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Structure, phonons, and orbital degrees of freedom inFe2Mo3O8
Physical Review B ( IF 3.2 ) Pub Date : 2020-09-17 , DOI: 10.1103/physrevb.102.094307 S. Reschke , A. A. Tsirlin , N. Khan , L. Prodan , V. Tsurkan , I. Kézsmárki , J. Deisenhofer
Physical Review B ( IF 3.2 ) Pub Date : 2020-09-17 , DOI: 10.1103/physrevb.102.094307 S. Reschke , A. A. Tsirlin , N. Khan , L. Prodan , V. Tsurkan , I. Kézsmárki , J. Deisenhofer
We report on the structural and spectroscopic characterization of the multiferroic . Synchrotron x-ray and neutron diffraction as well as thermal expansion measurements reveal a lattice anomaly at but do not show any symmetry lowering in the magnetically ordered state. The lattice parameter exhibits a nonmonotonic behavior with a pronounced minimum around 200 K, which is also reflected in an anomalous behavior of some of the observed infrared-active optical excitations and parallels the onset of short-range magnetic order. The infrared reflectivity spectra measured between 5 and 300 K in the frequency range of reveal most of the expected phonon modes in comparison with the eigenfrequencies obtained by density-functional calculations. The phonons show an overall hardening upon cooling, whereas a nonmonotonic behavior is observed for some of the modes. These modes also show a strongly increased phonon lifetime below , which we associate with the quenched direction of the orbital moment in the magnetically ordered state. A similar increase is observed in the lifetime of the higher-lying excitations of the tetrahedral site that become clearly visible below only.
中文翻译:
Fe2Mo3O8中的结构,声子和轨道自由度
我们报告了多铁性的结构和光谱表征 。同步加速器的X射线和中子衍射以及热膨胀测量表明在但在磁有序状态下不显示任何对称性降低。晶格参数呈现出非单调行为,其最小最小值在200 K附近,这也反映在一些观察到的红外活性光激发的异常行为中,并且与短程磁阶的发生平行。在5-300 K之间的频率范围内测得的红外反射光谱与通过密度泛函计算获得的本征频率相比,揭示了大多数预期的声子模式。的 声子在冷却时显示出整体硬化,而在某些情况下观察到非单调行为 模式。这些模式还显示,在以下情况下,声子寿命大大增加,它与处于磁有序状态的轨道矩的淬灭方向相关联。在高处的生命周期中观察到类似的增加 四面体的激发 在下面变得清晰可见的网站 只要。
更新日期:2020-09-17
中文翻译:
Fe2Mo3O8中的结构,声子和轨道自由度
我们报告了多铁性的结构和光谱表征 。同步加速器的X射线和中子衍射以及热膨胀测量表明在但在磁有序状态下不显示任何对称性降低。晶格参数呈现出非单调行为,其最小最小值在200 K附近,这也反映在一些观察到的红外活性光激发的异常行为中,并且与短程磁阶的发生平行。在5-300 K之间的频率范围内测得的红外反射光谱与通过密度泛函计算获得的本征频率相比,揭示了大多数预期的声子模式。的 声子在冷却时显示出整体硬化,而在某些情况下观察到非单调行为 模式。这些模式还显示,在以下情况下,声子寿命大大增加,它与处于磁有序状态的轨道矩的淬灭方向相关联。在高处的生命周期中观察到类似的增加 四面体的激发 在下面变得清晰可见的网站 只要。