Thermo-Optical Study of Short-Range Polar Order in a Ferroelectric Phase: The Ca2+ Impurity-Induced Ferroelectric Phase in SrTiO3

Abstract

The magnitudes and temperature dependences of the root-mean-square of polarization fluctuations, which characterizes short-range ordering below T_C, are determined for the first time for Sr_0.986Ca_0.014TiO₃ single crystals, using temperature measurements of light refraction made in a manner developed by the authors. Ab initio calculations of the equilibrium structures and total energies of three lowtemperature phases for SrTiO₃ and CaTiO₃ are performed and the symmetry of the ground state of their solid solution is identified on the basis of the obtained results. Features of short- and long-range ordering in the Ca²⁺-induced ferroelectric phase of the Sr_{1 − x}Ca_xTiO₃ system are discussed.