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Far-Infrared Spectroscopy in Spin-Peierls Compound CuGeO_3 under High Magnetic Fields

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 Added by Kanji Takehana
 Publication date 1999
  fields Physics
and research's language is English




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Polarized far-infrared (FIR) spectroscopic measurements and FIR magneto-optical studies were performed on the inorganic spin-Peierls compound CuGeO_3. An absorption line, which was found at 98 cm$^{-1}$ in the dimerized phase (D phase), was assigned to a folded phonon mode of B$_{3u}$ symmetry. The splitting of the folded mode into two components in the incommensurate phase (IC phase) has been observed for the first time. A new broad absorption centered at 63 cm$^{-1}$ was observed only in the ${bf E}parallel b$ axis polarization, which was assigned to a magnetic excitation from singlet ground state to a continuum state.



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81 - A. Meetsma 1998
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We report high-pressure x-ray diffraction and magnetization measurements combined with ab-initio calculations to demonstrate that the high-pressure optical and transport transitions recently reported in TiOCl, correspond in fact to an enhanced Ti3+-Ti3+ dimerization existing already at room temperature. Our results confirm the formation of a metal-metal bond between Ti3+ ions along the b-axis of TiOCl, accompanied by a strong reduction of the electronic gap. The evolution of the dimerization with pressure suggests a crossover from the spin-Peierls to a conventional Peierls situation at high pressures.
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