Nature of the low-energy excitations of a charge-ordered phase of La0.25Ca0.75MnO3 manganites
Nature of the low-energy excitations of a charge-ordered phase of La0.25Ca0.75MnO3 manganites
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La0.25Ca0.75MnO3 锰酸盐电荷有序相的低能激发性质
DOI：
10.1134/s0021364010070027
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发表时间：
2010
期刊：
影响因子：
1.3
通讯作者：
M. Dressel
中科院分区：
文献类型：
--
作者：
B. Gorshunov;E. Zhukova;E. Maksimov;A. S. Prokhorov;V. Torgashev;T. Zhang;D. Wu;M. Dressel
分析了多晶和纳米结构La0.25Ca0.75MnO_3样品的低能激发性质，以研究锰氧化物的电荷有序机制。结果表明，La0.25Ca0.75MnO_3在0.5-90 meV的能量范围和5-300K的温度范围内的电动力学响应谱没有可归因于电荷有序相的集体激发的共振特征。结果表明，在20-40和80-100 cm-1频率处观察到的吸收线归因于通常的声学声子由于结构相变而变得光学活跃，以及沿晶体a轴出现具有四个周期的四重超结构。在含有纳米晶(≤40 nm)的样品中发现了超结构的抑制。这种抑制表明电荷和磁序参数与声子子系统的耦合相对较弱。
The nature of the low-energy excitations of polycrystalline and nanostructured La0.25Ca0.75MnO3 samples has been analyzed in order to investigate the mechanisms of charge ordering in manganites. It has been found that the electrodynamic response spectra of La0.25Ca0.75MnO3 in the energy range of 0.5 to 90 meV and the temperature range of 5 to 300 K have no resonance features that could be attributed to the collective excitations of the charge-ordered phase. It has been shown that the absorption lines observed at frequencies of 20–40 and 80–100 cm–1 are attributed to usual acoustic phonons becoming optically active owing to the structure phase transition and the appearance of a fourfold superstructure with a quadruple period along the crystallographic a axis. The suppression of the superstructure has been revealed in samples with nanocrystallites (≤40 nm). This suppression indicates a relatively weak coupling of the charge and magnetic order parameters with the phonon subsystem.