Low-Temperature Single-Crystal Structure and Phonon Properties of A-Site Ordered Double Perovskite CaMnTi₂O₆

We have used high-pressure methods to synthesize CaMnTi₂O₆ single crystals with edge lengths of up to 70 μm. Compared to previously reported synthetic pathways, we were able to use gold capsules and smaller pressures of 4 GPa. X-ray diffraction analysis of the single crystals at low temperatures between 100 and 230 K confirmed that no phase transitions occur in this temperature range. We found square planar-coordinated Mn ions to shift further out of the plane with lower temperatures which could lead to a higher polarization. The measured Raman spectrum of CaMnTi₂O₆ has been compared with quantum chemically calculated Raman spectrum to assign the vibrational modes. Calculated single-crystal Raman spectrum has also been also analyzed from the point of view of direction dependency of the Raman intensities.