Investigation of Phonon Anomaly in the Orbital Order State of La_<1-x>Sr_xMnO_3 (x〜1/8) : Condensed Matter: Electronic Properties, etc.

概要

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Drastic changes have been observed in the temperature and doping dependence of the phonon l spectra in La_<1-x>Sr_xMn0_3 with x = 0.10-0.125. For the x = 0.11 and 0.125 samples, some of the bending (Mn-O-Mn bond angle modulation) modes show broadening and softening in the ferromagnetic metallic phase, which appears in intermediate temperature range. In the low-temperature orbital-ordered phase, these bending modes become sharper and the temperature dependence of the oscillator strength coincides with that of the orbital ordering order-parameter directly determined by resonant X-ray scattering. These facts indicate a strong correlation between the bending-type lattice distortion and the orbital ordering in the low temperature phase. For x = 0.10, the phonon spectrum shows similarity with that of the end material LaMnO_3 and no clear temperature dependence is found. The x-dependence of the phonon spectra is consistent with the existence of vertical phase boundary around x = 0.11 newly discovered by a recent X-ray powder diffraction study.
社団法人日本物理学会の論文
2001-03-15