6533b873fe1ef96bd12d55e2

RESEARCH PRODUCT

Ambient-temperature high-pressure-induced ferroelectric phase transition in CaMnTi2O6

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The ferroelectric to paraelectric phase transition of multiferroic ${\mathrm{CaMnTi}}_{2}{\mathrm{O}}_{6}$ 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 ${\mathrm{CaMnTi}}_{2}{\mathrm{O}}_{6}$ undergoes a pressure-induced structural phase transition ($P{4}_{2}mc\ensuremath{\rightarrow}P{4}_{2}/nmc$) at $\ensuremath{\sim}7\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$ to the same paraelectric structure found at ambient pressure and ${T}_{c}=630\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. The continuous linear decrease of the SHG intensity that disappears at 7 GPa and the existence of a Raman active mode at 244 ${\mathrm{cm}}^{\ensuremath{-}1}$ that first softens up to 7 GPa and then hardens with pressure are used to discuss the nature of the phase transition of ${\mathrm{CaMnTi}}_{2}{\mathrm{O}}_{6}$, for which a $d{T}_{c}/dP=\ensuremath{-}48$ K/GPa has been found. Neither a volume contraction nor a change in the normalized pressure on the Eulerian strain is 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 ${B}_{0}=182.95(2)\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$.