Spatially inhomogeneous metal-insulator transition in doped manganites
Spatially inhomogeneous metal-insulator transition in doped manganites
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DOI：
10.1126/science.285.5433.1540
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发表时间：
1999-09-03
期刊：
影响因子：
56.9
通讯作者：
Mydosh, JA
中科院分区：
文献类型：
--
作者：
Fäth, M;Freisem, S;Mydosh, JA
利用扫描隧道光谱研究了具有巨大磁阻的La1-xCaxMnO3单晶和薄膜（x约为0.3），其绝缘相（顺磁性）和金属相（铁磁性）的不同光谱特征使得其空间范围可以成像到10纳米左右的横向尺度。在体转变温度T-c以上，图像显示出大部分绝缘行为。在T-c以下，观察到相分离，其中金属的非均匀结构和更多的绝缘区域共存，并且它们的大小和结构强烈依赖于场。发现绝缘区域远低于摄氏温度。这些结果表明，转变和相关的磁电阻行为应被视为金属铁磁畴的渗透。
Scanning tunneling spectroscopy was used to investigate single crystals and thin films of La1-xCaxMnO3 (with x of about 0.3), which exhibit colossal magnetoresistance, The different spectroscopic signatures of the insulating (paramagnetic) and metallic (ferromagnetic) phases enable their spatial extent to be imaged down to a Lateral scale of the order of 10 nanometers. Above the bulk transition temperature T-c, the images show mostly insulating behavior. Below T-c, a phase separation is observed where inhomogeneous structures of metallic and more insulating areas coexist and are strongly field dependent in their size and structure. Insulating areas are found to persist far below T-c. These results suggest that the transition and the associated magnetoresistance behavior should be viewed as a percolation of metallic ferromagnetic domains.