The ferroelectric to paraelectric phase transition of multiferroic CaMnTi2O6 has been investigated at high pressures and ambient temperature by second harmonic generation (SHG), Raman spectroscopy, and powder and single-crystal x-ray diffraction. We have found that CaMnTi2O6 undergoes a pressure-induced structural phase transition (P42mc→P42/nmc) at ∼7 GPa to the same paraelectric structure found at ambient pressure and Tc = 630 K. The continuous linear decrease of the SHG intensity that disappears at 7 GPa and the existence of a Raman active mode at 244 cm−1 that first softens up to 7 GPa and then hardens with pressure, are used to discuss the nature of the phase transition of CaMnTi2O6 for which a dTc/dP=−48 K/GPa has been found. Neither a volume contraction nor a change of the normalized pressure on the eulerian strain are observed across the phase transition with all the unit-cell volume data following a second order Birch-Murnaghan equation of state with a bulk modulus of B0 = 182.95(2) GPa.
@article{arxiv.1708.08328,
title = {Ambient temperature high-pressure-induced ferroelectric phase transition in CaMnTi$_2$O$_6$},
author = {J. Ruiz-Fuertes and T. Bernert and D. Zimmer and N. Schrodt and M. Koch-Müller and B. Winkler and L. Bayarjargal and C. Popescu and S. MacLeod and K. Glazyrin},
journal= {arXiv preprint arXiv:1708.08328},
year = {2017}
}