La $_{0.67}$ Ca $_{0.33}$ MnO $_3$薄膜中Mn的价态和磁输运
Manganese valence and magnetotransport in ultrathin films of La$_{0.67}$Ca$_{0.33}$MnO$_3$
摘要：
我们报告了一个非常薄的La $_{0.67}$ Ca $_{0.33}$ MnO $_3$薄膜的性能的比较研究，在应变下外延生长的平面SrTiO $_3$（STO），晶格匹配的NdGaO $_3$（NGO），和应变$1^{\circ}$-错切STO。我们使用透射电子显微镜和电子能量损失谱研究的微观结构，组成和锰价态。在界面附近，我们没有发现显着的偏析，但电荷补偿层的化合价是提高超过标称值3.3+，和弛豫到这个值超过几个纳米。的传输特性显示出众所周知的行为，为平面STO和NGO上的膜，即金属-绝缘体转变温度的值，这是强烈（STO）或只有很少（NGO）减少相对于体值。然而，减少在膜上的错切STO是不太强的比在平坦的STO上的膜，即使它们出现类似的应变状态和界面层。在磁性上，我们发现应变膜的饱和磁化强度相对于体值，这不能只归因于界面层的值降低。
英文摘要：
We report a comparative study of the properties of very thin films of La$_{0.67}$Ca$_{0.33}$MnO$_3$ grown epitaxially under strain on flat SrTiO$_3$ (STO), lattice matched on NdGaO$_3$ (NGO), and strained on $1^{\circ}$-miscut STO. We use transmission electron microscopy and electron energy loss spectroscopy to study the microstructure, composition, and Mn valence state. Near the interface we find no significant segregation, but a charge compensation layer where the valence is enhanced over the nominal value of 3.3+, and a relaxation to this value over several nanometer. The transport properties show well-known behavior for the films on flat STO and NGO, namely values of the metal-insulator transition temperature which are strongly (STO) or only little (NGO) reduced with respect to the bulk value. The reduction in films on miscut STO however is less strong than in films on flat STO, even though they appear similar as to strain state and interface layer. Magnetically, we find reduced values of the saturation magnetization for the strained films with respect to the bulk value, which cannot only be ascribed to the interface layer.
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