The effects of the eg orbital order on the phonon modes were investigated by Raman scattering in LaCoO3. Raman scattering has an advantage to find out the change induced by the orbital states, because of Raman activity of all phonon modes are created by the distortion from the cubic perovskite structure. The quadrupole mode shows the anomalous softening, enhancement and broadening as the occupancy of the intermediate spin (IS) state increases. The results show that all Raman active phonon modes are affected by the excitation of IS Co3+ ions and shows anomalous temperature dependence.
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