High pressure behavior of Ga-doped LaMnO3: a combined X-ray diffraction and optical spectroscopy study
High pressure behavior of Ga-doped LaMnO3: a combined X-ray diffraction and optical spectroscopy study
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DOI：
10.1039/b914975a
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发表时间：
2008-07
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通讯作者：
M. Baldini;L.Malavasi;D. Castro;A. Nucara;W. Crichton;M. Mezouar;J. Blasco;P. P. Infm-P.;D. Fisica;UniversitaSapienza;Roma;Italy.;Dipartimento di chimicaM.Rolla;Instm;IENI-CNR;U. Pavia;Pavia;Italy.;European Synchrotron Radiation Facility;Grenoble;France.;Instituto de Ciencia de Materiales de Aragon-Instituto-de-Ciencia-de-Materiales-de-Aragon-1423124504;Departamento de Fisica de la Materia Condensada-Departamento-de-Fisica-de-la-Materia-Condensada-1768846650;CSIC-Universidad de Zaragoza;Zaragoza;Spain.
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文献类型：
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作者：
M. Baldini;L.Malavasi;D. Castro;A. Nucara;W. Crichton;M. Mezouar;J. Blasco;P. P. Infm-P.;D. Fisica;UniversitaSapienza;Roma;Italy.;Dipartimento di chimicaM.Rolla;Instm;IENI-CNR;U. Pavia;Pavia;Italy.;European Synchrotron Radiation Facility;Grenoble;France.;Instituto de Ciencia de Materiales de Aragon-Instituto-de-Ciencia-de-Materiales-de-Aragon-1423124504;Departamento de Fisica de la Materia Condensada-Departamento-de-Fisica-de-la-Materia-Condensada-1768846650;CSIC-Universidad de Zaragoza;Zaragoza;Spain.
利用x射线衍射和拉曼光谱研究了压力对LaMn1−xGaxO3 （x = 0.2, 0.3, 0.4）族化合物Jahn-Teller （JT）畸变的影响。选择了具有完全相干JT畸变结构（x = 0.2）、正八面体结构（x = 0.6）和中间构型（x = 0.3）的化合物。在所有样品中都观察到压力诱导的从正交Pbnm相向更高对称性结构的转变。拉曼和x射线数据都证实，压力最重要的结构效应是减少八面体畸变。在晶格参数行为中发现了与结构不稳定相关的特征，指出了JT畸变在稳定锰矿结构中的关键作用。另一方面，高压相的JT畸变不能被完全抑制。在一定压力范围内，畸变程度较高的化合物（x = 0.2, 0.3）上的拉曼光谱清晰地揭示了畸变和正八面体结构域的共存。绘制了压力与ga含量相图的第一张草图。
The pressure effects on the Jahn–Teller (JT) distortion of three representative compounds belonging to the LaMn1−xGaxO3 (x = 0.2, 0.3, 0.4) family were widely investigated by means of X-ray diffraction and Raman spectroscopy. A compound with a fully coherent JT distorted structure (x = 0.2), one with regular octahedra (x = 0.6) and one in an intermediate configuration (x = 0.3) were selected. A pressure induced transition from the orthorhombic Pbnm phase towards structures with higher symmetry was observed in all the samples. Both Raman and X-ray data confirm that the most important structural effect of pressure is that of reducing the octahedral distortion. The appearance of a feature in the lattice parameter behavior connected to a structural instability was also detected, pointing out the key role of the JT distortion in stabilizing the manganite structures. On the other hand, the complete suppression of the JT distortion in the high-pressure phases cannot be claimed. The Raman spectra collected on the more distorted compounds (x = 0.2, 0.3) reveal clearly the coexistence of domains of distorted and more regular octahedra in a certain pressure range. The first sketch of the pressure vs. Ga-content phase diagram was drawn.