Low-Temperature Limit of Spontaneous Polarization in BaTiO 3 Determined Using a (111)-Oriented Single Crystal

The spontaneous polarization of BaTiO 3 has long served as a standard in ferroelectric physics; however, its low-temperature limit has not been determined experimentally. In this study, we directly measured the spontaneous polarization of a BaTiO 3 single crystal cut into a (111)-oriented plate through pyroelectric charge measurements under field-cooling conditions. The polarization increased monotonically upon cooling and reached at least 32 µC/cm 2 at 0 K, consistent with the Berry-phase based first-principles predictions.