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arXiv 1306.5916cond-mat.mtrl-sci
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高压下BiMnO3的Jahn-Teller、极性和绝缘体-金属转变

Jahn-Teller, polarity and insulator-to-metal transition in BiMnO3 at high pressure

Mael Guennou, Pierre Bouvier, Pierre Toulemonde, Céline Darie, Céline Goujon, Pierre Bordet, Michael Hanfland, Jens Kreisel

摘要:

多铁性材料中共存的结构不稳定性的相互作用,在体材料和应变薄膜中产生了有趣的耦合现象和异常丰富的相图。在这里,我们研究了多铁性BiMnO 3与其独特的6s 2电子和四个相互作用机制:电极性,八面体倾斜,磁性,和合作Jahn-Teller失真。我们已经探讨了高压下的结构转变,同步辐射X射线衍射和拉曼光谱高达60 GPa。我们发现,BiMnO 3显示压力下丰富的序列的五个阶段具有各种各样的结构和性能,包括金属相高于53 GPa,并在37和53 GPa之间,一个强烈拉长的单斜相,允许铁电性,这与传统的预期,铁电性消失在压力下。在7和37 GPa之间,Pnma结构保持非常稳定,但以不同于在原型正交Jahn-Teller扭曲钙钛矿LaMnO 3中观察到的行为的方式显示出Jahn-Teller扭曲的减少。

英文摘要:

The interaction of coexisting structural instabilities in multiferroic materials gives rise to intriguing coupling phenomena and extraordinarily rich phase diagrams, both in bulk materials and strained thin films. Here we investigate the multiferroic BiMnO3 with its peculiar 6s2 electrons and four interacting mechanisms: electric polarity, octahedra tilts, magnetism, and cooperative Jahn-Teller distortion. We have probed structural transitions under high pressure by synchrotron x-ray diffraction and Raman spectroscopy up to 60 GPa. We show that BiMnO3 displays under pressure a rich sequence of five phases with a great variety of structures and properties, including a metallic phase above 53 GPa and, between 37 and 53 GPa, a strongly elongated monoclinic phase that allows ferroelectricity, which contradicts the traditional expectation that ferroelectricity vanishes under pressure. Between 7 and 37 GPa, the Pnma structure remains remarkably stable but shows a reduction of the Jahn-Teller distortion in a way that differs from the behavior observed in the archetypal orthorhombic Jahn-Teller distorted perovskite LaMnO3.

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