exhibited below Tp in the temperature dependence of MR, and MR decreased quickly with increasing temperature above Tp, namely, no MR peak was observed over the measured temperature range of 77K～302K. Furthermore, large low-field MR effect was observed at 77K. The above magnetotransport properties were related to the transport behavior of the carriers near the grain boundaries such as strong spin-dependent scattering and intergrain spin- polarized tunneling. Moreover, perpendicular anisotropy of MR was observed at 77K, which was ascribed to the demagnetizing effect.更多还原