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arXiv · 0806.0885

Raman spectra in iron-based quaternary CeO$_{1-x}$F$_x$FeAs and LaO$_{1-x}$F$_x$FeAs

S. C. Zhao·D. Hou·Y. Wu·T. L. Xia·A. M. Zhang·G. F. Chen·J. L. Luo·N. L. Wang·J. H. Wei·Z. Y. Lu·Q. M. Zhang
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Abstract

Raman spectra have been measured on iron-based quaternary CeO$_{1-x}$F$_x$FeAs and LaO$_{1-x}$F$_x$FeAs with varying fluorine doping at room temperatures. A group analysis has been made to clarify the optical modes. Based on the first principle calculations, the observed phonon modes can be assigned accordingly. In LaO$_{1-x}$F$_x$FeAs, the E$_g$ and A$_{1g}$ modes related to the vibrations of La, are suppressed with increasing F doping. However F doping only has a small effect on the E$_g$ and A$_{1g}$ modes of Fe and As. The Raman modes of La and As are absent in rare-earth substituted CeO$_{1-x}$F$_x$FeAs, and the E$_g$ mode of oxygen, corresponding to the in-plane vibration of oxygen, moves to around 450 cm$^{-1}$ and shows a very sharp peak. Electronic scattering background is low and electron-phonon coupling is not evident for the observed phonon modes. Three features are found above 500 cm$^{-1}$, which may be associated with multi-phonon process. Nevertheless it is also possible that they are related to magnetic fluctuations or interband transitions of d orbitals considering their energies.

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S. C. Zhao, D. Hou, Y. Wu, T. L. Xia, A. M. Zhang, G. F. Chen, J. L. Luo, N. L. Wang, J. H. Wei, Z. Y. Lu, Q. M. Zhang. 2008-06-05. Raman spectra in iron-based quaternary CeO$_{1-x}$F$_x$FeAs and LaO$_{1-x}$F$_x$FeAs. https://doi.org/10.1088/0953-2048%2F22%2F1%2F015017

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