Delicate balance between ferroelectricity and antiferroelectricity in hexagonal InMnO₃

The presence of ferroelectricity in hexagonal InMnO₃ has been highly under debate. The results of our comprehensive experiments of low-temperature (T) polarization, transmission electron microscopy, and high-angle annular dark-field scanning TEM on well-controlled InMnO₃ reveal that the ground state is ferroelectric with P6₃cm symmetry, but a nonferroelectric P3̄c1 state exists at high T and can be quenched to room temperature. We found that the competing ferroelectric and antiferroelectric phases coexist in mesoscopic scales and can be deliberately controlled by varying thermal treatments.