Nontrivial behavior of T_c at the small electric field in BaTiO₃ crystals, detected by means of acoustic emission

Cubic-tetragonal phase transitions of [100]-oriented BaTiO₃ crystals have been studied by means of an acoustic emission (AE) method, under an external electric field. The Curie temperature (T_c) reveals a nontrivial behavior at the small field, namely, it initially decreases with enhancement of the field, attains a minimum at the threshold field E _th = 0.256 kV cm^-1, accompanied by the AE count rate , and then starts increasing with a rate of 1.5 K m kV^-1 as the field is enhanced. Such nontrivial behavior of T_c is explained as due to the presence of polar nanoregions, recently revealed in BaTiO₃ crystals (Ko et al 2011 Phys. Rev. B 84 094123).