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标题：Microscopic origins for stabilizing room-temperature ferromagnetism in ultrathin manganite layers
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作者：L. Fitting Kourkoutis ; J. H. Song ; H. Y. Hwang 等
期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2010
卷号：107
期号：26
页码：11682-11685
DOI：10.1073/pnas.1005693107
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：La0.7Sr0.3MnO3 is a conducting ferromagnet at room temperature. Combined with thin SrTiO3 layers, the resulting heterostructures could be used as highly spin-polarized magnetic-tunnel-junction memories. However, when shrunk to dimensions below an apparent critical thickness, the structures become insulating and ferromagnetic ordering is suppressed. Interface spin and charge modulations are thought to create an interfacial dead layer, thus fundamentally limiting the use of this material in atomic-scale devices. The thickness of this dead layer, and whether it is intrinsic, is still controversial. Here we use atomic-resolution electron spectroscopy to demonstrate that the degradation of the magnetic and transport properties of La0.7Sr0.3MnO3/SrTiO3 multilayers correlates with atomic intermixing at the interfaces, and the presence of extended two-dimensional cation defects in the La0.7Sr0.3MnO3 layers (in contrast to three-dimensional precipitates in thick films). When these extrinsic defects are eliminated, metallic ferromagnetism at room temperature can be stabilized in five-unit-cell-thick manganite layers in superlattices, placing the upper limit for any intrinsic dead layer at two unit cells per interface.
关键词：electron energy loss spectroscopy ; manganites ; scanning transmission electron microscopy