Riedl Thomas, Gemming Thomas, Dörr Kathrin, Luysberg Martina, Wetzig Klaus
IFW Dresden, PF 270116, 01171 Dresden, Germany.
Microsc Microanal. 2009 Jun;15(3):213-21. doi: 10.1017/S1431927609090229.
This article presents a (scanning) transmission electron microscopy (TEM) study of Mn valency and its structural origin at La 0.7 Sr 0.3 MnO 3/SrTiO3(0 0 1) thin film interfaces. Mn valency deviations can lead to a breakdown of ferromagnetic order and thus lower the tunneling magnetoresistance of tunnel junctions. Here, at the interface, a Mn valency reduction of 0.16 +/- 0.10 compared to the film interior and an additional feature at the low energy-loss flank of the Mn-L3 line have been observed. The latter may be attributed to an elongation of the (0 0 1) plane spacing at the interface detected by geometrical phase analysis of high-resolution images. Regarding the interface geometry, high-resolution high-angle annular dark-field scanning TEM images reveal an atomically sharp interface in some regions whereas the transition appears broadened in others. This can be explained by the presence of steps. The performed measurements indicate that, among the various structure-related influences on the valency, the atomic layer termination and the local oxygen content are most important.
本文展示了一项关于La 0.7 Sr 0.3 MnO 3 /SrTiO3(0 0 1)薄膜界面处锰价态及其结构起源的（扫描）透射电子显微镜（TEM）研究。锰价态偏差会导致铁磁序的破坏，从而降低隧道结的隧道磁电阻。在此，在界面处，观察到与薄膜内部相比锰价态降低了0.16 +/- 0.10，并且在Mn-L3线的低能量损失侧翼处有一个额外特征。后者可能归因于通过高分辨率图像的几何相位分析检测到的界面处(0 0 1)平面间距的伸长。关于界面几何形状，高分辨率高角度环形暗场扫描TEM图像显示在某些区域存在原子级尖锐的界面，而在其他区域过渡似乎变宽了。这可以用台阶的存在来解释。所进行的测量表明，在对价态的各种与结构相关的影响中，原子层终止和局部氧含量是最重要的。
